Infomotions, Inc.Physical realism, being an analytical philosophy from the physical objects of science to the physical data of sense. / Case, Thomas

Author: Case, Thomas
Title: Physical realism, being an analytical philosophy from the physical objects of science to the physical data of sense.
Publisher: London, Longmans, 1888.
Tag(s): realism; descartes, ren‚e, 1596-1650; hume, david, 1711-1776; locke, john, 1632-1704; berkeley, george, 1685-1753; kant, immanuel, 1724-1804; psychical; external; berkeley; sensible; psychological idealism; infer; data; sensation; ideas; idealism; physical; theory; physical realism; philosophy; science; objects; locke; nervous system; idealism tart; analytical judgments; secondary qualities; qualities; object; sense; knowledge
Contributor(s): Eric Lease Morgan (Infomotions, Inc.)
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Identifier: physicalrealismb00caseuoft
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drrodflgui Ay/rt*caw AKISTOTLE 

L X G 11 A X S, GHEE X, A X I) C 0. 

AND NE\y YOliK : 15 EAST 10" STKEET 
1888 , 

All right. 3 ff*r r rr,l 

Neque tamen illis nihil adtli posse affirmamus : sed contra, 
nos, qui Mentem respicimus non tantuin in facultate propria, 
sed quatenus copulatur cum Rebus, Artem Inveniendi cum 
Inventis adolescere posse, statuere debemus. 

BACON, Nov. Org. i. 130. 












PART 11. 



VII. BERKELEY .... |fl(j 


IX. HUME O fj(j 





Itaqiie contemplatio fere desinit cum aspcctu ; adeo ut rerum 
invisibilium cxigua aut nulla sit observation 

BACON, Nov. Org. i. 50. 



NATURAL PHILOSOPHY, as now regarded, treats generally 
of the physical universe, and deals fearlessly alike with 
quantities too great to be distinctly conceived, and with 
quantities almost infinitely too small to be perceived 
even with the most powerful microscopes ; such as, for 
instance, distances through which the light of stars or 
nebulas, though moving at the rate of about 186,000 
miles per second, takes many years to travel ; or the 
size of the particles of water, whose number in a single 
drop may, as we have reason to believe, amount to 
somewhere about 10 2G , or 


Yet we successfully inquire not only into the composi 
tion of the atmospheres of these distant stars, but into 
the number and properties of these water-particles ; nay, 
even into the laws by which they act upon one another. 
This quotation from Professor Tait s Recent Ad 
vances in Physical Science is a recognition of the 
reality of the insensible, and of its knowledge by the 
natural philosopher, as facts. No metaphysical theory 
of existence can be complete, unless it recognises the 
known reality of the insensible physical world ; and 
no psychological theory of human knowledge can be 
accepted as even a probable hypothesis, unless it 

B 2 


explains how these scientific objects of human know 
ledge are known from the original data of sense. 

The distinction between the sensible and the scien 
tific-, the apparent and the real, the perceptible and the 
imperceptible, is not only a scientific fact but has be 
come a commonplace in natural philosophy, without 
having produced any marked effect in mental philo 
sophy. Astronomy has long opposed the real to the 
apparent motions of celestial bodies ; and Sir Isaac 
Newton carried this contrast so far as to oppose abso 
lute, true and mathematical, to relative, apparent and 
common, time and space. In physics, apparent size is 
the room which a body seems to occupy, physical size 
is the real space taken up by its particles. Not only 
physics, but chemistry and biology unite in the anti 
thesis of molar and molecular motion, in recognising 
therefore motions which are for the most part imper 
ceptible, in resolving what seem to our senses to be 
heterogeneous qualities into mere varieties of imper 
ceptible motion, and in referring these motions to 
particles which are as imperceptible as the motions 
themselves. In all these sciences the latent structures 
and processes of things are opposed to their external 
appearances and perceptible changes. 

I do not mean that these undeniable conclusions, 
very far removed as they are from the original data of 
observation and experiment, are at all inconsistent with 
the sensations, perceptions, observations, or experiences 
which ordinary men have, and from which the natural 
philosopher starts. On the contrary, the very untutored 
senses themselves are best explained nay, can be only 
explained by statements at first sight opposed to 
them. It is only in appearance that the motion of the 
earth round the sun contradicts our senses, for, though 


it contradicts one single appearance, the whole sum of 
astronomical observations is only to be explained by 
means of it. Similarly, when it is said that one thing is 
apparently larger and physically smaller than another, 
vision is contradicted, but the sense of touch is justified, 
and our experience as a whole explained. The latent 
motions of particles, into which sensible qualities are 
resolved, at first sight contradict but really explain 
the whole system of our sensations of touch, vision, 
and hearing. 

But though the results of science thus explain the 
data of sense, it must be remembered that they only 
explain them, and are not themselves data of sense. 
No man can make himself see the earth going round 
the sun, except by standing on the sun itself. No man 
can see light at the moment when it starts from a 
distant star years before it reaches his senses. Micro 
scopes can be multiplied in power, but they are 
millions short of the actual (I do not speak of the 
potential) divisibility of the particles of things. 

Moreover, the natural philosopher gives even greater 
reality to the imperceptible than to the perceptible. 
The astronomer not only opposes but prefers real to 
apparent motion, the physicist physical to apparent 
size, and all natural philosophers latent structures and 
molecular processes to masses and their molar motions. 
It is not too much to say, that the mission of modern 
as well as of ancient philosophy is to convince mankind 
that sense is unequal to the subtlety of things ; to get 
behind the scenes and see the machinery of nature at 
work ; to recognise the insensible as real, yes, and more 
real, than the sensible. Sense is not science. 

Our knowledge is not limited to sensible pheno 
mena. We are quite as certain of the existence of 


that which cannot be brought within our sensibility 
as of that which can, and of objects which we do 
not experience as of objects of experience itself. 
Further, we are quite as certain that they exist in 
space and in time ; for if they are not in space they 
have no size, if they are not in time they have no dura 
tion, and that which has neither any size nor any dura 
tion is nothing ; and, if they are neither in time nor 
space, they do not move, for motion is change of 
place in space during time. Space and time are not 
mere forms of our sensibility, but conditions of things 
and their motions beyond the range of our sensibility. 

We not only know that the imperceptible exists, and 
that it exists in space and time, but also we know im 
perceptible attributes both of the perceptible and of the 
imperceptible. For example, I know that the hour-hand 
of my watch moves, though I cannot perceive it moving, 
as well as that the minute-hand moves which I can per 
ceive moving with difficulty, or the second-hand which 
I can perceive moving with ease. I know that the im 
perceptible particles of matter gravitate imperceptibly 
towards one another, as well as I know that their masses 
gravitate, and that unless gravitation is true of the 
former, it is not true of the latter. Still more insensible 
are cohesion and chemical affinity, which are imper 
ceptible motions exerted between imperceptible particles 
and at imperceptible distances. The whole of modern 
science is based on the fact that there are numerous 
latent structures and latent processes which are known 
to be real attributes of particles themselves latent. He, 
then, who will venture to assert, as mental philosophers 
often do assert, that the attributes which we ascribe to 
things are simply the phenomena or the sensations 
which they cause in us, must be prepared to deny all 


the imperceptible structures and motions which are 
recognised as attributes of things in natural philosophy. 
Natural philosophy does not stop at the reality and 
knowledge of imperceptible things and their imper 
ceptible attributes. It takes one step further : it regards 
the imperceptible as not only real but causal. In the 
first place, among imperceptible objects there are latent 
processes of cause and effect, no part of which can be 
represented by a sensible object. When, for example, 
the physicist declares that the medium called aether 
remains fixed in space, while each successive part of it 
undulates in consequence of the previous undulation of 
another part, in the same manner as water communi 
cates successive waves, he affirms that the whole of this 
propagation of undulations through aether is real, though 
the whole of it is imperceptible. Secondly, he affirms 
still more ; he affirms that the imperceptible undula 
tions not only cause one another, but finally cause our 
sensations of light. In this instance of light, as well 
as in the parallel case of heat, natural philosophy un 
hesitatingly accepts the conclusion that imperceptible 
motions of imperceptible things not only exist but cause 
our sensations. In other words, secondary qualities as 
existing in nature are insensible primary qualities which 
are causes of secondary qualities, as sensible in us. 

Natural philosophy is not a sham. One or other, 
or many, of its propositions, may be untrue. But its 
whole fabric of the physical, but insensible, world 
which causes the sensible image of it to arise in us, 
cannot be an invention. There is a thing beyond sense, 
a reality beyond phenomena, not only actual in nature, 
but known to science. There is a thing real and known 
which is not a sensible phenomenon, because such 
things as imperceptible particles are known really to 


exist, though they are incapable of becoming sensible. 
There are attributes real and known which belong to 
this thing, but are not sensations or sensible phe 
nomena, because such attributes as the imperceptible 
motions of imperceptible particles are known really to 
take place, although they are not capable of becoming 
sensible. Finally, these real things by these real 
attributes are real and known causes of human sensa 
tions because the imperceptible motions of the imper 
ceptible are known really to cause sensations of light 
and other sensations in men, although the latent pro 
cess, by which an imperceptible motion such as the 
undulation of ether produces sensible light, is totally 
beyond the reach of sense, which perceives not the 
undulation but the sensible result. Thus real things 
and real attributes transcending yet really causing sensa 
tions are, in some way or other, known to the natural 
philosopher. The insensible, then, is not a simple 
reality, but contains three realities, all insensible : real 
substances, real attributes, real causes of sensations. 

There are things in themselves. A thing in itself 
might mean a thing out of all relations. In this sense 
nature contains no things in themselves ; it is a system 
of related things the universe of which is alone out of 
relation as the sum of all relations. But this is not 
what is meant by a thing in itself in philosophy : what 
is really meant is not a thing out of all relations, but a 
thing distinct from the phenomena it causes in us, a / 
thing in itself as opposed to its sensible appearance. In 
this meaning, nature contains infinitely more things in 
themselves than it contains phenomena ; and man, as a 
natural philosopher, knows things in themselves which 
are not phenomena, when he knows imperceptible 
particles ; knows not merely the phenomena which 



they cause in us, but their real attributes, when he 
knows imperceptible motions, and knows that the 
thing in itself, not as an unknown cause, but by its 
real attributes produces phenomena, when he knows 
that imperceptible things, by their imperceptible 
motions, cause human sensations. There are real things 
known, real attributes known, real causes known, 
beyond the phenomena of sense. All this knowledge 
does man as a natural philosopher possess of things in 

Two antitheses have been handed down to us from 
ancient philosophy, the natural and the supernatural, 
the visible and the invisible. These distinctions are 
often treated as convertible ; but they are not so. The 
natural and the visible are not identical ; and the super 
natural and the invisible are not identical : there is a 
natural yet invisible world. Between the extremes of 
visible nature and the invisible supernatural world 
there is an invisible nature, distinct from both ; a world 
which is neither in heaven nor in man, but in itself. 
If we combine both the antitheses, they cease to be 
double, and form this triple division : 

1. The natural and visible, e.g. sensible phenomena. 

2. The natural and invisible, e.g. insensible bodies 
and imperceptible particles. 

3. The supernatural and invisible, e.g. God. 
Natural philosophy is the science of nature visible 

and invisible. From the former it infers the latter. 
But it stops at nature. So far as it is the science of an 
invisible nature, it is a philosophy of the suprasensible, 
not a theology of the supernatural. It outruns sense, 
but walks with reason to knowledge, without flying to 
faith. That we know invisible nature beyond sense in 
natural philosophy is a simple fact, explicable by logical 


reasoning from sense. Can we in theology further know 
the invisible beyond nature as well as beyond sense ? 
Can we know the supernatural world and God by reason 
ing from sense ? These are questions beyond natural 
philosophy. But the theologian may be sure that, on 
the one hand, unless we can vindicate our knowledge 
of insensible nature, we can hardly hope for a know 
ledge of an insensible world beyond nature ; and that, 
on the other hand, reasoning from sense to nature 
encourages reasoning from nature to God. Natural 
philosophy is the first step beyond sense into the unseen 
world, within which natural theology soars heaven 
wards to tell 

Of things invisible to mortal sight. 

I will conclude this chapter by quoting, from Sir 
John Herschel s Discourse on Natural Philosophy, a 
passage which is sufficiently near to the existing state 
of science for our present purpose. Its value is that it 
groups together a number of scientific conclusions, 
which, as it seems to me, cannot be explained by any 
theory of reality except realism, or the theory that 
there is a real and known world beyond phenomena, 
or by any process of knowledge except syllogism, or 
deductive inference which carries reason beyond sense. 

What mere assertion will make any man believe, 
that in one second of time, in one beat of the pendulum 
of a clock, a ray of light travels over 192,000 miles, 
and would therefore perform the tour of the world in 
about the same time it requires to wink with our eve- 
lids, and in much less than a swift runner occupies" in 
taking a single stride ? What mortal can be made to 
believe, without demonstration, that the sun is almost a 
million times larger than the earth ; and that, although 


so remote from us that a cannon-ball shot directly 
towards it, and maintaining its full speed, would be 
twenty years in reaching it, it yet affects the earth by 
its attraction in an inappreciable instant of time ? a 
closeness of union of which we can form but a feeble 
and totally inadequate idea, by comparing it to any 
material connection ; since the communication of an 
impulse to such a distance, by any solid intermedium 
we are acquainted with, would require, not moments, 
but whole years. And when with pain and difficulty 
we have strained our imagination to conceive a distance 
so vast, a force so intense and penetrating, if we are 
told that the one dwindles to an insensible point, and 
the other is unfelt at the nearest of the fixed stars, from 
the mere effect of their remoteness, while among those 
very stars are some whose actual splendour exceeds by 
many hundred times that of the sun itself, although we 
may not deny the truth of the assertion, we cannot but 
feel the keenest curiosity to know how such things were 
made out. 

The foregoing are amongst those results of scientific 
research which, by their magnitude, seem to transcend 
oar power of conception. There are others again, 
which, from their minuteness, would elude the grasp of 
thought, much more of distinct and accurate measure 
ment. Who would not ask for demonstration, when 
told that a gnat s wing in its ordinary flight beats many 
hundred times in a second? or that there exist ani 
mated and regularly organised beings, many thousands 
of whose bodies laid close together would not extend 
an inch ? But what are these to the astonishing truths 
which optical inquiries have disclosed, which teach us 
that every point of a medium through which a ray of 
light passes is affected with a succession of periodical 


movements, regularly recurring at equal intervals, no 
less than five hundred millions of millions of times in a 
single second ; that it is by such movements, communi 
cated to the nerves of our eyes, that we see nay, more, 
that it is the difference in the frequency of the recur 
rence which affects us with the sense of the diversity of 
colour ; that, for instance, in acquiring the sensation of 
redness our eyes are affected four hundred and ei^htv- 

/ o / 

two millions of millions of times ; of yellowness, five 
hundred and forty-two millions of millions of times ; 
and of violet, seven hundred and seven millions of 
millions of times ? Do not such things sound more like 
the ravings of madmen, than the sober conclusions of 
people in their waking senses ? 

They are, nevertheless, conclusions to which any 
one may most certainly arrive, who will only be at the 
trouble of examining the chain of reasoning by which 
they have been deduced ; but, in order to do this, 
something beyond the mere elements of abstract science 
is required. Waiving, however, such instances as these, 
which, after all, are rather calculated to surprise and 
astound, than for any other purpose, it must be ob 
served that it is not possible to satisfy ourselves com 
pletely that we have arrived at a true statement of any 
law of nature, until, setting out from such statement, 
and making it a foundation of reasoning, we can show, 
by strict argument, that the facts observed must follow 
from it as necessary logical consequences, and this not 
vaguely and generally, but with all possible precision 
in time, place, weight, and measure. 




THE problem of this essay is to use the insensible 
world of science as a fact from which to find the nature 
and origin of knowledge. Science is systematic know 
ledge. Yet the mental philosopher usually contents 
himself with endeavouring to explain ordinary know 
ledge. If he is a mental physiologist, it is true, he 
also uses natural science to proceed from the organs to 
the functions of sense. But there is another use of 
natural science to mental philosophy, which has been 
too much neglected : the objects of science are as 
important as the bodily organs to the explanation of 
knowledge. Natural science should be used to ascer 
tain what we know as well as how we know it. More 
over, the insensible physical world of the natural 
philosopher ought to prove to the mental philosopher 
that neither all knowable objects nor all sensible data 
are psychical, but some are physical. I purpose to 
show that physical objects of science, being objects of 
knowledge, require physical data of sense. Hence this 
essay is called Physical Eealism. 

We must confront natural with mental philosophy. 
The former has outstripped the latter. Natural philoso 
phers have long ago discovered to a great extent how 
physical nature is the causa essendi of sensible data ; 
but mental philosophers have failed altogether to show 


how sensible data are the causa cognoscendi of physical 
nature. The reason is, the data are mainly unknown. 
The existing hypotheses of the origin of knowledge do 
not explain the facts of science, and too often end "by 
denying what they fail to explain. Especially to blame 
is the hypothesis that all the data of sense are psychical 
facts, such as sensations and ideas, from which there is 
no way to insensible but physical objects of scientific 
knowledge. This vicious hypothesis is psychological 
idealism. Hence this essay is designed to combat 
psychological idealism by means of physical realism, 
and to appeal from the hypothesis of psychical data to 
the physical objects of science. The physical world of 
science cannot be explained by the common hypothesis 
that all sensible data are psychical, nor without the more 
moderate hypothesis that some are physical. 

The motto of all idealism is ideate prius reale 
posterius. But it has many meanings. Anaxagoras 
founded philosophical idealism by the proposition that 
the Divine Intelligence is prior to the order of nature ; 
and in adding that soul is also prior to body Plato 
became its second founder. The Cartesian idealism 
means that knowledge begins with psychical ideas, and 
the Kantian idealism that it adds a priori mental ele 
ments. Of these idealisms two are of supereminent 
importance in the history of thought ; that which places 
God at the beginning of the world, and that which 
places psychical ideas at the beginning of knowledge. 
The former is the belief of the majority of mankind, the 
latter of most philosophers since Descartes. The former- 
is theological, the latter psychological idealism. 

Theological and psychological idealism are not 
necessarily connected. A philosopher may hold that 
God causes physical nature and man apprehends it. 


He may be theologically an idealist, psychologically a 
realist. On the other hand, he may suppose that all 
sensible data are psychical facts, and yet doubt the 
existence of God. He may be psychologically an 
idealist, theologically an atheist. The founders of 
natural theology had no thought of making psychical 
facts the beginnings of human knowledge. The 
followers of Hume hardly consider themselves supporters 
of the doctrine that God created the world. These 
distinctions are of importance, because there is a crude 
notion in our times that idealism in mental philosophy is 
necessary to theology. They are of special bearing on 
the scope of this essay, which is aimed, not at theo 
logical, but solely at psychological idealism. 

Psychological idealism began with the supposition of 
Descartes that all the immediate objects of knowledge 
are ideas. From Descartes it passed to Locke and 
Berkeley. But with Hume it changed its terms from 
ideas to impressions. Kant preferred phenomena, 
Mill sensations. The most usual terms of the present 
day are sensations, feelings, psychical phenomena, and 
states of consciousness. But the hypothesis has not 
changed its essence, though the idealists have changed 
their terms, Verbum, non animum, mutant. They at 
least agree that all sensible data are psychical objects 
of some kind or other. 

The psychological idealists differ widely about the 
origin of knowledge from these psychical data. Some 
of them hold that there are a priori elements contributed 
by mind to the psychical data of sense, others that these 
supposed elements are a posteriori. But this difference 
about the origin does not prevent them from agreeing 
about the object of sense, which they alike hold to 
be some kind of psychical fact, whether idea, im- 


pression, phenomenon, sensation, feeling or state of 

There is a further difference among the idealists. 
Some of them, beginning with Descartes, believe that, 
though the immediate objects of sense are psychical, 
reality also includes physical facts. Others, beginning 
with Berkeley, reply that psychical data cannot yield 
physical objects, and therefore the psychical is all that 
is known to be real. The former divide reality into the 
psychical and the physical, the latter resolve it wholly 
into the psychical. The former have been called 
Cosmothetic Idealists, and the latter Absolute or Pure 
Idealists. But, while they differ only about the objects 
which can be mediately known, they still agree about 
the immediate data. Starting from the common hypo 
thesis that all sensible data are psychical, the cosmo- 
thetic idealist nevertheless believes in physical realities, 
but the absolute idealist denies or doubts them. 

Cosmothetic idealists further differ among themselves 
about the physical world. Descartes held that a physical 
world can be known through the medium of ideas ; 
Locke, in one of his many moods, that it is a cause 
of ideas, but unknown. This difference is important, 
because cosmothetic idealism is the usual view of men 
tal physiology in our own time, and it is held in both 
forms. Mental physiologists have unwarily received 
from psychologists the hypothesis of psychical data, 
which they usually call sensations, and have at the 
same time learnt from nature that the data of sense 
are effects of physical structures and motions beyond 
sense. Hence they are cosmothetic idealists. But 
according as they are rather physiologists or rather 
psychologists, they lean to Descartes or to Locke. The 
former hold that, starting from psychical sensations as 


data, by inference we know their physical causes ; the 
latter, that the psychical sensations are produced by the 
physical causes, which are nevertheless unknown and 
unknowable. Their differences, however, do not dis 
turb the consensus that the immediate objects of sense 
are not physical, but purely psychical. 

It may be thought that this consensus of idealism 
is a proof of truth. But agreement is one of the chief 
causes of human error, because it tempts men to dis 
pense with further consideration of the question. More 
over, we shall find that the inconsiderate assent to this 
common proposition is the very reason why opposite 
schools of idealists cannot conclusively answer one 
another. Lastly, there are two kinds of consensus : 
one, assent to a self-evident principle, such as 1-f 1 = 2 ; 
the other, agreement in a common hypothesis. Now 
the proposition that all sensible data are psychical 
phenomena is not a self-evident principle, but a de 
batable hypothesis. 

Eealism is the philosophy of a reality beyond psy 
chical facts. The earliest form in which it was a 
conscious doctrine was the belief in the reality of 
universals. Plato thought that there were universal 
forms existing in themselves, incorporeal and super 
natural archetypes, in accordance with which similar 
individuals are produced in nature. Aristotle agreed 
that there are real universal forms, and even that they 
are incorporeal substances. He contended, however, 
that they exist not in themselves but only^as belonging 
to individual substances j _which are concretions of matter 
and form. TrT the Middle Ages the disciples of Plato 
and Aristotle were called Eeales, to distinguish them 
from the Nominales, who either contended that uni 
versals were merely general names, or else general 



conceptions. Those who adopted the latter view were 
afterwards called Conceptualists. 

It is not necessary to be either a Flatonist or an 
Aristotelian. There is a third realism of universals 
possible ; and that, too, without falling into nominalism 
or conceptualism. The theory of the reality of univer 
sals, though overlaid with many errors, contains two 
important truths. The first is, that science knows of 
classes which, have an indefinite number of similarities, 
such as triangles, colours, and living beings. The 
second is, that of these similarities some are fundamental, 
others derivative ; e.g. three-sided rectilineal figure is 
the foundation of innumerable other similarities of tri 
angle ; undulations of ether produce the facts of colour, 
metabolism is the basis of the facts of life. The first 
truth shows that a natural class, or real kind, is not a 
name, nor a notion, but a real sum of individuals form 
ing an indefinite number of similarities. The second 
truth shows that the distinction between essence and 
property is not a nominal difference depending on the 
meaning of a name, nor a notional difference depending 
on the analysis of a notion, but a real distinction depend 
ing on the fundamental character of the similarities, 
on which the rest depend. Without natural classes, 
whose similarities can be expressed in laws, there would 
be no science ; and without essences, or fundamental 
similarities of those natural classes on which other 
similarities depend, we could not have the mathematics 
of the triangle referring its propositions back to its 
being a three-sided figure, nor the physics of light ? 
referring all the facts of colour back to the undulation 
of rcther. 

A natural class, then, is the sum of individuals 
possessing an indefinite number of similarities. A real 


essence is the fundamental similarities of the individuals 
of a natural class. It is easy to make too much of it 
or too little. If we follow the nominalist, and make 
sethereal undulation the meaning of the name light, or 
the conceptualist, and make it the analysis of the 
notion, we make too little of it, because the undulation 
of gether began before, goes on without, and will last 
after, our names and notions. If, on the other hand, 
we follow Aristotle, and make it an incorporeal sub 
stance coexisting with matter, we make too much of it, 
because it is only a motion of matter after all ; while, 
if we try to soar with Plato into the supernatural world 
and make it a heavenly archetype of earthly light, 
we fail to explain the facts and desert science for 

The realism of universals, however, is not the 
business of this essay. There is another meaning of 
realism, which we may call the Eealism of Individuals. 
This is the theory that there is a physical world of 
individuals beyond psychical sensations and ideas. It 
may be held with any theory of universals ; the realist 
of individuals is not necessarily a realist of universals. 
It is also a later product. The realism of universals is 
rather a doctrine of ancient, the realism of individuals 
rather of modern, philosophers. Not that Aristotle 
rejected the distinct reality of physical individuals ; 
but it never occurred to him that it needed to be 
proved. There was, as Brandis remarked, an uncon 
scious realism in ancient philosophy. It seldom 
doubted a world beyond the psychical; the question 
was rather whether there were not three worlds; natural 
individuals, supernatural universals, and psychical in 
telligences. But in modern times the development of 
psychological idealism has brought even the physical 

c 2 


world of individuals into question. In opposition to 
this psychological idealism a conscious realism has 
arisen, the object of which is to show that there are 
physical things beyond psychical facts. This realism 
of physical individuals is part of the business of this 
essay, and for shortness will in the sequel be called 
simply Realism. 

Realism is constantly misunderstood. It is some 
times supposed to be a synonym for mere Sensualism, 
or the belief that physical things are as they appear to 
our senses. But sensualism is only a crude form of 
realism. There is a realism which goes beyond sense to 
science, and holds that things are not as they imme 
diately appear to sense, but rather as they are mediately 
inferred by science. A more serious misunderstanding 
is the confusion of realism with Materialism. Material 
ism is a kind of realism ; it is also more. It is a double 
hypothesis : first, that there are physical things ; secondly, 
that they are either the only realities, or at least are 
prior to psychical realities, whether in nature or in man. 

Only the first part of this hypothesis is essential to 
realism ; the second part, which contains, too, the real 
sting of the materialist, is unnecessary to the realist. 
A man ceases to be a materialist, but he remains a 
realist, if he holds that God is the Creator and 
Governor of the world, while the world is not a 
psychical fact of God s Intelligence but a physical effort 
of His Intelligent Will ; and that nature is posterior to 
God though prior to man. The motto of materialism is, 
reale prius ideale posterius : the motto of realism is reale 
non est ideale. In short, it is one thing to affirm a 
natural world of individual objects beyond sense, 
another thing to deny a supernatural world beyond 



Hence realism is not the exact contrary of all 
idealism. It is not opposed at all to the idealism of 
natural theology. It is not even the direct contrary 
to all psychological idealism. Idealism centres itself 
on the data, realism on the objects of knowledge. The 
former says that all sensible data are psychical, the 
latter that some objects are physical. Hence a difficulty 
in contrasting them, and even in keeping them distinct. 
Some idealists, as we have seen, though they regard all 
data as psychical, admit the independent reality of 
physical objects. As Hamilton has pointed out, the 
cosmothetic idealists are also hypothetical, or, as some 
would say, transfigured realists. The exact contrary 
of realism is not all idealism but pure or absolute 
idealism. The pure or absolute idealist denies the 
reality of aught beyond the psychical world, the realist 
affirms the reality of the physical. 

At the same time realism is not a single body of 
doctrines. Eealists agree only in one position the 
reality of physical things. In the foundations of that 
position, in the sensible data of knowledge, they differ 
toto ccelo. It is, therefore, necessary to classify them to 
prevent confusion, and that sort ofignoratio elenchi,wbich 
idealism and realism alike have to suffer from their 
opponents when they are not properly defined. 

Of the realism of individuals there are two species 
recognised among modern philosophers the Hypo 
thetical Eealism of the cosmothetic idealists, and the 
Intuitive or Natural Eealism of the Scotch philosophers, 
Eeid, Stewart, and Hamilton. Agreeing about know- 
able objects, hypothetical and intuitional realists differ 
about the data of sense. According to the former, the 
data are psychical ideas or sensations of the ego ; ac 
cording to the latter, they include the primary qualities 



of the physical non-ego. Agreeing in a physical world, 
they differ about the way in which it is to be reached, 
the former holding that it is inferred from psychical 
data, the latter, that it is immediately perceived. Hypo 
thetical or transfigured realism is the hypothesis that 
our senses present psychical ideas or sensations repre 
senting external physical objects ; intuitive or natural 
realism, the hypothesis that the senses present the pri 
mary qualities of external physical objects themselves. 

Modern philosophy exhibits a constant oscillation 
between the opposite poles of the ego and the non-ego ; 
and the two received kinds of realism are opposite cur 
rents in this oscillation. The cosmothetic idealist or 
hypothetical realist, learning from natural philosophy 
that his senses do not directly perceive external things, 
takes refuge in the psychical world of his own soul. 
Dissatisfied with this alternative, and conscious that 
he somehow apprehends something physical, the in 
tuitional realist flies forward to the direct perception of 
an external world. Extreme views are usually as untrue 
as extreme measures are dangerous. Is there a via 
media ? I venture to propose a new Eealism. 

When I consider the objects of science, I am struck 
by the enormous number of things and attributes 
entirely beyond the reach of sense and not even 
corresponding to any sensible object, I refer, espe 
cially, to corpuscles, their structures and motions. 
Secondly, on going further, I find that the whole ex 
ternal world has been discovered by sciences, such as 
optics, acoustics, and biology, to be insensible, and 
that nothing is sensible except what has been impressed 
on the body, and in the body on the nervous system, 
of a sentient being. Thirdly, I notice that a connection 
has been scientifically established between external in- 



sensible objects and the objects of which I am sensible. 
The former are causes of the latter. They are also 
found to resemble one another in primary qualities, 
such as duration, extension, motion, but not in secondary 
qualities, such as light, heat, and -sound; for the se 
condary qualities, as they are in external nature, are 
found by corpuscular science to be insensible modes 
of primary qualities ; light, heat, and sound being all 
insensible modes of motion producing a heterogeneous 
effect on the senses. 

I cannot believe that this whole fabric of insensible 
objects can be scientific, yet unknown. But it must be 
either physical or psychical. If the objects are psy 
chical, they are either sensations or ideas. But they 
are insensible and often inconceivable. Now what is 
insensible cannot be a sensation, and what is incon 
ceivable cannot be an idea. Not all objects of science, 
then, are either sensations or ideas ; therefore they are 
not psychical objects at all. It remains that they are 
physical objects. 

Again, I cannot believe that this whole fabric of 
physical objects of science can have been inferred 
without sufficient data of sense. I therefore proceed 
to inquire what data of sense are required to infer a 
physical object of science. This is a question of logic. 
Now the rules of logic teach me that whatever is inferred 
is inferred from similar data. If I infer that all men 
will die, it is because similar men have died. Now, as 
we have seen, physical objects are scientifically inferred 
from sensible data. It follows that the sensible objects, 
which are these data, must also be physical. The 
similar can be inferred only from the similar, therefore 
the physical can be inferred only from the physical. 
This conclusion, however, places me in a dilemma. 



Science shows me that the object of sense is internal, 
logic that it is physical. The former evidence might 
incline me to cosmothetic idealism, the latter to intui 
tive realism. Which shall I prefer ? Am I to say that 
the sensible data are psychical objects within me ? No, 
because I require physical data of sense to infer 
physical objects of science. Am I to say that the 
sensible data are physical objects without me? No, 
because no external object is sensible. I can be neither 
a cosmothetic idealist, because of logic, nor an intuitive 
realist, because of natural science. 

If, then, natural science requires that the object of 
sense must be within my nervous system in order to be 
sensible, and logic that it must be physical in order to 
infer physical objects of science in the external world, 
how can the sensible object be at once physical and 
internal ? I answer, it is the nervous system itself 
sensibly affected. The hot felt is the tactile nerves 
heated, the white seen is the optic nerves so coloured. 
The sensible object must be distinguished from its 
external cause on the one hand, and on the other hand 
from the internal operation of apprehending it : it is 
the intermediate effect in the nerves produced by the 
external cause, and apprehended by the operation of 
sensation. In particular, the operation and the object 
of sensation must not be confused, because the former 
may be psychical, the latter is physical. There is some 
plausibility in saying that the act of consciously touch 
ing is psychical, there is none at all in saying that the 
hot felt is psychical. Non sequitur. Vision may be a 
psychical sensation, but the white seen is a physical 
object. Nor is there any reason why a psychical opera 
tion should not apprehend a physical object. The sen 
sible object then is identical neither with the external 


cause nor with the internal operation of sensation. It 
is the effect in the nervous system produced by the one 
and apprehended by the other. For example, the hot 
felt and the white seen are produced by external objects 
and are apprehended by internal sensations of touch 
and vision, but are themselves respectively the tactile 
and the optic nerves sensibly affected in the manner 
apprehended as hot and white. 

From such sensible data, internal, as science re 
quires, and physical, as logic requires, man infers 
physical objects in the external world by parity of 
reasoning. Men in general begin by inferring that 
physical objects of sense are produced by physical 
causes exactly similar. Thus from the hot within we 
infer a fire without. Such objects, directly inferred to 
correspond with sensible data, may be called the 
originals represented by them. They are inferred, 
but are generally said to be perceived ; thus we speak 
of perceiving the fire though we only infer it. We 
may, perhaps, say then that the originals of the sensible 
are insensible objects inferentially perceptible. 

Afterwards, scientific men carry on this parity of 
reasoning, and infer that these originals beyond sense 
consist of further insensible particles similar to the 
originals, but not at all represented by sensible data ; 
and that many other objects, such, for example, as the 
side of the moon always turned from the earth, are 
incapable of producing sensible objects in us. These 
unrepresented objects may be said to be not only in 
sensible but imperceptible, and are objects of an infer 
ence which may be called transcendental, in the sense 
of transcending both sensitive and inferential perception. 

Lastly, science also finds that in another direction 
the ordinary man has carried his inferences from 



similar data to similar objects too fur. Physical objects 
are found to be like sensible in their primary, not in 
their secondary qualities ; for instance, external motion 
is like sensible motion, but external heat is an imper 
ceptible mode of motion while sensible heat is not 
sensibly a motion at all. How is -this inferred? 
Because, though at first sight sensible heat would 
demand a similar external object, when all the facts 
of sensible heat are accumulated they are found to be 
the kind of facts that are only produced by motion. 
Hence from sensible physical data we scientifically 
infer insensible physical objects, like sensible objects in 
primary but unlike in secondary qualities. 

Such is the realism proposed in this essay. It may 
be expressed in two propositions : there are physical 
objects of science in the external world ; therefore 
there are, as data to infer them, physical objects of 
sense in the internal nervous system. It is a via media 
between intuitive realism and the hypothetical realism 
of the cosmothetic idealist. As it recognises physical 
realities, it is realism. As the objects, which it sup 
poses to be sensible, are not external but internal, it is 
not intuitive realism. As the objects of sense, which 
it supposes to be the data of inferring an external 
physical world, are not psychical but physical, it is 
not hypothetical realism. As they are physical data 
within, to infer physical objects without, the realism 
which I advocate may be called Physical Eealism. 

There are three realistic ways of explaining our 
knowledge of an external physical world. The first is 
cosmothetic idealism, which supposes that we are sen 
sible of a psychical, but infer a physical world. This 
is against logic, which shows that all inference is by 
similarity. The second is intuitive realism, which 



supposes that we directly perceive an external physical 
world. This is against natural philosophy, which shows 
that we perceive nothing directly but what is propagated 
into our nervous system. The third is physical realism, 
which supposes that we sensibly perceive an internal 
but physical world, from which we infer an external 
and physical world. This agrees with both natural 
philosophy and logic. 

Physical Eealism must be especially distinguished 
from intuitive, or, as it is also called, natural realism. 
It is true that the theories have some common points. 
This essay owes to Eeid the instructive remark on the 
Sentiments of Bishop Berkeley, that there is no evi 
dence for the doctrine that all the objects of knowledge 
are ideas in my own mind. 1 The rejection of idealism, 
the reality of the physical world, the belief in a phy 
sical object of sense, and the possibility that a psychical 
subject may apprehend a physical object, are all points 
in intuitive realism which find a place in physical 
realism. But here the agreement ends. The intuitive 
realist holds an immediate perception of a physical 
world outside. I distinguish the immediate perception 
of the physical world within, and the inferential per 
ception of the physical world beyond myself. 

The intuitive realist follows the idealist in thinking 
too much of the sensible data, and too little of the 
insensible objects of science. He gives too much 
weight to consciousness, and too little to science, or 
rather too much to the ordinary and too little to the 
scientific consciousness. He appeals to common sense, 
which is the problem rather than the solution of philo 
sophy. He elevates the dicta of consciousness and 

1 Eeid, Essays on the Intellectual Powers. Essay II., chap. x. 
p. 283 (ed. Hamilton). 


common sense from unanalysed facts into self-evident 
principles. Hence, in asserting an immediate know 
ledge of external nature lie contradicts science. But 
we must appeal from common sense to universal science, 
and from ordinary to scientific realism. The idealist 
can never be answered by asserting the reality of the 
sensible world, which he admits, and, if it stood alone, 
could explain. He must be confronted with the in 
sensible world of science. 

The intuitive realists have an impossible theory of 
the data of sense, comprised of two incompatible ex 
tremes. On the one hand, they admit the idealistic 
position that secondary qualities, as sensible, are psy 
chical sensations ; on the other hand, they assert that 
external primary qualities of the non-ego are imme 
diately perceived. The admission is fatal, because the 
Berkeleian at once points out that primary qualities are 
apprehended in the same way as secondary, and there 
fore if one set, as sensible, are psychical sensations, why 
not the other ? The assertion is equally fatal, because 
scientific analysis shows that nothing external is imme 
diately perceived. Hence I retract the admission and 
reject the assertion. Whether directed to primary or 
to secondary qualities, sense apprehends neither a sen 
sation nor an external object, but an internal object in 
the nervous system. Everything external is inferred. 

Perhaps the chief reason of the defect in intuitive 
realism is the confusion of object and non-ego. Object 
is the res considerata apprehended either by sense or by 
reason. It is not always an external object. In sense, 
it is always internal, whether it be the hot or the moving, 
the white or the extended, secondary or primary. In 
reasoning, it is external, whenever we infer something 
beyond the sensible object within us. But the intuitive 


realists, having confused object and non-ego , supposed 
that whenever sense has an object it presents the non-ego. 
Keally, sense always apprehends an object distinct from 
the operation, but never a non-ego distinct from the ego, 
that is, the man himself. Hence, also, their erroneous 
belief that in apprehending a primary quality, as an 
object, sense presents a quality of the non-ego, and in 
not apprehending a secondary quality as it is in the 
non-ego, it presents no object. Eeally, as sensible, both 
primary and secondary qualities are apprehended as 
objects, but not as external. For example, the sensibly 
hot and moving are both apprehended as objects by 
sense, but entirely within the sentient being. 

The subordination of secondary to primary quali 
ties is not at all in the sensible effects, but in the external 
causes. In the external world, secondary qualities are 
found by science to be only specific varieties of primary 
qualities. In the internal world, all qualities appear 
to sense to be equally elementary. As sensible, a 
primary quality, such as motion, is not in the non-ego, 
and a secondary quality, such as heat, is not a mere 
sensation ; nor are they both sensations ; but they are 
both sensible objects, both internal to the sentient being, 
both physical, both parts of the nervous substance 
sensibly affected, both apprehended in the same way as 
objects by the operation called sensation. From these 
qualities, all apprehended in exactly the same way as 
sensible objects in our nervous system, the ordinary 
man infers a complete correspondence of qualities out 
side, the scientific man partly corrects him by reducing 
secondary qualities to primary qualities in the external 

The relativity of knowledge has become a common 
place. Is it a fact ? A sensible effect is the result of 


the combination of two causes. As active or efficient 
cause, the external world produces the sensible effect 
in the nervous system ; as passive or material cause, 
the nervous system receives this effect according to its 
susceptibility. Hence the effect is like or unlike to the 
efficient causes, according to the varying susceptibility 
of the nervous system. There is a variation in different 
animals and in different men, and even in the same man 
at different times. But in all men there is one differ 
ence of main importance. The nervous system is far 
more susceptible of similar effects from primary than 
from secondary qualities. It is more capable of re 
flecting the waves of the sea than the undulations of 
gether. Not that the effect is wholly alike in primary 
or wholly unlike in secondary qualities. The primary 
quality of distance is imperfectly reproduced in sense, 
the secondary quality of aerial vibration is to some 
small extent represented in the sense of hearing. But, 
on the whole, there is a general similarity of the 
sensible to the external in primary, and a general 
dissimilarity in secondary qualities, because of the 
inferior susceptibility of the nervous system to receive 
like effects from the latter qualities in external objects. 
In the sense, then, that the sensible effect only partly 
depends on the external efficient cause, and partly also 
on the matter of the nervous system, there is a rela 
tivity of knowledge to the structure of the nerves. 
There is also an evolution, which consists in the in 
creasing adaptation of the nerves to sustain the effect 
under the action of the external object. 

On the other hand, by the relativity of knowledge 
it is generally meant that the sensible effect produced 
is a psychical fact, not partly but wholly heterogeneous 
to the physical object, if there be one. In this sense 


physical realism is opposed to the relativity of know 
ledge. It is true that red refuses to appear to our 
senses as a motion representing the external motion 
which produces it. But the cause of this fact is to IK; 
found in the construction of the optic nerve, which, 
when acted on by a certain imperceptible motion of 
aether, receives a sensible colour apparently unlike 
motion, just as oxygen and hydrogen in certain pro 
portions, when acted on by electricity, become water. 
In the same way, when a wheel rotates too quickly, the 
sensible effect ceases to be a motion, because the nerves 
are insusceptible of taking on so rapid a motion in 
sense. The sensible effect is similar or dissimilar to 
the external object, so far as the nervous system is 
capable or incapable of being affected similarly to the 
external object. There is no occasion then to resort to 
the hypothesis of a psychical relativity : the nervous 
element is sufficient. 

Moreover, if there were a psychical relativity, it 
would be ineradicable, because the sensible effect would 
then be completely heterogeneous, and would there 
fore supply no data of inference to an external physical 
cause. Eeally, sensible effects are partly like and 
partly unlike the external causes, because the nerves 
are partly fitted and partly unfitted to represent 
them. Being partly like, the nervous unfitness to re 
present secondary qualities as they are in nature is 
being constantly eliminated by scientific reasoning. 
Thus, sense sometimes presents motion as motion, but 
cannot help presenting the hot, the red, &c., as 
heterogeneous to motion, because of the structure of 
the sensory nerves ; science, by comparing sensible 
motion with the sensible facts of the hot, the red, &c., 
infers that the external cause of the latter is really a 


mode of motion. In secondary qualities the sensible 
effect is heterogeneous, but the cause inferred by science 
is identical with the external object. Not that scien 
tific elimination of the defects of sense ever becomes 
so complete as to end in absoluteness of knowledge. 
But there is a constant progress towards making science 
the mirror of being. Sense starts with physical data 
partly like and partly unlike external nature ; science, 
by progressive inferences, tends more and more to dis 
cover the external qualities which cause not only the 
like but the unlike data in the nervous system. The 
sensible, therefore, is not a psychical effect completely 
heterogeneous to the external physical cause, but a 
physical effect partly relative to the nervous system ; 
and science is perpetually correcting this partial re 

It is usual to divide theories of sensation and per 
ception into presentative and representative. There 
are two presentative theories, respectively characterising 
the pure idealist and the intuitive realist. The former 
holds that there is no distinction between sensation and 
perception : sense, according to him, immediately per 
ceives psychical facts, which are the sum of known 
existing objects. The latter distinguishes sensation and 
perception, because he distinguishes the psychical and the 
physical : sensation, in his view, is limited to psychical 
sensations, perception immediately apprehends the pri 
mary qualities of an external physical world. The 
pure idealist says, What I see is what exists ; the intui 
tive realist, What exists I see : the former reduces 
nature to perception, the latter brings perception to 
nature ; one holds esse is percipi, the other esse per- 
cipitur. But the point is that, according to both, the 
real is the sensible world, which is directly presented, 



not represented, in perception, without an inference to 
an external original. The representative theory, on 
the other hand, distinguishes the data of sense, as pre 
sented, from the external world, as represented, in 
perception. It exists in many forms, according to 
various theories of the data of sense. But the current 
form is that of cosmothetic idealism, which holds that 
sense presents psychical data of some kind, representing 
physical objects in the external world. 

Physical realism must accept the representative 
theory, but not in its idealistic form. The data pre 
sented to sense are internal, yet not psychical. They 
are physical parts of the nervous system, tactile, optic, 
auditory, &c., sensibly affected in various manners, repre 
senting, but only partly resembling, the external world. 
Further, in sense, the object is not the operation, the hot 
is not touch, the white is not vision, the loud is not 
hearing. From these points I form the following theory 
of sensation. In that the sensible object is internal, sen 
sation is not the immediate apprehension of an external 
object. In that the sensible object is physical, sensation 
is not the immediate apprehension of a psychical fact. 
In that it is the immediate apprehension of an object, 
though internal, it is a kind of perception. I should 
define sensation, or sensitive perception, as the im 
mediate apprehension of an internal physical object 
within the nervous system of a sentient being. 

But perception cannot be confined to sensation. 
Although it is true that sense feels the hot, and reason 
infers the fire, everybody talks of perceiving the fire. 
The philosopher will find it vain to fly in the face of 
the universal language not only of ordinary life but 
even of science. He must recognise this perception 
and analyse it. There is, then, besides sensitive or 




immediate perception, inferential or mediate perception. 
The former is limited to the internal object of sense, the 
latter extends to the external original. Moreover, so 
long as we remember that there is an inference in this 
latter operation, the term perception not only does no 
harm but serves to mark a most important distinction. 
We first infer external originals of sensible objects, e.g. 
the fire, the sea, &c. ; we cannot be said to see, but we 
may be said to perceive, these external objects, and also 
to observe and experience them, though indirectly. 
Afterwards, we go on to infer other external objects not 
represented by any sensible object, e.g. a corpuscle, 
aether : these we cannot be said either to see or per 
ceive ; they are not only insensible but imperceptible, 
and we infer them by reasoning which transcends per 
ception. In short, we must distinguish sensitive 
perception, inferential perception, and transcendental 

Hence the following classification of physical objects 
knowable, and of the operations concerned with them : 

1. Internal parts of the nervous system sensibly 
affected: sensible data : immediately perceptible, objects 
of sense, or of sensitive perception, observation, ex 

E.g. the sensibly moving, the sensibly hot. 

External parts of the universe: insensible objects : 
objects of inference. 

(1) Originals represented by sensible objects, and 
resembling them in primary not in secondary 
qualities: insensible but mediately perceptible 
objects of inferential perception, observation, 
E.g. the fire, the waves of the sea. 


(2) Objects unrepresented, though causing some 
sensible objects by imperceptible secondary 
qualities : the imperceptible : objects of trans 
cendental inference. 
E.g. corpuscles, the undulations of aether. 

This essay contemplates not only a new realistic hypo 
thesis, but a different method from that usually used in 
mental philosophy. Every philosophy must have a 
beginning. But the beginning must be what is best 
known ; and in mental philosophy the present objects 
of science are better known than the original data 
of sense. The method in use takes too direct a way 
of getting at the original data. It is true that the 
beginnings of human knowledge are sensible data. 
But the philosopher does not stand at the beginning of 
human knowledge. Philosophy did not begin with the 
infancy of the human race. The philosopher cannot 
observe his own infancy. The sensible data have long 
since been overlaid with an immense mass of inferences. 
Hence, though man may have begun once, it is impos 
sible for the philosopher to begin now, with the data. 
Yet most books on knowledge begin with the dogmatic 
assertion that the immediate objects of the senses are 
psychical sensations, from which they proceed to allow 
man as much knowledge of nature as can be squeezed 
out of the original hypothesis. But the assertion itself 
must be proved. 

Besides the induction of causation, we may either 
reason synthetically from cause to effect, or analytically 
from effect to cause. But the latter is the more usual 
method, because man knows so much more about 
facts than about their causes. Hence the order of 
science is usually the reverse of the order of nature. 

D 2 



Nature always proceeds from cause to effect, science 
usually from effect to cause ; so that science becomes 
an analysis of the synthesis of nature. 

Similarly, the order of mental philosophy is the 
reverse of the order of human knowledge. It is true 
that the order of human knowledge is from cause to 
effect in the sense that sensible data are the causes cog- 
noscendi of physical knowledge. We begin with them 
as children ; hence also we are tempted to begin with 
them again as psychologists. But the procedure is 
fallacious ; we must begin with the more knowable. 
Now every mental philosopher is an adult man, and 
every adult man is more certain what he now knows, 
than how he originally came to know it, of the dis 
coveries of science than of the secret springs and 
principles by which the human mind is actuated in its 
operation, of the known objects than of the sensible 
data. Accordingly, as, in the science of nature, we 
must generally begin with present facts and go back 
wards to the causes essendi, so, in the science of know 
ledge, we must generally begin with the facts of 
scientific knowledge and go backwards to the causa? 
cognoscendi. Modern philosophers have made the mis 
take of attempting to repeat the synthesis of know 
ledge from the original data of the child and the 
race. But we must rather retrace our steps from the 
present to the past; instead of trying to follow the 
synthesis of knowledge from an unknown beginning, 
we must make an analysis from the present objects 
of scientific knowledge to the original data of sense. 
In a word, our method must be an analysis from science 
to sense. 

Hence, I began with attempting to give an outline 
of the kind of objects recognised in science. This 


beginning lias several advantages. First, science is 
knowledge ; hence to begin with its objects is an 
appeal not from knowledge to reality, but from the 
data to the objects of knowledge. It is not a dogmatic 
assertion of what is, but an historical description of what 
is known. Secondly, science is knowledge at its widest 
extent, knowledge proceeding from the sensible through 
the insensible, but perceptible, to the imperceptible 
world. Hence we get a more extended view of know- 
able objects than that usually attained by mental 
philosophers, who tend to concentrate themselves on 
the world of sense and perception. Thirdly, science is 
knowledge at its best, whereas the hypotheses of mental 
philosophers about sensible data can hardly be called 
knowledge at all. In appealing from the hypothetical 
origin of knowledge to what is actually known in science, 
we are appealing from the less known to the more 
known. In short, we are getting the facts of knowledge, 
wherewith to test our hypothesis of its causes. 

The next step is analytically to find the sensible 
data required to cause the knowledge of the objects of 
science as facts. All theories of the sensible data and 
of the origin of knowledge, idealistic and realistic, must 
be treated and compared as hypotheses. We must ask, 
indeed, what is their direct evidence, but also and 
mainly whether they account for the knowledge of the 
objects of science. The general examination of these 
hypotheses will follow in the next chapter. Afterwards, 
the various hypotheses of Psychological Idealism will 
be taken in detail. The elimination of these hypotheses 
will finally bring us to Physical Eealism. 

Philosophy began with the external object, which 
was first of all treated as a pure reality by the Pre-So- 
cratic philosophers. Gradually it came to be regarded 


as also an object of knowledge, a view which culminated 
with Aristotle. Aristotle s method was essentially to be 
gin with being as being, then to consider it secondarily as 
a knowable object, and thus to proceed from the known 
object to the knowing subject. Objective are generally 
the foundation of subjective distinctions in his writings. 
Descartes revolutionised philosophy by beginning with 
the conscious subject and passing through its conscious 
operations to the object apprehended. From his time 
the general order of mental philosophy has been syn 
thetic, from the subjective operations to the objective 
world. I propose to revert to the old order, and pro 
ceed analytically from object to subject, but in a new ^ 

Ancient philosophy rightly began with the object, but 
considered it too much as being, and too little as known. 
Consequently, it had a tendency to multiply entities 
without considering whether they are knowable. Hence 
the Cartesian revolution and the synthetic method 
from subject to object. But after the first consciousness, 
I think, the object is on the whole better known than 
the subject ; else natural philosophy would not be more 
advanced than mental philosophy. In order to avoid 
at once the dogmatism of ancient, and the doubtfulness 
of modern, philosophy, I propose to begin with the 
object, not as being, but as known in science, the most 
perfect form of knowledge. I proceed to ask what 
sensible objects are required as data for science to X 
know these objects. Of the knoAving subject I treat 
only so far as it bears on the objects known by sense 
and reason, because, though I know well that I am, I 
know less what I am than what I know. The ancient 
method from being to knowing was the right order, 
though too dogmatic in application. The modern 


method inaugurated by Descartes, from the subject 
through the data of sense to the objects of science, was, 
after its first step, fallacious, because it then proceeded 
synthetically from the less to the more knowable. The 
analytic method of physical realism, without neglecting 
direct evidences of the data, proceeds, on the whole, 
from the more knowable objects of science to the less 
knowable data of sense. 


(1)A11 sensible (1) All sensible (1) All sensible (1) Some sensible 
data are psy- data are psy- data are inter- data are exter- 

chical. chical. nal but some nal and physi- 

are physical. cal. 

(2) All objects ( 2) Some objects (2) Some objects (2) Some objects 
knowable are are physical. of science are are physical. 

psychical. physical. 




Nihil est in intellectu, quod non prius in sensu. How 
far is this time-honoured proposition true? As we have 
seen, it is not true of the objects of science. The whole 
physical world is beyond the reach of sense, insensible ; 
the corpuscles, of which it consists, are beyond the reach 
of inferential perception, imperceptible. It is true that 
objects of science are similar to sensible objects, but 
they are not the same. They are objects of intellect 
which are inferred from sensible objects but have never 
been in sense. But even this more modest statement 
must be qualified. 

In the first place, it requires Locke s correction that 
knowledge has two sources sensation and reflection, 
outer and inner sense, or sense and consciousness. We 
immediately apprehend not only the objects of, or 
rather in, our senses, but also ourselves apprehending 
those objects, and performing many other conscious 
operations. Secondly, there is also a simpler source 
than sensation the feelings. We immediately feel 
pleased and pained, and that too without apprehending 
any object ; as in the pain of hunger, the pleasure of 
nutrition. Sensation is more complex than feeling, be 
cause it is the apprehension of an object ; touch the 
apprehension of the hot, vision of the coloured, hearing 
of the sounding, &c. Frequently we have a feeling and 

CHAP. in. 


a sensation together ; for example, when we feel pleased 
or pained at the same time as we taste sweet or bitter. 
But it is of the greatest importance to distinguish feeling 
as a source of knowledge, especially as it is not at all 
improbable that it was the original source even of sensa 
tion. Even now that feeling and sensation are distinct, 
feelings are still the raw experiences of volitions, passions 
the beginnings of actions. We feel pleasure and pain 
before we will to pursue the one and avoid the other. 
All knowledge, then, does not begin with sensation, but 
with feeling, sensation, reflection. 

It is true, however, that all knowledge of nature 
begins with sensation. Yet even this modified proposition 
must be carefully guarded. In the first place, though phy 
sical knowledge begins with the operation of sensation, it 
does not follow that the object, in apprehending which 
the operation of sensation consists, is also a sensation. 
Yet this non-sequitur appears in the first few pages of 
most books of modern philosophy. The causes of the 
confusion of sensation with its object are to be found 
partly in the structure of modern languages, which, 
being far richer in abstract than in concrete terms, 
tempt philosophers to fall into a loose way of speaking 
of perceiving a sensation instead of perceiving a sensible 
object ; but mainly in another confusion, that of object 
and non-ego, which makes philosophers shrink from 
speaking of perceiving a sensible object, lest they should 
seem to assert an intuition of the external world. But 
an object (TO avTLKeiptvov) is merely that which is 
apprehended as opposed to the operation of apprehend 
ing it, and is not necessarily external to the apprehend 
ing subject. In sense, without being external, the 
object is still distinguishable from the operation ; the 
hot from touch, the sweet from taste, the coloured from 


vision, the loud from hearing, the scented from smelling. 
Although, therefore, physical knowledge begins with 
sensation as an operation, it does not begin with sensa 
tion as a sensible object. Given, then, that physical 
knowledge begins with sense, we still have to ask, what 
is the object apprehended immediately by sensation ; 
what is the sensibly hot, sweet, coloured, loud, scented ? 
This is the question of the present chapter. 

There are two main evidences of hypothesis the 
direct and the indirect. Direct evidence is the best, if 
possible, but it is seldom attainable ; for example, there 
is no direct evidence for the hypothesis of gether. But 
where direct proof fails, indirect should be all the 
stronger in compensation. It consists in using the 
facts to test the hypothesis, and that in two ways. 
First, the facts must be explained by the hypothesis ; 
secondly, they must eliminate other explanations. Thus 
the hypothesis of an undulating aether, as the vehicle of 
light, though wanting in direct evidence, is proved by 
its power of explaining all the facts of light, and by the 
elimination of the hypothesis of emission, which explains 
some, but not all the facts. 

I propose to apply these rules to the various 
hypotheses of sensible data, stated in the last chap 
ter. Are the objects of sense, which form the data 
of science, psychical or physical ; and, if physical, ex 
ternal or internal ? On the one hand, how far is 
there direct evidence for any of these hypotheses ? 
On the other hand, how do they stand the indirect test 
of the facts of science ? That is, can the objects of 
science as facts of knowledge be explained by any 
hypothesis of the data of sense ; and can the other 
hypotheses be eliminated ? Being hypotheses, idealism 
and realism alike must be treated by the logical rules 



of hypothesis. Sensible data must be made to explain 
the scientific facts, as aethereal undulations have been 
made to explain luminous facts. We must be on our 
guard against synthetic hypothesis. What would be 
thought of a natural philosopher, who dared to start 
with the hypothesis of emission and denied all the facts 
of light, which cannot be deduced from the emission 
of corpuscles by a luminous body ? What, then, shall 
we think of mental philosophers, who start with the 
hypothesis of sensations and deny all the insensible 
world which cannot be deduced from the contempla 
tion of sensations by sensation? I admit that there 
may be direct evidence of an hypothesis. But even 
so, unless that evidence be mathematical certainty, the 
hypothesis must also be submitted to the indirect or 
analytical evidence of explaining the facts. Now it 
cannot be pretended that the direct evidence of the 
hypothesis of perceiving sensations or any other hypo 
thesis of sensible data is mathematically certain. There 
fore all the hypotheses of idealism and realism must pass 
through the alembic of analysis. 

The first direct evidence is that of consciousness. 
Consciousness is the immediate apprehension of oneself 
performing some operation. Thus I am conscious 
that I feel, that I perceive through my senses, that I 
imagine, remember, reason, desire, will, act. Unfor 
tunately, however, this operation of apprehending other 
operations has come to be confused in psychology 
with the operations themselves. Hamilton, seeing that 
perception requires an object, and consciousness of 
perception requires perception, falsely concluded that 
the consciousness includes the perception of the object, 
whereas it only requires it as a condition. He com 
mitted the common fallacy of confusing a thing with 


its condition. Eeally, perception is the apprehension 
of the object, consciousness of perception the apprehen 
sion that I am apprehending the object. Mill, again, 
seeing that feeling pleasure and pain are the same as 
being conscious of feeling them, falsely concluded that 
every operation is the same as its consciousness. He 
committed the fallacy of over-generalisation. In feeling 
pleasure and pain there is no distinction between opera 
tion and object, and hence none between feeling and 
consciousness. But whenever there is a distinction 
between operation and object, the operation is concerned 
with the object and the consciousness with the operation. 
Hence to see white is different from being conscious of 
seeing white. So with other operations. Reasoning is 
a mediate operation from premises to conclusion. The 
consciousness of reasoning is an immediate apprehension 
that I am performing that mediate operation. Will 
is an active operation, the determination to act ; its 
consciousness an intellectual operation, apprehending 
that I determine to act. To reason and to will, then, 
are not the same as being conscious that I reason and 

It is not improbable that the lowest potency of sensi 
tive life may have been mere feeling, and the beginning 
of consciousness mere conscious feeling ; and that as, 
in the growth of the senses, the operation and the object 
became distinguished, consciousness became distinct 
from the operation, the operation being concerned with 
the object, and the consciousness with that relation of 
oneself to the object, in which an operation about an 
object consists. But whatever may have been the 
genesis of consciousness, its nature consists not in being 
the sense of objects but the sense of operations. When, 
as in feeling, there is no distinction between operation 


and object, there is none between consciousness and 
operation. When, as in sensation, there is a distinction 
between operation and object, the operation is con 
cerned with the object, the consciousness with the opera 
tion. Not that consciousness has no reference to the 
object, but only that it is not the apprehension of it. 
The operation, which is the apprehension of the object, 
is a certain relation of subject to object : the conscious 
ness, which apprehends the operation, is an apprehension 
not of the object, but of the relation of the subject to the 
object. For example, I see white, I am conscious that 
I am seeing white. 

It was necessary to have thus defined consciousness 
on account of the mass of confusion and inconsequence 
imported into psychology by regarding consciousness 
as identical with all the conscious operations. Hamilton, 
seeing that consciousness is intuitive, but falsely identi 
fying it with the perception of an external world, falsely 
concludes that perception of an external world is also 
intuitive. He ought by the same argument to have 
made reasoning immediate, or else consciousness mediate, 
either of which alternatives is absurd. Mill, seeing that 
consciousness is limited to the apprehension of mental 
operations, and falsely identifying it with the mental 
operations, falsely concludes that the mental operation 
of sensation is also limited to the apprehension of 
mental operations. He might as well have said that 
will, being identical with its consciousness, is an intel 
lectual apprehension of a mental operation. But as 
will is an active determination to do something, while its 
consciousness is an intellectual apprehension that one 
has that active determination, so sensation is an appre 
hension of an object, while its consciousness is an 
apprehension that one is performing that operation. 


Sensation says, This is white or sweet ; consciousness 
says, I am seeing something white or tasting something 

This being consciousness, one operation of which I 
am conscious is that I know objects. What knowledge 
of objects am I conscious of possessing ? In answering 
this question, it must be remembered that science is a 
kind of knowledge of which we are conscious. There is 
an ordinary consciousness and a scientific consciousness. 
The ordinary man thinks little or nothing about it, but 
the man of science is conscious that science passes 
beyond sense into the insensible, and beyond the objects 
represented by sense into what I have called the im 
perceptible world. We are conscious of knowing a 
sensible, an insensible, and an imperceptible world by 
natural philosophy. 

Now, this knowledge does not appear to conscious 
ness to apprehend a psychical object. When I reflect 
on my inferential knowledge of the number of corpuscles 
in a drop of water, or of the distance of the sun from 
the earth, or of the size of the earth ; when, again, I 
reflect on my indirect perception of a fire, or the waves 
of the sea ; when, finally, I reflect on my sensation of 
the white object I see or the hot object I feel ; in all 
three instances, I appear to my consciousness to be 
apprehending not psychical, but physical facts. The 
conscious subject maybe psychical, the conscious opera 
tions may be psychical ; but I am not conscious that 
the vision of white, or the perception of a fire, or the 
inference of a corpuscle, apprehends a psychical object. 
So far as I am conscious of the sensations of my five 
senses, a white object in vision, a hot object in touch, 
a scent in my nostrils, a sound in my ears, a flavour 
in my mouth, cannot but seem to be apprehended as 


physical objects. Consciousness of the apprehension of 
objects is in favour of realism. 

But when I apprehend the white, the hot, a scent, a 
sound, even a flavour, I further appear to be appre 
hending an object not only physical, but also external 
to myself. This seemingly conscious appearance is the 
strong point of intuitive realism, which depends on it to 
claim an intuition of an external world. Nevertheless, 
the appearance is a delusion, which we can trace to its 
source. From my earliest infancy, whenever a sensible 
effect has been produced in my nervous system, I have 
been accustomed to infer an external object. By asso 
ciation, perhaps also facilitated by evolution, the in 
ference has become so automatic as to be unnoticed. The 
consequence is, I think I am intuitively sensible of the 
external object when I am really inferring it. Nothing 
can prevent the delusion. I appear to see the paper 
and its distance from me. I cannot now consciously 
disengage the sensation of the sensible object from the 
inference of the perceptible original. 

Hence the limits of consciousness as an evidence. 
Consciousness does not become reflective, and therefore 
a source of psychology, till many operations have 
already become automatic in the conscious subject. 
The process from the sense of the insensible object to 
the inference of the perceptible original has been re 
peated an incalculable number of times before any man 
is sufficiently adult to consciously reflect on what he 
has been doing. Accordingly, consciousness is the 
source rather of the nature than of the origin of 


knowledge ; invaluable for what we know now, delusive 
for how we came to know it. I am conscious that 
I somehow apprehend a sensible and an insensible 
world ; but I am not conscious of the exact point at 


which it ceases to be sensible, and becomes insensible 
and inferred. Intuitive realists were right in appealing 
to consciousness for the nature of knowledge ; only 
they should have appealed from the ordinary to the 
scientific consciousness. But they were quite wrong in 
appealing to consciousness for the ultimate origin of 
knowledge. They said truly, I apprehend an external 
world ; they said falsely, I apprehend it intuitively/ 

Nevertheless, the antithesis between the nature and 
origin of knowledge must not be exaggerated. Con 
sciousness tells us something of the origin of our know 
ledge. We are not conscious of the inferences of child- 


hood : when we are old enough to take notice we 
become conscious of new inferences. We are not con 
scious of inferring an external world : we are conscious 
of inferring corpuscles. The exact limit is that we 
are not conscious of the primary data and the first 
inferences, but of adult inferences. But, again, con 
sciousness has something to tell us concerning even 
the primary data of sense. It is not their direct but 
their indirect evidence. It tells us what is our know 
ledge of objects, and this conscious knowledge must 
be explained by the primary data. Thus consciousness, 
on the whole, is the apprehension of our knowledge 
of objects and the test of the primary data and origin ; 
it is the direct evidence of the nature, the indirect 
evidence of the origin of knowledge. The facts of con 
sciousness must be first described and then explained 
by all scientific psychology. The main fact to be ex 
plained is our consciousness that we somehow appre 
hend a sensible and an insensible physical world. 

There is a superficiality of consciousness as there is 
of sensation. Yet each is the origin of a philosophy. 
Without sensation there would be no natural, without 


consciousness no mental philosophy. Sensation is neces 
sary to the science of nature, consciousness to the 
science of in hid. Sensation apprehends what is sensible, 
consciousness what is knowledge. Sensation carries us 
some little distance into physical causation, conscious 
ness into the origin of knowledge. But sensation leaves 
us to infer causes essendi in external nature, conscious 
ness causce cognoscendi in internal knowledge. Yet 
sensation is the indirect test of all hypotheses to ex 
plain the causes of sensible objects, consciousness of all 
hypotheses to explain the origin of conscious know 
ledge. Nevertheless, both in themselves are superficial ; 
for sensation has no immediate intuition of the external 
causes of nature, and consciousness none of the internal 
data of knowledge. As direct evidence, sensation tells 
ns only the bare sensible effect and not its external 
causes, consciousness only what we know now, not how 
we came to know it. Sensation and consciousness are 
twT> senses, the outer and the inner. Neither is false ; 
both are limited. Truth is in pro/undo ; yet not in a 
bottomless abyss, but in depths to be plumbed only by 
reason, and that reason not a priori, but logical inference 
from the outer and inner senses. Not sensation, but 
reasoning from sensation, discovers external causes ; 
not consciousness, but reasoning from consciousness, 
discovers the primary data and origin of knowledge. 

Consciousness, then, does not aid the idealist in his 
assertion that all the immediate objects of sense are 
psychical. It tells us that we somehow know physical 
objects. It is so far in favour of realism. Having, 
however, inferred long ago from sensible data that- 
physical objects exist in the external world, we cannot 
now help seeming to be conscious of perceiving them 
intuitively. This confusion favours intuitive realism. 



But consciousness cannot be used as direct evidence to 
tell us what we intuitively perceive, because our intui 
tions were overlaid with our inferences long before our 
consciousness became attentive. Moreover and this is 
the main point the confusion of what we intuitively 
perceive by our senses with what we mediately infer by 
our reason is cleared up by philosophy. What philo 
sophy ? This question brings us to the second kind of 
direct evidence for the data of sense. The philosophy 
which has distinguished the data of sense from their 
inferred causes is natural philosophy. 

Natural philosophy has shown that the sensible 
object is not really identical with, but is an effect distinct 
from, its external original. When a person hears a 
cannon fired at a considerable distance, his first impres 
sion is that he hears the sound at the very moment the 
ball issues from the cannon s mouth, and that the cannon 
sounds as he hears it. But if he ascends a hill, and the 
cannon again fires, he finds that he sees the smoke of the 
camion long before he hears the sound, and can count 
several seconds between the object seen and the object 
heard. There is only one possible explanation of this 
distinction. The object seen and the object heard are 
neither identical with one another, nor with the external 
object which produces them. The smoke ascends from 
the cannon and reflects the undulations of light, at the 
same moment as the ball leaves the camion and com 
municates vibrations to the air. But the undulations 
of light travel faster than the vibrations of air, and 
produce a visible effect on the person before the audible 
effect is produced by the slower mode of motion. The 
visible effect produced by the undulations is not the 
smoke, and the audible effect produced by the vibra 
tions is not the cannon s roar : else thev would be 



apprehended at the same moment. Both are effects of, 
neither identical with, the external object. 

Again, natural philosophy in the department of 
physics has shown that external things do not in all 
their attributes precisely correspond to their effects on 
our senses. They have duration, extension and motion 
corresponding to their attributes as sensibly perceived ; 
but they have not heat or colour in the way in which 
we touch what is hot or see what is coloured. On the 
contrary, the causes of sensible heat and colour are in 
sensible motions. The attributes which are in nature 
as they are in our senses, are called primary; while 
those which are not in nature as they ara in our senses, 
are called secondary qualities. 

Again, natural philosophy has proved that external 
things affect our senses by the causation of motion. To 
begin with motion before it affects the senses ; either a 
given external thing may itself move from a distance, 
until it comes into contact with a sensitive subject, as 
a cannon-ball does when it hits a man ; or it propagates 
a motion from particle to particle until the particles im 
mediately in contact with the sensitive subject receive 
the motion, a process which takes place in the propaga 
tion of the undulations of light. In both cases the result 
is the same : the object immediately apprehended could 
not be the thing at a distance, but the thing immediately 
next to the sensitive organ. But we shall find that it is 
not even the nearest thing, as a matter of fact, but an 
effect within our senses. 

Again, biology, from Galen onwards, has shown that 
the nervous system is the material cause susceptible of 
the effect produced by the efficiency of the external 
object. It has discovered much of the structure of the 
nervous system. The peripheral terminations of nervous 

E 2 


PAhT I. 

fibres are not actually exposed to external tilings. 
Hence the motion lias to be propagated through a non- 
sensitive covering before it is actually brought to the 
nerve. It is impossible, therefore, to be sensible of an 
external object, from which the nervous substance is 
divided by a medium in the body of the sentient being. 
Moreover, when the peripheral termination of a nervous 
fibre has been reached, the effect is still insensible till 
the motion has been communicated to the brain. When 
a nerve has been cut off from the brain, if the part 
between the peripheral termination and the section be 
irritated, no sensible effect takes place ; but if the part 
between the brain and the section be irritated by pres 
sure, or electricity, or disease, the effect is sensible. 
The brain, therefore, is an integral part of the nervous 
material susceptible of a sensible effect. I say a part, 
because there is no evidence that the brain alone would 
be sensitive, if a whole nervous structure up to the 
point at which it loses itself in the brain were removed. 
But the whole evidence together clearly shows that no 
sensible effect is produced by an external object until 
the propagation of motion from the external object has 
passed, not only the external medium, but what may be 
called the internal medium of the periphery, has reached 
the nervous fibres, and communicated itself to the brain. 
The nervous system is the primary matter susceptible 
of a sensible effect, and the sensible effect, therefore, is 

It is further evident that, like other material causes, 
the nervous system partly determines the effect. It is 
susceptible of effects, like the primary qualities of ex 
ternal objects, but not like their secondary qualities. 
Probably its structure is adequate to the former, but 
not sufficiently subtle for the latter. Hence the dura- 


tion, extension and motion of external bodies is able 
to produce similar sensible duration, extension and 
motion in the nervous system. But when the delicate 
vibrations of the air and the still more subtle undula 
tions of ajther strike upon the organs of hearing, 
touch and vision, the nervous structure of these 
organs is too coarse-grained to reproduce them, and 
substitutes the heterogeneous effect of sensible sound 
and the still more heterogeneous effects of sensible heat 
and light. 

Lastly, evolution has made it exceedingly probable 
that, like other material causes, the nervous system has 
itself been modified by the repeated action of the ex 
ternal efficient on its structure. It is probable that, by 
the frequent operation of appropriate stimuli on parti 
cular parts of the general sensitive system, the original 
sense of touch has been differentiated into the five senses. 
I would make two further suggestions. First, it is 
probable that as touch preceded the other senses, so the 
feelings preceded touch. In this case, the sentient being 
at first simply felt mere pleasure and pain from external 
objects; afterwards proceeded to the more complex 
operation of touch, in which the sensation of touching 
is distinct from the sensible object, hot or cold, in the 
tactile nerves, and the consciousness of touching distinct 
both from the sensation and the sensible object ; and, 
last of all, proceeded to infer external causes. Secondly, 
it is probable that, as the nervous system has become 
more differentiated, it may also become more subtle, and 
therefore more discriminative of secondary qualities. 
Some approach to this ideal may be found in sensible 
sound, in which there is some trace of vibrations, though 
not adequate to the external vibrations. Why, then, 
may not the nervous system some day become more 


attuned to represent aethereal undulations to some 
extent in the wonderful sense of vision ? 

The discoveries of natural philosophy eliminate 
intuitive realism, by proving that the external is not 
identical with the sensible object, but is the cause 
which produces it in the nervous system. Contenting 
himself with crude consciousness and common sense, 
forgetting how late consciousness becomes reflective, 
and that common sense never becomes a science, the 
intuitive realist takes the appearance that we have an 
intuition of the external world for a fact, and some 
times even converts it into a first principle. But he 
comes into contradiction with science. Natural philo 
sophy shows that the external world affects us indi 
rectly, and that we have no empirical intuition except 
of ourselves. We might doubt between consciousness 
and science, if we could not see that the supposed in 
tuition of the external world is a delusion of association, 
and that consciousness is put out of court by its in 
ability to reflect at the time when the inference of the 
external world was being made ; made so often then as 
to have become automatic, and now made so quickly 
as to seem an intuition. On the strength of science, 
then, we must reject the hypothesis that the data of 
sense are to be found in the external world, in the 

The same scientific discoveries raise a strong p re _ 
sumption in favour of physical realism, which simply 
adopts the scientific account without further hypo 
thesis. In the first place, I suppose that the effect 
produced on the nervous system is the sensible physical 
object, which we are conscious of apprehending, but by 
a confusion believe to be an object external to ourselves : 
for instance, when we see something white, it seems to 


be the external paper, or what not, but it is really the 
effect produced by the paper reflecting undulations on 
the optic nerve. Secondly, I suppose that as we know 
the external physical cause to produce the sensible 
physical effect, and as we must start from sense, we 
must use the sensible physical object impressed on o in 
ner ves to infer the external physical object, as cause. 
The scientific account of the causation of the sensible 
effect leads directly to physical realism, which simply 
reads the process of causation backwards into a process 
of knowledge. 


Biology has brought the sensible effect within the 
nervous system. Has it carried it further ? The 
attempt has often been made by biologists. They sup 
pose that the physical effect produced in the nervous 
system is not yet sensible, even when it has reached the 
brain ; that it remains a mere impression, no more 
sensible than the external object ; and that when the 
motion of the external object has produced the motion 
of the medium, the motion of the medium the motion of 
the nerves, the motion of the nerves the motion of the 
brain, the process is not yet finished. They suppose 
that the cerebral motion, which is physical, produces a 
sensation which is psychical ; and they do not ordi 
narily distinguish the sensible object from the sensation. 
From this hypothesis it would follow that the hot felt, 
the white seen, the sweet tasted, the durable, extended, 
and moving, apprehended by any sense are psychical 
affections produced by cerebral motion. The sensible 
object will be neither the external object nor the in 
ternal effect in the nervous system, but the internal 
psychical sensation. If so, realism will have to succumb 
to idealism. 

The question we now have to ask ourselves is not 



whether the external object causes our sensation in some 
way or other. The scientific evidence of the propa 
gation of motion from external objects to our bodies 
and the conscious involuntariness of sensation are suffi 
cient proofs that the external object does cause our 
sensation. It is, however, a different question how one 
causes the other. Secondly, the question we now have 
to ask ourselves is not whether there is any evidence at 
all that the sensation produced is purely psychical. 
What is to be said on this point will follow when we 
come to the Cartesian philosophy in detail. The 
present questions are, first, whether biology proves that 
within ourselves nervous and cerebral motion produces 
a psychical sensation ; secondly, if so, whether it follows 
that the sensible object also becomes a psychical sensa- 
The answer is that biologists have gone beyond 
biology, and that no affirmative answer can be ^iven to 
these questions from the observations, or direct in 
ferences from sense, which are the evidences of their 

In the first place, the nervous system is imperfectly 
known. It is quite clear that external objects propa- 
ate motions to the nerves, but it is not at all clear 
what happens when the effect has been produced. In 
optics, for example, so long as we are reading of the 
undulations of light, of the manner in which rays are 
communicated to the eye, of the structure of the lens 
by which the rays are made to converge on the retina 
and of the general structure of the retina, and even of 
nervous elements, everything is clear. But the 
further we penetrate from the retina along the optic 
nerve to the optic centres at the base of the brain, the 
darker the subject becomes, and fact seems to pass into 
hypothesis. It is the same witli all our senses 


difficulties begin at the very terminations of the nerves. 
What, for example, are the precise functions of the 
tactile corpuscles, of the rods and cones of the retina, 
of the rods of Corti in the ear ? 

We know more of nervous structure than of nervous 
action. What is nervous action ? This is an unsolved 
problem. What is cerebral action ? This is a more 
unsolved problem. The structural connections of 
afferent nerves with centres, of centres with efferent 
nerves, of efferent nerves with muscles, and to some 
extent the structural constituents of nerves and muscles 
are fairly made out. It is also found that an appre 
ciable interval takes place between the stimulation of 
an afferent nerve and the muscular motion which it 
indirectly but ultimately produces. This interval proves 
an important point about nervous action ; it is a motion 
because it takes time to go from place to place. 

The genus of nervous action, then, is known to be mo 
tion. But what is its differentia ? After the first crude 
hypothesis of animal spirits moving in the nerves, nervous 
motion was supposed to be the simplest form of me 
chanical motion by impact, as if the impression were 
pushed along to the brain, as a series of bricks knock 
one another over. Then it was supposed to be vibra 
tion. Later researches tend to show that it has relations 
to the motions of electricity and of chemical action. It 
is, no doubt, some molecular motion allied to other 
motions of the same kind ; but its peculiarity is its 
slowness, compared, for instance, with electricity. Its 
precise differentia is at present unknown. Cerebral 
motion is still more unknown. It has been found, 
by experimenting on various parts of the brain, that 
different parts are to some extent connected with 
different muscular motions, from which it is inferred 



that they are also connected with different nervous 
motions. But how the brain moves between the stimu 
lus of an afferent nerve and its effect on an efferent 
nerve is unknown. He would be a bold man who 
would come forward and say he knows the motion by 
which the effect impressed on the nerves is communi 
cated to the brain and there made ready for sensation. 
How, then, can he say he knows that cerebral motion, 
of which in biology he is ignorant, produces a psychi 
cal sensation, which is beyond the venue of a physical 
science ? 

. Secondly, the so-called transmutation of cerebral 
motion into psychical sensation is admitted to be per 
formed in some mysterious way, unknown and inex 
plicable. This point may be made clear by the following 
quotation from Professor Huxley s Lay Sermon on Des 
cartes Discourse, in which the Professor is trying to 
prove that thought is existence, and, so far as we are 
concerned, existence is thought : 

For example, I take up a marble, and I find it to be 
a red, round, hard, single body. We call the redness, 
the roundness, the hardness, and the singleness, " quali 
ties " of the marble ; and it sounds, at first, the height 
of absurdity to say that all these qualities are modes of 
our own consciousness, which cannot even be conceived 
to exist in the marble. But consider the redness to 
begin with ; how does the sensation of redness arise ? 
The waves of a certain very attenuated matter, particles 
of which are vibrating with vast rapidity, but with very 
different velocities, strike upon the marble, and those 
which vibrate with a particular velocity are thrown off 
from its surface in all directions. The optical appa 
ratus of the eye gathers some of these together, and 
gives them such a course that they impinge upon the 



surface of the retina, which is a singularly delicate 
apparatus, connected with the termination of the fibres 
of the optic nerve. The impulses of the attenuated 
matter, or aether, affect this apparatus and the fibres of 
the optic nerve in a certain way, and the change in the 
fibres of the optic nerve produces yet other changes in 
the brain ; and these, in some fashion unknown to us, 
give rise to the feeling, or consciousness, of redness. 
If the marble could remain unchanged, and either the 
rate of vibration of the aether, or the nature of the 
retina could be altered, the marble would seem not red, 
but some other colour. There are many people who 
are what are called colour-blind, being unable to distin 
guish one colour from another. Such an one might 
declare our marble to be green, and he would be quite as 
right in saying that it is green as we are in declaring it 
to be red. But, then, as the marble cannot, in itself, be 
both green and red at the same time, this shows that 
the quality " redness " must be in our consciousness, and 
not in the marble. 

Thirdly, the hypothesis of this unknown transmuta 
tion is inconsistent with one of the best established 
facts of the nervous system its physical continuity. It 
supposes that physical motion of afferent nerves and 
brain causes psychical .sensation, which causes psy 
chical volition, which causes physical motion of efferent 
nerves, which causes physical motion of muscles. But 
wherever nervous structure is accessible to observation, 
the afferent nerves finally communicate with centres 
which communicate with efferent nerves, without any 
rupture of physical continuity. It might, indeed, be 
urged that the intermediate purely psychical processes 
nevertheless intervene insensibly in the centre between 
the afferent and efferent nervous processes. But this 


hypothesis is rendered most difficult by the phenomena 
of reflex action. In reflex action, the afferent and 
efferent nervous processes are certainly connected with 
out any breach of physical continuity. It might again 
be objected that only the nerves of reflex processes are 
continuous. But we cannot divide the nerves of reflex 
action from those of conscious action, and say that 
the former nerves are physically continuous, whereas 
the latter are interrupted by purely psychical sensations 
and volitions, because the very same nerves, which are 
used in conscious, are used also in reflex actions. For 
example, we may wink either voluntarily or automati 
cally. An object strikes the eye, transmits its motion 
to the afferent optic nerve, which communicates with 
the brain, which transmits the motion to the efferent facial 
nerve, governing the orbicular muscle of the eyelids, 
which makes them close. The whole of this process often 
takes place automatically, without any rupture of phy 
sical continuity. When it takes place consciously, 
are we to say that the physical motion, having arrived 
from the optic nerve to the brain, does not produce the 
motion of the efferent nerve, but produces a psychical 
sensation instead, which produces a psychical volition, 
which at length affects the efferent nerve? There is 
not a tittle, of biological or any other evidence that the 
physical continuity is sometimes preserved sometimes 
broken in this manner in the very same series of nerves. 
To escape this gratuitous hypothesis of psychical 
interruption, some of the mental physiologists resort to 
paradoxes, in order at once to preserve the physical 
continuity of the nervous system, together with purely 
psychical sensations. Allowing that in all cases the 
motion of the afferent nerves propagated through the 
centres produces the motion of the efferent nerves in a 


continuous manner, some suppose that, standing quite 
apart from these physical processes, the conscious sub 
ject is a sort of impartial spectator, performing purely 
psychical operations that have no physical effects, while 
others positively go the length of supposing that not 
only in sentient beings, but in all nature, there are 
always two independent but parallel streams, the well- 
known physical motions and supposititious psychical 
processes accompanying them. These hypotheses are 
exceedingly like the Pre-established Harmony, and like 
it in being made to get over a self-made difficulty. 
They are hypotheses to cover an hypothesis. The 
former alternative does not go beyond conscious beings, 
but it fails to explain a fact of consciousness far more 
certain than the hypothesis. We are certainly con 
scious that external objects somehow affect our feelings 
and sensations, that our sensations, desires and infer 
ences affect our volitions, that our volitions somehow 
affect the motions of our bodies. It is absurd to suppose 
that our conscious operations are inert and idle, when 
they are consciously both passive and active, and that 
the conscious subject is like a child, given his opera 
tions like a toy to make believe he is very busy, but 
really to keep him quiet. The latter alternative which 
carries this inert psychism into everything whatsoever, 
without any evidence, except the original hypothesis 
of two parallel streams in a sentient being, would have 
us believe that the wind blows, the waves swell, the 
earth moves, with some obscure sentience. Such a per 
sonification of nature was excusable in primitive religion, 
but it is not worthy of modern science. 

Lastly, to return to the usual hypothesis that nervous 
motion produces psychical sensation, which again issues 
in nervous motion, one cannot help asking what can be 


the source of a biological hypothesis so foreign, nay, 
so contradictory to the evidence of biology ? Biologists 
have become psychologists, and have fallen under the 
dominion of the idealists. Without any criticism, with 
out any biological proof, simply because it is the fashion, 
and as if it were a first principle, they have accepted 
the idealistic hypothesis of purely psychical sensation, 
and thereon have reared an hypothesis of their own, that 
nervous motion produces this psychical sensation, which 
reproduces nervous motion. 

Now, the present question, as I said before, is not 
whether there is a purely psychical sensation, but 
whether there is any evidence that motion propa 
gated from the afferent nerves to the brain produces 
such a tertium quid, instead of producing motion 
from the brain to the efferent nerves. There is no 
evidence, either psychological or biological. As a 
psychologist, I am conscious that I perform the opera 
tion of sensation, which for argument s sake may be 
assumed as purely psychical ; but I am not conscious of 
my nervous motion. I am not, therefore, conscious of 
sensation arising out of nervous motion. A biologist, 
not in himself but in another body, can observe a nervous 
system, its physical continuity, and the time of its 
action proving motion ; but this dissector cannot either 
observe or be conscious of the sensation of another 
nervous system ; he cannot, therefore, observe nervous 
motion issuing in sensation. That there is such a pro 
cess from the physical into the psychical and back is 
sheer hypothesis, an arbitrary concordance of idealism 
and biology, 

Nor is this all ; they proceed to suppose that the 
effect produced by the external object on the internal 
nervous system is not yet sensible, but that, when the 


psychical sensation is produced, the effect for the first 
time becomes sensible, so that the sensible object is 
either identical with the sensation, or at all events is 
equally psychical. But, in the first place, even if a 
purely psychical sensation is produced in this manner, 
it does not follow that the sensible object becomes , 
psychical. There is no reason, except the /old and ex 
ploded hypothesis similia similibus cognoscuntur, why 
a psychical operation may not apprehend a physical 
object. Secondly, whatever may be the nature of the 
operation, it is most improbable in itself that the hot felt 
through one s body, the white seen through one s eyes, 
the loud heard through one s ears, is anything but a 
physical condition of the tactile, optic and auditory 
nerves in connection with the brain. The idealistic 
hypothesis of psychical sensation, then, does not prove 
the biological hypothesis of the transmutation of nervous 
motion into psychical sensation, nor either hypothesis 
the third hypothesis that the sensible object is psychical. 

Ter sunt conati imponere Pelio Ossam 

Scilicet atque Ossse frondosum involvere Olympum. 

The study of the mental physiology of the present 
day suggests several reflections. In the first place, the 
insensible and imperceptible motions of asther, their 
reflections from other bodies, and their impact on the 
senses are now well-established discoveries of science. 
They are known qualities, which are not sensations, but 
the insensible causes of sensations. Not all knowable 
qualities, therefore, are sensations. Secondly, as we 
recede from the external world behind the periphery 
into the nervous system, science becomes more vague. 
What are nervous and cerebral motions ? Thirdly, we 
are told that cerebral motion, which is physical, pro 
duces a heterogeneous sensation, which is psychical. 


But we are given no evidence of this transmutation. We 
cannot observe it in a dissecting-room. If it be said we 
are conscious of it, we answer that we are conscious of 
sensation, but not of cerebral motion, and therefore not 
of cerebral motion producing psychical sensation as a 
separate and indeed heterogeneous fact. Fourthly, this 
transmutation of one unknown into another unknown 
is admitted to take place in an unknown manner. 
Fifthly, we are illogically asked to infer from this trans 
mutation of cerebral motion into psychical sensation 
that the sensible object, e.g. the red seen in vision, is 
also a psychical sensation. Sixthly, we are not told 
how, if the object of sense thus becomes psychical, we 
infer the external causes, which, as we have seen, are 
much the clearest part of the whole business. Seventhly, 
we often find that, with more logic than consistency, 
the external objects which were previously made the 
scientific causes of sensation are nevertheless afterwards 
declared unknown and unknowable. Meanwhile, the 
fallacy of this so-called biology is its assumption of 
psychological idealism. All that is really proved by 
natural philosophy is that external redness, for example, 
is an insensible quality of insensible aether, consisting of 
a vibration of a certain velocity ; and that, reflected 
by an external object, it produces in the optic nerves of 
a sentient being a sensible redness, which is not iden 
tical with the external vibrations nor itself a sensible 
vibration at all. The simple conclusion from these 
scientific facts would be that the nervous effect is the 
sensible redness, from which, together with sensible 
motion, the external motions of vibration are inferred. 
Nothing more is proved by mental physiology. 

When we look back at the whole light thrown by 
natural philosophy on the sensible object, we shall find 


that it is known that external physical objects produce 
internal physical effects in the nervous system, but it is 
not known that these internal physical effects in their 
turn produce an internal psychical object of sense. 
Meanwhile, we are conscious that, when we use our 
senses, we somehow apprehend a physical object, which 
seems by an illusion to be also external. The simplest 
hypothesis, which can be made in these circumstances, 
is that the sensible object is neither external on the one 
hand nor psychical on the other, but the internal 
physical effect on the nervous system. In other words, 
there is a via media between intuitive realism and 
idealism of all kinds, closer to the scientific facts than 
either hypothesis ; namely, physical realism. 

At the same time, scientific observation is not a 
positive proof of physical realism. It brings the sensible 
object within the man : it cannot decide whether it is 
or is not within the soul. Its ultimate result is that 
the sensible object is not external but internal, not 
without but within the sentient being, not identical with 
the physical object in the outside world but produced 
in the interior microcosm of the animal organism. This 
negative conclusion eliminates intuitive, but it does not 


positively establish physical realism. As a direct 
evidence, natural philosophy, being founded on obser 
vation, is able to show that the sensible object is not 
the physical object outside, but is within the nervous 
system ; not being founded on consciousness, it is not 
able to decide whether this internal sensible object is 
physical or psychical, whether it is the nervous effect, 
or something even more internal. It leaves this problem 
unsolved. Accordingly, there still remain two pos 
sible alternatives physical realism and psychological 



Nevertheless, scientific observation makes physical 
realism the more probable alternative, because this 
hypothesis simply accepts the proved nervous effect as 
the sensible object, instead of hypothesising a further 
psychical object, which is unproved, and breaks the 
nervous continuity. When as a mental philosopher one 
adds consciousness to scientific observation, the proba 
bility of physical realism is increased. Consciousness 
tells us that we somehow apprehend physical objects, 
which appear also to be sensibly external. Scientific 
observation disabuses us of the appearance that the 
sensible object is external, but not of the consciousness 
that it is physical. Natural philosophy, as a direct 
evidence, may be said to remove the physical object 
of sense from the external to the internal world, but no 
further than the nervous system. The most probable 
mental philosophy would simply conclude that it there 
becomes sensible though only the most probable. 

We asked for direct evidence that the immediate 
object, hot, coloured, &c., perceived by our senses is a 
psychical phenomenon, and we find there is none. Con 
sciousness is so far from saying so, that it confuses the 
immediate and the mediate, and leads us to think that 
the immediate object is not only physical but external. 
Scientific analysis corrects this confusion, and teaches us 
that the immediate object is not external but internal, 
but does not go on to show that it is not only internal 
but psychical. I suspect that the idealists by a kind of 
confusion have changed the truth that the object of 
sense is not external but internal into the hypothesis 
that it is not physical but psychical. 

The idealist may reply that direct evidence is not 
required for an hypothesis, and that the psychical object 
is like ether something inaccessible to direct evidence, 


but needed to explain the facts. I accept this issue. 
I admit that, if the idealistic hypothesis of the sensible 
object could explain the facts of the known world and 
eliminate the hypothesis of physical realism, it would be 
proved by this indirect evidence. There would still be 
no direct evidence that a hot or coloured object is not a 
physical but a psychical fact. But, contrary to all ap 
pearance, we should be obliged to conclude that, as 
light is paradoxically but really an undulation of aether, 
so is the seen, or felt, or heard, or tasted, or smelt, a 
psychical, and not a physical, fact. 

The gist of the idealistic hypothesis is that not some 
but all the immediate objects are psychical, and that 
no physical object whatever is apprehended by sense. 
The consequence is that all our sensitive experience 
will be limited to psychical objects; for, so far as it is 
sensitive, experience is merely the sum of our sen 
sations. Moreover, the supposition of a priori elements 
of knowledge will not help us, for nobody pretends 
that we have an a priori apprehension of the physical 
to add to an a posteriori apprehension of the psychical : 
such an hypothesis would be too great an inversion. 
The consequence is that all the data of our knowledge 
will be psychical. No doubt different idealists will pro 
vide more or less of such psychical data. Some will 
have merely psychical sensations, others will add a 
psychical subject, and others again psychical apprehen 
sions a priori. But at the widest the data will all be 
psychical facts of some kind or other. 

Now the question arises, what can be known from 
psychical data? If all the immediate objects I touch, 
see, taste, smell, and hear are psychical, and I am psychi 
cal, and all my apprehensions are psychical, if all my 
sensitive experience is of nothing but psychical phocno- 

F 2 


inena, if all the data which form the immediate premises 
of my mediate knowledge are psychical, what can I 
infer from such facts in the premises ? To answer this 
question we must consult the logical rules of inference. 
All inference is by similarity. Not to enter into the 
question whether there is one fundamental type, there 
are three apparent kinds of inference induction, deduc 
tion, and analogical inference. All these are different 
modes of reasoning from similar to similar. In induction 
we apprehend that similar particulars have a similar 
characteristic, and infer that the class, including those 
and all other particulars similar to them, have that 
similar characteristic. In deduction we start with a 
proposition stating the similar characteristics of a class, 
either inferred by induction or otherwise known, as 
major premise ; we combine it with a minor premise, 
asserting that something is one of the class of similar 
particulars ; and from this combination we infer that this 
new but similar particular has the similar characteristic 
already known to belong to the class. In analogical in 
ference, which is an imperfect substitute for induction 
followed by deduction, we apprehend that a particular 
has a characteristic, or several similar particulars have 
a similar characteristic; we apprehend by analogy 
that another particular is similar to the given parti 
cular or similar particulars ; and from the analogy we 
infer that this new but similar particular may have the 
characteristic similar to that of the given particular 
or particulars. Various men are mortal, . . all men 
are mortal : all men are mortal, I am a man, . . I am 
mortal : the earth is inhabited, Mars is like the 
earth, . Mars may be inhabited : these inductions, 
deductions, and analogical inferences are nothing but 
inferences from similar to similar. They are founded 


also on the reality and knowledge of classes and laws. 
But what is a class except similar things, and what is a 
law except the fact that similar things possess similar 
characteristics ? 

From this limitation of inference to similarity it 
follows that whatever the character of the data, such 
will be that which is inferred. If all the data were 
psychical, then, by parity of reasoning, we could only 
infer the psychical. If we never had direct experience 
of anything physical whatever, then, there being nothing 
physical in the premises, nothing physical in the con 
clusion could possibly be inferred. From the similar 
the similar is inferred ; from the psychical the psychical. 
But in order to infer the physical we must have some 
physical data. 

The universal similarity between the data in the 
premises and the inferred in the conclusion requires to 
be guarded from misapprehension. I said above that 
the old hypothesis like is known by like is a fallacy. 
I now say that like is known from like. These positions 
are not inconsistent. The former refers to the relation 
of subject and object, the latter to the relation of object 
to object. There is no reason why the object appre 
hended should be like the subject apprehending ; but 
there are reasons why objects inferred should be like the 
objects from which they are inferred the rules of logic. 
If the subject has constantly had physical objects pre 
sented to it, it must apprehend them, or be useless. 
But when the subject has before it the immediate objects 
which can be presented to it, whether a posteriori or 
a priori, it has all the data from which reasoning can 
start ; and if that reasoning is to maintain the consistency 
of truth, it can add nothing in the conclusion which is 
not justified by the presence of something similar in the 



premises. If reasoning contains, on the Kantian hypo 
thesis, a priori apprehensions, these will be part of the 
data ; but if it adds anything, not in the data but in 
the conclusion, which has no analogue in the premises, 
reasoning becomes paralogism. This fallacy is well 
known in deduction ; but it is equally true of induction, 
which only generalises the subjects and predicates con 
tained in the particular instances, and of analogical 
idference, which infers that one particular similar to 
another may be similar also in a characteristic already 
apprehended in that other. Therefore, although like 
objects are not necessarily immediately apprehended by 
a like subject, only like objects are inferred from like 
objects, not by any necessity in the relation of subject 
and object, but by the nature of reasoning. Hence a 
psychical subject may immediately perceive physical 
objects ; but if it were a psychical subject and perceived 
psychical objects it could infer nothing but psychical 
things, similar either to the psychical subject perceiving 
or to the psychical objects perceived. 

Again, the logical canon, like is known from like, 
must not be confused with the metaphysical hypothesis, 
like causes have like effects. Aristotle extended the 
principle of the propagation of the species from the 
organic to the inorganic world, and thought that every 
cause is homogeneous with its effect. Modern science 
has discountenanced this view, except in the far-off sense 
that all physical causation may be the propagation of 
motion in various forms. But when I say that we can 
only infer like objects, what I mean is not that we must 
infer causes like the effects, but causes like the causes 
which we have already known. For example, Newton, 
already knowing the effects requiring gravitation to 
cause them in terrestrial bodies, when he found similar 


effects in celestial bodies, inferred that their cause also 
is a celestial, similar to terrestrial, gravitation. Now, if 
all the data of sense \vere psychical, not only the effects 
but also the causes in sense would be psychical : conse 
quently, when we came to a sensible effect, similar to 
other sensible effects, but not due to any sensible cause, 
we should have to infer a similar cause beyond sense ; 
and, as all the causes in sense w^ould ex hypothesi be 
psychical, we should have to infer, by parity of rea 
soning, a psychical cause, not because the effect was 
psychical, but because all previously known causes 
would be psychical. If, on the other hand, there were 
physical causes in the data of sense, we could then, and 
only then, infer a similar physical cause beyond sense. 

Again, when I say that only like objects are inferred 
from like, I do not mean that nothing new can be inferred, 
but only nothing new which is not similar to the data. 
The conclusion is no mere restatement of the premises. 
What is inferred need not have been already experi 
enced, nor is reasoning confined to merely reproducing 
the immediate data of the senses. But what is inferred 
must be similar to what has already been experienced. 
What is new, and has never been, nor ever will be, in 
experience, such as an ^ethereal undulation, can be in 
ferred. But the ethereal undulation is a motion similar 
to the experienced motion of waves of water. Nothing 
new, which is not similar to the data, can be inferred. 
It is true of the Deity Himself, who, though not experi 
enced, is inferred to be like man, but infinitely intensi 
fied in the attributes which we already know in our 
selves. Consequently, if all the data were psychical, we 
should be able to draw inferences to similarly psychical 
subjects and similarly psychical objects, new but similar 
to the data. But we should not be able to infer some- 


thing wholly new, dissimilar and heterogeneous, for 
which there was no analogue either in the sentient sub 
ject or in the sensible objects. Hence, the physical, 
for which there would be ex hypotliesi no analogue in 
the premises, could not be inferred. If, on the other 
hand, as I suppose, the sensible data are physical facts 
in my organism, I can then infer new but similar physical 
objects outside, although I have never immediately per 
ceived them by sense. 

Another misapprehension will immediately arise. It 
is said that one opposite implies another, and, therefore, 
though we experience only one opposite, we infer the 
other. Thus, it is supposed, from psychical data we 
infer their opposites, physical things. I am almost 
ashamed to write down Aristotle s distinction of con 
tradictories and contraries ; but it is necessary in an 
illogical age. Contradictory opposites are the positive 
and its negative, as relative and not relative, finite and 
not finite. Contrary opposites are the furthest removed 
positives, as white and black. Now contradictory op 
posites in a sense imply one another, but contrary 
opposites do not. White implies not white : it does not 
imply black. We might have apprehended white without 
having any conception of black, much less having proof 
of its existence. Secondly, great harm is done by such 
vague terms as imply and implication, which some 
times mean conceiving and sometimes inferring. The 
positive, when apprehended, makes us conceive the con 
tradictory negative, but does not make us infer that it 
exists. Are we to fall into the old sophism of arguing 
that as something is contradicted by nothing, nothin^ 

o 7 O" O 

exists ? 

It is a common argument that the relative which 
we experience implies the non-relative and absolute, 


the finite implies the infinite. This is an utter confu 
sion of contradictories and contraries. The relative im 
plies the not relative ; but the contradictory, not 
relative, is not necessarily the positive contrary, abso 
lute, for it also includes nothing ; and the relative, in 
implying the not relative, does not decide whether it is 
absolute or nothing. As white implies not white, but 
not necessarily black or any other particular colour, so 
the relative implies not relative, but not necessarily the 
particular species of not relative, absolute. The same 
remark applies to the opposition of finite and infinite, 
except that in this case the term infinite is ambiguous, 
being properly the not finite, but including both that 
which is not finite, because it is nothing, and that 
which is not finite, because it extends without limit. 
The finite implies its contradictory, not its contrary : it 
implies the negative not finite, but does not imply 
the particular positive species, the infinite which 
extends without limit. Secondly, the relative and 
finite imply only in the sense of making us conceive 
the mere contradictories, not relative and not finite. 
The positive sides of the contradictions not only leave 
the content of the negatives undetermined, but also 
leave the question undecided whether we can infer 
that there is anything corresponding to the ideas of 
the negatives. Nor do they even give us the ideas 
till we have not only apprehended the positives, but 
also apprehended that they are relative and finite. 
The relative and the finite, then, when apprehended to 
be such, make us conceive the ideas of the not relative 
and not finite, but give us no idea of a positive some 
thing absolute and extending without limits, much less 
make us infer that this species of not relative and not 
finite is something real as distinguished from nothing 


at all. When we merely experience something which 
happens to be finite, we need not think of any opposite ; 
if we think of it as finite, we must have an idea of the 
not finite ; but we need not form an idea of the positive 
infinite, much less can we prove that there is something 
infinite, and say, I experience the finite and relative, 
therefore there is an infinite and absolute. Men accept 
such arguments because they think it helps to prove 
the existence of a Deity. But the finite and relative do 
not make us conceive a positive infinite absolute, much 
less infer its existence ; and theology has better argu 
ments for a Deity than the confusion of negative and 
positive, of contradictory and contrary opposition, of 
conception and inference, of ideas and judgments. 

Similarly, the psychical does not imply the physical. 
The physical and the psychical are contraries, not con 
tradictories. The contradictory of the psychical is the 
not psychical, which may be anything else or nothing. 
Suppose that I had experienced nothing but psychical 
data. If I had never thought of them as psychical, but 
only as hot, red, and so on, I should have had no reason 
to conceive the not psychical. If I had thought of them 
as psychical, I must then have had the bare idea of not 
psychical as its contradictory. But I should neither 
have been able to have inferred that it existed nor what 
it was. The content of the idea would have been the 
bare negation or contradictory of the psychical. I 
should have had no idea of the physical as a positive 
contrary, much less have proved its existence. Just as 
the apprehension of white makes me conceive the idea 
of not white, but does not infer that there is any other 
colour, much less the contrary black, and just as the 
apprehension of the relative and finite makes me con 
ceive the idea of not relative and not finite, but does not 


infer that there is anything which is not relative and not 
finite, much less the contrary absolute and extending 
without limits, so the apprehension of the psychical 
would make me conceive the idea of not psychical, but 
would not tell me that there is anything positive which 
is not psychical, much less that it is the contrary, 
physical. To infer the existence of the positive con 
trary, the physical, I should have required other than 
psychical data, which would, however, have been ex 
hypotliesi all the data possible. 

In all cases the existence of a contrary is a matter not 
of implication in the knowledge of the opposite con 
trary, but a matter of independent inference. Human 
reasoning would indeed be easy, if without further 
question the moment one had ascertained a thing, one 
knew that its contrary existed ; when one had experi 
enced white, one knew black ; when all experience had 
been of the relative and finite, one knew the absolute 
and infinite ; when all the immediate data of all reason 
ing were psychical, one straightway knew that there 
are physical things. Why, one contrary does not even 
make us conceive the idea of another, much less infer its 
existence. The white makes us conceive the idea, not 
white : we want other evidence to infer the existence of 
the black. The psychical makes us conceive the idea, 
not psychical : we want other evidence to prove the 
existence of the physical. A synthesis from psychical 
data to physical things must be founded on some better 
device than the fallacy of the implication of opposites. 
But in reality the whole hypothesis of such a synthesis 
is illogical. To infer physical things we require more 
than psychical data, and their implications, and their 
consequences : we require physical data in the premises 
similar to the physical objects in the conclusion. 


The canons of inference, then, teach us, first, that 
from similars similars are inferred ; secondly, that what 
is inferred may be something new so long as it is similar 
to some of the data ; and thirdly, that it cannot be the 
contrary of all the data. Therefore, on the idealistic 
hypothesis that all the data are psychical, in the first 
place, what is inferred would also be psychical ; secondly, 
it would include other psychical subjects and other psy 
chical objects similar to those which ex Jiypotliesi form 
the data of inference ; but, thirdly, it would not include 
physical things, for which there would be no analogy, 
and which are not implied in merely psychical data : for 
psychical data would not make us even conceive, much 
less infer their contraries, physical things. On the 
other hand, if some of the data are physical, what is 
inferred can be physical like the data, different yet 
similar objects, the data being in our own bodies, the 
inferred objects in the external world. 

We constantly hear at the present day of two worlds 
and their correspondence the psychical and the physical. 
It is not the purpose of this essay to deny this anti 
thesis, nor to depend upon it. But it is also commonly 
supposed that all the data of our knowledge belong to 
the former world, from which the latter is inferred. 
Against this hypothesis I direct this essay. If all the 
data of sense were psychical, the parity of reasoning 
would have no data to infer the physical. But the 
physical world is the object of natural science, which is 
knowledge. Therefore, not all the data of sense are 
psychical. There must be similar physical data to infer 
similar physical objects. 

Such, then, are the data required by the rules of 
reasoning to infer a physical world. We began by 
saying that, if the idealistic hypothesis led to the 


only possible explanation of the facts, we must accept 
it even on this indirect evidence. We now see to 
what it logically leads. All that is inferred as well 
as all that is perceived, all that is immediate and all that 
is mediate, all that is apprehended in us and all that is 
known beyond, will be psychical. That is, all known 
realities will be psychical facts of some kind or another. 
As Berkeley says, the whole known world will be mind 
and ideas ; with Hegel, thought will be being and 
being will be thought. These are the logical idealisms. 
Nothing physical, and not psychical, will be inferrible, 
still less knowable. 

This logical consequence of all psychological idealism 
must be confronted with the discoveries of natural philo 
sophy. A survey of these discoveries shows an enormous 
mass of insensible and inconceivable realities, which 
are scientifically known by inference from sensible data. 
But they are physical realities, incapable of being re 
solved into any kind of psychical fact ; being insen 
sible they are not sensations, being inconceivable they 
are not ideas. It follows, therefore, that some things 
physical, and not psychical, are knowable, and not all 
known objects are psychical. 

The physical objects of scientific knowledge directly 
eliminate pure idealism. Starting synthetically from 
the common idealistic hypothesis that the sensible data 
are psychical, the pure idealist draws the strictly logical 
conclusion that all known objects, inferred from these 
psychical data of sense, must also be psychical. Accord 
ing to him, then, there are no physical objects of know 
ledge. His logic is consistent, but his conclusion is 
false. He has omitted the physical world which, being 
beyond our sensations and ideas, cannot be resolved 
into sensations or ideas, but which yet is an object of 


8( .i ence _the most perfect form of knowledge. Not all 
known objects, therefore, are psychical; some are phy 
sical. Pure idealism then is false, and some form of 
realism true. As intuitive realism has already been 
eliminated by natural philosophy, it only remains to 
decide between the hypothetical realism of the cos- 
mothetic idealist and the physical realism of this essay. 
The physical objects of scientific knowledge in 
directly eliminate cosmothetic idealism with its hypo 
thetical realism. The cosmothetic idealist tries to 
reconcile the idealistic theory, that the sensible data 
are psychical, with the realistic theory that some objects 
knowable by inference from these data are physical. 
We have found that the realistic part of his theory is 
correct. He has the merit of admitting that there are 
physical objects of knowledge : this is his superiority to 
the pure idealist. He has the merit of admitting that 
they are not intuitively perceived by sense, but inferred : 
this is his superiority to the intuitive realist. But he is 
illogical. His defect is the inconsequence of supposing 
that physical objects, though not intuitively perceived, 
could be inferred from purely psychical data. But we 
have seen that all inference is by similarity, and there 
fore physical objects could not be inferred from purely 
psychical data. The physical would be the object 
of a new term in the conclusion, absent and un 
justified in the premises. If all the data of sense 
were psychical, then, by parity of reasoning, all objects 
knowable from them would be psychical. But by the 
discoveries of science, and by the admission of the 
cosmothetic idealist, some objects knowable by inference 
from the data of sense are physical. Therefore not all 
the data of sense are psychical. Sublata consequent 
tullitur antecedens. 


Cosmotlietic and pure idealism are mutually destruc 
tive of each other. The former admits that some objects 
are physical, which prove that the latter is wrong in 
supposing all objects to be psychical. The latter admits 
that only psychical objects can be inferred from psychi 
cal data, so that the former is wrong in supposing that 
physical objects are inferred from psychical data. Pure 
idealism fails to recognise, cosmothetic idealism fails to 
explain, the knowledge of an insensible and inconceiv 
able physical world. If we combine both we destroy 
the common data of both. As the pure idealist says, 
if all the data were psychical all the objects would be 
psychical ; but as the cosmothetic idealist admits, not 
all the objects are psychical. It follows that both are 
wrong in saying all the data are psychical. Their data 
fail to explain the physical objects of scientific know 
ledge. Science eliminates all psychological idealism. 

Meanwhile the physical objects of scientific know 
ledge are not merely destructive of psychological 
idealism, but are also constructive of physical realism. 
They prove in themselves that some objects of know 
ledge are physical, and, in combination with the logical 
rules of inference, that some data of sense must be 
physical, to infer them. Similars are inferrible only 
from similars. Therefore the physical is inferrible only 
from the physical. But some objects of science are 
physical ; therefore they are inferrible only from physi 
cal data. These data of sense, however, though physical, 
are proved by scientific analysis to be internal ; there 
fore the data of sense are physical objects within our 
nervous system, from which we infer physical objects in 
the external world. This is the theory of physical 
realism, established by the logical rules of hypothesis. 

I admit that the direct evidences are not a positive 


proof of physical realism. Consciousness, alone, is even 
in favour of intuitive realism. But scientific analysis 
destroys this hypothesis by separating the sensible 
effect from the external cause, and showing that the 
sensible object must be internal. On the other hand, it 
does not show that the sensible object is not only in 
ternal but psychical, and therefore does not favour 
idealism. It makes the intermediate theory of physical 
realism possible, even probable. I do not believe, how 
ever, that the data of sense are recoverable by any 
direct method, because from our very birth, and with 
inherited power, we overlay them with inferences. 
Hence the shipwreck of modern philosophy, which sup 
poses its hypotheses of sensible data to be first principles, 
and has alternated between the opposite but equally 
futile attempts to grasp physical things by sense, or to 
leap from psychical data to physical things. 

I admit, therefore, that the crucial evidence must 
be indirect. That hypothesis of the data of sense must 
be accepted, which explains the knowledge of the objects 
of science. This insensible, this inconceivable, this 
physical world of science is not an object of intuition, 
is not a sum of psychical sensations and ideas, is not 
inferrible from psychical sensations and ideas. Its 
knowledge then must be accounted for otherwise. It 
is inferrible from internal and physical data, the nervous 
system sensibly affected by external objects. The data 
of sense, then, are neither physical objects without, 
which are the causes not the objects of sense ; nor 
psychical objects within, from which nothing physica 
could be inferred ; but physical objects within, from 
which physical objects without are inferred by all, and 
known by science. Physical realism, therefore, or the 
theory of internal physical data to infer external physi- 


cal objects, is, in accordance with the logic of explana. 
tion and elimination, the only hypothesis of the data of 
sense sufficient to explain the knowledge of the objects 
of science. It is a mental philosophy born of natural 
philosophy, that great mother of sciences. 

1 Bacon, Nov. Org. i, 80. 





ABISTOTLK remarks that we ought not only to criticise 
our opponents, but also to point out the causes of their 
errors. The origin of intuitive realism and its presen- 
tative theory of perception, is the inevitable tendency 
of ordinary man to confound sense with reason, and his 
sensations with his inferences. He has so long been 
accustomed to infer an external world, that at last he 
cannot but fancy his senses perceive it. He seems to 
himself even to be conscious that it is so, calls his con 
fusion common sense, and at last defies philosophers to 
distinguish the sensible and the real. To have dis 
abused philosophy of this confusion is one of the 
many services owed by mankind to Greek philosophers. 
The distinction of sense and reason soon dawned on the 
Greeks, and with it the discovery that the object of 
sense is not the external thing at a distance from our 
selves, but some sort of result on our senses, from 
which the external tiling is inferred by reason. In 
short, the Greek philosophers founded the representa 
tire theory of sensitive perception. But they did not 
agree about the nature of the sensible object, or repre 
sentative of the external thing impressed on the senses. 
Without pretending to give a history of their views, we 
may distinguish two great epochs : the first, that in 
which the sensible object was regarded as a corporeal 


effect ; the second, that in which it began to be regarded 
as an incorporeal essence in our senses. In this second 
epoch the Greeks prepared the way for the theory that 
the sensible object is an incorporeal idea. But they 
never actually reached the idealistic theory. 

The first approach to a scientific theory of the 
objects of knowledge is to be found in the Atomists, 
Leucippus and Democritus of Abdera, the pioneers of 
a sound philosophy of nature. To them we owe the 
dawn of the truth, afterwards developed into the dis 
tinction of primary and secondary qualities, that the 
real and original qualities of particles are figure, position 
and arrangement, whose different combinations, together 
with motion, give rise to qualities, such as heat and 
colour, which, though really derivative, appear equally 
original to our senses. 

The manner, however, in which this important doc 
trine was presented to the world was not purely unex 
ceptionable. The Atomists, it is true, admitted that 
there is for every variety of sensible quality a distinct 
mode, or schema in their language, of the original qua 
lities ; for example, a sharp taste arises from angular, 
a sweet from round schemata. But, to say nothing of 
their crude speculations on corpuscular structure and 
motion, they fell into the fallacy of confusing the deri 
vative quality with its sensible effect in the famous 
dictum, Conventionally there is sweet, conventionally 
bitter, conventionally hot, conventionally cold, conven 
tionally colour ; but really atoms and void. * From 
this Atomistic identification of secondary qualities with 
their sensible effects, assisted by the Heraclitean identity 
of contraries, it was but a short step to the sceptical 
theory of Protagoras, that all qualities are merely the 

1 Scxt. Einp. Adv. Math. vii. 135. 

G 2 


appearances in our senses, without any correspondents 
in the fluent matter of nature. 

The Atomists did not recognise sufficiently, the 
Sceptics not at all, the fact that derivative or secondary 
qualities are qualities of external things. There is 
also a common tendency in modern mental philo 
sophy to identify secondary qualities with their sen 
sible manifestations. But for every sensible quality, 
which is the product of an external object, there is a 
distinct quality in the external object. A primary 
quality is also like the sensible quality. A secondary 
quality, such as heat or colour, is not, indeed, like the 
sensible effect, being a mode of a primary quality, such 
as motion ; but it is a distinct and specific variety of 
that primary quality ; it is the motion of a different kind 
of matter, it goes on independently of the sensible effect, 
and it is a knowable object of science. Thus, it has 
been discovered in natural philosophy that heat and 
lio-ht are not molar but molecular motions, that they 


are motions of sether ; that they are, in rerum natura, 
different motions of different lengths, the waves of mere 
heat being longer than those of light, and that they are 
so disseminated throughout the universe as to produce 
no sensible effect incalculably oftener than they excite 
touch or vision. 

It was perceived by the genius of Bacon that heat is 
of two kinds, in or dine ad universum and in ordine ad 
sensum, the former being an insensible mode of corpus 
cular motion, the latter the same thing but with a rela 
tion such as -is competent to sense. 1 The Atomists were 
too narrow in confining heat to the sensible effect of a 
distinct mode of matter in the external world, and 
Protagoras quite wrong in denying the distinctness of 

1 Bacon, Nov. Org. ii. 20. 


the external quality ; Bacon was right in regarding heat 
as a mode of motion in the external world, as well 
as a sensible quality in our senses. So with all other 
secondary qualities ; they are modes of primary qualities, 
but distinct modes ; they have a generic resemblance to 
other modes, but they have also specific differences. 
Sound is a vibration of air, heat and light undulations 
of rcther. 

The only plausible objection to this view would be 
that the names heat, light, and so on, should be 
confined to the sensible effects and not extended to 
their external causes. It must be confessed, also, 
that so long as distinctions of things are observed, 
the use of names is comparatively unimportant. But 
names are the vehicles of distinct ideas, and it is the 
duty of every science to have some distinct name for 
every real distinction of things. The specific modes 
of primary qualities must receive some name or other. 
It will not suffice to leave the external cause of sensible 
sound to the periphrasis, vibratory motion among the 
particles of an elastic aerial medium ; or that of light to the 
periphrasis, undulations in an ethereal medium per 
vading interstellar spaces and bodies formed of ponder 
able matter. New names might be invented, but they are 
not forthcoming, and it is doubtful whether they would 
be superior to, and still more doubtful whether they 
would be victorious over, the old names, sound and 


Secondary qualities are real, though derivative, 
qualities of external objects, as well as qualities of 
sensible objects ; and their names should be equally 
extensive. In support of this view, let us quote a 
passage from Professor Stokes, On the Beneficial Effects 
of Li^ht, all the more valuable because it was not 


written to support any general philosophy of secondary 
qualities : 

Beyond both ends of the visible spectrum there lie 
radiations which do not affect the eye, but are never 
theless, as we have every reason to believe, of the same 
physical nature as those which do, from which they do 
not differ by any inherent quality. As the agent which 
excites vision has been called from time immemorial 
" light," or whatever may be the corresponding term in 
other languages, it will be convenient to use the same 
word to designate the agent considered in itself, and 
irrespectively of its capacity for exciting vision, a 
capacity which would be regarded as a mere accident 
of light, in the technical logical sense of that word. 
Accordingly I shall now use the word " light " to 
designate what, for want of a better term, I have just 
been calling "radiation," a word which would more 
properly denote the process of radiation than the thing 
radiated, be it the material or immaterial, be it matter 
or undulations (p. 6). 

Qualities, then, as distinguished by natural philo 
sophy, are divided as follows : 

I. External, in or dine ad universum. 

1. Primary, original qualities; e.g. duration, 

extension, motion. 

2. Secondary, specific modes of primary quali 

ties ; e.g. sound, heat, light, as modes of 

II. Internal, in or dine ad sensum. 

1. Primary, and like external primary qualities, 

which cause them. 

2. Secondary, unlike external secondary quali 

ties, which cause them. 


It is to be noticed, in this division, that the derivative 
character of secondary qualities refers not to their 
sensible but to their external aspect. As sensible, we 
apprehend them in exactly the same way. Again, the 
ordinary man infers external qualities alike in both 
cases. The difference entirely arises when the scientific 
man begins to infer that external secondary are modes of 
primary qualities, because their sensible effects are so 
similar to those of primary qualities; for instance, 
the effects of external sound, heat and light are 
effects of motion by the laws of motion. 

To the Atomists is due, not only the foundation 
the theory of primary and secondary qualities, but also 
the discovery that the object of sense is not the external 
thin- itself, but an effect produced by the external thin 
on the senses. They supposed that effluxes, continual!; 
thrown off from bodies, come into contact with on 
oro-ans. 1 They thus anticipated modern physical inquiry 
on the senses, although their necessary ignorance of the 
laws of motion prevented them from realising the vibra 
tions and undulations, which have taken the place oi 
emissions, in the case of hearing, sight, and the perception 
of temperature by touch. The consequence of this 
position to the theory of knowledge in Greek philosophy 
was that its immediate object was henceforward 
rally agreed to be not the thing at a distance, 1 
result of the thing on the organs of sense. 

In the Atomistic theory the immediate object ^ c 
sense, though internal and representative, is neither im 
material nor psychical : it is a physical object, 
point has never been disproved. Modern physiology 
we have seen, has brought the motions of matter j 

i Arist. DC Divin. per Somn. 2 = 4G4 A G (Berlin cd.) ; cf. Pint. DC Plac. 
Phil iv. 8. 


as the physical substances of the nerves ; but it has 
never shown that this physical object is converted into 
a psychical sensation, either at the extremities of the 
nerves, or in the nervous fibres, or in the nerve centres, 
or in the brain itself, or beyond it. Why, then, should 
we not perceive the physical effect in our internal 

organs ? 

The physical character of the immediate object of 
sensible knowledge was not at first forgotten. It sur 
vived in the Epicurean philosophy. It even left a relic 
in the philosophy of Plato, who always represents 
sensation as a motion communicated from matter 
through body to soul. 1 Hence sense never appears in 
any Platonic dialogue as a part of the soul, nor the 
sensible object as something purely psychical. It is not 
in his theory of sense, but of reason, that Plato becomes 
idealistic. The objects of sense are, according to him, 
results of material motion communicated from body to 
soul ; the objects of rational knowledge are results com 
municated from immaterial forms to the pure soul. 

Aristotle was the author of a new theory of the sen 
sible object. He had an aversion to atomism, perhaps 
because he confused it with materialism. For atoms he 
substituted primary matter ; instead of figure, position, 
and arrangement, he regarded heat and cold, dry and 
liquid, as its primary contrarieties. 2 The Atomists 
considered the external thing to be wholly corporeal ; 
Aristotle divided it into two heterogeneous substances 
corporeal matter and incorporeal form 3 the former 
of which was different for each individual, the latter the 
same for all individuals of one kind. While the Atomists 
had held that the sensible object which results from the 

1 Plato, Phil 34 A ; Tim. 42 A, G4. 2 Arist. DC Gen. et Corr. ii. 1. 
3 Id. Met. Z 7 = 1032 B 14. 


external thing is a corporeal efllux, Aristotle persuaded 
himself and his followers that it is the identical incor 
poreal form transferred without the different corporeal 
matter from the external thing into the sensitive faculty, 
as an impression is transferred without the metal from 
a metallic seal into wax. 1 For example, vision, accord 
ing to him, receives the essence of white without the 
matter of the external wax into the visual faculty. 
Hence his distinction of nutrition and sensation : in 
nutrition we receive the whole thing, in sense the form 
without the matter of the thing. He agreed, indeed, 
with his predecessors in the fundamental point that the 
external thing is not presented, but that the sensible 
object presented is a representative result of the external 
thing. But this object in our senses, which, according 
to the Atomists, was a corporeal efflux, was, according 
to Aristotle, an incorporeal form, called by himself 
ala-O^rov elSo?, and by his scholastic followers, species 
sensibilis. From his time onwards, the object of sense 
began to be usually regarded as not only internal, but 
also incorporeal, though not yet as a purely psychical 

Aristotle s new theory of the object and nature of 
sensitive perception is charged with errors. He substi 
tuted for the explanation of the world by particles, the 
abstractions of matter and form ; he inverted the real 
order of primary and secondary by making heat and 
cold original qualities ; he arbitrarily severed a single 
corporeal thing into a corporeal and an incorporeal half, 
and by this latter figment endeavoured to explain the 
object of sense. We see here the beginning of the false 
hypothesis that the object of sense is not a corporeal 
fact. Aristotle was right in thinking that sense does 

1 Arist. De An. ii. 12. 


not perceive the external thing, wrong in thinking that 
what it perceives within is an incorporeal form. 

Hamilton has misunderstood these Aristotelian errors. 1 
He says truly enough that Aristotle distinguishes proper 
from common objects of sense, 2 and that the former 
agree with the secondary, the latter with primary quali 
ties. 13 ut he misses the real point by supposing that 
Aristotle meant to derive the former from the latter. 
Aristotle distinguished proper and common sensibles 
solely in relation to the senses which perceive them. 
Heat and cold, for example, are proper sensible objects 
of touch ; but so far from being regarded by Aristotle 
as secondary qualities, they form one pair of his primary 
contrarieties of matter. The classification into common 
and proper is not intended by Aristotle for a classifica 
tion into primary and secondary ; so far from it, his 
primary qualities are falsely taken from what are really 
secondary qualities, heat and cold, dry and moist. 

Secondly, Hamilton rightly says that Aristotle calls 
such qualities as heat and cold affective qualities, be 
cause they produce affections in us. 3 But we must not 
therefore infer that lie meant either that they produce 
this effect through insensible primary qualities, or that 
they are themselves mere affections in us, or that, being 
qualities outside, the affections are not like them. These 
are opinions of people who hold an atomistic theory 
of primary and secondary qualities, but they are not 
Aristotelian. In fact, the most fundamental defect in 
Aristotle s natural philosophy is the supposition that 
heat and cold are primary contrarieties of matter in 
capable of further resolution. His opinion was that 

1 See Eeid s Works, ed. by Hamilton, Note D, on Primary and 
Secondary Qualities. 

2 Arist. De An. ii. G. 3 Id. Cat. 8 = 9 A 28 seq. 


heat and cold are real and original qualities of matter, 
derived from no others, and that they produce in us 
affections of heat and cold similar to themselves. This, 
morever, was his theory of the perception of all 

Thirdly, Hamilton is right in saying that, according 
to Aristotle, there is an identity between the external 
object and the object perceived. 1 But he is wrong in 
inferring from this identification that, according to 
Aristotle, the external object is presentatively perceived 
without any intermediate object. The identity is not of 
existence but of essence, not numerical but specific, 
not numero but specie. Aristotle supposed that in all 
members of a kind there is one form, and that, when 
one member of a kind produces another member, it pro 
pagates the form, or, as we say to this day in organisms, 
the species, from its own matter to the matter of the 
new recipient of the form or species. Thus he supposed 
man to beget man. 2 Hence, in sensible knowledge, he 
supposed that the external object propagates the form 
of the sensible quality, such as heat, without its own 
matter into the matter of the sense, which thus receives 
the form or species of heat into its own matter without 
receiving the matter of the body which propagates the 
heat. Therefore the hot body and the hot affection of 
sense are the same only as the impression on the seal 
is the same as the impression on the wax, or as the 
father is the same as the son ; that is, the same in form 
or essence, not in matter or existence, the same specie 
but different numero, like but not the same objects. 

According to Aristotle, then, the sensible object is 
not numerically identical with the sensible object, but 

1 Arist. De An. in. 2 = 425 B 25-7. 

2 Id. Met. Z 7-8, esp. 1033 B 29-1034 A 8. 


only identical in essence. It is the form or species, 
without the matter of the external object,, propagated 
into the senses. Aristotle was no intuitive realist. He 
held, indeed, that sense perceives the identical essence 
of the external thing, but not the external thing itself; 
and he held that it receives this essence into the sensi 
tive faculty, and does not apprehend it in the external 
world. In short, his theory was a new form of repre 
sentation, in which the object of sense was regarded 
no longer as a corporeal efllux, but as an incorporeal 
essence received without the corporeal matter from a 
corporeal object into the senses, and there perceived. 

As the objects of sensible knowledge are sensible 
species, so the objects of rational knowledge are intel 
ligible species, according to Aristotle. The difference 
is in the mode of production. The former are propa 
gated by external objects into the sensitive faculty, the 
latter by active intelligence into passive intelligence. 
Aristotle has not explained this mysterious influence of 
intelligence on intelligence in the same soul ; nor is it 

O o 

probable that he proceeded on any other fact than the 
consciousness that, while we depend on externals to 
perceive, we can command our own thoughts. It would 
be, however, useless to go into this question. The 
important point for our present purpose is that both 
sensible and intelligible species are, in the view of 
Aristotle, immaterial, not material, objects. In his philo 
sophy, for the first time, we come to the view that all 
the immediate objects of knowledge are immaterial facts. 
We must not therefore fly to the supposition that 
Aristotle thought them to be psychical because they 
were immaterial. We have not yet exhausted the mys 
teries of the Aristotelian form. A form is supposed 
by him to be not only one in connection with many 


matters of different members of the same kind, but also 
to be something different from matter, even when so 
closely conjoined with matter in fact, and so inseparable 
from it in definition, as concavity with nose in snubnose, 
and soul with body in an animal. Every form, the form 
of a triangle, the form of a stone, the form of a house, 
is an immaterial substance, even when conjoined with 
matter in a material substance. The form of God Him 
self is pure, not in the sense of being less material than 
other forms, but only in the sense of never being con 
joined with matter. Hence, sensible and intelligible 
species or forms are immaterial, not because they are 
in the soul, but simply because all forms are immaterial, 
according to Aristotle, who thought that if I per 
ceive a white paper, I receive from the paper into my 
sensitive faculty an identical essence of white, which 
was already incorporeal in the paper before it was com 
municated to the sensitive faculty of my soul. The 
object of sense, then, had, in his philosophy, ceased to 
be material, but had not yet become a psychical fact : 
it is an essence, which is not matter, whether it is 
without or within a soul. 

Descartes completed the separation of the sensible 
object from the external world. The Atomists had 
taken the first step by discovering that the object of 
sense is not the external thing, but an internal effect ; 
but they admitted that it is, like its external cause, 
purely physical, and no more has been proved to this 
very day. Aristotle, however, had proceeded to apply 
the hypothesis of incorporeal forms to sense, and sup 
posed that the object of sense is a sensible species, 
similar to the physical cause in identical incorporeal 
essence, but not in diverse corporeal matter. It remained 
for Descartes to take the final step and destroy the last 


vestige of resemblance to the physical cause by identi- 

O -L " J 

fying the object of sense with a psychical idea. 

The history of philosophy had insensibly led, or 
rather misled, Descartes into his ideal theory. In the 
philosophy of Aristotle the incorporeal is wider than 
the psychical, because all essences are incorporeal even 
in physical things. But in the interval between ancient 
and modern philosophy, the hypothesis of the incor- 
porealism of essences was discredited, partly by the 
attacks of Nominalism, but more successfully by the 
revival of natural philosophy, and especially by the 
return to Atomism, inaugurated by Bacon, from whom 
it passed to Descartes. Bacon discovered that the 
essence of anything physical is nothing but a uniform 
mode of its matter. 1 Descartes thought that it is only 
a psychical idea. 2 In these circumstances his hypo 
thesis of the sensible object developed itself, as it 
were, from the course of history. The sensible object 
had been identified by Aristotle with the incorporeal 
essence ; the incorporeal had been recently expunged 
by Bacon from the physical world ; the essence was 
limited by Descartes himself to the psychical idea. 
What more natural than to regard the sensible object 
also as a psychical idea ? 

Descartes, it is true, went back to the Atomists 
for the analysis of nature into corpuscles. lie might 
also, especially since Galen s discoveries in the nervous 
system, have restored the Atomistic theory that the 
object of sense is a physical effect on our organs, and 
have added that it is an effect on the nervous system. 
His writings do, indeed, show that he was not always 
certain whether the sensible effect is physical or psy 
chical. Sometimes he even seems almost to express 

1 Nov. Org. i. 51 ; ii. 17, 20, 52. 2 Princ. i. 58. 


himself as if the idea itself were not distinct from the 
nervous imprint. But he finally and deliberately sepa 
rated it from the physical effect in the brain in his 
Replies to the Objections raised against his Medita 
tions. The Eesponsio ad Secundas Objectiones con 
tains a synthetic statement of reasons for the exist 
ence of God, arranged in geometrical order, and the 
second definition is a formal definition of the idea, as 
follows : 

6 By the name, Idea, I understand that form of any 
thought, by whose immediate perception I am conscious 
of that same thought ; so that I can express nothing 
in words in understanding that which I say, but that 
from this very fact it is certain there is in me an idea 
of that which is signified by those words. And so 
it is not only the images depicted in the fancy that I 
call ideas : nay, these I here by no means call ideas, 
so far as they are depicted in the corporeal fancy, 
that is, in some part of the brain, but only so far as 
they inform the mind itself turned towards that part 
of the brain. 

The influence of Descartes did not at once make 
itself felt in all parts of philosophy. English natural 
philosophy in this as in other matters took an indepen 
dent course, which accounts for one finding Aristotle s 
theory of the sensible object surviving in Newton s 
Optics. In Quasst. 20 Newton asks : Aiinon sensoriuni 
animalium est locus cui substantia sentiens adest, et 
in quern sensibiles rerum species per nervos et cerebrum 
deferuntur, tit ibi prsesentes a prsesente sentiri possint ? 
Similarly English theology did not at first think it 
necessary to salvation to consider sensible objects, or 
sensation, or even consciousness itself, to be psy 
chical, as we may see from the following passage in 



Tritlieism charged upon Dr. Sherlock s new Notion 
of the Trinity, by a Divine of the Church of Eno*- 
land l :- 

I deny that there is any such thing as sensation, 
whether internal or external, belonging to spirits not 
vitally united to organised bodies. For sensation is 
properly the perception of a sensible object by a sensible 
species of it imprinted upon and received into the proper 
organ by which each sensitive faculty operates and 
exerts itself. This, I say, is sensation, and accordingly, 
as it is external or internal, so it has external or internal 
organs allotted to it; but still both of them corporeal. 
And therefore for this man to talk of spiritual sensa 
tion is nonsense and a contradiction in the terms, and 
consequently not to be allowed (p. 15). 

But mental philosophers, not only on the Continent 
but also in England, more quickly received the hypo 
thesis of a psychical object of sense. At first, Locke 
simply accepted the Cartesian idea. Then Hume dis 
tinguished the impression from the idea. Kant made 
6 phenomenon the fashionable term. Mill preferred 
sensation. But all agree in some psychical object or 
other. Moreover, mental physiologists have passed over 
from Aristotle and Newton to Descartes, when they 
ought rather to have retraced their steps from Newton 
through Aristotle to the Atomists. The Cartesian hypo 
thesis, that the object of sense is a purely psychical idea, 
is not so near the truth as Aristotle s hypothesis, that 
it is an incorporeal but not psychical species in the 
sensitive faculty ; nor is the Aristotelian so near as the 
Atomistic hypothesis, that it is a purely physical effect 
on the bodily organs. All that is required to make 
this last, or rather this first, the truth is to substitute 

1 Dr. South. 


for eilluxes mechanical motions, and for the bodily 
organs the nervous system sensibly affected. 

Meanwhile, says Bacon, let nobody expect great 
progress in the sciences (especially on their productive 
side) unless natural philosophy has been extended to 
the special sciences, and the special sciences reduced to 
natural philosophy. Hence it happens that astronomy, 
optics, music, most of the mechanical arts, and (what 
may seem more strange) moral and political philosophy, 
and the logical sciences, have little or no extent in 
depth, but only slide over the surface and variety 
of things : because, as soon as those special sciences 
have been divided and established, they are no longer 
nourished by natural philosophy ; which, from the 
sources and true contemplations of the motions, rays, 
sounds, texture, and structure of bodies, affections, and 
intellectual apprehensions, had been able to impart to 
them new force and increase. It is not at all wonderful, 
if sciences do not grow, when they have been separated 
from their roots. 1 The revival of Atomism by Bacon, 
together with the gradual establishment of the laws of 
motion in mechanics, from Galileo to Newton, produced an 
instauration of natural philosophy. Let us now, in the 
same spirit, return to natural philosophy, in order to 
restore mental philosophy. Iiiteritus rei arcetur per 
reductionem ejus ad principia. 

1 Bacon, Nov. Org. i. 80. 




Pcssimwni cnim omnium cst aiigurium quod ex Conscnsu capitur in rclus 

BACON, Kov. Org. i. 77. 

H 2 




PHILOSOPHY ought to begin in doubt. But I cannot 
doubt that I think. Cogito, ergo sum. As a thinking I 
being, I am a soul, distinct from the body. Soul is ; 
thinking substance; body is extended substance; they ; 
are heterogeneous to each other. The soul immediately 
apprehends ideas, innate, adventitious, and fictitious. 
The clearness and distinctness of ideas are a criterion of 
truth, and by the veracity of God, enable me to know 
objects beyond ideas. Starting from ideas, I infer a 
physical world of bodies and insensible corpuscles, whose 
qualities are partly like and partly unlike those which I 
perceive as sensible ideas, and whose insensible modes 
produce sensible ideas. These are the cardinal points 
of Cartesian idealism. 

Cogito, ergo sum. I think, therefore I am. This is 
the indubitable fact, which Descartes had the undying! 
merit of elevating into a principle in mental philosophy.) 
The proposition was not new. Aristotle asserted our 
consciousness of our operations, 1 and even recognised 
this fact as a proof of our existence. But he did not 
convert the proposition into a psychological principle. 
He rightly founded the distinctions of operations on the 
distinctions of their objects: hence his discovery of 
nearly all that is known in mental philosophy. He 

1 Eth. Nic. ix. 9, 9. 


wrongly neglected the consciousness of the operations 

about those objects : hence his tendency to dogmatism. 

Descartes supplied a defect in psychology when he 

discovered the necessity of using as a principle the con- 

jsciousness which says to each of us: I think; that 

is, I feel, perceive, remember, imagine, judge, reason, 

^ desire, will : I therefore am. 

It is a principle. Is it the only principle of psycho 
logy ? How far will this conscious fact, that I am, carry 
me ? I am conscious that I am a thinking subject. 
But two further questions immediately present them-, 
selves : what am I, and what do I apprehend ? What 
is the thinking subject, and what the apprehended ob 
ject? Now the mere consciousness that I think will 
v not of itself solve the nature of either subject or object. 
The new principle of thinking was no more fitted than 
the old principle of contradiction to be a universal 
source of all philosophy : it must be accepted, without 
pledging us to all the Cartesian deductions. 

What" is the thinking subject? What am I? This 
terrific question is answered by Descartes, as if it im 
mediately followed from the principle, I think therefore 
I am, but really by another argument. He cannot say, 
I am conscious that I now think, as soul, without a 
body. He therefore substitutes the hypothesis, I can 
suppose that I had no body and was still thinking. He 
then concludes that I, as thinking subject, am not body 
but soul. Thus, by an easy transition, he leads his 
readers from thinking subject to soul, and makes, not 
the original principle, but an hypothesis and a problem 
atic conclusion the real premises of his philosophy. 

In order that we may feel the weakness of this non 
sequitur, let us quote from the Discussion on Method, 
Part IV., the passage which immediately follows the 


enunciation of the principle, I think therefore I 
am : - 

In the next place, I attentively examined what I 
was, and as I observed that I could suppose that I had 
no body, and that there was no world nor any place in 
which I might be ; but that I could not therefore sup 
pose that I was not ; and that, on the contrary, from 
the very circumstance that I thought to doubt of the 
truth of other things, it most clearly and certainly fol 
lowed that I was ; while, on the other hand, if I had 
only ceased to think, although all the other objects 
which I had ever imagined had been in reality existent, 
I would have had no reason to believe that I existed ; I 
thence concluded that I was a substance whose whole 
essence or nature consists only in thinking, and which, 
that it may exist, has need of no place, nor is dependent 
on any material thing ; so that " I," that is to say, the 
mind by which I am what I am, is plainly distinct from j 
the body, and is even more easily known than the 
latter, and is such, that although the latter were not, it 
would still continue to be all that it is. 

I could suppose I had no body. What is the 
nature of this proposition ? It is an hypothesis of what j 
might be but is not. I am not conscious that I have no / 
body ; I am at best only conscious of the supposition, 
which does not become any less a supposition through 
my being conscious of making it. Nor is it deduced 
from the consciousness that I think, but is a separate 
hypothesis. Again, how do we get to the proposition, ; 
I am a thinking substance wholly distinct from the 
body ? It is a conclusion not from the original principle 
alone, but also from the subsequent hypothesis, requiring 
also a second hypothesis, that without a body I should 
still be thinking. 


We must, therefore, most carefully distinguish the 
original principle, cogito, ergo sum, from the subsequent 
conclusion, I am a soul. In the first place, I am con- 
cious of the former, not of the latter. I am conscious 
that I am a thinking subject : I am not conscious that 
jthis thinking subject is not body but soul. Secondly, 
in order to deduce the conclusion, the principle requires 
the intervention of two hypotheses that I could have 
no body and that I should still be thinking ; and in both 
/ cases I am conscious of making the suppositions, but 
\ not conscious of the facts that I have no body and am 
1 still thinking. But sectetur partem conclusio deteriorem. 
An hypothetical premise produces an hypothetical con 
clusion. The conclusion, then, that the thinking subject 
is not body but soul, has not the certainty of the 
rinciple, coqito, ergo sum, but is vitiated by the hypo- 
heses coy w ^ f h ^ Thus does Descartes lead his 


reader to confuse the thinker and the soul, and transfer 
tHe conscious certainty of being res coqitans to the hypo 
thesiiTof being res a corpore plane distincta. 

"That T am a thinking subject is a fact of conscious 
ness ; but what I am, as thinking subject, is a matter of 
argument. There are three possible alternatives : Jiie 
^body, the_soul, the man. Nor can we decide between 
these three alternatives by consciousness alone. Con 
sciousness, without hypothesis, never made a philoso 
pher either a materialist or a spiritualist. We must 
not make a fetish of consciousness, but interrogate it 
carefully, remember its superficiality, add to it observa 
tion, and combine both with reasoning. 

In discussions of this kind a false issue is generally 
raised at once by speaking of the consciousness of 
thoughts. This is an abstraction, useful indeed f r 
some purposes, but still an abstraction, or rather a 



double abstraction. There is no such a thing as con 
sciousness, and no such a thing as a thought ;_ I am 
conscious, and I am conscious that 1 think. Conscious 
ness and thought are not there, waiting for a subject ; 
they already have a subject, or rather subjects myself, 
yourself, every other thinker. Descartes, in a great 
measure at all events, avoided this fallacy of hypostasis- 
ing abstractions. He was aware that there is no con 
sciousness of thoughts, but I am conscious that I think. 
He surreptitiously changed the thinker into soul, but 
not into abstract thoughts. Those modern philosophers 
who suppose consciousness of thoughts are not votaries 
of consciousness, but victims of abstraction. 

I am, then, not thoughts, but a thinker or thinking 
subject. But what is this subject which thinks ? What 
part of me is the factor, or what parts are the factors of 
thinking ? In this mortal state, in which I cannot ap 
prehend myself without my body, I am not conscious 
that I think without my body. Nay, I am conscious that 
I think with my body. Whatever operation I take, I in 
variably find that I am conscious, not of the operation, 
which I may afterwards abstract, but of myself per- j 
forming it ; I am not conscious that I perform it by my 
soul without my body, because, though I am conscious, 
that I am a thinking subject, I am not conscious that) 
this is a soul ; nor am I conscious that I do it by my 
body without my soul, for reasons to follow presently. 
I am conscious that I perform every operation by my 
body, partly, somehow, and somewhere. I consciously 
feel pleased and pained in various parts of my body. I * 
cannot disengage my consciousness of toothache from / 
my mouth, or of headache from my head. LjLHL_coj}- 
scious of using my bodily senses in touch, taste, vision, 
hearing, and smell. I do not Consciously first feel the 


sensation and then refer it to the bodily member ; I am 
not conscious of these two steps. Seasoning is the 
highest kind of thinking ; I am conscious of doing it 
, in my head, and by no force of abstraction can I get it 
twJ out f m J bead. Similarly I am conscious that I will 
^ ^ in my head, and I am conscious that my head may ache 
w ith reasoning, and deliberating, and resolving. My 
(body is not a mere companion but a pnrf.npr 
f all jny thoughts. 

Bui consciousness is a superficial power. "In speak 
ing of the data of sense I remarked that by an illusion, 
arising from the confusion of sense and inference, we 
^cannot help seeming to be conscious that sense per- 
jpeives an external object, though we can make ourselves 
independent of the illusion by science, which dis- 
jtinguishes the external from the sensible. There is a 
similar illusion about our consciousness of the thinking 
subject, and fortunately we can explain it and conquer 
it by science. The illusion is that we perform some of 
our operations on the surfaces by the superficial mem 
bers of our bodies. The causes of the illusion are that 
we often observe the outer surfaces of our bodies when 
we are performing an internal operation, and we are at 
the same time unconscious of the inner structures and 
] motions of our nerves and brain. The way to make 
| ourselves conquer the illusion is by the study of science, 
j which shows that what performs the operation is not 
I the outer surface but the inner nervous system. For 
example, we are conscious that we see something red 
somehow by our bodily organs of sight. Now, though 
we are sensible of the optic nerve so far as it is sensibly 
affected with red, we are neither sensible nor conscious 
of it as nervously constituted. But from very early 
infancy we observe, i.e. directly infer from sensation, 



the surfaces of our bodies. By putting our hands on 
our eyes we find that they no longer see red, and we 
infer that it was our eyes that saw red. It is so with 
all our external senses, as they are called from this 
illusion of observation. Not consciousness, but obser 
vation from very early infancy, made us believe that it 
was the periphery that is sensitive. But the inference 
became automatic before we were attentively conscious, 
and we cannot help seeming to be conscious that our 
eyes see. Eeally, however, as science discovers at last, 
the eyes are but avenues to vision, and wliaLsees is not 
Qur_eyes but the optic nerve in connection with the 
brain. A more complicated instance is when a person 
who has lost a limb believes that the pain, which he 
really feels in the nerves, is still in the limb. His con 
sciousness told him but vaguely where he feels the pain, 
his observations connected it with the surface of the 
limb; hence the illusion. Science alone can conquer 
such illusions of observation. 

The rough-and-ready way of dealing with this evi 
dence is to draw the further inference that we do not 
localise any operation except by observation and ana 
tomy, and that consciousness has nothing to do with the 
body. But this inference goes far beyond the facts. 
Observation is limited to the surface of the body, but 
the operations, of which we are conscious, are not. 
Now, even when they are purely internal, we are still 
conscious that they are somehow performed by the 
body, without observation and before science. For 
example, we are conscious of the pangs of hunger in 
the region of the stomach, to descend to the depths of 
consciousness : to rise to its summit, we are conscious 
of the process of reasoning in the region of the head. 
But in neither case does observation of the surface of 


the body reveal the whereabouts of the operation : yet 
we are conscious of the body performing it, without 
waiting for science. 

But there is another defect, for which the conscious 
ness of the body as a factor in thinking is responsible. 
lit tells me very indefinitely what part is engaged in a 
[particular operation. The cause of this indefiniteness 
;is the unconsciousness of nervous structure and motion. 
The correction of it is the science of nervous structure 
and motion. Thus, confining ourselves entirely to in 
ternal operations, the locality of which is not accessible 
j to external observation, I am conscious of the pain of 
I hunger somewhere in the region of the stomach ; sciejq.ce 
\reduces this indefinite verdict to definiteness by proving 
jthe connection of the nerves of that region with the 
/brain. Consciousness again says indefinitely, I think 
in my head ; science tells me, Yes, in your brain. 

Here science only corrects consciousness : it does not 
contradict it. Consciousness apprehends the indefinite 
region at work, science discovers the definite nervous 
structure in the direction of that region. Secondly, 
unless consciousness apprehended the region, science 
could not assign the nervous structure ; if we were not 
I already conscious of reasoning in the head, anatomy 
1 would not convince us that we reason in the brain. 
Thirdly, sometimes consciousness apprehends the region 
without science having yet discovered the nervous 
structure ; for example, we are conscious, in what is 
inadequately called muscular sense, not indeed of mus 
cular motion but of the action of our limbs, though 
but vaguely and indefinitely ; but on this occasion 
science is still more vague and indefinite, having dis 
covered the nervous mechanism of muscular motion, 
but not of muscular sense. Finally, however wrong 



consciousness may be in the definite locality of a parti 
cular operation, science never disproves that we are 
conscious of its being performed somewhere in the 
body. I am conscious that I perform all my operations 
somehow or another, partly by the body, with more or 
less definiteness ; science discovers the definite locality, 
still within the body. 

There are two points, which sometimes appear in 
biological treatises, but are not proved. In the first 
place, as we have already seen, there is no biological > 
proof that cerebral motion is transmuted into a psy 
chical sensation. Secondly, biologists often distinguish 
a sensation from its localisation ; at the same time they 
sometimes confuse its localisation in the body with the 
inference of its external cause. There is a great differ-j 
ence between a sensation of an internal sensible object 
and the inference of its external cause, as we hav3 
already seen in this essay. But there is no difference 
between the sensation and its internal localisation in 
the sentient subject ; there is no proof of these two 
steps. I am conscious of the sensation in a locality of 
my body. Neither consciousness nor science proves 
that I first have a sensation, then localise it in my 
body, and, thirdly, infer its external cause. They prove 
together that I first have a sensation located in some 
part of my body, and then infer the external causa; 
which produces it. 

There is another point, which is proved in biology, 
but does not disprove the consciousness of the body as 
a factor in thinking. I refer to subjective sensations. |/ 
We have sensations similar to our ordinary sensations, 
but not produced by the ordinary external cause. Thus, i 
a prize-fighter may be made by a blow to see stars ; a 
drunkard under the influence of delirium tremens may 



have a vision of tlie devil. Such sensations are excel- 
ent instances to sliow that the sensible object is different 
from the external original, and is not always caused by 
it ; that there are internal causes of sensations in the 
/ nerves ; and that the superficial structure of the eye is 
\ a cause, not a subject, of vision. But they do not show 
jthat the soul is the sole subject of vision. A prize 
fighter seeing stars, a drunkard s vision of the devil, 
are odd proofs of psychical sensations. The term sub 
jective sensations is misleading, because, in the recent 
sense of the word, it suggests psychical, without 
proving it. 

There is no evidence that sensation, or any other 
| operation, is purely psychical. There is evidence that 
Jthe body is a factor in all thinking. It is the evidence 
of consciousness, interpreted by science. I am not 
conscious first of a sensation, and then of its locali- 
\sation. I am conscious that I feel, perceive, reason, 
/ will, partly by my bod}? . External observation connects 
some of these operations with the surface of the body. 
Science shows that I do all of them by my nervous 
system. Science dispels the illusion of observation, and 
corrects the indefiniteness of consciousness. Science 
further traces the continuity of the nervous system, and 
leaves no gap for purely psychical operations, . Xow, 
\ ordinary and scientific observation being limited to the 
jbody, if I were only conscious of mere thinking, I should 
know my body only as an unthinking cause. But when 
I cannot be conscious that I perform any operation 
Without being conscious that I perform it somehow in 
/my body, that I feel headache, that I use my bodily 
senses to see, touch, hear, and so on, and that I reason 
\in my head, scientific observation becomes an inter 
preter of my consciousness that I use my body to think, 


and shows that the part which I use is the brain in con 
nection with the nervous system. The body is a patent 
factor of the thinking subject. The neglect of it is the 
fallacy of spiritualism. 

It does not follow that the body is the sole factor of 
thinking. Man does not know the whole of himself, 
either by consciousness or by scientific observation ; the 
former is superficial, the latter limited. I am conscious/ 
that I perform my operations partly by my body : science 
observes the nervous system, and in combination with! 
consciousness, infers that the nervous system is that by 
which the body in part performs these operations. But 
I am not conscious that my body, nor does science 
observe that the nervous system, is the whole thinking 
subject. There is no operation which can be traced 
throughout its whole course. I am conscious that I 
use my bodily senses in sensation and my head in 
reasoning. Science observes the nervous system and 
brain. But it has not solved the problem of nervous 
and cerebral motion. If it solved that problem, it would 
still remain to prove that nervous motion is completely 
identical w r ith the operation of which I am conscious. 
It is partly so, because I am conscious of partly per 
forming the operation by the body, in which science ob 
serves the nervous system and the motion it performs 
during the operation. . But it is another thing to prove 
that the conscious operation and the nervous motion 
are completely identical, because I am conscious of the 
operation without observing it, and science observes 
the motion without being conscious of it. This differ 
ence of evidence does not, indeed, prove a complete 
difference, because nervous motion and conscious opera 
tion may be the same fact approached from different 
sides, but the very difference of evidence makes it dim- 


cult to prove a complete identity of fact. Another 
evidence might be evoked the method of explanation. 
If all the facts of conscious operations were known, and 
nervous motions were known, it might be urged that 
the former are explicable by the latter, as the facts of 
light are explicable by undulating motion. But there 
is a great difference in the two cases. In the case of 
li<rht, we can say that its facts are such as the known 
effects of undulation by the laws of motion. But the 
Operations, of which we are conscious, do not seem to 
Consciousness to be the kind of effects produced by any 
known motion according to any known laws of motion. 
{There is a latent factor in all thinking, the soul. The 
/neglect of it is the defect of materialism. 

Two opposite errors must be avoided, spiritualism 
and materialism. The former neglects the patent, the 
latter the latent, factor of the thinking subject. The 
former despises the consciousness of the body as a factor, 
and the science of the nervous system as the part of 
that factor, engaged in every conscious operation : the 
latter transgresses the limits of science. Hence the 
f former falsely supposes the subject to be all soul, the 
latter all body. Both neglect the man ; yet as men we 
think. There is room for an intermediate theory of the 
thinking subject ; for a theory which is founded on the 
combined evidence of consciousness, of observation, 
ordinary and scientific, and of reasoning about oneself; 
for a theory which avoids the opposite difficulties of 
disturbing the physical continuity of the nervous system, 
and of inventing a mere parallelism of neurosis and 
j psychosis. I suppose that brain and soul are co-opera 
tive factors in all conscious operations, in passive opera 
tions together affected by external causes, in active 
Operations together producing external effects. The 


thinking subject is man, thinking partly by his body, 
that is, his nervous cerebral system, and partly by a 
latent factor, his soul, co-operating, as by the composi 
tion of forces, in every operation. 

But what are the objects which I apprehend in think 
ing ? This is the second question, suggested by the 
consciousness that I think, but not answerable without 
further argument. Descartes assumed that all the 
immediate objects are psyehiral ideas, while physical 
things are only mediate objects known through the 
medium of ideas. So far as this theory recognises the 
distinction between the internal objects of sense and 
external objects of inference, it is correct, and in accord 
ance with the scientific evidences already given in the 
First Part of this essay. But it contains a further sup 
position, namely, that objents^of sense and all other 
immediate objects are not only internal but psychical, 
arejdeas. Descartes never proved this ideal theory. 

In the Third Meditation we find the following 
passage : 

Nevertheless I before received and admitted many 
things as wholly certain and manifest, which yet I after 
wards found to be doubtful. What, then, were those ? 
They were the earth, the sky, the stars, and all the other 
objects which I was in the habit of perceiving by the 
senses. But what was it that I clearly (and distinctly) 
perceived in them ? Nothing more than that the ideas 
and the thoughts of those objects were presented to my 
mind. And even now I do not deny that these ideas 
are found in my mind. But there was yet another 
thing which I affirmed, and which, from having been 
accustomed to believe it, I thought I clearly perceivedl 
although, in truth, I did not perceive it at all ; I mean 
the existence of objects external to me, from w 



those ideas proceeded, and to which they had a perfect 
/resemblance ; and it was here I was mistaken, or if I 
judged correctly, this assuredly was not to be traced to 
any knowledge I possessed. l 

Now Descartes does not state precisely how he 
arrived at this conclusion that what he perceived were 
ideas. No doubt he was unconsciously influenced by 
the previous course of philosophy, detailed in my last 
chapter, and thought himself entitled to accept the con 
clusion much more rapidly than he ought. But he 
probably also thought that it followed in some way 
from the principle, cogito from the consciousness, I 
think. Now it is true that I think includes the con 
sciousness, I sensitively perceive. But I am not con 
scious that my senses apprehend ideas. As I walk in 
the fields, I am conscious of perceiving something green, 
which, so far from being an idea or any psychical fact, 
appears to be not only physical but also external. 
yScience disabuses me of the externality, but not of the 
(materiality of the sensible object. What further evi 
dence, then, had Descartes to disprove its physical and 
prove its psychical character ? 

Descartes derived his ideal theory of the sensible 

object apparently from his principle, cogito, ergo sum, 

but really from his secondary hypothesis, I am a soul. 

Having convinced himself that the whole subject is soul, 

jljlie defined soul as a purely thinking substance, and 

jody as a purely extended substance. From these 

definitions he deduced the heterogeneity of mind and 

natter, of soul and body. Hence he thought it would 

follow that the soul by its very essence thinking cannot 

apprehend body by its very essence extended, but is 

limited to its ideas. The real Cartesian evidence is this : 

1 Ex vi meae perceptions, in the Latin edition. 


the subject is soul, the soul is such as to apprehend only/ 
ideas,; therefore all immediate objects are ideas. Bun / 
neither premise is proved. ** 

It is not true that the whole subject is the soul. 
Descartes, as we have seen, exaggerated the soul from 
a part to the whole thinking subject. The man is the 
whole subject : ffine body is part of that by which he 
Jhinks; and, being a factor in thinking as well as extended, \ 
it is not a purely extended substance. The assumption/ 
at the bottom of the Cartesian definition of body is thatf\ 
thinking and extension are different. So they are in) 
the abstract ; but the same thing may possess both attri- ( 
butes in the concrete. Number is not extension, but t 
the same thing is numerable and extended ; extension is 
not thinking, but the same body may be both extended I 
and think. When we appeal from abstractions to con- i 
sciousness, we find it does think. The body, therefore, 
is not purely extended substance, but also thinking. 
Again, the smil is a factor in thinking and is in other 
respects latent : it does not follow that it is nothing else. 
Rather such a supposition is impossible ; for, as Locke 
wittily remarked, men think not always, and if the soul 
were purely thinking substance, either it must always 
think in order to be, or it must have an intermittent 
existence, both of which alternatives are impossible and 
absurd. Descartes resolved body and soul into the two 
opposite abstractions of extension and thinking. But 
he did not thereby prove that body is purely extended, 
nor that soul is purely thinking, nor their heterogeneity, 
nor that the body is no factor in thinking, nor that the 
whole thinking subject is the soul. 

But if we concede that the soul is the whole thinking 
subject, and that thinking is accordingly a purely 
psychical operation, whether it be feeling, perceiving, 

i 2 


reasoning, willing, or what not, what do we know about 
its nature ? On this point we have a dictum of Sir W. 
Hamilton, so admirable that we cannot pass it by. We 
know, he says, and can know, nothing a priori of what 
is possible or impossible to mind, and it is only by obser 
vation and generalisation a posteriori that we can ever 
hope to attain any insight into the question. x The- 
iiost we know of the soul is that it thinks, whatever 
?lse it is ; we cannot enter further into its secret nature 
o determine what it thinks. We must, therefore, judge 
of it by its fruits. Now, when I appeal to conscious 
ness, I am not conscious of perceiving only ideas, but 
(physical things apparently external ; and when I correct 
the illusion of externality by science, I find that sense 
(perceives internal things, but not ideas ; and further, 
that it must perceive physical things within in order to 
linfer physical things without. I conclude, therefore, 
that, as we apprehend the physical as a fact, the soul 
must have a power of apprehending it ; for we only 
know what the soul must by what it does apprehend, 
lit is not true, then, that the soul is such as only to per- 
Iceive ideas. 

Even, therefore, if the first premise of Descartes be 
true, his second is false, so that his conclusion does not 
follow. If the soul is the whole thinking subject, it is 
not true that its nature is such as only to immediately 
i perceive ideas ; for all we know of its thinking is that, 
as a matter of fact, it immediately perceives physical, 
though internal, effects on the nervous system. Thinking 
we know is not extension, but know nothing about 
thinking to prevent it perceiving the extended, nor any 
thing about the psychical to prevent it perceiving the 
physical. Let vision be purely psychical, white seen can 

1 Hamilton s Metaphysics, Lect. xxv. p. 122. 



still be physical. Granted, then, that the subject is the / 
soul, it is a non sequitur that it perceives only psychical I 

A fortiori, if the subject is the man, he can perceive 
the physical in himself. A certain conditional plausi 
bility is given to the idealistic theory of the sensible 
object by the spiritualistic theory of the sentient subject. 
Although we cannot say that if the subject is purely 
psychical the object is psychical, we can say that the 
object is not psychical unless the subject is purely psychi 
cal. But if the body is a factor of the thinking subject 
there no longer remains any plausibility in the idea 
theory of the sensible object. The physical can appre 
hend the physical, the extended the extended, withi 
the nervous system. The thinking subject, body and 
soul, does apprehend the physical: it therefore can.j 
What we apprehend as a fact is better known than what 
we are to apprehend it. Knowable objects must be 
explained, not denied, by knowing subjects. 

Descartes was a_lear and distinct_ssxlter ; he was 
not so clear and distinct a thinker. His works are 
full of confusion. He was the first to confuse the 
object with the operation of sense. Hence, when he 
speaks of an idea of white, we never feel quite sure 
whether he means the white perceived or the sensa 
tion of white. Now, if the subject is soul, the operation 
is purely psychical ; and, if the object be undistinguish- 
able from the operation, it also becomes psychical : if 
the white perceived is the same as the vision of white, 
and this be psychical, that becomes psychical. But we 
found in the First Part that the white seen is not the vision 
of white, the sensible object is not the operation of sensa 
tion. Hence, it does not follow, even if the operation 
of vision be psychical, that the white seen is psychical. 


A further confusion was necessary before Descartes 
could call a sensible object an idea. Confusing it with 
a sensation would only have enabled him to call it a sen- 
Isation. But why an idea ? Because he merged sensation 
(in conception. There are two kinds of simple appre 
hension : sensation, the apprehension we have of an 
object when the original is present ; and conception, 
when the original is absent or non-existent. Aristotle 
had clearly distinguished them as cuo-#r?cris and <ai/- 
racrta, and their objects as aio O rjpa and <f)dvTao-p.a. But 
the poverty and abstractness of modern languages and 
the growth of conceptualism obliterated these dis 
tinctions, and enabled Descartes first to confuse the 
sensible with its sensation, and then the sensation with 
the conception or idea. Nothing can be more mislead 
ing than the word idea, because it may signify either 
the conception or the concept, to use later phraseology. 
But Descartes arrived at his theory that the sensible 
object is an idea by a fusion of sensible object, sensa 
tion, conception, and concept. 

A final confusion followed the rest. Wherever there 
is no distinction between object and operation, as in 
i feeling, there is none between the operation and its con- 
( sciousness. Accordingly, Descartes, having first confused 
the sensible object with the sensation and then the sen- 
. sation with the idea, having no object left, confused 
\ the operation of sensation with its consciousness. 1 The 
? white, its vision, its idea, its conception, its conscious 
ness became all merged : there was no distinction left 
between sensible object, sensation, idea, conception, and 
consciousness. Thus the sensible object historically be 
came a state of consciousness by a series of confusions, 

1 Cf. Princ. i. 9. 



from which mental philosophy has never quite recovered 

So much for the evidence of the Cartesian theory I 
that all immediate objects are ideas. He derived it 
not from the principle, Cogito, ergo sum, but from at least ) 
four hypotheses : 

(1) The subject is the soul. 

(2) The soul is such as to perceive ideas. 

(3) The sensible object is undistinguishable from 
the sensation. 

(4) The sensation is undistinguishable from the idea. ; 

Not one of these hypotheses is true ; at any rate, all 
are uncertain. But if any one of the hypotheses is 
false, it vitiates the reasoning ; and if any one is un 
certain, it renders the reasoning uncertain. The Car 
tesian method is apparently synthetic demonstration, 
but really synthetic hypothesis. There is a lesson of 
psychological method to be derived from it. We can 
not logically start with the subject, and from its sup 
posed nature deduce the immediate and mediate 
objects of knowledge ; but we must first find what ob-, 
jects the subject knows, as a fact, in the sciences, then 
the immediate objects of sense, and finally conclude that 
the nature of the subject is such that it can know what 
it does know. The method must be not synthetical but 
analytical, because it must proceed from the more cer 
tain to the less certain, not from hypotheses to facts, but 
from facts to hypotheses. 

We have not yet, however, exhausted the Cartesian 
theory of ideas as the immediate objects of knowledge. 
Although he thought that all sensible objects are ideas, 
Descartes was well aware that there are ideas which 
are net sensible. There are, according to him, three 1 


\Jsorts of ideas innate, adventitious, and fictitious. 
This celebrated theory of the origin of ideas has at all 
events two very great merits : first, it called attention to 
the important problem of the origin of ideas ; secondly, 
hinder the head of innate ideas, it recognises ideas 
kvhich are not sensible. He remarks that the philoso- 
Shers of the schools accept as a maxim that there 
s nothing in the understanding which was not pre- 
dously in the senses, in which, however, it is certain 
hat the ideas of God and of the soul have never 
jeen. l 

It is well known that Descartes repudiated the 
theory that some ideas are innate in the sense of being 
always present. In his replies to the objections raised 
against his Meditations, the Responsiones Tertias con 
tain the following passage : Denique quum dicimus 
ideam aliquam nobis innatam, non intelligimus illam 
nobis semper observari, sic enim nulla prorsus esset 
innata ; sed tantum nos habere in nobis ipsis facultatem 
illam eliciendi. 2 This doctrine of ideas, innate in the 
isense of elicited from one s own faculty of thinking, is 
developed at length in the c Notes on the Programme 
of Regius/ 3 and was the foundation of the celebrated 
maxim of Leibnitz : Nihil est in intellect!! quod non 
\prius in sensu nisi ipse intellectus. By innate ideas 
[Descartes meant ideas, not acquired, like adventitious 
jideas, by sense from external objects, nor yet inborn, 
but capable of being elicited from the faculty of think 
ing, which is supposed to be endued with a capacity of 
conceiving them. 

This Cartesian mystery of eliciting ideas from the 
I faculty of thinking is nothing really but the ordinary 

1 Discourse on Method, Part IV. 2 Page 102 (ed. 1685). 

3 Id. pp. 184-6. 


operations of consciousness and reasoning, hidden under 
a fine-sounding phrase. It is quite true that we find 
certain ideas in ourselves which have never been in 
sense. We arrive at some of them, such as that of 
thought and that of truth, not from sensation but from 
consciousness. But consciousness is a kind of sense, 
and ideas derived from consciousness of oneself are not 
elicited from oneself, but apprehended as belonging to 
oneself. They are, as Locke afterwards showed, ideas 
of reflection, not innate, but acquired by apprehending 
ourselves performing conscious operations. There are, 
indeed, other ideas of the insensible, which are not 
acquired either by sensation or by consciousness. We 
neither see God nor are conscious of God in us. Such 
ideas also are, according to Descartes, elicited not from 
sense, but from our faculty of thinking. In his Notes 
on the Programme of Eegius, after disposing of tradi 
tion and observation, he thinks himself entitled to con 
clude that the idea of God is innate in the sense of 
elicited from the faculty of thinking. But there is 
another alternative reasoning from sensation and 
consciousness. Logical reasoning is an. indirect origin 

When Descartes said that ideas were elicited from 
the faculty of thinking, perhaps he had some obscure 
unanalysed hint of ideas generated by reasoning. But, 
then, such ideas are not innate, but acquired, and are 
the most deviously acquired of all ideas. In the first 
place, we reason from sensation, and infer that there are 
objects, like the sensible, but insensible. We then con 
ceive an idea of the insensible. This is plainly the 
origin of the idea of a corpuscle, which is an idea 
neither sensible, nor conscious, nor innate, but acquired 
by reasoning from sense. Secondly, we reason from 



I sensation and consciousness, and infer other thinkino* 


beings. For example, we are conscious of being able by 
reason and will to produce good effects. By reasoning 
from sense we infer the goodness of nature. By com 
bining these evidences we infer a being who reasons 
and wills to produce the goodness of nature. We then 
conceive an idea of this being similar to ourselves, but 
infinitely more perfect in reason and will. This is at least 
(one origin of the idea of God, which is neither an idea 
iof sensation, nor of consciousness, nor innate, but ac- 
I quired by reasoning from sensation and consciousness. 

Before a theory of the origin of ideas can be ad 
mitted two conditions of hypothesis must be satisfied. 
Other hypotheses must have been eliminated ; and 
any hypothesis, which without going beyond known 
operations explains the facts, must be preferred to an 
hypothesis which supposes an unverified power. But 
1 the theory of innate ideas is imperfect in elimination 
jand in verification. It shows that not all ideas arise 
immediately from sensation, but it fails to show that 
the rest are not due to consciousness and reasoning, 
and accordingly the unverified power of eliciting ideas 
must yield to the verified powers of sensation, conscious 
ness, and reasoning, which are together a sufficient ex 
planation of the origin of ideas. 

We have now all the immediate data of knowledge,- 
and their origin, according to Descartes. They are the 
soul known as subject, and its ideas, innate, adventitious 
and fictitious, known as objects. What knowledge, then, 
even if we have innate ideas, should we get ? What 
apprehension of reality, immediate and mediate ? We 
should know that we really are souls. We should also 
know that we really apprehend ideas. But what else 
should we know mediately beyond the soul and its 


ideas ? Descartes replies : from our ideas \ve should [ 
know that there are real objects beyond them. 

Aristotle had distinguished simple and complex ap 
prehension, conception and judgment, and had pointed 
out that truth and falsity arise with judgment. As long 
as we merely apprehend an idea, e.g. of a man or a 
centaur, we express no belief about the existence of an 
object. But when we judge about objects we appre 
hend a relation of combination or separation, which, in 
its simplest but not its only form, is a relation of exist 
ence or non-existence ; e.g. a man exists, a centaur does 
not exist. Hence our judgment may be either true or 
false : true, if it agrees with a real relation of combina 
tion or separation ; false, if it does not. The question 
is, how are we to know that our judgments about objects 
are true? How are we to know that there is a real 
relation ? 

Descartes, though he confused two kinds of simple 
apprehension, sensation and conception, was aware of 
the distinction between conception and judgment. He 
also saw that the possibility of falsity begins with judg 
ments. 1 But he thought that true judgments can be 
derived from ideas themselves, by their own inherent , 
characteristics. He proposed a new criterion of truth, 
and a new method of forming true judgments from 
ideas themselves. 

In the first place, he thought that the mere idea of 
God proves God s existence. This theory he applied in 
two arguments, one of which proceeded from the idea 
of necessary existence. The mind, he says, from per 
ceiving necessary and eternal existence to be comprised 
in the idea which it has of an all-perfect Being, ought 

1 Meditation III. 


I manifestly to conclude that this all-perfect Being exists. 1 
This ontological argument, as it is called, which has 
become famous from the criticisms upon it, especially 
that of Kant, 2 and from its revival by Hegel, 3 is a most 
transparent fallacy. Descartes surreptitiously omitted 
the word idea. An idea only comprises ideas, and 
ur idea of God comprises, not necessary and eternal 
xistence, but only the idea of necessary and eternal 
xistence, which only proves that the idea of this all- 
perfect Being exists. 

The other argument proceeded from the objective 

reality of an idea ; that is, according to the proper 

meaning of objective, the reality of an idea quatenus 

objicitur intellectui. This argument follows the former 

argument in the Principles, 4 but is stated at greater 

length in the Third Meditation. Shortly, it comes to 

Jiis : more reality cannot be produced by less ; the idea 

>f God has more objective reality than the actual, or 

brmal, reality, of a finite substance ; therefore it cannot 

je produced by a finite substance, but must be received 

rom God Himself. The major is true ; the minor is 

alse, because the objective reality of an idea is always less 

real than the actual reality of the thinker, and therefore 

can be produced by him. God has more reality than 

man ; the idea of God has more reality than the idea 

bf man ; but man has more reality than his own 

jdea of God. We can therefore retort on Descartes 

the following syllogism : the less real can be produced 

by the more real ; the idea of God is less real than the 

thinker ; therefore the idea of God can be produced by 

the man who thinks it. As for the way in which a 

man produces, not God, but his idea of God, we have 

1 Princ. i. 14. 2 Critique, pp. 364-70 (Bohn). 

3 Logic of Hegel (Wallace), pp. 91 2. 4 i. 17-19. 



already described it. He produces it, not by the bare! 
idea of his own finite substance, but by reasoning from| 
nature to nature s God, and then forming an idea of 
a Being, reasoning and willing like himself, but infi 
nitely more perfect. Man has no power to produce 
God ; but, by reasoning to God s perfect existence, he 
can produce his very imperfect idea of God. The origin; 
of natural theology is reasoning : the origin of the idea[ 
of God is rational idealisation. 

Secondly, conceding the reality of God, though not 
proved by these two arguments from ideas, but rather 
by a third argument which he adds from our not having 
made ourselves, let us proceed to the further use of 
ideas as a criterion of truth by Descartes. He accepted 
the Christian doctrine that God is not the cause of our \ 
errors. 1 He pointed out that some of our ideas are ! 
clear and distinct, 2 others obscure and confused. He 
concluded that those ideas, which are clear and dis 
tinct, must be true, otherwise God would be a deceiver. 3 
In short, he made the clearness and distinctness of ideas, 
backed by the veracity of God, a criterion of truth, by 
which we may argue from ideas to objects beyond 

By this internal criterion of ideas, he supposed 
that from our psychical ideas we may infer a physical 1 
world 4 : 

Although we are all sufficiently persuaded of the j 
existence of material things, yet since this was before 
called in question by us, and since we reckoned the 
persuasion of their existence as among the prejudices 
of our childhood, it is now necessary for us to investigate 
the grounds on which this truth may be known with 
certainty. In the first place, then, it cannot be doubted 

1 Princ. i, 29. 2 Id. i. 45. 3 Id. i. 30. 4 Id. ii. 1. 


(that every perception we have conies to us from some 
object different from our mind ; for it is not in our 
power to cause ourselves to experience one perception 
rather than another, the perception being entirely 
dependent on the object which affects our senses. It 
may, indeed, be matter of enquiry whether that object 
be God, or something different from God ; but because 
we perceive, or rather, stimulated by sense, clearly and 
distinctly apprehend, certain matter extended in length, 
breadth, and thickness, the various parts of which have 
different figures and. motions, and give rise to the sensa 
tions we have of colours, smells, pain, &c., God would, 
without question, deserve to be regarded as a deceiver, 
if He directly and of Himself presented to our mind the 
idea of this extended matter, or merely caused it to be 
presented to us by some object which possessed neither 
extension, figure, nor motion. For we clearly conceive 
(this matter as entirely distinct from God, and from our 
selves or our mind ; and appear even clearly to discern 
that the idea of it is formed in us on occasion of objects 
existing out of our minds, to which it is in every respect 
similar. But since God cannot deceive us, for this is 
repugnant to His nature, as has been already remarked, 
.we must unhesitatingly conclude that there exists a 
certain object extended in length, breadth, and tliick- 
jness, and possessing all those properties which we clearly 
apprehend to belong to what is extended. And this 
extended substance is what we call body or matter. 

By the same internal criterion of ideas he thought 
that he could infer that distinction in nature which 
Locke called the distinction of primary and secondary 
qualities 1 : 

J As belonging to the class of things clearly appre- 
1 Meditation III. 




bended, I recognise the following, namely, magnitude, 
or extension in length, breadth, and deptli ; figure, 
which results from the termination of extension ; situa 
tion, which bodies of diverse figures preserve with 
reference to each other ; and motion or change of situa 
tion ; to which may be added substance, duration, and 
number. But with regard to lights, colours, sounds, 
odours, tastes, heat, cold, and the other tactile qualities, 
they are thought with so much obscurity and confusion, 
that I cannot determine even whether they are true or 
false ; in other words, whether or not the ideas I have 
of these qualities are in truth the ideas of real objects. 

The clearness and distinctness of our ideas are facts 
of our consciousness ; but we are also conscious that 
they do not always correspond to our knowledge. 
Many ideas are clear and distinct where the objects 
are known to be unreal. Nothing can be clearer or 
more distinct than the ideas I have of Achilles and 
Agamemnon, of Ulysses and Nestor. Am I, then, to 
infer that these Homeric heroes lived in the flesh? 
Many ideas are obscure and confused where the objects 
are known to be real. The idea of the earth as a vast 
globe revolving round the vaster sun is neither clear 
nor distinct. Yet the earth revolves round the sun. 
Nor do the degrees of truth correspond with the 
degrees of clearness and distinctness. My ideas of 
Hamlet and Macbeth are clearer and more distinct than 
my ideas of the Prime Minister and the Leader of the 
Opposition Am I to infer that the persons are also 
more real ? I have proofs to prevent such an inference, 
you will say. But that is to introduce another criterion, 
over and above the clearness and distinctness of ideas. 

Ideas are clear and distinct by proximity to sense, \ 
as well as by accuracy of science : hence, as science 



Irecedes from sense, it often proves insensible objects 
\to exist, of wliicli it forms but obscure and confused 
ideas. Science assures me that matter consists of incon 
ceivably small particles moving with inconceivable 
rapidity on the one hand, and on the other hand that it 
Bxtends over an inconceivable immensity of space. These 
things are known to exist. Yet the ideas of them are 
so far from being clear and distinct that I cannot be 
said to have any direct ideas of them at all. If I try to 
form an idea of a particle in a drop of water, I divide it 
and divide it, but the division baffles my conception. 
If I try to conceive the immensity of space, I enlarge 
my idea of a limited space, as the frog tried to swell 
himself out to the size of the ox, and with much the 
same success. Are we to say that these scientific facts 
are not real, because we have but obscure and indistinct 
ideas or rather have no direct ideas of them at 

Again, science is based on the distinction of the 

apparent and the real, in time and space, in bulk and 

\\ motion. The real in all cases is regarded as more truly 

freal than the apparent ; but the apparent is more 

^clearly and distinctly conceived. My idea of the ap- 

, parent sun moving apparently over the apparent earth 

! is clear and distinct : my idea of the real earth movino- 

{really round the real sun is obscure and indistinct. 

i Am I then to infer that the sun moves over the earth, 

|and not the earth round the sun ? Again, the ideas of 

secondary qualities in sense are as clear as, if not clearer 

than, the ideas of primary qualities. For example, the 

idea of sensible heat is as clear and distinct as that of 

(sensible extension. The difference is not in the ideas, 

but in the inferences of the qualities ; and there must 

be some other ground than ideas, which are equally 



clear and distinct, to justify the differences between our! 
inferences of insensible heat and insensible extension. 

To say that God does not deceive us is to raise a ! 
false issue. He does not deceive those who use sensej 
and reasoning by the laws of logic. But we should! 
deceive ourselves if we were to follow Descartes and 
substitute mere ideas for the logical organs of truth. 
We are often deceived when we have clear and distinct / 
ideas. We are deceived about the bodily locality of 
our sensations and the externality of the object of 
sense, about the reality of secondary qualities, about 
the beautiful and about the good. A man often has 
a clear and distinct idea of a duty which is no duty. 
I might justify any wickedness, if I allowed myself to 
argue, I have a clear and distinct idea of the rightness 
of this action, and God will not deceive me, therefore 
it is right. The Inquisition, no doubt, had a clear and 
distinct idea of the justice of punishing heretics, and a 
belief that God never deceived them : on the logic of 
Descartes, they would have been justified in punishing 
Galileo as a heretic, for saying that the earth goes 
round the sun. This lazy logic of ideas would justify I 
any arbitrary conclusion, and defy all rational criticism. 
For, who is to know whether or not one has clear and 
distinct ideas? But Descartes lived in a reaction 
against logic. 

An idea is an apprehension in the absence of an ex 
ternal object. It contains no opinion whether the object 
is only absent or also non-existent. Its clearness and 
distinctness depend on other causes besides the belief of 
existence, and especially on the proximity of the idea to 
sense. Hence conception does not in itself guarantee 
the existence of an external object. Moreover, we are 
conscious of its limits : everybody knows that however 



(well lie conceives, lie is not justified in judging without 
further evidence. If we were not conscious of the 
frequent disagreement of ideas with facts, God might 
have been a deceiver ; but, as it is, He does not deceive 
us into thinking that our clear and distinct ideas con 
form to facts, but, on the contrary, makes us conscious 
that they often do not, and gives us an opportunity of 
going beyond them by reasoning. We are conscious 
that our ideas do not justify judgments of existence 
without rational proof. 

But the words, conception and idea, are so vague 
that they often get confused with belief, just as the 
inconceivable is often confounded with the incredible. 
Descartes shows traces of this confusion, in the very 
act of drawing a valuable distinction between imagina 
tion and pure intellection, in the Sixth Meditation : 

To render this plain, I first examine the difference 
which there is between imagination and pure intel 
lection. For example, when I imagine a triangle, not 
only do I understand that it is a figure comprehended 
by three lines, but at the same time I intuite those three 
lines as formed by the glance of my mind ; and this is 
what I call imagining. But if I wish to think of a 
chiliagon, I equally well understand that it is a figure 
consisting of a thousand sides, as I understand that a 
triangle is a figure consisting of three, but I do not in 
^he same way imagine those thousand sides, or intuite 
tlhem as present. 

Everybody would at once suppose that by intellection 
he simply meant the belief that there is such a figure as 
a chiliagon ; but, if we look a few lines further down, 
we find the very reverse. He says that the mind, 
which understands, turns itself in a way towards itself 
/and considers one of the ideas which are in it ; and he 



repeats the same view in the Responsiones Quintae. 
According to Descartes, then, the pure intellection that 
a chiliagon is a figure consisting of a thousand sides is 
a consideration of ideas. When he thus merged the 
conception of ideas and the understanding of objects, 
no wonder he thought that clear and distinct ideas 
enable us to know objects beyond ideas. But, really, 
we judge very clearly that a chiliagon is a figure with 
a thousand sides, but we conceive a very obscure idea 
of so many sides, if we can be said to have any direct j 
idea of them at all. Conception is not co-extensive 
with understanding. The criterion of truth is not in 
herent in ideas. 

As it requires something more than clearness and 
distinctness of ideas to know objects, how do we know 
them? How do we know when our judgments agree 
with them ? What is the criterion of truth ? Objects 
are twofold, internal and external. About the internal 
we judge immediately by sensation and consciousness, 
the objects of sensation being effects of external objects 
on the nervous system, the object of consciousness, 
oneself as subject thinking in the widest sense : about 
external but similar objects beyond ourselves we judge 
from sensation and consciousness mediately by infer 
ence. Truth is the agreement of a judgment with the 
sensible, the conscious, or the inferred from the sensible 
and the conscious, on the logical rule that, if the 
premises are true, the conclusion is true. The criterion 
of truth is double ; being first the immediate appre- ! 
hension of the sensible and the conscious within, and 
thereupon the mediate apprehension of the similar 
but insensible and unconscious without, by parity of 
reasoning. Reasoning without the immediate data is 
mere consistency, upon them it is the consistency of 

K 2 


,rutli. Knowledge is tlie apprehension of reality, imme 
diately by sensation and consciousness, mediately by 

ogical reasoning therefrom. To know by reasoning 
equires at least two conditions ; sensible data and 

ogical consistency. Whether it requires more, we will 
decide, when we come to Hume and Kant. 

As, then, we know objects beyond ideas, not by the 
clearness and distinctness of these ideas, but by rational 
inference, what are the data required for this inference ? 
This question is the crucial test of the Cartesian philo 
sophy, which aspires to a knowledge of things through 
ideas. Descartes did not supply adequate data to infer 
the knowledge he admitted. Hence his philosophy 
ends in inconsequence. We have already seen, in the 
First Part, that it requires like data to prove like con 
fusions, and, therefore, physical data to prove physical 
conclusions. If all the data were psychical, physical 
objects would not be inferrible. If all the data of 
a man s knowledge were his soul and ideas, he could 
know nothing but other souls and ideas. But Descartes 
admitted that physical objects beyond souls and ideas 
are knowable. The data of knowledge, then, cannot 
fill be, as he supposed, a soul and its ideas. 

Descartes was a man of subtle genius, retiring, as it 
were, within the chamber of his own soul to survey his 
own ideas, and trying to think what they could reflect 
of a world without. Let us follow him into this retlre- 
pnent, and imagine ourselves each to be a pure soul 
contemplating pure ideas. A man must have a diili- 

ulty in performing this feat, because he neither is the 

me nor does the other. He cannot rid himself of his 

jody, nor fail to contemplate the effects on his nerves. 

Philosophers take advantage of this superhuman difu- 

bulty ; feigning a psychical man, but knowing all the 



time that each of us will add the physical factor and! 
complete his human being. Hence a man fails to realise! 
the extraordinary consequences that follow, if he really 
has to suppose himself to be a disembodied soul, per-j 
ceiving nothing immediately but incorporeal ideas..! 
However, let me try. 

I should not be able, in the first place, to infer that 
the body is a material cause of my ideas, nor that my 
ideas are an efficient cause of moving the body. As all 
the causes and effects immediately perceived by me 
would be my psychical soul and its ideas, all those that 
I could mediately infer would be psychical souls and 
ideas. Now, Descartes asserted the heterogeneity of soul 
and body, but not exactly their incommunicability, still 
less the non-existence of the body. His view was that 
soul and body are in contact in the pineal gland, that 
the motions of the body cause ideas and ideas volitions, | 
while this interaction requires the concourse or assistance! 
of God. This hypothesis, or series of hypotheses, is \ 
anatomically false, because it disturbs nervous continuity ; 
without proving any connection between the pineal 
gland and thinking. Logically, it is false on Cartesian 
principles, not merely because soul and body are sup 
posed heterogeneous, but because all the causes and 
effects immediately perceived being supposed psychical, 
a physical body either as cause or effect of ideas could 
not be inferred. There is no proof that Descartes him 
self ever drew this conclusion, though involved in the 
Cartesian theory. He kneiv that the body is scientifi 
cally inferred to be cause and effect. Consequently, his 
theory that soul and ideas are all the data of inference 
must be false, because they cannot be the data of that 
scientific inference. 

It was left for his successors to draw the logical 


conclusion and contradict science. The Cartesian School 
denied that the body is either cause or effect of ideas. 
Instead, Geulinx invented occasionalism, or the hypo 
thesis that on the occasion of bodily changes God calls 
forth an idea of perception in our soul, while on the 
occasion of an idea of volition in our soul He moves 
our body for us. Malebranche developed this doctrine 
into the vision of all things in the Deity. Leibnitz, 
rightly characterising occasionalism as a perpetual 
miracle, had recourse to a pre-established harmony 
between body and soul, established by God before our 
creation. But the pure idealists have a more logical way 
out of the difficulty than any of the Cartesians. It is 
that no body is known to exist at all. If all immediately 
known causes and effects were my soul and its ideas, I 
should have no data to infer a physical body, much less 
that it is wound up like a clock to go with my soul. 
Nevertheless, Descartes was right in saying that I have 
a body, whose motions science proves to be causes 
and effects of thinking. Therefore, immediately known 
^causes and effects are not all my soul and its ideas, from 
which no body could have been inferred. 

Secondly, if all the data were my soul and its ideas, 
and I could somehow or other infer the body, at any 
rate I could not infer that my body was a part of 
myself. How should I know that I have a body ? 
Precisely as I should be supposed to know any other 
external object, mediately through ideas. I should 
have an idea of warmth, and refer it to a fire ; an idea 
lof toothache, and refer it to the body. But if I knew 
my body in this indirect manner, I should not regard it 
any more than the lire as part of myself. It may be 
(objected that I should find it always with me. But so I 
ido the earth and the atmosphere. It would seem with 



tliem part of my environment ; not a part of me, but 
only my nearest and dearest companion. Descartes 
vacillated on this point. When he is deducing the con 
sequences of his hypothesis, he says, I am the mind by 
which I am what I am, as distinct from the body. l 
When he is saving facts, he contradicts his hypothetical 
deductions. Nature, he says, teaches me by those 
senses of pain, hunger, thirst, &c., that I am not only 
present in my body as a sailor in a ship, but so closely 
conjoined with it, and, as it were, intermixed, that I 
compose something one with it ; !} and, again, it is 
plainly certain that my body, or rather myself as a 
whole, so far as I am composed of body and mind, can 
be affected by various advantages and disadvantages 
from surrounding bodies. Quite so ; but he has given , 
us two inconsistent theories of personal identity, of 
which the first is false, the second true, but quite incon 
sequent, if I am a soul perceiving my own ideas. 

If, then, I steadily suppose myself a soul perceiving 
its ideas, I find that I cannot infer my own body to be 
a part of myself. This is a conclusion so impossible, 
so absurd, so ludicrous, yet so common to idealists, that 
it is no credit to modern thought to have tolerated for 
so long a time hypotheses from which it logically fol 
lows. Eeally, Descartes was right in inconsequentlyj 
and inconsistently admitting that he is body and soul. 1 
But the admission is fatal to the hypothesis that he is 
a soul, and to the hypothesis that the objects of all im 
mediate perceptions are ideas. If I perceived nothing 
but ideas, I could not know my body. Since I do 
know my body, I must perceive something else but 
ideas. The truth is, I know my body in four ways : 
first, I am conscious of it as a factor of myself as 

1 Discourse on Method, Part IV. a Meditation VI. 


thinking subject ; secondly, my senses perceive my own 
nervous system as sensibly affected, although . I have 
long confused this sensible object with the external 
cause I infer; thirdly, from one part of my body 
sensibly affected I infer another part ; e.g. I see a re 
flection on my optic nerve, and infer that it represents 
my hand ; fourthly, by science, founded on all these 
evidences, I know that I am a single organism. By 
combining all these ways of knowing my body, I know 
it better than anything else, and to be a part of myself. 

Having feigned myself to be a pure soul contem 
plating pure ideas, I could not infer my own body, or 
at any rate not as part of myself. But could I infer 
any external body ? Descartes, in a passage already 
^quoted, 1 dwells on the involuntariness of sensible effects, 
and many of the idealists have relied on this argument 
for an external cause. I freely admit the force of the 
argument. But what sort of external cause ? I could 
infer only causes similar to those in the data. Either 
fcy sensation or by consciousness, or by both, I should 
apprehend an interaction of my soul and ideas, and 
of my ideas among themselves; and also that some 
of my ideas are involuntary ; from which the parity of 
reasoning would then allow me only three logical alter- 
jnatives : another soul ; this would be Berkeley s Divine 
Spirit : a cause unknown ; this would be Hume s inex- 
.plicable something : another idea ; this would be Hegel s 
absolute idea. 

A logical idealism would further conclude that, so 
far from being known to be a physical part of myself, 
interacting with my soul and ideas, my body, if known, 
is something psychical, and, not being my soul, is a 
system of my ideas, while any other soul, if there is 

1 Princ. ii. 1. 



iSuch a thing, must follow from another similar system 
of my ideas. Such a logical deduction escaped Des- 

I cartes, but it has not escaped Mill, who only sub- 

stitutes sensations for ideas : 1 

Whatever sensation I have, I at once refer it to 
one of the permanent groups of possibilities of sensa 
tion which I call natural objects. But among these 
groups there is one (my own body) which is not only 
composed, like the rest, of a mixed multitude of sensa 
tions and possibilities of sensation, but is also connected, 
in a peculiar manner, with all my sensations. Not only 
is this especial group always present as an antecedent 
condition of every sensation I have, but the other 
groups are only enabled to convert their respective 
possibilities of sensation into actual sensations by 
means of some previous change in that particular one. 
I look about me, and though there is only one group 
(or body) which is connected with all my sensations in 
this peculiar manner, I observe that there is a great 
multitude of other bodies, closely resembling in their 
sensible properties (in the sensations composing them 
as groups) this particular one, but whose modifications 
do not call up, as those of my own body do, a world of 
sensations in my consciousness. Since they do not do 
so in my consciousness, I infer that they do it out of 
my consciousness, and that to each of them belongs a 
world of consciousness of its own, to which it stands in 
the same relation in which what I call my own body 
stands to me. 

Now, the scientific Descartes knew well that bodies 
are neither non-existent nor unknown, neither sensations : 
nor ideas. He admitted that involuntary sensible dataj 

1 Examination of Sir William Hamilton s Philosophy, pp. 244-5 
cf. Lotze, Metaphysics, Book III. chap. iv. 


[enable us to infer physical bodies as causes beyond 
\sense and conception in the external world, that these 
bodies consist of insensible particles, that the external 
/world is like the sensible in some qualities, unlike in 
lothers, and that the modes of insensible particles pro 
duce sensible effects on our bodies, which are physical 
parts of ourselves ; after the first step, proceeding 
logically enough from inference to inference. Let us 
add to our previous quotations one passage as a sample 
of this profound scientific spirit : 

But to the insensible particles of bodies, I assign 
determinate figures and magnitudes and motions, as if I 
had seen them, and yet I confess them to be insensible ; 
and therefore some will perhaps ask, whence then I 
recognise them such as they are. I answer that I first, 
-from the simplest and most known principles, whose 
knowledge has been implanted by nature in our minds, 
jconsidered generally, what could be the principal differ 
ences among the magnitudes and figures and positions 
)f bodies, insensible only on account of their smallness, 
ind what sensible effects would follow from those various 
concourses. And then when I noticed some similar 
effects in things sensible, I considered that they arose 
from a similar concourse of such bodies ; especially since 
no other mode of explaining them seemed capable of 
being excogitated. l 

But the psychological Descartes could not logically 
[take the first step. He had supposed, as the simplest 
and most known principles, hypotheses about the 
/subject and its data, which never could have been the 
I premises of such a science of bodies and their insensible 
particles. If all immediately perceived effects and 
Icauses had been soul and ideas, there would have been 

1 Princ. iv. 203 



no primary data to infer bodies not even one s own 
body, much less other bodies, and their corpuscles! 
whose structures and motions cause sensible effects in 
one s own body. But, as Descartes admitted, bodies are 
known and inferred from sensible data. Therefore the! 
data cannot be soul and ideas. From similars dis- 
similars cannot be inferred. From soul and ideas, no 
thing else follows. But something else is known to 
science; therefore, not from soul and ideas. Physical! 
bodies and corpuscles, structures and motions, require I 
physical data of sense. 

After the dogmatism of medieval philosophy, Dggr., 
cartes was right to doubt. He was right also in begin 
ning with the certain fact of consciousness; I think, 
therefore am. But, at the same time, he forgot that 
there are other facts of consciousness. There is a 
universal consciousness of the thinking subject, but 
there is also a scientific consciousness that the thinking 
subject knows physical objects. Instead of this, Des 
cartes substituted the hypothesis that the thinking sub 
ject is a soul which perceives ideas, and then, in defiance 
of logic, attempted a synthetical deduction from this 
idealistic hypothesis of psychical data of sense to a real 
istic knowledge of physical objects of science. The de 
duction may be attacked both by enstasis and elenchus ; 
in its premises and in its conclusion. On the one hand, 
the subject is not purely psychical, and, if it was, would 
not be limited to psychical data : on the other hand, if 
the data were psychical, we could not infer physical 
objects of science, which are admitted by Descartes, and j 
are more certain than any hypothesis of the nature of 
the subject and its data. Hence the hypothesis of soul 
and ideas must be surrendered, because the thinking) 
subject is not the soul but the man, because sensible i 


objects are not ideas but physical effects on the nervous 
system, and because soul and ideas would not enable 
man to infer physical objects of science. Descartes, the 
original genius of modern idealism, was too introspective. 
Of himself he says, Totos dies solus in hypocausto 
morabar, ibique variis meditationibus placidissime vaca- 
bam. l This seclusion in a hot room is an admirable 
way of distilling thoughts, provided only these vapours 
of the heated brain can be condensed into a knowledge 
of the outside world. 

1 Diss. dc Methodo, ii. 




LOCKE, at the outset -of the c Essay concerning Human 
Understanding, states that it is his purpose to enquire 
into the original, certainty and extent of human know 
ledge and opinion, without troubling himself about the 
essence of mind. 1 That js^ he r eject s_tlie Cartesian 
method of using the nature of the thinking subject to 
cTecluce our knowledge ; and rightly, because it was a 
method from the less to tlieTmore certain. But he leaves 
the Cartesian deduction, that the data o the under 
standing are ideas, simply removes the hypothesis from 
the premises to the conclusion, and no where throughout 
gives any new evidence that ideas are flip ^ Q * Q r>f Irnrror. 
jedge. The hypothesis of the soul is thus replaced by 
The hypothesis ot ideas, as a principle. Now, there had 
been some plausibility in the argument the subject 
is the soul, therefore its immediate objects are ideas. 
There was iiotliing butpetitioprincipii in the hypothesis - 
the immediate objects of understanding are ideas. Yet 
this hypothesis in one form or other has remained ever 
since Locke s time as the putative principle of all idealism. 
Many a philosopher, who has with Locke recovered 
from the Cartesian hypothesis that the subject is soul, 
and has followed Hume in correcting Locke s confusion 
of sensations and ideas, nevertheless clings to the hypo- 

1 Essay, I. 1, 2. 


thesis that all immediate objects are some psychical state 
or other, without any evidence, whether of Cartesian 
deductions, or of psychological consciousness, or of 
natural science. 

Locke, having begun at a new beginning, pro 
ceeds to his method, which is as synthetical as that of 
Descartes : 

I shall pursue this following method. 
*- First, I shall inquire into the original of those ideas, 
notions, or whatever else you please to call them, which 
a man observes, and is conscious to himself he has in 
his mind; and the ways whereby the understanding 
comes to be furnished with them. 

Secondly, I shall endeavour to show what know 
ledge the understanding hath by those ideas, and the 
certainty, evidence, and extent of it. 

Thirdly, I shall make some inquiry into the nature 
and grounds of faith or opinion, whereby I mean that 
assent which we give to any proposition as true, of 
whose truth yet we have no certain knowledge. And 
here we shall have occasion to examine the reasons and 
degrees of assent! l 

From this passage w^e can see how vain is psycho 
logical synthesis. The smallest mistake at the beginning 
vitiates the whole procedure and every consequence. A 
man is here said to be conscious of having ideas in his 
mind. It is true that he is conscious of having ideas. 
But even the followers of Locke himself would deny 
that this is all he is conscious of. Hume would say 
that he is also conscious of impressions, and Mill would 
add judgments. Yet to a philosophical use of the syn 
thetic method by Locke it was necessary that ideas should 
be all the materials of knowledge ; for the next question 

1 Essay, I. 1, 3. 

CHAP. vr. LOCKE 143 

is -wlial knowledge can be gained by ideas; which is 
a false issue, if ideas are not the whole material of 
knowledge. But as they are not the whole, it is not to 
be wondered at that, in the sequel, Locke oscillates 
between two contrary tendencies, a logical but false 
^reduction of knowledge to ideas, and an illogical but 
true extension of it to things beyond. Moreover, to 
inconsequence he adds inconsistency. He tries to begin 
with an understanding of ideas and end with a know 
ledge of things. 

The firstfruits of idealistic hypothesis are at once 
manifest. Having assumed that ideas are all the materials, 
he consistently assumes that they are all the objects of 
understanding : 

Thus much I thought necessary to say concerning 
the occasion of this inquiry into human understanding. 
But before I proceed on to what I have thought on this 
subject, I must here, in the entrance, beg pardon of my^ 
reader for the frequent use of the word idea, which he 
will find in the following treatise. It being that term 
which, I think, serves best to stand for whatsoever is 
the object of the understanding when a man thinks, 1^ 
have used it to express whatever is meant by phantasm, 
notion, species, or whatever it is which the mind can be 
employed about in thinking ; and I could not avoid 
frequently using it. l 

These words, which, if anywhere, ought to have 
come as a proved conclusion at the end, occur as an 
undoubted principle at the entrance of the Essay. They 
contain a double hypothesis ; first, that ideas are the 
immediate, secondly, that they are all, the objects of ^ 
understanding,(and therefore of knowledge. ?/ The first 
part is the ideal hypothesis of Descartes, the second is 

1 Essay, I. 1, 8. 


Locke s corollary. It is a logical corollary, not however 
scientific, but hypothetical from an hypothesis. Three 
hypotheses started modem idealism; the subject is 
psychical, the data are psychical, the objects are 
psychical. Never was such a gigantic system of petitio 


The aftermath of idealistic hypothesis appears at the 
very end of the Essay. After adopting ^the Stoic divi 
sion of the sciences into physics, ethics and logic, he 
concludes in the spirit of science, but in utter contra 
diction of his original hypothesis, with the following 
peroration : 

This seems to me the first and most general, as well 
as natural division of the objects of our understanding. 
For a man can employ his thoughts about nothing, but 
either the contemplation of things themselves, for the 
discovery of truth, or about the things in his own power, 
which are his own actions, for the attainment of his own 
ends ; or the signs the mind makes use of, both in the 
one and the other, and the right ordering of them for its 
clearer information. All which three, viz. things as they 
are in themselves knowable ; actions as they depend on 
us, in order to happiness ; and the right use of signs in 
order to knowledge, being toto cado different, they seemed 
to be the three great provinces of the intellectual world, 
wholly separate and distinct one from another. l 

In the same chapter he has already told us what he 
includes under things and signs. On the one hand, by 
signs he means ideas and words. 2 On the other hand, 
under things, he includes, as objects of understanding, 
the nature of things, their relations and their manner 
of operation ; while physics is, as he says, the know 
ledge of things, as they are in their own proper beings, 

1 Essay, IV. 21, 5. = Ib. IV. 21, 4 ; cf. IV. 5. 


their constitutions, properties, and operations, whereby 
I mean not only matter and body, but spirits also. * 
He finally admits, then, that things and ideas are toto 
ccelo different, that not ideas but things and their rela 
tions are the objects of physics and natural philosophy, 
and that not only ideas, but also things, are objects of 
understanding, knowledge, and science. Which was 
right, the original hypothesis of ideas, or the final admis- ^ 
sion of things ? The latter, because things inconceiv 
able but not incredible are objects of science. Locke, like 
Balaam, came to curse, but went away blessing. 

To return to the original hypotheses : the conse- 
quence is that the whole emphasis of the Essay falls, on 
the origin of ideas, as Locke himself admits at the very*- 
beginning of the Second Book. 2 Every man being 
conscious to himself, that he thinks, and that which his 
mind is applied about, whilst thinking, being the ideas 
that are there : this is his assumption : it is in the 
first place to be inquired, how he comes by them : this 
is his hypothetical conclusion. Meanwhile, the origin 
of knowledge is postponed till the Fourth Book, and the" 
Second and Fourth Books are never welded together. 
This is the beginning of a serious evil in modern philo 
sophy, the emphasis laid on the origin of ideas in pre 
ference to the far more important problem of the origin 
of knowledge, and the tendency to let the limits of ideas 
determine the extent of knowledge. But ideas do not 
dictate knowledge so much as knowledge dictates ideas. 

Locke begins the problem of the origin of ideas well by 
rejecting innate ideas. No doubt most of his objections 
touch the broader form of inborn ideas rather than the 
elicited ideas of Descartes. But they have the merit of 
pointing out that many ideas, supposed universal, are not 

1 Essay, IV. 21, 2. 2 Cf. also I. 1, 8. 



possessed by savages, and Locke in this respect has been 
confirmed by modern travellers. 1 Moreover, he touches 
Descartes himself, when he shows that experience has 
not really been eliminated, 2 and that consciousness, or, 
* as he usually says, reflection, is not a mystical revela 
tion, but an inner sense. As sensation apprehends sen 
sible objects only when present, so consciousness appre 
hends one s own operations only when one performs 
them. There is no greater source of error in philosophy 
Jhan the confusion of the intuitive with the a priori^ and 
of the conscious with the innate. Consciousness is an 
intuitive, not innate nor a priori, experience of oneself 
performing operations. 

Locke did a signal service in showing that there are 
two kinds of sense, sensation and reflection : 

Let us then suppose the mind to be as we say, 
white paper, void of all characters, without any ideas ; 
how comes it to be furnished ? Whence comes it by 
that vast store, which the busy and boundless fancy of 
man has painted on it, with an almost endless variety ? 
Whence has it all the materials of reason and know 
ledge ? To this I answer in one word, from experience : 
in that, all our knowledge is founded ; and from that it 
ultimately derives itself. Our observations employed 
either about external sensible objects, or about the internal 
operations of our minds, perceived and reflected on by our 
selves, is that which supplies our understandings with all 
the materials of thinking. These two are the fountains of 
knowledge, from whence all the ideas we have, or can 
naturally have, do spring. 3 

Modern criticisms of this theory often turn on the 
comparison of the mind to white paper, which is said to 

1 Cf. Moffat, Missionary Labours in South Africa, chap. ix. 
* Cf. Essay, I. 2, 1 ; II. 1, 1. II. 1, 2. 

CHAP. vi. LOCKE 147 

be inconsistent with evolution. But Locke rather over 
looks evolution than contradicts it. The theory of 
evolution is often exaggerated. It shows that our senses 
become more and more readily adapted to apprehend 
their objects when presented. It does not show that 
they ever come to evolve ideas or apprehend anything a 
priori. Its evidence is in favour not of a priori ideas, but 
only of intuitive perception. For example, the more the 
senses have been exposed to light the quicker and clearer 
they have apprehended its sensible effects when presented; 
by its action a special sense of vision has been gradually 
evolved to perceive them ; but there is no evidence that 
at last vision will, of itself, without light being presented, 
apprehend sensible light a priori. Such a jump from 
light presented in sense to light constructed by sense is 
not proved by evolution, but arises from confusing the 
intuitive with the a priori. Evolution has shown that 
we hereditarily tend to use our organs better, and that 
by use the organs become more differentiated ; but it 
has not shown that they ever evolve an a priori idea. 
Now Locke, it is true, overlooked hereditary adapta 
tion ; but he was quite right, and would be right to-day, 
in resisting a priori ideas, in saying that we begin 
without any ideas, and in recognising two kinds of 
sensitive intuition, sensation and reflection, both pre- 

The really vital question for the critic of the Essay 
is a question seldom asked. All knowledge begins^ 
with sense ; but what are the objects of sense ?_ Locke s 
answer is, ideas ; ideas presented to both senses ; ideas 
of sensation and ideas of reflection. His doctrine of ideas 
was modelled on that of Descartes. Perhaps he dis 
tinguished sensation from conception better than his pre 
decessor, but he left the consequences of the Cartesian 

L 2 


confusion of these operations in his doctrine that ideas 
are the objects alike of sensation and conception. Again, 
he followed Descartes in confusing object and operation, 
the idea and its perception. 1 The object of sensation, 
then, being regarded as an idea, the idea as nothing 
but its perception, and the perception as psychical, it 
follows that the object of sensation, with Locke as with 
Descartes, becomes a psychical result in our minds, dis 
tinguished not only, as it should be, from the external 
object, but also from the nervous impression, as it should 
not. If then, says he, in speaking of the ideas of 
primary qualities, external objects be not united to 
our minds when they produce ideas in it, and yet we 
perceive their original qualities in such of them as singly 
fall under our senses ?/ tis evident that some motion * 
must be therein continued by our nerves, or animal 
spirits, by some parts of our bodies, to the brain, or the 
seat of sensation, there to produce in our minds the 
particular ideas we have of them." 2 Thus the ideal 
hypothesis of Descartes was accepted by Locke, and 
without further evidence. Moreover, it remains to this 
day the current hypothesis, with the sole alteration of 
idea into sensation. But, as we have already found, the 
sensible object, though internal, is not the sensitive opera 
tion. Even, then, if the sensation were a purely psychical 
operation, it would not follow that the sensible object 
is either a psychical sensation or a psychical idea. 

Locke also added to the doctrine of ideas ; and his 
fir^t addition was the sensible idea of resistance. 3 Des 
cartes, with his mathematical genius, had emphasised 
the mathematical qualities of body, and especially exten 
sion, by which he defined it. 4 Locke accepted extension 

1 Essay, II. 8, 8 ; II. 10, 2 ; II. 19, 1. 
- II. 8, 12. :i II. 4. 4 Descartes, Princ. ii. 4. 


LOCKE 149 

and the sense of extension, but went on to show that 
resistancejs also necessary to body, and therefore added 
a sense of resistance. But he spoilt this great contri 
bution to the philosophy of matter and sense by his 
theory of ideas. If I perceived nothing but sensations 
or ideas, I should perceive only a sensation or an idea of 
resistance. I should not perceive one part of my body, 
JDP. nervous system, resisting jm_other ; I should have to 
infer it. But there would be no data for the inference,. 

for from psychical sensations or ideas physical resist 
ance between parts of a body would not follow. The 
sense of resistance, therefore, supplies a new argument 
to prove that the real object of sense is the nervous 
system, and its various parts resisting one another. 

A^ain, Descartes had confined the ideal theory to 
sensation ; he had allowed a direct consciousness of 
thinking. Locke, with more consistency though with 
less truth, interposed an idea not only between outer 
sense and the nervous impression, but also between 
inner sense audits operations ; so that the direct objects* 
are ideas of sensation and ideas of reflection. But 
Descartes rightly regarded consciousness as a direct 
apprehension of thinking ; and Locke, instead of trans 
ferring the ideal theory to consciousness, should have 
retracted its application to sensation, and regarded sen 
sation as a direct apprehension of the nervous impression. 

Thirdly, Descartes had begun by saying, I am 
conscious that I think, not of thinking. The object of 
consciousness is not the quality, thinking, but a thinking 
subject. Inconsistently with this truth, when he came to 
substance, he had fancied that we do not directly per 
ceive it, but from perceiving that some attribute is 
present, we conclude that some existing thing, or sub r 
stance to which it can be attributed, is also necessarily 


present ; l and he had applied this theory both to soul 
and body. Locke developed this hint into a formal 
theory that we perceive the simple ideas of qualities, 
while we accustom ourselves to suppose some sub 
stratum, wherein they do subsist and from which they do 
result, which, therefore, we call substance. 2 This theory 
he applied to body and spirit ; and from him has de 
scended the ordinary hypothesis that the objects of 
sense and consciousness are qualities, while substance 
is inferred without data to infer it. 

This error will meet us again in this chapter. At 
present it will be sufficient to quote a passage from 
another part of Locke s Essay : Our simple ideas have 
all abstract as well as concrete names : the one whereof 
is (to speak the language of grammarians) a substan 
tive, the other an adjective ; as whiteness, white ; 
sweetness, sweet. 3 This is the well-known logical dis 
tinction of abstract and concrete, but its consequences 
are often overlooked. Locke, for instance, forgot to 
1 ask in which meaning he should call a simple idea. a.r> 
object of sense, The abstract whiteness is a quality ; 

the concrete white is the qualified. Now, nobody ever 

saw whiteness ; the object of vision is the white, the 
red, &c. Similarly, the object of taste is not sweetness, 
but the sweet ; and so on with all sensible objects. 
Universally, then, an object of sense is never a quality^ 
but always the qualified ; and a quality is an abstrac- 
tion; and, though we may sometimes speak of perceiving 
it, we do so only for convenience. But the qualified is 
a substance ; whiteness and sweetness are qualities, but 
the white and the sweet are substances. The object of 
jsense, therefore, is always a subatanr.p. I do not mean 
that sense perceives a whole substance at once, but only 

1 Princ. i. 52. 2 Essay, II. 23, 1. 3 III. 8, 2. 


LOCKE 1-jl 

so far as it is sensible to a given sense ; sight perceives 
a substance so far as it is white ; taste perceives a sub 
stance so far as it is sweet, and so on. Nor do I mean 
an external substance, for I am a substance, consisting, 
too, of an immense plurality of substances, which I per 
ceive so far as they are sensibly affected. 

These conclusions apply both to outer and inner 
sense. In sensation, I perceive not a mere quality, nor 
a whole substance at once, nor an external substance ; 
I perceive my nervous system, not so far as it is ner 
vous structure moving, but so far as it is sensibly 
affected in different parts, the optic nerve so far as it is 
visibly white, the gustatory nerve so far as it is sweet 
to taste, and so on. Similarly in consciousness, I perceive, 
not mere thinking, nor the whole of myself, but myself 
thinking, in the manner described in the last chapter. 
The object of my sensation is myself as a physical sub 
stance sensibly affected ; the object of my consciousness 
is myself as a thinking substance. Descartes rightly said, 
I think. He ought not to have deserted this prin 
ciple. Locke ought to have returned to it, and have 
applied it from consciousness to sensation. Modern 
philosophy ought now to give up the sensation of 
qualities and inference of substance, because there is a 
direct sensation of my nervous system sensibly affected, 
and a direct consciousness of myself thinking, both of 
which are senses not of qualities, but of the qualified. 
We have a sense of substances, in order to infer them. 
Locke s complete theory is that alj_sense perceives 
a^ simple idej^. Ttegjty sense always perceives a. sub 
stancejgualified. It is doubtful whether the substance, 
as perceived, is ever simply qualified ; for instance, 
even when I feel simply pained, I doubt whether I do 
not feel pained for a time. But, in any case, I do not 



perceive anything simple in the sense of a simple 
quality, which is only simple in the sense of abstract ; 
but I perceive at least the simply qualified. Secondly, 
I do not perceive anything simple in the sense of a simple 
idea, which is really conceived, not perceived ; but I 

perceive, in sensation, my nervous system sensibly 
affected, and in reflection, myself thinking. The object 
of sensation, and the object of consciousness, so far 
from being simple ideas, are not ideas at all. They 
are two sets of materials of knowledge, of which 
neither is a quality, and neither is an idea, but each 
a substance. Locke s attempt to make the origin of 
ideas determine the origin of knowledge breaks down 
at the very outset by substituting abstractions for con- 

^crete data of sense. 

At the end of what he has to say on simple ideas, 1 
Locke comes to the operations which he supposes to 
make other ideas out of them, and to the ideas thus 
made. 2 The acts of the mind, says he, wherein it exerts 
its power over its simple ideas, are chiefly these three : 
First, combining several simple ideas into one compound 
one, and thus all complex ideas are made. The second, is 
bringing two ideas, whether simple or complex, together, 
and setting them by one another, so as to take a view of 
them at once, without uniting them into one, by which 
way it gets all its ideas of relations. The third, is separat 
ing them from all other ideas that accompany them in 
their real existence. This is called abstraction, and 
thus all its general ideas are made. 3 He then re 
marks that ideas, made up of several simple ones put 
together, he calls complex ; such as are beauty, grati 
tude, a man, an army, the universe. Next he divides 
complex ideas under three heads: modes, substances, 

1 Essay, II. 2-11. 2 II. 11 scq. to the end of the Third Book. 3 II. 12. 1. 


LOCKE 15o 

relations. Complex ideas of modes are ideas of affec 
tions of substances, subdivided by him into simple, 
or combinations of the same simple idea, e.g. a 
dozen, formed of units, and mixed, or combinations 
of simple ideas of several kinds, e.g. beauty, theft. 
Complex ideas of substances are such combinations of 
simple ideas as are taken to represent distinct particular 
things subsisting by themselves, in which the supposed, 
or confused idea of substance, such as it is, is always 
the first and chief ; l they are subdivided into ideas of 
single substances, e.g. a man, and collective ideas of 
several substances, e.g. an army. The last sort of 
complex ideas, 9 he says, is that we call relative, which 
consists in the consideration, and comparing one idea 
with another, 2 e.g. father and son, bigger and less, 
cause and effect. 3 The consideration of all these com 
plex ideas in their order occupies the remainder of the 
Second Book ; while that of abstract ideas follows, along^ 
with general words, in a general treatment of language 
in the Third Book. 4 

The whole discussion is full of variety. But it is 
vitiated by two incurable errors. In the first place, 
the objects of knowledge are complicated with their " 
mere ideas. But many scientific objects are known to 
exist, without being conceivable. Secondly, no thorough 
analysis is attempted of the three acts of mind, which* 
are supposed to be the sole causes capable of producing 
out of simple ideas^ all other ideas. Locke calls them 
composition, comparison and abstraction ; 5 making the 
first to be the origin of all complex ideas of modes and 
substances, the second the origin of all complex ideas 
of relations, the third the origin of all general ideas. 

Essay, II. 12, 6. 2 II. 12, 7. 3 II. 25, 2. 

4 Of. II. 33, 19. 5 II. 11. 


PART 11. 

He saw the foundation of these operations on sense ; but 
he forgot to ask their relation to reason. 

After sense, we conceive particular ideas in the 
^reproductive imagination, and general ideas by abstrac 
tion from sense. It does not follow that all general ideas 
are thus formed ; on the contrary, it is impossible that the 
idea of an insensible object should be either reproduced 
or abstracted from sense, in which it has never been. 
Again, we may compare and compound ideas. But at 
the same time we also judge about sensible objects 
and apprehend their relations. In judgment we use 
ideas, particular and general. But, as Mill has pointed 
out, 1 we also judge about sensible objects in order to 
apprehend their relations. I am in pain; this is a 
judgment that I, who am real, am in pain, which is 
real. Now, reasoning starts from such judgments about 
the relations of sensible objects, and sometimes by 
analogy, sometimes and better by induction and deduc 
tion, infers rational judgments, no longer about simple 
objects, nor about ideas, but about the relations of real 
objects; on the principle, if the premises are true, 
the conclusion is also true. That is, starting from 
judgments of sense, we infer rational judgments on evi 
dence about relations, as real as the sensible relations. 
Nor is this all ; as I showed in the last chapter, reason, 
having from sensitive concluded rational judgments, 
forms indirect ideas, roughly corresponding to the objects 
inferred, like to the ideas of sensible objects but not 
the same, and only capable of being made by reason. 
For instance, reason, having inferred that there are 
particles in bodies, causes the idea of a corpuscle ; a 
general idea of corpuscles, which is not a result of mere 
abstraction, and particular ideas of this or that cor- 

1 Mill, Logic, i. 5, 1. 


LOCKE 155 

puscle, which are not results of composition and com 
parison of ideas, but of inference from judgment to 
judgment. Beyond sense and imagination, besides 
composition, comparison and abstraction of ideas, there 
are also judgments of sense about the relations of sen-/ 
sible objects, and reasoning from these judgments to 
the relations of insensible objects, producing rational 
conceptions of ideas, due to no other source but reason 
ing. The narrow problem of the origin of ideas cannot 
be separated from the whole problem of judgment, "^ 
reasoning, and the origin of knowledge. 

Locke, in the Second and Third Books, saw only 
one side of thinking, and that its weakest side : 
imagination and abstraction, comparison and com- 6 
position, of ideas from sense. Eational inference of 
realities, beyond sense and ideas, he allowed to fade 
into the distance of the Fourth Book. Consequently, 
he found only the direct sources of ideas, and missed 
their indirect source in reason. No doubt he was in 
fluenced by the Cartesian logic of his day, which knew 
only the order idea, judgment, reason. But there is 
a second order reason, judgment, idea. As soon as 
judgment begins to act on the senses, reason begins 
with it, and, never stopping except to sleep and rise 
again refreshed, constantly forms new judgments issuing 
in new ideas. But Locke postponed reasoning, ignored 
rational conception, and therefore always fell short even ^ 
of the origin of ideas. 

Even in the ideas of simple modes, the very simplest 
department of complex ideas, this defect is noticeable. 
After sensations of motion, we may form ideas of motion 
by imagination ; and the ideas of simple modes of 
sensible motion by composition. 1 But reason also 

1 Essaij, II. 18, 1-2. 


infers simple modes of insensible motion in nature, 
such as electricity and magnetism, cohesion and chemi 
cal attraction, which were never in sense, and frames 
indirect ideas of these motions. Similarly, we may 
imagine ideas of sensible duration and extension, 
and compound ideas of these simple modes ; but when 
Locke goes on to suppose that the mind extends itself 
to infinity simply by repeating these ideas, he neglects 
the rational evidences of the unbounded nature of time 
and space. Unless men had thought they had reason 
to infer infinity, no mere repetition of ideas of the finite 
would ever have given the idea of the infinite, which is 
always accompanied by a rational inference that the in- 
* finite itself is beyond any idea we can possibly form 
of it. 

The mischievous consequences of omitting reason in 
the formation of ideas are best seen in Locke s doctrine 
of mixed modes and relations. Without reasoning, mere 
composition and comparison, as soon as they go beyond 
sense, would produce at most artificial ideas, the va 
garies of imagination. Consequently, it is not sur 
prising that Locke treats the ideas of mixed modes and 
relations, which he supposes to be formed by pure com 
position and comparison from and beyond sense, as 
artificial, and even goes so far as to contend that not 
merely the ideas, but mixed modes and relations them 
selves, have no other reality but what they have in the 
minds of men, and are real only in the sense of being 
consistent, not in the sense of representing real things. 
This paradox is a serious matter, for it affects the reality 
not only of a mixed mode, such as beauty, or a rela 
tion, such as father and son, but all moral modes and 
relations. It reduces morality itself to an idea. 1 ^ 

1 Cf. Essay, II. 22, 2 ; II. 25 ; II. 30, 4 5 ; II. 32, 10 ; III. 4, 2; III. 5. 

CHAP. vi. LOCKE 157 

But obligation is a mixed mode, which is real ; theft, 
drunkenness, lying, are mixed modes which are only too 
real, and the conformity of morality to law is a rela 
tion, which is also real, though perhaps less common ; and 
the complex ideas of these mixed modes and relations 
are not artificial, but really, though inadequately, corre 
spond to real morality and immorality. We may admit 
that morality is not altogether immutable ; it is not 
therefore unreal. We may admit that the ideas of the 
beautiful, of the good, and of law, are differently com 
pounded in ancient and modern morals ; they are not 
therefore artificial. We may admit that actions of 
virtue are uncommon ; but virtue is not an idea. By 
reasoning, man finds out the moral relations suited 
partly to humanity in general, and partly to the cir 
cumstances of his time. By rational conception, he 
apprehends ideas of moral relations, immutable and 
mutable. Happy he who can also realise these ideas, 
and be 

Virtu tis verse custos rigidusque satelles. 

There is even a certain fashion of ideas, which 
Locke illustrates by the Greek idea of ostracism and the 
Eoman idea of proscription. But these ideas were not 
on that account artificial : they represented real mixed 
modes at Greece and Borne : to be ostracised or pro 
scribed was anything but a mere idea. The Greeks and 
Romans inferred -that these institutions would serve 
certain purposes, and thus both established the real 
mixed modes and represented them by corresponding 
ideas. The modern historian from his evidence infers 
that these mixed modes existed in the past, and con 
ceives the ideas in the present. Similarly, the relation 
of paternity is not the idea of that relation, nor a mere 
product of comparison. It is a real relation of generation, 


which from sensible data we infer really to take place, 
and of which we afterwards form an idea, rational and by 
no means artificial, though but superficially represent 
ing the actual physical process of propagation. Mixed 
modes and relations, and their ideas beyond sense, are 
not always artificial constructions of composition and 
comparison of sensible ideas ; but reasoning from judg 
ments of sense discovers real mixed modes and relations, 
and then forms indirect ideas, really, though inade 
quately, corresponding to these realities, in science, in 
art, and in morals. 

The fallacy of omitting reason again appears in 
Locke s treatment of universals in the Third Book. 
He thinks that the sole source of general ideas is direct 
abstraction from sense. The consequences he draws are 
that all classes are abstract ideas, that no real essence 
is knowable beyond ideas, that simple ideas are unde- 
finable, and that universal truths are merely the agree 
ments and disagreements of our abstract ideas. 1 All 
these consequences would follow if we had no higher 
power than abstracting general ideas from particular 
sensible objects. All classification would be artificial. 
But there is a second source of general ideas. Eeason, 
by discovering the numerous similarities of particulars, 
infers real kinds or natural classes, which are not indeed 
eternal but as constant as the similarities, and thereby 
causes new, general, often very indirect ideas repre 
senting these real classes, but not identical with them ; 
e.g. the rational general idea of a corpuscle. Again, 
a simple idea of sensible light is undefinable ; but light 
in the universe is not, as Locke thinks, undefinable. 
On the contrary, optical reasoning proves that the real 
essence or fundamental similarity on which its pro- 

i Essay, IV. 3, 31 ; IV. 12, 7. 

CHAP. vi. LOCKE 159 

perties depend is an gethereal undulation, and defines 
it accordingly. Lastly, whatever we may think of 
essences and definitions, if Locke s theory that direct 
abstraction is the sole source of general ideas, and that 
classes are abstract ideas, were true, it would follow 
that all uniformities would be universal relations of 
abstract ideas ; and he accepted the consequence ; even 
the variety of Locke s mind refusing to entertain a con- 
ceptualism of classes along with a realism of natural 
laws. If ships and liquids were abstract ideas, the laws of 
flotation would be universal relations of abstract ideas. 
These laws, however, are universal relations of real ships 
and real liquids, inferred by reason. Therefore the 
classes so related are realities beyond abstract ideas. 
Abstraction of ideas from sense is not the sole source of 
generality, as Locke thought : reason infers natural 
classes and laws, and indirectly produces general ideas, 
not identical with them, but representing them, not arti 
ficially but really, though inadequately. 

Curiously enough, Locke himself saw, through a glass 
darkly, the interference of reason in the origin of one 
complex idea, that of substance. If sense perceived 
simple ideas of qualities, and composition united simple 
into complex ideas, the only complex ideas we could 
have would be complex ideas of qualities. We might 
have, for example, a complex idea of a combina 
tion of extension, solidity, motion, thinking, and no 
thing more. But Locke saw that we have something 
more. He, therefore, suddenly introduced, beyond 
sense and over and above composition, a supposition ; 
and says that not imagining how these simple ideas 
can exist by themselves we accustom ourselves to ^ 
suppose some substratum, wherein they do subsist 
and from which they do result ; which, therefore, 


we call substance 1 Secondly, lie allowed that this 
supposition causes an obscure and confused idea of the 
supposed but unknown support of qualities. He re 
cognised two such supposed and conceived substances : 
body, the substratum to those simple ideas we have 
from without ; and spirit, the substratum to those we 
have from within. 2 Finally, he regarded both these 
substances as unknown, and neither of their ideas as 
clear and distinct. Nevertheless, he thought that the 
ideas of substance were real in a different way from those 
of other complex ideas. The complex ideas of mixed 
modes and relations were, according to him, real if con 
sistent ; those of substances real only if agreeing with 
things without us. 3 It is the supposition of existence, 
over and above the composition of ideas, which made 
him allow this agreement with existence to ideas of 
substances. Inconsistent as this supposition is with 
his general theory of the composition of complex 
ideas, it is nevertheless the truth, though in a very 
imperfect shape. Let us then proceed to correct it, 
by showing what is the real nature of this inference, 
which Locke calls a supposition. 

It is true that external substances are inferred. But 
there are three views of what a substance is inferred to 
be. Some say that it is only a combination of qualities. 
But qualities are abstractions ; and a body is not ex 
tension, solidity, motion, or any number of further 
abstractions, combined, but the extended, solid, moving, 
&c Locke went to the opposite extreme of supposing 
a substance to be a substratum or kind of support on 
which the qualities rest, and this is the ordinary view, 
^ descended indeed from the compound, or concrete, 
substance of Aristotle, composed of matter and form. 

1 Essay, II. 23, 1. ~ See II. 23, 1-5. 3 II. 30, 4-5. 


But here are two abstractions, the subject abstracted 
from the qualities and the qualities from the subject. 
If a body ceased to be extended, solid and moving, it 
would cease to be ; there would be no substratum or 
support left. Hence the third view, that a substance is 
a qualified subject, the extended, solid, moving, &c. ; in 
which the qualities are nothing except as characterising 
the subject, and the subject nothing except as charac 
terised by the qualities ; from which subject or sub 
stratum, qualities or attributes are opposite abstractions. 

Secondly, external substances must be inferred from 
similar data. To infer qualified subjects beyond sense, 
there must be qualified subjects in sense. If the data 
were ideas, we could only infer other ideas. If the 
data were qualities, we could only infer qualities. A 
fortiori, if the data were ideas of qualities we could 
never infer a real qualified subject, for which there 
would be no analogue. Therefore, again we find that 
Locke s sensible data were false. He thought that by 
sense we perceive simple ideas of extension, resistance 
or solidity, motion, &c., and then without rhyme or 
reason suppose something totally different, a real sup 
port in the external world. Eeally, sense perceives 
qualified subjects, the extended, resisting, moving, &c. 
within ; hence reason infers similar extended, resisting, 
moving, qualified subjects without. It must not be 
forgotten that muscular sense was not noticed in Locke s 
day ; but the logic of reason had been known since 
Aristotle s day, and he ought not to have neglected it. 

Thirdly, substances are not unknown : they are the 
only things that are known. Everything else is real/ 
and is known, only so far as it belongs to substance ; 
and although qualities are abstracted and spoken of as 
real and known for mere convenience, what is really 



known in mathematics is not the quality of extension, 
but the extended ; in physics, not the quality of gravity, 
but the gravitating ; in morals, not the quality of good 
ness, but the good. Substances would be unknown, and 
uninferred, on Locke s data. But substances are known, 
because sense perceives them within, and reason infers 
them without, by parity of reasoning. They are the 
data and conclusions of all our knowledge. Sensation 
perceives the nervous system in different parts as sensibly 
white, sweet, extended, moving, &c. Eeason infers 
similar physical substances or bodies. Science goes on to 
infer similar corpuscles. Nor does it stop till it infers the 
body of the universe. Consciousness perceives myself 
as thinking subject, partly body, partly soul. Eeason, 
from the signs of bodily organs, language, actions, and 
productions of others, infers similar thinking subjects. 
Natural theology, not from bodily organs, but from 
physical creations, infers God, not as a body, but as a 
Creator. All this is knowledge of substance, logically 
inferred from sensation and consciousness ; and only 
because the objects of outer and inner sense are sub 
stances, can reason logically infer substances, physical 
and psychical. It does not follow, however, that reason 
is infallible : it is fallible so far as not logical from sense. 
Nor does it follow that we know substance completely. 
We begin with sense, and perceive subjects only as 
sensibly qualified. Eeason reveals subjects insensibly 
qualified. But we never know the whole of any sub 
stance whatever, not even ourselves, not even a crystal 
which we seem to see through and through. This 
imperfection of human knowledge misleads philosophers 
into agnosticism. But the truth is, sense and reason 
enable us to know substances not wholly but partially. 
Finally, the knowledge of substance creates the idea 

CIFAP. vi. LOCKE 103 

of it. The original ideas are derived from my own sub 
stance. From myself as sensible I derive my idea of a 
physical subject ; from myself as conscious, my idea 
of a thinking subject, partly physical, partly psychi 
cal ; from both, my idea of a qualified subject. But 
my ideas of all other known subjects are results of 
reasoning, which first infers similar subjects, and then 
forms ideas of them. Ideas of substance are right, so 
far as they correspond to really known substances 
sensible and inferred, and their correctness varies in 
accordance with sense and reason. They are clear, 
distinct, and adequate, in proportion partly to their 
proximity to sense, and partly to the extent of reasoning 
about any given substance ; but they are seldom or 
never adequate to what is known of a substance. 

Locke, though inconsistent, was justified in allowing 
that the complex ideas of substances are not due to 
mere composition of simple ideas ; and he ought to 
have made the same admission in the case of other 
ideas, because not all ideas of mixed modes are due to 
composition, nor all ideas of relations to comparison, 
nor all general ideas to abstraction. He was justified 
in allowing that we infer substance, in order to conceive 
the idea of it, beyond ourselves. He was justified in 
allowing that ideas of substances are right, so far as 
they represent real objects. But he was unable to 
found a philosophy of substance, because, in the first 
place, he failed to apprehend that sensation and reflec- * 
tion both perceive substances within ; secondly, he was 
accordingly, but falsely, constrained to reduce the in 
ference of substances without to a mere supposition a 
supposition without any data, illogical, and impossible 
to reason ; thirdly, he had to call all substances, all 
qualified subjects, the only things in the world we 

M 2 


know, unknown ; and all ideas of substances obscure 
and confused, when really the clearest and distinctest 
ideas we have are those of stones, waters, houses, plants, 
animals, cats, dogs, men and other substances. 

There are many sources of ideas. Sensation and 
V reflection are not directly concerned with ideas, as 
Locke thought, but with sensible objects. But after 
sense, reproductive imagination without reasoning con 
ceives particular ideas of the objects of sense, memory 
refers the ideas to their objects, and abstraction con 
ceives general ideas of the objects of sense. Eeasoning 
infers insensible objects and forms their ideas. There is 
a rational imagination of ideas. Eational ideas of known 
objects are not artificial. Locke partly saw this in the 
case of substance. But the ideas of modes and relations 
are also rational and correct, so far as they agree with 
modes and relations properly inferred as belonging to 
external substances. While, however, rational ideas of 
the insensible are not artificial, they are often inade 
quate ; e.g. of a corpuscle, of infinite space and time, 
of gravitation, of the universe, of God. Lastly, the 
inventive imagination makes artificial ideas-, such as 
those of a centaur, a fairy, The Iliad, A Midsummer 
Night s Dream. But it has never yet been successfully 
analysed. Perhaps even the comparison and composi 
tion of artistic imagination are founded on reasoning, not 
to the actual and real, but to the possible and ideal. 

Let us now suppose that Locke s general account of 
the origin of ideas is immaculate and superior to our 
objections, that sensation and reflection perceive simple 
ideas ; that comparison, composition and abstraction 
are the three acts which form compound ideas ; and 
that the introduction of a supposition of substance was 
a momentary lapse of a philosopher from the consis- 



tency of philosophy. What will be the consequence ? 
As he says himself, ideas will be the instruments and 
materials of our knowledge. 1 Then, by parity of reason 
ing, all that we can know from such materials will be 
other ideas, and, as he has said himself, ideas will be 
also all the objects of our understanding. 2 Locke you 
would imagine to be the founder of pure idealism. We 
should have expected him to go on to show that every 
thing in the world of science is an idea. At the end 
we should have been inclined to say- 
There are more things in heaven and earth, Horatio, 
Than are dreamt of in your philosophy. 

But Locke had a various, though not a logical mind. 
He was a student of Descartes ; he was also imbued 
with the English devotion to nature. From the former 
source he derived the theory of ideas, from the latter 
the reality of things. Locke, after assuming that all 
objects of understanding are ideas, admitted that ex 
ternal realities exist. The Essay contains an undercur 
rent of ontology, which comes up first in the famous 
distinction of primary and secondary qualities, 3 recog 
nising external qualities as real, as external causes of 
our ideas of sensation, and even as externally related 
as cause and effect to each other : 

The qualities then that are in bodies, rightly con 
sidered, are of three sorts. 

First, the bulk, figure, number, situation, and 
motion or rest of their solid parts ; those are in them, 
whether we perceive them or no ; and when they are 
of that size, that we can discover them, we have by 
these an idea of the thing, as it is in itself; as is plain 
in artificial things : these I call primary qualities. 

1 Essay, II. 33, 19. 2 I. 1, 8. 3 II. 8. 


Secondly , the power that is in any body, by reason 
of its insensible primary qualities, to operate after a 
peculiar manner on any of our senses, and thereby pro- 
7 duce in us the different ideas of several colours, sounds, 
smells, tastes, &c. These are usually called sensible 

Thirdly, the power that is in any body, by reason 
of the particular constitution of its primary qualities, to 
make such a change in the bulk, figure, texture, and 
motion of another body, as to make it operate on our 
senses differently from what it did before. Thus the 
sun has a power to make wax white, and fire to make 
* lead fluid. These are usually called powers. * 

The same undercurrent of ontology reappears in the 
admission of substances, and real essences, though 
unknown. It becomes most marked in the Fourth 
Book, where Locke adds to all his other entities, one s 
own existence, the existence of God, and the existence 
of other things, such as the clippings of our beards and 
the parings of our nails. Finally it springs up into an 
.elaborate picture of the insensible universe beyond the 
reach of our ideas. 2 It is a dangerous thing to be 
an unconscious metaphysician. Locke s metaphysical 
theory of existence is quite outside his psychological 
theory of ideas. How does it agree with his logical 
theory of knowledge ? If it be true to say, that beyond 
ideas there is an external world of qualities, real and 
causal, real substances and real essences, my own ex 
istence, God s existence, the existence of bodies, and of 
insensible corpuscles, what is truly said by a philoso 
pher, who is after all but human, must be known to a 
man. What then does Locke, the philosopher who says 
all this, say about the knowledge of man ? 

1 Essay, II. 8, 23. 2 IV. 3, 24. 



The Fourth Book, which is on knowledge and 
opinion, starts with a theory quite consistent with the 
previous Books, on the origin of ideas : 

4 Since the mind, in all its thoughts and reasonings, 
hath no other immediate object than its own ideas 
which it alone does or can contemplate, it is evident 
that our knowledge is only conversant about em. 

Knowledge then seems to me to be nothing but the 
perception of the connection and agreement, or disagree-*- 
ment and repugnancy of any of our ideas. In this alone 
it consists. * 

Locke proceeds to divide knowledge into intuition 
and reasoning. He says that < sometimes the mind per 
ceives the agreement or disagreement of two ideas 
immediately by themselves without the intervention of 
any others: and this, I think, we may call intuitive^ 
knowledge:* He adds that when the mind cannot so 
bring its ideas together, as by their immediate com 
parison, and as it were juxtaposition, or application 
one to another, to perceive their agreement or disagree 
ment, it is fain, by the intervention of other ideas (one 
or more, as it happens), to discover the agreement or 
disagreement, which it searches : and this is what we 
call Reasoning! 3 Afterwards, he writes a whole chapter 4 
on Reason, in which he again defines it as the percep- ^ 
tion of the agreement or disagreement of ideas by 
intermediate ideas. At the same time he rejects the 
syllogism, although the process which combines two 
extremes by the intervention of a middle is clearly the 
same process as his own. But the main point to be 
observed is that, according to him, reasoning begins 
with an intuitive perception of the relation of ideas 
i IV. i, 1-2. 2 IV. 2, i. 

3 iv. 2, 2. 4 IV. 17. 


and ends with a mediate perception of the relations of 

A theory of reasoning such as this must con 
fine all reasoned knowledge, and therefore all science, 
to relations of ideas. This actually is his view of 
mathematics and morals. I doubt not, he says, but 
it will be easily granted, that the knowledge we have of 
mathematical truths is not only certain, but real know 
ledge ; and not the bare empty vision of vain insignifi 
cant chimeras of the brain : and yet, if we will consider, 
we shall find that it is only of our own ideas l He 
says the same of moral knowledge, which he also holds 
to be as certain as mathematics. 2 I admit that if all 
objects of reasoning are ideas, mathematical knowledge 
is only of our ideas. But, in this case, it is not of the 
bulk, figure, number, structure and motion of bodies 
and particles, which Locke himself recognises beyond 
our ideas. Sir Isaac Newton, then, must have been 
wrong in saying that all the particles of matter gravi 
tate to one another with a force varying inversely to 
the square of the distance ; for he was pretending to a 
mathematical knowledge of the motions of particles 
beyond ideas. What a curious contretemps, that in 
1687 Newton should discover to mankind the Mathe 
matical Principles of Natural Philosophy in every 
particle of matter, and in 1690 Locke should publish 
an Essay concerning Human Understanding to prove 
that the knowledge of mathematical truths is only of 
our own ideas ! 

We are relieved from further criticism of this pure 
^dealism, however logical, because Locke himself deserts 
it for realism, however hypothetical. At first he delibe 
rately confines all knowledge to the perception of the re- 

1 Essay, IV. 4, 0. 2 



lations of ideas, and throughout applies tliese limits strictly 
to mathematics and morals. But all of a sudden he in 
troduces us to a knowledge of real things in other de 
partments of knowledge, and, as it were, writes a second 
essay on another human understanding. The manner in 
which he makes this abrupt transition is highly instruc- 1 ^ 
tive. Having defined knowledge to be only conversant 
about ideas, and to be nothing but the perception of 
the agreement and disagreement of ideas, 1 he reduces 
these agreements and disagreements of ideas to four 
sorts identity or diversity, relation, coexistence, and 
real existence. 2 The knowledge of the first three sorts * 
proceeds consistently enough, when suddenly, without 
any previous preparation, much less argument, he lays 
down the following dogma :- 

Fourthly. The fourth and last sort is that of actual 
real existence agreeing to any idea? 3 

On, his original hypothesis that ideas are all the 
objects of understanding, on his theory of the origin of 
ideas in the Second Book, on his definition of know 
ledge in the very same chapter of the Fourth Book, he 
ought to have said, the knowledge of the idea of actual 
real existence agreeing to any idea. But just as Des 
cartes passed from the idea of God s existence to His 
existence, so Locke passed from the knowledge of the^ 
idea of existence to the knowledge of existence agreeing 
to any idea. But while Descartes had been inconse 
quent, Locke to inconsequence added inconsistency ; he 
had begun by saying that all objects of understanding 
are ideas ; he afterwards admitted a knowledge of exist-* 
ence agreeing to any idea. 

He afterwards divides this knowledge of existence 
into three departments an intuitive knowledge of our 

1 IV. 1, 1-2. 2 IV. 1, 3. 3 IV. 1, 7. 


own existence, a demonstrative knowledge of the exist- 
"ence of a God, a sensitive knowledge of objects present to 
the senses, 1 and devotes a chapter to each. 2 In Locke s 
philosophy, all three ought to have been knowledges 
of ideas ; they are knowledges of the real and actual 
existence of things. Again, the Fourth Book presents 
us with two theories of a proposition to support this 
inconsistency. First, he divides propositions into two 
kinds ; mental, wherein ideas, and verbal, wherein words, 
the signs of our ideas, are put together. 3 Afterwards, he 
says that there are two sorts of propositions; one, con 
cerning the existence of anything answerable to an idea, 
r and the other, concerning the agreement or disagree 
ment of our abstract ideas. 4 I am not referring to all 
these places to criticise Locke for inconsistency, which 
is a weakness of human nature, a weakness even of 
philosophers, who are but men, and an amiable weak 
ness, because one of two contradictories must be true. 
My object is rather to show that Locke at last came to 
the truth, that not all objects of knowledge, of proposi 
tions, of understanding are ideas. But there is a further 
question, How do we know these actual existences ? or, to 
use Locke s own phrase, How shall the mind, when it 
perceives nothing but its own ideas, know that they 
agree with things themselves ? 5 

The intuitive knowledge of our own existence is 
settled in a single section, short but significant, in which 
he gives up his original theory that we perceive nothing 
but ideas : 

As for our own existence, we perceive it so plainly, 

^ and so certainly, that it neither needs, nor is capable of 

any proof. For nothing can be more evident to us than 

1 Essay, IV. 3, 21 ; IV. 9, 2. 2 IV. 9-11. 3 IV. 5, 5. 

4 IV. 11, 18. 5 IV. 4, 3. 


LOCKE 171 

our own existence. I think, I reason, I feel pleasure or 
pain : can any of these be more evident to me than my 
own existence ? If I doubt of all other things, that 
very doubt makes me perceive my own existence, and 
will not suffer me to doubt of that. For if I know I 
feel pain, it is evident I have as certain perception of 
my own existence as of the existence of the pain I feel : 
or if I know I doubt, I have as certain perception of the 
existence of the thing doubting as of that thought which 
I call doubt. Experience then convinces us that we 
have an intuitive knowledge of our own existence, and an 
internal infallible perception that we are. In every act 
of sensation, reasoning or thinking, we are conscious to 
ourselves of our own being ; and, in this matter, come 
not short of the highest degree of certainty! l 

This passage breathes the very spirit of Descartes. 
Cogito, ergo sum. I am conscious that I am a thinking 
subject. This is the fact that never ought to have been * 
deserted. Descartes deserted it for an inference of 
substance, and Locke followed him out of the right path, 
but he had to come back to it after all. Consciousness 
reveals to me not thoughts but a thinker. This con 
sciousness is indeed inconsistent with the previous state 
ments of Locke ; first, that reflection perceives the ideas 
of operations, whch is two removes from consciousness ; 
secondly, that there is a supposition of a substance as 
unknown substratum to those operations, which would 
be a baseless inference from data containing nothing but 
ideas of operations. Nevertheless, the direct conscious 
ness of our existence is the fact. How then is it that it 
is constantly disappearing out of philosophy, not only 
in the seventeenth, but also in the succeeding centuries ? 
Because philosophers are perpetually confusing abstract 

1 IV. 9, 3. 


and concrete, forgetting that thoughts are abstract 
qualities but the thinker the real being, and thus 
concluding that consciousness and reflection reveal 
thoughts, leaving the subject to inference and supposi 
tion, when really consciousness and reflection tell me 
that I am a thinking subject, from which I infer other 
thinking subjects. 

Unfortunately, in another part of the Essay, Locke 
had exaggerated the truth, I am conscious that I am a 
person, a thinking intelligent being, into the falsity, I 
am that very consciousness. 1 But in the first place, 
I am conscious that I perform numerous operations 
besides the operation of being conscious, that I am a 
sensible, remembering, reasoning, desiring, willing sub 
ject ; consciousness therefore itself tells me that I am 
more than itself. Secondly, it is not my only source of 
information about myself. I am conscious that I am 
partly body thinking, but I also indirectly observe my 
body. I reason from my consciousness and observa 
tions, and infer that I am a permanent substance, 
when I am asleep as well as when I am awake, when I 
am conscious and when I am unconscious. Thirdly, 
consciousness is interrupted ; if I were consciousness I 
should have an intermittent existence. Finally, Locke 
has confused the causa cognoscendi with the causa essendi. 
Consciousness is necessary to tell me, I am a person ; 
but it does not make me a person ; this am I made by 
being a permanent substance, partly body and partly 
soul, capable, when awake, of reasoning, and therefore 
of the status of a rational being. 

At the end of Butler s Analogy, the Dissertation on 
Personal Identity contains an excellent statement of its 
relation to consciousness, as follows : 

1 Essay, II. 27, 9 seq. 


LOCKE 173 

But though consciousness of what is past does thus 
ascertain our personal identity to ourselves, yet to say 
that it makes personal identity, or is necessary to our 
being the same persons, is to say that a person has not 
existed a single moment, nor done one action, but what 
he can remember, indeed none but what he reflects 
upon. And one should really think it self-evident that 
consciousness of personal identity presupposes, and 
therefore cannot constitute, personal identity ; any more 
than knowledge, in any other case, can constitute truth, 
which it presupposes. 

Locke, then, is right in saying that consciousness 
is an intuitive knowledge of oneself, wrong in saying ^ 
that it is oneself. Not from the false identification of 
self and consciousness, but from the consciousness of 
self, that is, from the intuitive knowledge we have of our 
own existence, as cogitative beings, Locke deduces our 
knowledge of the existence of a God by an argument, 
which is an extension of the third argument in 
the Principia Philosophise of Descartes. 1 A finite 
thinking subject requires an infinite thinking subject 
to create it. Yes, but this argument holds only 
if we are conscious of ourselves as thinking subjects. 
God is not an idea, and consequently cannot be inferred 
from mere ideas. Thus, if Locke had clung to his 
ideas of reflection, he could not have proved a God : 
the consciousness, not of mere thoughts, but of a think 
ing subject, is necessary to natural theology. Simi 
larly, it is necessary to infer any other thinking subject 
but myself. If, then, I were conscious only of ideas of 
operations, and even if I were conscious directly of 
operations, I could not infer thinking subjects, and I 
could not infer God. The object of consciousness, there- 

1 IV. 10 ; cf. Descartes, Princ. i. 20. 


fore, is not op 3rations, still less their ideas, but thinking 
subjects. Here again, too, we find that not all objects, 
and not all data, of understanding are ideas. Locke 
was obliged to surrender his theory of ideas in order to 

/prove his own existence, the existence of others, the 
existence of God. 

Next, we come to what Locke calls our sensitive 
knowledge of objects presented to our senses. Here, 
with Cartesian inconsequence, he tried to maintain his 
theory of ideas, and yet show how we know external 
realities, or originals, by inference. In the Fourth 
Book he returns to this point again and again. He 
begins by proposing this problem. There can be 
nothing more certain, he says, than that the idea we 
receive from an external object is in our minds. But 
whether there be any thing more than barely that 
idea in our minds, whether we can thence infer the 
existence of any thing without us, which corresponds 
to that idea, is that, whereof some men think there may 
be a question made ; because men may have such ideas 
in their minds, when no such thing exists, no such 
objects affect their senses. l He answers the question by 
saying that a man is conscious of a different perception 
when he looks on the sun by day and thinks on it by 
night, and concludes that this is a knowledge not intuitive 

^nor demonstrative, but sensitive. Again, he divides 
the problem by simple ideas and complex ideas of sub 
stance ; and argues that, in the first place, simple ideas, 
which the mind can by no meairs make to itself, must 
necessarily be the product of things operating on the mind 
in a natural way, and that the idea of whiteness in the 
mind answers that power which is in any body to produce 
it there ; 2 and, in the second place, the reality of our 

1 Essay, IV. 2, 14. - IV. 4, 4. 


LOCKE 175 

knowledge of substances is founded on our complex 
ideasof them being such as are made up of such simple 
ones as have been discovered to coexist in nature. 1 
Finally, he devotes to the knowledge of objects without 
us a chapter, 2 in which he contends that its certainty is 
as great as we are capable of concerning the existence 
of anything but oneself and God, and that it deserves 
the name of knowledge. He adds four arguments to 
the preceding : first, that those who want the organs of 
sense want the ideas of that sense ; secondly, that some 
times I cannot avoid the having those ideas produced,, 
in my mind ; thirdly, that many of these ideas are pro 
duced with pain, which afterwards we remember with 
out offence ; fourthly, that our senses in many cases 
bear witness to the truth of each other s report. Finally, 
he falls back on the practical argument that we have at 
all events a knowledge of the external world by the 
happiness and misery we receive from it. The whole of 
these arguments are summed up in this one : I have 
ideas of sensation, which I do not produce myself ; I 
infer that they are produced by external bodies. It is 
the Cartesian argument from the passivity or involun- 
tariness of sensations and ideas. 

Locke s admission of the reality and knowledge of 
external bodies is right and honest, but completely 
destructive of his original hypothesis of the objects 
and data of understanding. It is true, as he admits, 
that we know external bodies. But this admission de 
stroys his original doctrine that knowledge is always^ 
concerned with ideas. Again, it is true, as he admits, 
that we know bodies by inference. But this destroys 
his doctrine that reasoning begins and ends with ideas. 
Both admissions also destroy his original doctrine that 

1 IV. 4, 12. - IV. 11. 


* ideas are all the objects of understanding. It is also 
true, as lie says, that we infer external bodies from the 
passivity of sensation. But is it true that we could 

have drawn this inference from sensible data, if sensa 
tion had been a perception of nothing but ideas ? This 
is what Locke makes no attempt to prove. It is con 
tradictory to his own logic. Like Descartes, he recog 
nised that real truth is the agreement of our propo 
sitions with external reality. 1 But unlike Descartes, he 
has given up any special criteria of truth. The vera 
city of God he uses only for revelation ; 2 and regards 
the inherent clearness and distinctness of ideas not as 
positive criteria, but only as conditions of truth. 3 The 
consequence is that he has no organon except the 
rules of reasoning ; and he is aware that, as the data of 
reasoning are, according to him, ideas with their agree 
ment and disagreement, so the conclusions are logically 
confined to the agreement and disagreement of ideas. 4 
Yet he expects us also to believe that reasoning starting 
with ideas of sensation can be logically extended to ex 
ternal bodies. 

All logic demands that, as are the data, so are the 
conclusions. I find that some of the sensible objects 
I perceive are passive. I have a right to infer some 
other cause. But I must by parity of reasoning infer a 
cause similar to those already known. Now, what data 
does Locke supply me ? Granting him every advantage 

V and all his inconsistencies, I should have ideas of sensa 
tion and reflection, and compound ideas from the Second 
Book : from the Fourth Book, I should have conscious- 

* ness of myself, and a demonstration of other thinking 
subjects, and of God. These, ex hypothesi, are all the data, 

1 Essay, IV. 5. - IV. 16, 14. 

3 IV. 2, 15. 4 IV. 17. 

CHAP. vi. LOCKE 177 

direct and indirect, at the very best. What would be 
the logical inference ? I could infer, from the passivity 
of sense, that it resulted either from other ideas, or from 
other thinking subjects, or from God. I could not, being 
without bodily data, infer that it resulted from external 
bodies. Locke saw the importance of the passivity of 
sense, but forgot the rules of logic. 

Newton and Locke were contemporaries. What, 
then, was Locke s attitude to natural philosophy ? He 
recognised its discoveries, and especially the corpus 
cular philosophy revived by Bacon, developed by Des 
cartes, and brought to its perfection by Newton. We 
have followed him in his little excursion into natural 
philosophy to distinguish primary and secondary 
qualities. He there admits the existence of corpuscles, 
real qualities, primary and secondary, though insensible, 
and real powers between qualities, e.g. the power of fire 
to make lead fluid. There is no fault to find here 
except with his definition of a quality as a power to 
produce any idea in our mind. 2 A quality is really a 
characteristic of a subject or substance. It has various 
powers, and among them the occasional power of affect 
ing our senses. For instance, motion is a characteristic 
of every corpuscle, and has a power of affecting every 
other corpuscle, and sometimes of affecting human senses 
in the way of sensible motion, light, heat, sound, and so 
forth. But to define it by its sensible power, would be 
to convert a very occasional accident into the essence of 
motion, forgetting that there are myriads and millions 
of motions which come nowhere near the earth, much 
less man, and are not powers of producing any ideas in 
his mind. 

Locke defined quality by a separable accident. 
1 II- 8, 22. 2 ii. s, 8. 



Hence also a mistake in his definition of a secondary 
quality as a power of an insensible primary quality 
to produce in our senses a sensible idea. This is only 
an occasional and accidental power ; and a secondary 
quality is a specific modification of a primary quality, 
which exists whether it produces a sensible effect or 
not. Thus heat is a mode of motion transferred from 
star to star, and before the origin of animals much of 
it was exhausted without having the power of produc 
ing sensible heat With these corrections, Locke ex 
presses the scientific distinction of primary and second 
ary qualities in the universe. He fully recognises the 
existence of that part of insensible nature, which I have 
called the imperceptible, to distinguish it from the in 
sensible but inferentially perceptible originals of sensible 
objects. He recognises corpuscles as well as masses, the 
particles of this paper as well as the paper. 

But when he came to give these imperceptible cor 
puscles a place in the human understanding, he began 
to vacillate. In the Fourth Book, he distinguishes 
knowledge and opinion, as respectively the perception 
and the presumption of agreements and disagreements 
of ideas, as certain and probable. Strictly, he could put 
natural philosophy in neither, because he admitted that 
it was not about ideas, but things. But the alternative 
to which he leaned was to draw the line between know 
ledge and opinion, exactly between the paper and its 
particles, between the mass and the corpuscle, between 
the perceptible and the imperceptible ; and, therefore, to 
call the first inferences from sense knowledge, and the 
subsequent inferences of science opinion. On the whole, 
according to him, knowledge 1 includes mathematics and 
morals because they are about ideas, knowledge of self 
1 Essay, IV. 3, 5 ; IV. 10, 6 ; IV. 11, 9 ; IV. 11, 13. 


LOCKE 179 

because it is intuition, knowledge of God because it is 
demonstration from this intuition, and knowledge of ex 
ternal originals directly inferred from sense : here ends 
knowledge. In opinion falls natural philosophy. Why? 
Because the further from sense the less, he thought, our 
knowledge. Because we are not capable of the ideas 
of things so remote and minute, and this defect, as he 
thought, keeps us in ignorance of the things. Because 
we merely make experiments which are not science 
Because we can only guess and probably conjecture, 
use hypothesis and analogy. Analogy, says he, in 
these matters, is the only help we have, and tis from 
that alone we draw all our grounds of probability. Thus 
observing that the bare rubbing of two bodies violently 
one upon another, produces heat and very often fire 
itself, we have reason to think that what we call heat 
and fire consists in a violent agitation of the imper 
ceptible minute parts of the burning matter : observing 
likewise that the different refractions of pellucid bodies 
produce in our eyes the different appearances of several 
colours ; and also that the different ranging and laying 
the superficial parts of several bodies, as of velvet, 
watered silk, &c., does the like, we think it probable 
that the colour and shining of bodies, is in them nothing 
but the different arrangement and refraction of their 
minute and sensible parts. 1 But knowledge of these 
insensible qualities he denies. He doubts that how 
far soever human industry may advance useful and 
experimental philosophy in physical things, scientifical 
will still be out of our reach ; 2 and he suspects that 
natural philosophy is not capable of being made a 
science. 3 Yet this very Locke winds up his Essay by 

1 IV. 1G, 12 ; cf. IV. 3, 16 ; IV. 3, 24-end ; IV. 6 ; IV. 12, 9 13. 
~ IV. 3, 26. 3 IV. 12, 10. 


a triple division of science, one of which is Physics 
or Natural Philosophy, the knowledge of things. 1 

It is a matter of deep regret that Locke should have 
written thus of natural philosophy in the very time of 
Newton. There is some truth in what he says, but 
marred by exaggeration. There is a huge abyss of 
ignorance, but it is not altogether an incurable igno 
rance. Much of what is called science is opinion, but 
fresh evidences convert opinion into science. Because 
there are probabilities in natural philosophy, it does not 
follow that there is nothing certain. We cannot have 
a perfect knowledge of nature, but we can know some 
thing without knowing everything. We cannot always 
discover real essence, but there is a knowledge of co 
existences and causes, of the conservation and correlation 
of physical forces, as in electricity and magnetism, with 
out always knowing their essences. Locke rightly saw 
that there is more of the universe unknown than known, 
and much which is only opined ; but he lost sight of 
the main fabric of science. By the mere elimination of 
chance such a concatenation of laws cannot but be true. 

Locke was ignorant of the logic of science. The 
two greatest men of science in his own country were 
Bacon and Newton, of whom the former had shown 
that there is an experimental science of nature, the 
latter that natural science is capable of physical deduc 
tions from mathematical principles. But Locke, like 
Hobbes, was silent about Baconian induction, and 
oblivious to everything except the old method of intui 
tion and demonstration, which suits mathematics, but 
not the whole of natural philosophy. Everything out 
side demonstration, he calls hypothesis and analogy. 
He did not recognise the variety of method, the ana- 

1 Essay, IV. 21. 


LOCKE 181 

logia demonstrationum pro natura subjecti, desiderated 
by Bacon. He did not see that the corpuscular 
philosophy is made independent of this hypothesis and 
that analogy, by many different evidences in many 
different departments gravity, light, heat, sound, elec 
tricity, magnetism, chemical attraction, nervous and 
muscular motion all of which point to corpuscles, their 
motions, according to Newton s laws, their modifications 
constituting secondary qualities, their convertibility 
and indestructibility as motion. He did not recognise 
that there is a circumstantial evidence, which in law is 
sufficient to hang a man, in nature sufficient to prove a 
fact; and an approximate certainty, by accumulation 
of evidence, ever indefinitely approaching absolute 

But his greatest, though characteristic, blunder was 
his attempt to carry inference beyond sense to the ex- 
ternal original inferentially perceptible and then stop 
short ; to allow us to know the paper and not the par 
ticle, the mass and not the molecule. Such a logic 
is arbitrary. If insensible modes of primary qualities 
are truly said to be, as Locke allows, then they are 
knowable. The same laAVS of reasoning which enable 
us to infer from sensible effects an external cause, en 
able us from that cause to infer another cause, and so on 
till we have completely explained facts of sense by laws 
of science. If it were not so, how could science correct 
ordinary knowledge? Ordinary knowledge infers an 
external object, like in secondary as well as primary 
qualities. Science declares that the external world is 
like in primary but not in secondary qualities to the 
sensible effect. But if the former is knowledge and the 
latter opinion, by the first principle of method ordinary 
knowledge, as more certain, is to be preferred to the less 


certain science ; so that the ordinary man is right in 
his theory of external light and heat, and the natural 
philosopher wrong ! Locke s line between knowledge and 
science gives the ordinary man, with his inference of 
bodies, knowledge, but the scientific man, with his 
inference of corpuscles, opinion. He elevates ordinary 
above scientific knowledge, which is absurd. 

There is a standing difference between natural and 
mental philosophy, and Locke has done much to pro 
duce it. He would make theology and morals not only 
sciences, which they are, but more scientific than natural 
philosophy, and tells man, whose real function is to 
know all and do all, that his proper business is his moral 
duties and his future state. 1 Newton had just written 
the Optics and the Principia, but Locke s theory of 
science would reduce these works to mere opinions. 
The whole history of science is against him. On the 
foundation of Newton s mechanics of motion has been 
gradually reared a system of science which has eventually 
revealed to us the insensible and imperceptible causes 
of our sensations in the external world. On the 
other side stand the mental philosophers, philosopTiantes 
secundum sensum, considering primarily their sensations 
and ideas, and with difficulty extending their thoughts 
even to the external originals, then gazing stupidly at the 
perceptible world, and never dreaming that they have to 
explain the knowledge of imperceptible nature. Locke s 
hypothesis that we have a sensitive knowledge from 
ideas of objects presented to sense, a mathematical and 
moral science of ideas, and an uncertain opinion of the 
physical universe, undervalues natural philosophy. It 
immediately produced the false attitude of Berkeley and 
Hume towards nature, but it has affected the whole 

1 Essay, IV. 12, 11. 

LOCKE 183 

course of mental philosophy, which has unduly neglected 
the problem of knowledge, presented to it by natural 
philosophers. Hence, while natural philosophy has 
shown that the insensible is the causa essendi of the sen 
sible, mental philosophy has never yet shown how the 
sensible is the causa cognoscendi of the insensible. 

But let us suppose that the whole fabric of science 
is opinion, the whole imperceptible world unknown. 
Yet it is at least an object of understanding and reason 
ing, because, as Locke himself says, not but that it is 
the nature of the understanding constantly to close with 
the more probable side, 1 and, as he admits, reason may 
end either in certainty or in probability, either by 
demonstration or an argumentum ad judicium. 2 This 
beino- so, imperceptible probabilities are objects of 
understanding and reason, but are not all ideas ; there 
fore not all objects of understanding and reason are 


Nor could they be reasoned from ideas as their data. 
This want of consequence brings us to another defect in 
Locke s theory of primary and secondary qualities ; his 
false view of their sensible aspect. In his opinion, as 
external they are powers, as sensible they are ideas. 
But they are neither mere powers nor mere ideas. 
If, as sensible, they were ideas, we could not logi 
cally infer insensible primary qualities, which are ad 
mitted not to be ideas, yet inferrible. Therefore, even 
as sensible, primary and secondary qualities are not 
ideas, but physical qualities in sense, from which to infer 
physical qualities beyond. So universally, the inference 
of imperceptible corpuscles with real qualities and 
powers beyond sense, even if only probable, could not 
be drawn from mere ideas of sensation. The natural 
1 IV. 20, 12. 2 IV. IT. 


philosophy of the physical world, whether it be know 
ledge or opinion, demands physical data of sense. 

How came Locke, having said that whatsoever the 
mind perceives in itself or is the immediate object 
of perception, thought, or understanding, that I call 
idea, l immediately to conclude real primary qualities of 
matter ? Through the Cartesian habit of surreptitiously 
passing from the idea to the thing, and his own supposi 
tion of a bastard sensation of the thing. His one argu 
ment for the reality of primary qualities is that they are 
such as sense constantly finds in every particle of matter, 
which has bulk enough to be perceived. 2 But according 
to him sense is of ideas. All then he could consistently 
say would have been that primary qualities are such as 
sense constantly finds in the idea of every particle of 
the idea of matter, which has the idea of bulk enough 
to be perceived. But this consistency with his hypothesis 
would not have proved the fact of the material reality 
of primary qualities beyond ideas. At the same time, 
his lapse into a direct sense of matter is of interest, 
because it is a distinct anticipation of intuitive realism. 
It exhibits the constant tendency of the philosopher to 
relapse into the ordinary man, and to fancy he directly 
perceives the external thing, or, using the inaccurate ter 
minology of modern psychology, after contending that 
what we are conscious of is subjective affections, to sup 
pose a consciousness of objective existence. As Locke 
tried to bridge over the gulf from ideas of sensation to 
qualities by a kind of bastard sensation of qualities, 
so his modern followers try to bridge the gulf from 
subjective affections of consciousness to objective exist 
ence by an undefinable consciousness of objective exist 
ence. But it is certain that sensation perceives not the 

1 Essay, II. 8, 8. 2 II. 8, 9. 

CHAP. vi. LOCKE 185 

external thing, but its internal effect ; and the only way 
in which we can reach external qualities of things is not 
by sense but by inference from adequate internal data, 
which cannot be mere ideas, nor any psychical states of 
subjective consciousness. 

The Essay concerning Human Understanding 
begins by assuming that all objects of understanding,*, 
as well as all data of sense, are ideas : it ends by ad 
mitting that things beyond ideas are objects of under-^ 
standing, reasoning, science. The end is better than 
the beginning, though the conclusion does not follow 
from the premises. External bodies are properly in 
ferred by ordinary men, as Locke admitted ; and 
imperceptible corpuscles and their qualities are known, 
with more certainty than he admitted, by men of science. 
Therefore, in the first place, not all objects of under- ^ 
standing, reasoning, science, are ideas. Secondly, the 
data of sense are neither ideas of sensation nor externals 
qualities of matter, but internal effects on the nervous 
system, sensibly qualified as extended, moving, hot, 
coloured, and by other primary and secondary qualities. 
From internal, ordinary knowledge infers external, sub- t 
stances. From these again science, correcting ordinary 
knowledge, infers imperceptible corpuscles, qualities 
primary and secondary as the modifications of primary 
powers exerted between those corpuscles, and powers 
of affecting our senses. Locke s Essay throughout, to 
make it thoroughly correct, consistent, and consequent, 
would need two fundamental alterations : 

1. Some objects of understanding are physical things. * 

2. Some data of sensation are physical effects 

the nervous system. 




THE two philosophers hitherto discussed assumed 
hypotheses, but admitted facts, and tried to explain 
them. Descartes assumed that ideas are the data of 
sense, but admitted the knowledge of physical objects, 
and broke down on the inconsequence of reasoning 
from psychical data in the premises to physical objects 
in the conclusion. Locke made the same assumption, 
the same admission, and the same failure. But he went 
further into hypothesis, and to inconsequence added 
inconsistency. He assumed that ideas are not only 
all the data but also all the objects of understand 
ing, and then admitted that physical objects are also 
objects of understanding. The admission is true, and 
therefore, while it contradicted, also destroyed the 
double hypothesis. We now come to a philosopher 
who, accepting the whole ideal hypothesis, consist 
ently denied facts. Berkeley assumed, with Descartes, 
that ideas are the data, and with Locke, that they are 
the objects, of human knowledge, and consistently, but 
falsely, deduced man s ignorance of a physical world. 

The Principles of Human Knowledge, after an 
Introduction on Abstract Ideas, begin in the following 
manner : 

It is evident to any one who takes a survey of the 
objects of human knowledge, that they are either ideas 

CHAP. vii. BERKELEY 187 

actually imprinted on the senses, or else such as are 
perceived by attending to the passions and operations 
of the mind, or lastly, ideas formed by help of memory 
and imagination, either compounding, dividing, or 
barely representing those originally perceived in the 
aforesaid ways. By sight I have the ideas of light and 
colours with their several degrees and variations. By 
touch I perceive, for example, hard and soft, heat and 
cold, motion and resistance, and of all these more or 
less either as to quantity or degree. Smelling furnishes 
me with odours, the palate with tastes, and hearing 
conveys sounds to the mind in all their variety of tone 
and composition. And as several of these are observed 
to accompany each other, they come to be marked by 
one name, and so to be reputed as one thing. Thus, 
for example, a certain colour, taste, smell, figure and 
consistence having been observed to go together, are 
accounted one distinct thing, signified by the name 
" apple." Other collections of ideas constitute a stone, a 
tree, a book, and the like sensible things ; which, as 
they are pleasing or disagreeable, excite the passions of 
love, hatred, joy, grief, and so forth. l 

Here are most of the errors in the Second and Third 
Books of Locke s Essay accepted as principles. With 
out proof, ideas alone are supposed to be perceived ; 
ideas of qualities without a qualified subject, and 
ideas of operations without a thinking subject. Beason- 
ing from the data of sense to their causes is entirely 
postponed in favour of representing, compounding and 
dividing ideas. Ideas, simple or complex, are consist 
ently declared to be all the objects of human knowledge. 
But these so-called principles are mere hypotheses. 
There is not one word of proof that either the data or 

1 Princ. i. 


the objects of human knowledge are ideas. Locke, not 
human nature and not even the whole of Locke was 
the oracle of Berkeley. 

Berkeley, however, being a less various but a more 
logical thinker than Locke, was truer to the data of his 
predecessor. Locke, as we found, having assigned 
comparison, composition and abstraction as the three 
acts, which form new ideas from sense, suddenly, and 
without any justification, introduced a fourth act of 
supposition, which is a kind of reasoning, to account 
for our idea of substance. Berkeley avoided the after 
thought, and, at the same time, the truth, that reason 
does intervene in the formation of ideas from sense. 
Adhering to Locke s first thoughts, he perceived that 
what his predecessor had allowed about other complex 
ideas equally applied to complex ideas of substances. 
If we start from ideas of sensation, such as those of 
colour, taste, smell, figure and consistence, and merely 
compound these ideas, we can construct a collection of 
ideas and account it one distinct thing, called an apple ; 
but we cannot, without introducing a qualified physical 
substance into sense, and restoring its privileges to 
reason, either perceive or infer an external physical 
substance. Berkeley thus reduces Locke to logic ; nor 
has mental philosophy ever recovered this purely hypo 
thetical theory of substance. 

Berkeley also made an important correction in one 
of Locke s three acts, abstraction. Locke had supposed 
that we can form a perfectly abstract idea of a triangle, 
which is neither equilateral, equicrural, nor scalenon, 
but all and none of these at once. l Berkeley devoted 
the Introduction of the Principles to a criticism of this 
modern conceptualism, and founded modern nominalism. 

1 Essay, IV. 7, 9. 

CHAP. Til. 


He denied that he could abstract or conceive separately 
qualities which cannot exist separately, or form a 
general notion in Locke s sense. 1 He admitted that 
he could consider a figure merely as triangular, without 
attending to its particular qualities, but not form an 
abstract general inconsistent idea of a triangle. 2 Simi 
larly, Hume afterwards said, that all general ideas are 
nothing but particular ones annexed to general terms. 3 
The essential truth at the bottom of this theory is 
that abstraction is only a kind of attention. But, as 
often happens, one extreme view begets another. We 
cannot rise to a purely abstract idea, nor need we fall 
to a purely particular idea ; we cannot form an idea of 
triangle in general, nor need we think of a single 
triangle. We can frame a general idea of a miscella 
neous assemblage of similar individuals. 4 Secondly, 
the point about classes is, not what we conceive, but 
what we infer and know. But, while correcting 
Locke s exaggeration of abstraction, Berkeley left its 
independence of reasoning. The consequence is that, 
according to him, the limit of generalisation would be 
some single simple idea or some single collection of 
simple ideas of sense viewed generally. This narrow 
ness pervades his whole philosophy. There is, indeed, 
such a simple abstraction of ideas from sense, as we ad 
mitted in the last chapter. But reason, at the same 
time, starts from sense and first infers classes of in 
sensible objects, and then constructs general ideas of 
them in the rational imagination. Finally, this rational 
imagination of general ideas accompanies a rational 
abstraction ; like direct abstraction, attention, but atten 
tion to objects of reason. We can abstract, in the sense 

1 P-rinc. Introduction, x. 2 Id. xvi. 

3 Treatise, ii. 7. 4 Cf. Mill, Logic, iv. 2, 1. 


of attending to, an insensible object, not apart from the 
qualities which belong to it, but apart from the quality 
of being sensible, which does not belong to it. The idea 
of an object will indeed contain some sensible qualities, 
and usually some visible colour. But having inferred that 
the invisible object is coloured only in the sense of reflect 
ing sethereal undulations, by abstraction I consider the 
object as so qualified, without attending to it as visibly 
coloured. In short, I know by scientific reasoning that 
objects exist apart from merely sensible qualities, and 
I can attend separately to their existing apart. Berke 
ley fell into the error of postponing inference about 
classes, and therefore of limiting abstraction to direct 
formation of ideas from sense. Really, there are objects 
known by sense, and objects known from sense by 
reason ; and there is an abstraction from sense, and an 
abstraction from reason, though in both cases the ab 
straction is but attention to sensible and rational objects 
of knowledge. 

According to Berkeley, then, starting from the 
Second and Third Books of Locke s Essay, all the objects 
of human knowledge are ideas of sensation and reflec 
tion, and the collections of ideas made out of them by 
memory and imagination, to which lie reduced abstrac 
tion of ideas, and without reasoning about causes. But 
it is impossible for errors to remain perfectly logical. 
Though he had just said that all objects known to us are 
ideas, he proceeds, like Locke, dogmatically to assert 
that a thinking subject exists : 

6 But besides all the endless variety of ideas or objects 
of knowledge, there is likewise something which knows 
or perceives them, and exercises divers operations, as 
willing, imagining, remembering about them. This 
perceiving active being is what I call mind, spirit, soul, 



or myself. By which words I do not denote any one of 
my ideas, but a thing entirely distinct from them, 
wherein they exist, or which is the same thing, whereby 
they are perceived ; for the existence of an idea con 
sists in being perceived. 1 

Berkeley was dogmatic, but right, in asserting the 
existence of himself ; but he was wrong in calling this 
thinking subject a thing entirely distinct from his ideas, 
and in supplying no data for his knowledge of it. 
I am a thinker, from whom the subject and the 
thoughts are opposite abstractions. But, in spite of his 
criticism of abstract ideas, Berkeley had already fol 
lowed Locke s Second Book in supposing all the objects 
of reflection to be mere ideas of operations. The ques 
tion then arises, how he could possibly know that he 
was also a thinking subject. Locke had said that the 
thinking subject is a matter of mere supposition. 
Berkeley went a stage further : he said that it cannot 
be of itself perceived, but only by the effects which it 
produceth. 2 But there are several difficulties in al 
lowing him to take this view on his hypotheses. 
In the first place, if it is true, there is something which 
is known, though indirectly, without being an idea ; 
therefore, not all objects of understanding, but only all 
objects of sense, will be ideas. Secondly, if all the objects 
of sensation and reflection were ideas of sensible qualities 
and ideas of operations, as he supposes, the whole of 
these data would contain no subject, not of course a 
physical nor even a psychical subject, and nothing like 
a subject, for a subject is, as Berkeley admits, not an 
idea ; therefore, no subject, even no psychical subject, 
could be logically inferred. We must choose, therefore, 
between the original data and the illogical conclusion. 

1 Princ. ii. ~ Id. xxvii. 


But Berkeley was riglit in admitting the existence and 
knowledge of a thinking subject. Therefore, the data 
of sensation and reflection cannot be mere ideas. Even 
if not sensation, at least reflection must be perception 
of myself as a thinking subject, from which I infer 
other thinking subjects, and God Himself. 

Berkeley ought to have returned to Descartes, and 
-sjiegun with the consciousness, I think. But, although 
he saw that we cannot abstract what cannot exist sepa 
rately, he was so enthralled by Locke that he began by 
supposing that we perceive ideas of qualities and ideas 
of operations, when we cannot even abstract these ob 
jects except in the sense of attending to them in their 
subjects. The idea of colour and the idea of willing 
are as much abstractions as the idea of a triangle. We 
really perceive, by sensation, at least, the coloured, and 
by consciousness, at least, the willing. But Berkeley, 
like Locke, began all sense with abstract ideas of 
qualities and operations. Though, unlike Locke, he saw 
that he could derive no physical subject from the 
former, he illogically thought he could derive a thinking 
subject from the latter ideas, although, like Locke, he 
had no data for a logical sequence from the conscious 
ideas of operations to the thinking subject. 

Curiously enough, he ended, like Locke, in after 
all returning to Descartes, and in admitting, I know 
or am conscious of my own being. 1 This admis 
sion that I am conscious of myself is quite incon 
sistent with the original hypothesis that I perceive ideas 
of operations directly, and the subsequent corollary 
that I perceive myself only indirectly by my effects. 
Nevertheless, the admission is true, and the hypothesis 
and its corollary false. I cannot infer a thinking sub- 

1 Hylas and PJiilonous, Third Dialogue. 

CHAP. vii. BERKELEY 193 

ject from mere operations. I am not conscious of 
operations, still less of ideas of operations an abstrac 
tion, two removes from the truth. I am conscious of 
myself, as thinking subject. 

But Berkeley involved his admission of a thinking 
subject with another hypothesis. He accepted the 
Cartesian transition from self to soul without a word of 
proof. 1 As I have already shown, I am not conscious of 
this identification, I am conscious of the very reverse. 
The combined evidence of consciousness, observation, 
and reasoning teaches me that I am a man thinking 
partly by my body and partly by my soul. But, you 
will say, Berkeley was a theologian, who, knowing that 
God is a spirit, rightly inferred that man is a spirit. 
The answer is that man is not God. It is true that 
there is a resemblance, but there is also a difference. 
When I infer that there are other men, I observe, by 
direct inference from sense, two sorts of signs, bodily 
organs and physical works, from both of which I infer 
a man like myself, body and soul. But God only offers 
me one of these signs, His works of nature, but no signs 
of a body. Hence I have a right to infer that He is 
similar to myself, so far as He by intelligence and will 
produces works of order, beauty, and goodness, similar 
to those of man, but I have no right to infer either that 
He, like man, is also a body, or that man, like Him, is a 
pure spirit. Nor have I a right to infer that- 
All are but parts of one stupendous whole, 
Whose body nature is, and God the soul. 

Nature is to God as works are to man ; and as a man s 
body is not his works, so neither is nature the body of 
God. Hie omnia regit, says Newton 2 about the Deity, 

1 Princ. ii. 

2 Newton, Principia, Lib. III. Scholium Generate (sub fin.). 



non ut anima mundi, sed ut universorum dominus. 
God lias no body ; for how could He have a body pro 
portionate to His infinite intelligence and will, and show 
it not ? God, then, is a spirit ; man is not. 

Now, it is true that God, for a time, gave a bodily 
sign, when He took upon Himself a body and made 
Himself man. But the incarnation of Christ is a very 
proof of the difference between God and man. Christ 
ceased to be a pure Spirit, became flesh, and dwelt 
among us. Berkeley cannot explain this union of the 
Divine and the human in Christ. God is a spirit ; but 
if man is also a spirit, what is the incarnation ? 
Berkeley s only logical answer would be the gratuitous 
hypothesis that Christ took upon Himself certain ideas, 
called the human body. But Christ had the ideas already 
from eternity. What He wanted was the very body, re 
presented by those ideas, for a time. There is nothing 
for it, but that God is a spirit, and Christ took upon 
himself a body and became man, and man is both body 
and spirit in one. The idealistic hypothesis that I am 
a spirit is inconsistent both with philosophy and with 
Christianity. Yet in our own time a false philosophy 
of man as a purely spiritual subject is supposed to be 
a justification of Christian theology. 

Berkeley, in the Introduction and the first two sec 
tions of his Principles, furnished himself with his pre 
mises. They are anticipations of human nature, mainly 
derived from Descartes and Locke, with an occasional 
assumption of his own. Let it be granted, from Des 
cartes, that the thinking subject, myself, is a mind, 
spirit, soul. Let it be granted, from Locke s Second 
Book, that not only all data, but all objects of know 
ledge, are simple ideas of sensation and reflection, 
and ideas compounded by memory and imagination, 



without taking any notice of reasoning ; and let us 
avoid Locke s inconsistency of supposing an external 
physical substance beyond a collection of ideas, and his 
error of purely abstract ideas. Let the premises, which 
he owes to Descartes and Locke, be granted to Berke 
ley, without his proving them. What follows ? Why, 
the purely hypothetical, fairly logical, wholly synthetic 
deduction from false and unproved hypotheses, known 
as the Berkeleian philosophy. He who is foolish enough 
on the mere authority of this doctor to swallow the 
hypotheses, like pills, will find that the deductions will 
purge him of all knowledge beyond spirit and ideas. 

Berkeley begins his deductions by explaining the 
existence of what he calls sensible things, and denying 
that what he calls unthinking things exist except as 
perceived : The table I write on, I say, exists, that 
is, I see and feel it ; and if I were out of my study I 
should say it existed, meaning thereby that if I was in 
my study I might perceive it, or that some other spirit 
actually does perceive it. There was an odour, that is, 
it was smelled ; there was a sound, that is to say, it was 
heard ; a colour or figure, and it was perceived by sight 
or touch. This is all that I can understand by these 
and the like expressions. For as to what is said of the 
absolute existence of unthinking things without any 
relation to their being perceived, that seems perfectly 
unintelligible. Their esse is per dpi ^ nor is it possible 
that they should have any existence out of the minds 
of thinking beings which perceive them. l 

So far as this argument follows from its premises it 
is hypothetically unanswerable. The esse of ideas is 
per dpi-, if, then, all objects of human knowledge are 
ideas, their esse will be per dpi ; and again, an unthink- 

1 Princ. iii. 

o 2 


ing tiling, which is not an idea, will not be humanly 
known to exist. Berkeley was entitled to these hypo 
thetical conclusions. But his argument conceals a 
further false hypothesis, namely, that what is unknown 
by man to exist, being unintelligible to him, is non 
existent ; from which he concluded that a purely un 
thinking thing is not only unknown by man, but also 
non-existent. Thus to hypotheses and hypothetical de 
duction Berkeley added dogmatism. He dogmatically 
asserted the existence of mind and the non-existence 
of matter. 

The importance of the deductions which immediately 
follow consists in their entire omission of reasoning 
from the data of sense to their causes, and its conse 
quences, when combined with Locke s premises. 
Houses, mountains, rivers, and, in a word, all sensible 
objects, are supposed to have a separate existence. 
Now, says Berkeley, they are what we perceive by sense, 
and what we perceive are ideas or sensations ; therefore 
they are ideas or sensations. 1 He adds that it is only 
the doctrine of abstract ideas which makes us dis 
tinguish the existence of sensible objects from their 
being perceived. 2 But it is not true that a house is 
a sensible object which we perceive by sense ; sense 
perceives only a sensible effect of an external house, 
which is inferred by reasoning, and can be distinguished 
from the sensible effect by the attention of abstraction. 
But it is true that if We choose to omit reasoning about 
causes, and suppose that sense perceives ideas or sen 
sations, the only house we should know would be, not 
the house now inferred, but only what we should then 
perceive, a mere collection of ideas or sensations, in 
capable of being abstracted from being perceived. 

1 Princ. iv. 2 Id. v. 



This strict though hypothetical logic from Locke s 
Second Book removed Berkeley into another arena of 
philosophy. Descartes and Locke had admitted the 
existence and knowledge of an external world, not 
merely psychical but also physical ; that a house is an 
external object causing our ideas ; and, in accordance 
with the representative theory, that perception presents 
ideas but represents external objects. Berkeley, agree 
ing both with Descartes and Locke in the perception of 
ideas, but aware that neither philosopher supplied data 
from which to infer an external object, and following 
Locke in postponing reasoning about it, logically con 
cludes that the external object and the sensible object 
are one, and that in perceiving an idea or sensation, we 
are perceiving not a sensible effect of an external house, 
but the house itself. His pure idealism produced the 
metaphysical theory that objects, supposed to be ex 
ternal, are nothing but ideas or sensations in the mind, 
and the psychological theory of a presentative percep 
tion of ideas or sensations, representing nothing. 

Having hypothetically deduced that the esse of all 
objects known to man is per dpi, and that what are called 
external objects are really ideas or sensations, Berkeley 
proceeds to the conclusion that all the choir of heaven 
and furniture of the earth ; in a word, all those bodies 
which compose the mighty frame of the world, exist 
in my mind, or in that of some created spirit ; or else 
subsist in the mind of some eternal spirit. 1 This con 
clusion also follows from the premises. If all objects 
of knowledge are ideas, and ideas subsist in the mind of 
some spirit, it follows necessarily that the whole known 
world subsists in the mind of some spirit. So far, 
indeed, as the human spirit goes, we could only speak 

1 Princ. vi. 


of tlie whole known world. We saw above that Berke 
ley, while speaking even of man, 1 denied the existence 
of what was not an object of human knowledge. He 
now corrects this defect by the addition of the eternal 
spirit, 2 to whom whatever exists is known, while what is 
not known does not exist. Of the Divine spirit at least 
Berkeley could say, whatever exists is an object of His 
knowledge; if, then, all objects _of knowledge are ideas, 
and ideas subsist in the mind of a spirit, whatever exists 
subsists in the mind of the eternal spirit of God. Even 
so, however, it might be objected that, if ideas are the 
objects of human, it does not follow that they are the 
only objects of Divine knowledge. But in Berkeley s 
Principles there is a perpetual equivoque between the 
sensible ideas of man and the intellectual ideas of God. 
From what has been said it follows that there is 
not any other substance than spirit ; this is the next 
hypothetical consequence. 3 It is an immediate corol 
lary. If there were only man, the only known substance 
would be spirit, but add God and it would follow that 
the only existing substance is spirit, so that there remains 
no unthinking substance. 4 Berkeley further proceeds to 
deduce this denial of matter from the hypothesis of 
ideas. He is perfectly logical. Ideas cannot exist in 
an unthinking substance ; if then sensible qualities were 
ideas, there would be no unthinking substance or substra 
tum of those ideas or qualities. 5 Again, he warns us 
against those who maintained that, though unthinking 
substance is not the substratum of sensible ideas, ideas 
are nevertheless the copies or resemblances of unthinking 
substance. I answer, he says, an idea can be like no 
thing but an idea. G This memorable sentence marks 

1 Princ. iii. 2 Id. vi. 3 Id. vii. 4 Id. 

5 Id. 6 Id. viii. 


the return of the logic of reasoning into mental philo 
sophy. Berkeley at this point begins to think about 
reasoning, though too late ; for he had already fixed the 
objects of knowledge without it. But he thinks about 
it as a logician, and gives the answer to the illogical 
attempt of Descartes and Locke to first enclose man 
within psychical ideas, and then, without any clue in the 
data, expect him to discover physical objects. In the 
case of physical substances, if the data of inference were 
sensible qualities as ideas, we could infer a similar col 
lection of qualities as ideas ; if they were qualities with 
out beim? ideas, we could infer a similar combination of 
qualities^; but in neither case could we infer a physical 
substance, for which we should have no analogue in 

sense. 1 

This rigorous logic from Locke s hypotheses of ideas 
enabled Berkeley to destroy Locke s theories of material 
substance and its primary qualities at a blow :- 

6 Some there are who make a distinction betwixt 
primary and secondary qualities : by the former, they 
mean extension, figure, motion, rest, solidity or impene 
trability, and number ; by the latter they denote all 
other sensible qualities, as colours, sounds, tastes, and so 
forth. The ideas we have of these they acknowledge not 
to be the resemblances of anything existing without the 
mind or unperceived ; but they will have our ideas of 
the primary qualities to be patterns or images of things 
which exist without the mind, in an unthinking sub 
stance which they call matter. By matter, therefore, we 
are to understand an inert, senseless substance, in which 
extension, figure, and motion do actually subsist. But 
it is evident, from what we have already shown, that 
extension, figure and motion are only ideas existing in 

1 Cf. Princ. xxxvii. 



the mind, and that an idea can be like nothing but 
another idea, and that consequently neither they nor 
their archetypes can exist in an unperceiving substance. 
Hence it is plain, that the very notion of what is called 
matter or corporeal substance involves a contradiction 
in it. 1 

Yes ; if, and only if, qualities as sensible are ideas, 
an idea is like nothing but another idea, and therefore 
we could infer no external qualities of matter ; neither 
insensible primary qualities like primary qualities as 
sensible, nor insensible secondary qualities as modifi 
cations of primary qualities and causes of secondary 
qualities as sensible. Now, matter is nothing without 
qualities ; therefore, we could not infer matter at all. 
The argument is quite logical, if we once admit with 
Locke, that, as sensible, all qualities are ideas. If with 
modern idealists we should substitute sensations, it 
would equally follow that we could infer no insensible 
qualities of matter, and therefore no matter at all. 

Berkeley added a second argument to prove that all 
qualities exist only as ideas in the mind and not in 
matter and its particles : 

They who assert that figure, motion and the rest 
of the primary original qualities do exist without the 
mind in unthinking substances, do at the same time 
acknowledge that colours, sounds, heat, cold, and such 
like secondary qualities, do not, which they tell us are 
sensations existing in the mind alone, that depend on 
and are occasioned by the different size, texture, and 
motion of the minute particles of matter. This they 
take for an undoubted truth which they can demonstrate 
beyond all exception. Now if it be certain that those 
original qualities are inseparably united with the other 

1 Princ. ix. 



sensible qualities, and not, even in thought, capable of 
being abstracted from them, it plainly follows that they 
exist only in the mind. But I desire any one to reflect 
and try whether he can, by any abstraction of thought, 
conceive the extension and motion of a body without all 
other sensible qualities. For my own part, I see evi 
dently that it is not in my power to frame an idea of a 
body extended and moved, but I may withal give it 
some colour or other sensible quality which is acknow 
ledged to exist only in the mind. In short, extension, 
figure, and motion, abstracted from all other qualities, 
are inconceivable. Where, therefore, the other sensible 
qualities are there must these be also, to wit, in the 
mind, and nowhere else. l 

This argument does not touch Locke, so far as it 
depends on the admission that secondary qualities are 
mere sensations ; for Locke said that, as sensible, they 
are ideas, and, as external, powers. But it touches 
later theories of secondary qualities, realistic and 
idealistic. It is true that if secondary qualities are 
sensations, primary qualities, as sensible, will also be 
sensations, from which no external quality, and there 
fore no matter, could be inferred. Moreover, the argu 
ment is interesting as another instance of Berkeley s re 
duction of the external to the sensible. He saw that on 
the conjoint hypothesis that sense perceives qualities as 
sensations, with abstraction of ideas, but without 
reasoning to causes, we should only be able to infer and 
attend to qualities, primary and secondary, as they are 
fused in sensation. Hence his followers invariably re 
gard primary and secondary qualities merely as various 
kinds of sensations, and not as external qualities. 

By this series of hypothetical arguments Berkeley 

1 Princ. x. 


arrived at tlie following conclusions : all subjects are 
spirits and all objects ideas of spirits. This absolute 
universality logically applies only to the eternal spirit. 
As far as the human spirit goes, Berkeley s conclusions, 
so far as they are logical, must be put in a more 
moderate form. If there are spirits, and all objects of 
knowledge are ideas, then all known subjects are spirits 
and all known objects are ideas ; a physical subject of 
qualities is not known to exist, and qualities, primary 
and secondary, are known as ideas or sensations in our 
minds, but are not known to be external qualities of 
physical subjects, bodies and corpuscles, in an external 
world. What, then, is to become of the minute particles 
of matter, their latent sizes, textures, and motions ; to 
say nothing of their priority, and their production of 
our sensations ? What, again, are the causes of the ideas 
or sensations in the mind of a human spirit ? Berkeley, 
like Locke, at last found himself face to face with the 
problem of reasoning to causes. Given ideas of spirits 
as all the data and objects of knowledge, what causes 
can reason infer ? 

We might feel tempted now to say that Berkeley, 
having the universe of Divine ideas, as it were, in his 
grasp, would at once say that the external world of 
bodies, their corpuscles, and their qualities, which the 
natural philosopher has discovered to be the insensible 
causes of sensible qualities, even asther and its motions, 
are Divine ideas, by which the Deity produces the sen 
sations of man. But Berkeley no more than the modern 
Berkeleian resorts to this Hegelian alternative. He 
precluded himself from taking it, both by his identifica 
tion of the external with the sensible object, and by 
his doctrine of the inactivity of ideas. As the former 
deprived him of the external world as a distinct object, 



so the latter prevented him from regarding insensible 
causes as ideas. All our ideas, says he, sensations, 
or the things which we perceive, by whatsoever names 
they may be distinguished, are visibly inactive ; there 
is nothing of power or agency included in them, so 
that one idea or object of thought cannot produce or 
make any alteration in another. l So far from resolving 
insensible scientific causes into Divine ideas acting on us, 
he uses the theory of the inactivity of ideas to deny in 
sensible scientific causes. Whence, it plainly follows, 
lie concludes, that extension, figure, and motion cannot 
be the cause of our sensations. To say, therefore, that 
these are the effects of powers, resulting from the con 
figuration, number, motion, and size of corpuscles, must 
certainly be false. 2 

Berkeley, having decided that the cause is not the 
qualities of corpuscles, proceeded to infer that it is the 
spirit of God : 

We perceive a continual succession of ideas, some 
are anew excited, others are changed, or totally disap 
pear. There is, therefore, some cause of these ideas 
whereon they depend, and which produces and changes 
them. That this cause cannot be any quality or idea, 
or combination of ideas, is clear from the preceding 
section. It must, therefore, be a substance ; but it has 
been shown that there is no corporeal or material 
substance. It remains, therefore, that the cause of 
ideas is an incorporeal active substance or spirit. a 

Berkeley, like Descartes and Locke, saw that there is 
an involuntariness in our sensations which requires 
some cause. They might have all stopped there, and 
said that the nature of the cause is unknown ; but 
they were too philosophical to be agnostics. Descartes 

1 Princ. xxv. 2 Id. 3 Id. xxvi. 


and Locke, however, were not logical enough to see 
what cause could be inferred from their data; but 
guided by real facts rather than by their theories 
illogically supposed that, without anything physical in 
the data, we could infer a physical cause. Berkeley, 
on the other hand, was the first of the psychological 
idealists to see that the data and objects of knowledge 
must determine the inference ; so that, if the data and 
objects are mind and ideas, when we find ideas in 
sensation, which are due neither to one s own ideas nor 
to one s own mind, we cannot infer a corporeal or 
material substance, but must infer that the cause is 
either other ideas or another mind. He had elimi 
nated other ideas by his doctrine of the inactivity 
of ideas. There remained another mind. Now, proceeds 
he, though we are conscious of being able to produce 
some ideas by will, yet the ideas of sense have not 
a like dependence on our will ; there is therefore some 
other will or spirit that produces them, and in an order 
which proves that this cause is the spirit of God. 1 Thus, 
the solution, which was suggested by Descartes, as a 
possible alternative in his Principia Philosophise, 2 and 
which ought to have been taken by Locke in the 
Fourth Book of his Essay, when he had deserted mere 
ideas in favour of an intuition of oneself and a demon 
stration of God, was at length adopted by Berkeley in 
his Principles. If all the data are ideas and minds, 
created and eternal, and if ideas are inactive, the only 
logical conclusion is that the sensible ideas of created 
minds are direct imprints of the eternal Spirit of God. 

This logical conclusion of psychological idealism, 
evaded by Descartes and Locke, was accepted by 
Berkeley, with all its hypothetical consequences. As 

1 Princ. xxviii.-xxx. 2 Descartes, Princ. ii. 1. 

CHAP. vii. BERKELEY 205 

usual, he felt the double edge of his weapon, and was 
prepared not only with what is, but with what is not. 
On the one hand, he concluded that God is, and on the 
other hand, that matter is not, the cause of our sensa 
tions. 1 Secondly, he concluded that the set rules or 
established methods, wherein the mind we depend on 
excites in us the ideas of sense, are called the laws of 
nature 2 Thirdly, he concluded that God is not merely 
the prime cause, but the immediate and sole cause of 
sensible effects, setting aside second causes, such as the 
sun and the motion of bodies : 

And yet this consistent uniform working, which 
so evidently displays the goodness and wisdom of that 
governing spirit, whose will constitutes the laws of 
nature, is so far from leading our thoughts to him, that 
it rather sends them a-wandering after second causes. 
For when we perceive certain ideas of sense constantly 
followed by other ideas, and we know that it is not 
of our own doing, we forthwith attribute power and 
agency to the ideas themselves, and make one the cause 
of another, than which nothing can be more absurd and 
unintelligible. Thus, for example, having observed 
that when we perceive by sight a certain round luminous 
figure, we at the same time perceive by touch the idea 
or sensation called heat ; we do from thence conclude 
the sun to be the cause of heat. And in like manner 
perceiving the motion and collision of bodies to be 
attended with sound, we are inclined to think the latter 
an effect of the former. 3 

Finally, he presents us with his complete theory of 
real things, when second causes have been expunged : 4 

The ideas imprinted on the senses by the author of 
nature are called real things ; and those excited in the 

1 Berkeley, Princ. xxvi. 2 Id. xxx. 3 Id. xxxii. 4 Id. xxxiii. 


imagination, being less regular, vivid and constant, are 
more properly termed ideas or images of things, which 
they copy and represent. But then our sensations, be 
they never so vivid and distinct, are nevertheless ideas, 
that is, they exist in the mind, or are perceived by it, 
as truly as the ideas of its own framing. The ideas of 
sense are allowed to have more reality in them, that 
is, to be more strong, orderly and coherent than 
the creatures of the mind ; but this is no argument 
that they exist without the mind. They are also less 
dependent on the spirit, or thinking substance which 
perceives them, in that they are excited by the will of 
another and more powerful spirit ; yet still they are 
ideas, and certainly no idea, whether faint or strong, 
can exist otherwise than in a mind perceiving it. 

This passage marks a turning-point in the history of 
idealism. Hitherto, the line between ideas of sensation 
and ideas of conception had not been so carefully 
drawn as that between all ideas and the physical 
realities which cause them. Now, Berkeley, having 
deduced the destruction of physical realities, while still 
preserving the hypothesis that ideas are the objects of 
sensation, was puzzled to find some boundary between 
the real and the ideal. He drew it between the ideas of 
sensation and the ideas of imagination, partly by their 
vividness and faintness, but mainly because the former 
are directly produced by God. Hence, he identified 
sensible ideas with real things, at the same time explain 
ing that they are after all only ideas. 

Sensible ideas he declared to be his rerum natural 
He even admitted corporeal substances, taken in the 
vulgar sense for a combination of sensible qualities, not 
in the philosophic sense for a support of accidents or 

1 Princ. xxxiv. 



qualities without the mind. 1 So sure was he that sensible 
ideas are the real things, that he even said that we are fed 
and clothed w r ith these things which we perceive im 
mediately by our senses ; that is, by sensible ideas. 2 
Thus did he reduce reality to ideas imprinted on our 
senses by God without the intervention of physical 
causes, sense to the presentation of sensible ideas repre 
senting no external bodies, and knowledge to collections 
of ideas inferring no external cause except God. He 
took the show of sense for the nature of things, and 
thought that, if the veil were uplifted, we should see 
nothing but God. 

This doctrine of reality, much more logical, but 
also far narrower than that of Descartes and Locke, is 
the transition to Hume s distinction of impressions and 
ideas, and has ended in the ordinary sensationalism of 
modern Berkeleians, such as Mill, who do not indeed say 
that God is the direct cause of our sensations, but give up 
the problem and leave sensations in mid-air, nor dogma 
tise about all reality but confine themselves to known 
reality, in other respects differing in nothing but ter 
minology from Berkeley. The fundamental character of 
Berkeleianism is the theory that everything real is either 
my sensations and combinations of sensations, or those 
of other minds. I do not believe, says Mill, that the 
real externality to us of anything, except other minds, 
is capable of proof. 3 

It is often said that Berkeley is unanswerable, in his 
final position that the real world consists of ideas im 
printed on our senses, not by nature, but by the spirit 
of God. He cannot be answered by the hypothetical 

1 Princ. xxxvii. 2 Id. xxxviii. 

3 Examination of Sir W. Hamilton s Philosophy, chap, xi., note, 
sub Jin. 


realism of cosmothetical idealists, sucli as Descartes and 
Locke and tlieir modern successors, because they start 
knowledge, like Berkeley, with nothing but psychical 
data, from which nothing but the psychical could be 
inferred, and only suppose it to infer physical causes, 
by bad logic. Berkeley was the first logician of idealism. 
Cosmothetic idealism is an inconsequence, which must 
end in pure idealism at last. 

Again, he cannot be answered by intuitive realism, 
because it rests on the false identification of the sensible 
and external world by common sense, instead of appealing 
to the distinction of the sensible effect from the external 
cause by science. It is no use to knock the stick on the 
ground, when Berkeley resolves the ground and the stick 
into ideas, and the agent into a spirit. It is no answer 
to assert that the things immediately perceived are real 
things ; for Berkeley admits it, but says that they are 
also sensible ideas or sensations. 1 It is no answer to 
oppose a presentative perception of apples and houses 
to a philosopher, who agrees but rejoins that the things 
presented are only collections of ideas. If Berkeley is 
equal to the intuitive realist on the ground of common 
sense, he is superior on the ground of science and philo 
sophy. The intuitive realist supposes that the real world 
directly perceived is external ; science shows that it is 
within ; Berkeley adds that it is within the mind. The 
intuitive realist supposes that a secondary quality is 
directly perceived as a mere sensation in the mind, a 
primary quality as a real quality in the external world ; 
Berkeley, in a far more philosophic spirit, shows that 
they are directly perceived in the same manner, for, as 
sensible it is impossible to separate extension, figure and 
motion from other sensible qualities. Both confuse two 

1 Princ. xxxiii. scq. ; Hylas and PJiilonous, Third Dialogue, sub fin. 

CHAP. vii. BERKELEY 209 

realities, distinguished by science, the sensible and the 
external ; but, if this common confusion could be over 
looked, it would be more scientific to make the real 
object of immediate perception, with Berkeley, entirely 
internal, than, with intuitive realism, partly internal and 
partly external as if I could perceive the light of a 
candle within me, and its extension in the outside world. 

The truth is that idealists and realists have had too 
many errors in common with Berkeley to answer him. 
Idealists share his error that the data are ideas, realists 
that the real world is the object of immediate percep 
tion. All of them, also, confine themselves too much 
to perceptible bodies, to the neglect of imperceptible 
corpuscles. Within that narrow circle Berkeley has 
no difficulty in resolving apples and houses, and even 
mountains and rivers, into sensible ideas. But we must 
turn the corner of pure idealism. The question is not 
what it makes of the sensible and the perceptible, but 
what it does with the imperceptible. The true contra 
dictory instance against Berkeley s position is the 
natural philosophy of the imperceptible world of cor 
puscles, which cause, but are not, and cannot be inferred 
from, sensations or sensible ideas. This is the answer of 
physical realism. Let us proceed to its details. 

In one way God, in another way nature, causes our 
sensations. There are two opposite extremes to be 
avoided the substitution of nature for God, and that 
of God for nature : the former the temptation of the 
natural philosopher, the latter that of the natural 
theologian. The natural philosopher prolongs the 
chain of physical causes, until at last he feels tempted 
to believe that he has expelled intelligence from nature, 
and say, I have swept the universe with my telescope 
and cannot find God. The natural theologian, dazzled 


by the universal cause, is apt to neglect the subordinate 
agency of physical causes, and forget nature in the love 
of God. 

Natural philosophy is limited by the nature of its 
evidence. God is inferred by combining the evidence of 
outer and inner sense ; but natural philosophy reasons 
only from sensation and observation, without conscious 
ness and reflection. Of itself, nature can neither prove 
nor disprove a deity. Even within its own limits natural 
philosophy is limited. Evolutionists, for example, have 
been more successful in dealing with organisms than in 
the far larger problem of the inorganic world. Evolution 
consists in the differentiation of homogeneous matter. 
Now differentiation invariably requires one of two condi 
tions : either one efficient cause must act on different 
materials, as when the same kind of motion produces 
molar motion in one body and molecular in another ; or 
different efficient causes must act on one kind of material, 
as when different lengths of undulation produce sensible 
heat or sensible light in the nervous system. Both 
alternatives presuppose difference ; the former difference 
in the patient, the latter difference in the agent. There 
is no known instance of one kind of cause acting on 
one kind of material and producing different kinds of 
effects. Hence, if we suppose matter, absolutely homo 
geneous, universally diffused, and reciprocally acting in 
its various parts, it would contain no difference either 
of agent or patient to produce the different effects of 
actual nature ; but all its particles, at equal distances, 
would exert all forces equally in all directions, and 
produce an exact balance, with no differences whatever. 
The theory of evolution, therefore, is no explanation of 
the beginnings of difference. But given a pre-existing 
difference, even of two groups of particles with dif- 

CHAP. vir. BERKELEY 211 

ferent arrangements of their primary qualities, how 
ever slight, evolution is the further differentiation, 
not of the absolutely, but of the relatively homo 
geneous into the more heterogeneous, arising from 
different structures acted on by one kind of agent, or 
different agents acting on one kind of structure, or 
different agents acting on different structures, and so on 
ad infinitum, not a parte ante, but a parte post. There 
must, however, be something else to cause an original 
difference in things. But limited as natural philosophy 
is within, it is still more limited from without. Having 
only reasoning from outer sense and observation, it dis 
covers physical causes ; but it cannot tell what else they 
may be. 

Natural theology now steps in, to supplement sensa 
tion by consciousness, observation by reflection, and to 
reason from both outer and inner sense. To observa 
tion, a workman and a product have the mere appear 
ance of cause and effect ; but when we add conscious 
reflection, we infer that he is an artist using means to an 
end ; and, when we observe again a similar work, we still 
infer an artist. So from His work, natural theology 
infers a Divine Architect of nature, establishing the 
original difference of things, and developing further 
differences, by using physical causes of effects as means 
to ends. Omnia qua? agunt in virtute primi agentis 
agunt. When science shows that evolution develops 
living organs, this is no reason why this very evolution 
should not be a Divine means of producing fresh life. 
The growth of a tree has not been regarded as inconsis 
tent with Divine agency ; why, then, should not Divine 
power be exercised in the whole growth of the world ? 
On the other hand, the natural theologian must not 
forget that, after all, the existence of nature must be 

r 2 


more certain than that of God, and that, indeed, without 
the order of nature the main part of the evidence for a 
God disappears. If God is the intelligent cause, most 
certainly the means used are physical causes. AK 
attempts to argue that because God is the cause of all 
effects, insensible motions are not causes, or that there 
can be no evolution, must fail, because nothing is more 
surely established than the powers and laws of motion. 
To convert God from an Intelligent Will using physical 
means into the direct and sole cause of every effect, 
even to the threshold of our senses, is the greatest 
danger that can befall natural theology, which must 
then yield to the laws of the communication and conser 
vation of motions. 

No reconciliation of theology and science will be 
found superior to that of Bacon, 1 which admits too of 
being perpetually enlarged with every physical dis 
covery : God having made nature uses it as a means ; 
the more physical causes, the more means at His com 
mand ; the more elaborate and indirect the physical 
process, the more subtle the Divine Architect ; who, 
having established a difference in corpuscular structure, 
uses the evolution of one particle acting on another as 
His further process of differentiation and His most in 
genious plan ; and natural philosophy is always, how 
ever unconsciously, prolonging the chain of physical 
causes to the throne of God. Sic Dei sapientia effulget 
mirabilius, says Bacon, cum Natura aliud agit, Provi- 
dentiaaliud elicit, quam sisingulis schematibusetmotibus 
naturalibus Providentias characteres essent impressi. 

Berkeley for nature substituted God. By his hypo 
theses and logical deductions he was compelled to say 

1 De Augmentis Scientiarum, iii. 4, sub fin. (Ed. Ellis and Speddmg, 
Vol. i. p. 570.) 



that ideas are imprinted on our senses, not by the in 
sensible motions of physical substances, but by the 
direct agency of God Himself. Instead of an Intelligent 
Agent, using nature as the means to produce effects on 
our senses, God, without the intervention of insensible 
nature, thus becomes the direct and sole cause of every 
sensible effect. There is God, then, and no nature, but 
the nature of man. The good bishop flattered himself 
that he was thus serving the cause of his religion. But 
how different is the doctrine of the Bible ! In the 
beginning God created the heavens and the earth ; and, 
only after nature, man. This is the meeting-point of 
religion and science. 

In substituting God for nature, and denying second 
causes, Berkeley not only falsified religion but also 
contradicted science. He said that God is, but nature 
is not, the cause of our sensations. His followers have 
deserted his theory of religion, but they have supplied 
no adequate theory of science. Any mental philoso 
pher, who says that real things are our sensible ideas or 
sensations, whether he says that they are produced by 
God, with Berkeley, or, with the modern Berkeleian, 
gives up the knowledge of the causes of our sensa 
tions, in either case he is following Berkeley in rejecting 
the positions of natural philosophy that the external 
sun is the cause of sensible heat, that the motion and 
collision of particles of air insensibly proceed till at last 
they produce sensible sounds, and that imperceptible 
corpuscles, with their configuration, number, motion, 
and size, cause our sensations. 1 

Psychological idealism had gradually brought mental 
philosophy into this state of paradox by the very poverty 
of its data. Descartes was a scientific genius, labouring to 

1 Cf. Princ. xxv., xxxii. 


bring a narrow mental into harmony with a wider natural 
philosophy. Locke, beginning to feel the difficulty, depre 
ciated natural philosophy, because he could not explain 
it. Berkeley, logically deducing the vanity of the 
attempt at explanation, boldly wrote a polemic against 
the natural philosophy of corpuscles and their motions. 1 
This sad, but inevitable, defect is generally omitted or 
extenuated by historians of philosophy. But Berkeley 
himself was well aware what were the logical conse 
quences of idealism. One passage from his polemic will 
be sufficient : 

Some have pretended to account for appearances 
by occult qualities, but of late they are mostly resolved 
into mechanical causes ; to wit, the figure, motion, 
weight, and such-like qualities of insensible particles : 
whereas, in truth, there is no agent or efficient cause 
than spirit, it being evident that motion, as well as all 
other ideas, is perfectly inert. (See sect, xxv.) Hence 
to endeavour to explain the production of colours or 
sounds by figure, motion, magnitude, and the like, 
must needs be labour in vain. Accordingly, we see the 
attempts of that kind are not at all satisfactory. 2 

But we have seen, since Berkeley s time, a sure 
progress in the natural philosophy of mechanical 
causes. A striking contrast to the passage just quoted 
may be found in the following quotation from Professor 
Tyndall s Fragments of Science 3 : 

The domain in which this motion of light is 
carried on lies entirely beyond the reach of our senses. 
The waves of light require a medium for their forma 
tion and propagation ; but we cannot see, or feel, or 
taste, or smell this medium. How, then, has its exist 
ence been established? By showing that, by the 

1 Princ. ci. seq. 2 Id. cii. 3 Pp. 72-3. 



assumption of this wonderful intangible cether, all the 
phenomena of optics are accounted for, with a fulness, 
and clearness, and conclusiveness which leave no desire 
of the intellect unsatisfied. When the law of gravi 
tation first suggested itself to the mind of Newton, 
what did he do ? He set himself to examine whether it 
accounted for all the facts. He determined the courses 
of the planets ; he calculated the rapidity of the moon s 
fall towards the earth ; he considered the precession of 
the equinoxes, the ebb and flow of the tides, and found 
all explained by the law of gravitation. He therefore 
regarded this law as established, and the verdict of 
science subsequently confirmed his conclusion. On 
similar, and, if possible, on stronger grounds, we found 
our belief in the existence of the universal aether. It 
explains facts far more various and complicated than 
those on which Newton based his law. If a single phae- 
nomenon could be pointed out which the aether is 
proved incompetent to explain, we should have to give 
it up ; but no sucli phenomenon has ever been pointed 
out. It is, therefore, at least as certain that space is 
filled with a medium, by means of which suns and 
stars diffuse their radiant power, as that it is traversed 
by that force which holds in its grasp, not only our 
planetary system, but the immeasurable heavens them 

Berkeley s idealism is unscientific. From this point 
we must retrace our steps by the method of analysis. 
By the falsity of the consequences we must destroy the 
original hypotheses and find the real data of reasoning 
from sense to science. By a chain of logic, he had hypo- 
thetically deduced that, if all objects of human know 
ledge are ideas, derived from outer and inner sense, and 
by the help of memory and imagination variously com- 


pounded into collections of ideas, in the minds of created 
spirits, then such a spirit will be able to infer nothing 
but ideas and spirits, and to conclude that, if all ideas 
are inactive, our sensible ideas, which are passive and 
not caused by our own will, must be imprinted on our 
senses by the will of the eternal spirit of God ; so that 
real things, as distinguished from mere ideas of imagina 
tion, will be the sensible ideas directly imprinted on our 
senses by Divine, without the intervention of physical 
causes. Now, the flaw in this chain is in its last link, 
in the logical but false rejection, with which it ends, of 
the bodies, corpuscles, and mechanical causes, discovered 
by natural philosophy. 

What is corpuscular science ? In brief, there are 
bodies insensible and imperceptible, or corpuscles. They 
possess primary qualities, various species of which are 
secondary qualities ; especially, they possess motion, a 
primary quality, whose secondary species are undula 
tions of cether, vibrations of air, &c., and which also exists 
in various forms, such as cohesion, gravitation, chemi 
cal attraction, electricity, magnetism, &c. Corpuscles 
have innumerable similarities and uniform relations or 
laws of nature, and especially the laws of motion 
and of the causation of motion by motion. They 
are also the particles of masses, or larger bodies, which 
are partly inorganic and partly organic. Among organ 
isms are bodies containing nervous systems, which 
consist, like other masses, of corpuscles having the 
various motions of bodies in general and a peculiar ner 
vous motion, combined with muscular motion. Lastly, 
some of the other bodies, among their innumerable pro 
cesses of cause and effect, produce in nervous systems 
sensible effects, such as sensible motion, sensible heat, 
&c. Such are the objects of corpuscular science. 


Corpuscular science destroys Berkeley s idealism in 
his logical conclusion from his original hypotheses. He 
denied second causes ; but motions producing motions 
are second causes. He said that God s will is the sole 
cause of sensible effects ; but corpuscular motions, 
acting on the corpuscles of the nervous system, also 
produce sensible heat, colour, sound, &c. If God is 
the prime cause, nature is the second cause, by means 
of which He acts on man. He said that the rules wherein 
God excites in us the ideas of sense are the laws of 
nature. But the uniform relations of corpuscular mo 
tions among themselves are an immense system of laws, 
compared with which the laws of their action on the 
nervous system and the senses are but a diminutive 
fraction. What account would it be of the universal 
law of gravitation, of every particle to every particle 
in the universe, to say that it is merely a rule to 
excite in us the sensible idea or sensation of weight ? 
God, then, is not the only cause, but under Him nature 
is also the cause and law of sensible effects. Again, 
Berkeley said that sensible ideas imprinted on sense by 
God are the real things, and external bodies are not : 
the Berkeleian says the same thing of sensations, only 
without dogmatism about the sole causation of God 
and about the absolute non-existence of external bodies. 
But the natural philosopher knows that external bodies 
are not sensations, but the causes of sensations and 
sensible ideas. For example, the gravitations of par 
ticles are not sensations, but are the known causes of 
sensible weight being felt by us. Therefore, so far 
from being non-existent, or so far from not being known 
to exist, external bodies and their motions are known 
to exist as causes of sensible effects. To the Berkeleian, 
then, we must answer, not all known realities are sensa- 


tions ; to Berkeley himself, not all realities are sensible 
ideas imprinted on our senses by the Author of our 
being ; but some known realities are external bodies and 
their qualities producing sensible effects in us. There 
is a known world of real bodies, intervening between 
God and man, and used by God as a means to cause 
effects in our senses. 

Corpuscular science destroys Berkeleian idealism not 
only in its hypothetical conclusions but also in its 
original hypotheses of the objects and data of human 
knowledge. Insensible corpuscles and their qualities are 
not our ideas, but the causes of our ideas. They are objects 
of natural philosophy, which, in the hands of Newton 
and his successors, is a kind of knowledge. Therefore, 
not all objects of knowledge are ideas, and some of the 
objects are corpuscular causes of our ideas. Again, if 
the original data were ideas, these corpuscular causes 
could not be inferred, as Berkeley logically showed. 
But they are scientifically inferred by natural philo 
sophy. Therefore, neither the original objects nor the 
original data are mere ideas. Corpuscular science deals 
double death to logical idealism. 

Berkeley had logically deduced from his hypothesis 
that all qualities are only sensible ideas. But natural 
philosophy has shown that insensible corpuscles have 
the primary quality of insensible motion, obeying various 
laws, and that insensible modes of corpuscular motion 
are the secondary qualities of light, heat, and sound 
in the universe. Sir Isaac Newton showed that, beyond 
the sensible resistance or weight which we feel, there is 
an insensible gravitation of particles which pervades 
the universe, which connects parts of bodies inaccessible 
to our senses, and which, in one of its myriad appli 
cations, causes bodies to feel heavy in our hands. 


Qualities, then, primary and secondary, are known in 
natural philosophy to belong to external bodies, as well 
as cause sensible effects in us. Moreover, their range in 
the insensible world of science is infinitely more extensive 
than their perception by sense. Qualities, therefore, 
are not mere sensible ideas or sensations, but are mainly 
the external characteristics of masses and corpuscles in 
nature. But, again, external qualities of bodies could 
not be inferred from sensible ideas of minds. There 
fore, qualities, even as sensible, are not sensible ideas. 
Berkeley was compelled by the logic of his idealism to 
reduce all qualities to sensible ideas, but he was doubly 
wrong in point of fact. Primary and secondary qualities, 
as known to corpuscular science, are neither reducible 
to, nor inferrible from, sensations or sensible ideas. 

Again, from Locke s hypothesis that sense always 
perceives ideas of qualities, Berkeley consistently de 
duced that we cannot suppose an unthinking substance, 1 
that Locke s substratum is an abstraction, like materia 
prima^ 2 and that the only known substance is a combina 
tion of sensible qualities, or ideas, with which we are 
fed and clothed. 3 But are these conclusions true and 
scientific ? The matter, known to natural science, is 
durable, extended, moving, causing and receiving mo 
tion ; it is not, indeed, also something else distinct from 
being these things ; nor, however, is it mere duration, 
extension, motion, causation, and reception of motion, 
distinct but combined. In other words, matter or body 
is not the abstract substrate supposed by Locke, nor 
the equally abstract combination of qualities substituted 
by Berkeley, but a qualified subject, characterised 
by a number of qualities. Now, besides all this, it is 

1 Princ. vii. 2 Id. xi., xvi. 

3 Id. xxxvii.-xxxviii. 


not, though it sometimes causes, a collection of sensible 
ideas. A drop of water contains the particles enume 
rated in the first page of this essay ; but the sensible 
effect of it on any of my senses, and the ideas I after 
wards form of it, do not contain anything of the kind, 
and are totally incapable of containing such a number 
of units of any kind, which are only inferred by reason. 
If there are so many particles in a drop of water, how 
many in a river, and how many in the ocean ? The 
truth is, that an analysis of a substance into particles is 
not a division of the sensible object, sensation, or sensible 
idea, but of the external object inferred. Corpuscles, 
then, are a proof of external bodies. Hence it follows 
that known substances are not abstract substrates of 
qualities, nor abstract collections of qualities, nor still 
more abstract ideas of collections of ideas of qualities, 
but qualified subjects, some of which are thinking and 
partly psychical, others unthinking and entirely phy 
sical. Again, as physical substances are not qualities 
nor ideas, so neither could they be inferred from such 
data. If sense never perceived anything but spiritual 
sensations or sensible ideas or qualities, science could 
not infer durable, extended, moving bodies containing 
corpuscles. But these substances are the very subjects 
of the laws of motion and gravitation. It follows, then, 
that the data of sense from which they are inferred are 
not mere qualities, still less sensations, least of all 
ideas, but the nervous substance sensibly qualified. 

To return at last to Berkeley s first principle. He 
said that all the objects of human knowledge are ideas 
imprinted on the senses, or else such as are perceived 
by attending to the operations of the mind or collections 
of these ideas. This supposed principle is a false 
hypothesis containing two fundamental errors ; an error 


about objects known, and an error about objects per 
ceived. The insensible and imperceptible corpuscles 
discovered by natural philosophers are not ideas of any 
of these kinds, though they are causes of them. Not 
all the objects of human knowledge, then, are ideas. 
Secondly, if the objects imprinted on the senses were 
ideas, the insensible corpuscles could not have been 
inferred. Not all the objects of human perception, then, 
are ideas. Insensible imperceptible corpuscles are 
physical objects of knowledge inferred from physical 
data of sense. Similarly their esse is not perdpi, as it 
would be if they were ideas. The esse of ideas of sen 
sation is per dpi. The esse of a sensible object is per- 
cipi by sense. An accident of the esse of an external 
body, e.g. water, is per dpi by inference. But the esse 
of an imperceptible corpuscle, e.g. in a drop of water, 
is not perdpi at all. 

Berkeley, by a confusion of esse and perdpi, adopted 
a presentative theory of perception, like the intuitive 
realists ; by a confusion of the sensible object with a 
sensible idea, his presentative theory is not realistic 
but idealistic ; by a confusion of the sensible and the real, 
it is a theory that we present sensible ideas as the real 
things. 1 He recurs again to this theory, as the very 
kernel of his philosophy, at the end of the Third 
Dialogue between Hylas and Philonous : 

Phil. I do not pretend to be a setter-up of new 
notions. My endeavours tend only to unite and place 
in a clearer light that truth, which was before shared 
between the vulgar and the philosophers ; the former 
being of opinion, that those things they immediately per 
ceive are the real things ; and the latter, that the things 
immediately perceived are ideas which exist only in the 

1 Cf. Princ. iv. 


mind. Which two notions put together do, in effect, 
constitute the substance of what I advance. 

Each one of the propositions in this theory is false. 
First, the things we immediately perceive are real things, 
but not the real things. There is an immense multi 
tude of real things known to science, but not im 
mediately perceived. The apple, the table, the house, 
the river, the mountain, cause sensible effects, which 
are real enough ; but they are external bodies whose cor 
puscles are known to have a like but different structure 
from that of the sensible effects ; the particles of a table 
are not the particles of my hand lying on it, nor of my 
tactile nerves, still less of the operation of sensation. 
Secondly, the things immediately perceived are not 
ideas which exist only in the mind. It is true that 
they are within me, and here is Berkeley s superiority 
over the intuitive realist. But, apart from the absence 
of direct evidence that the hard, or hot, or heavy felt 
is an idea within my mind ; if it were so, I could never 
infer the bodies and corpuscles, which, as we have 
found, are too well established in natural philosophy to 
be any longer denied. Therefore, things immediately 
perceived are, not ideas which exist only in the mind, 
but bodily effects of bodies on the nervous system. 
Lastly, Berkeley wishes us to draw the conclusion that 
ideas which exist in the mind are the real things, and 
that physical objects are not real things. His premises 
to prove it, however, are both false ; for, as we have seen, 
the things immediately perceived are neither the real 
things, nor ideas. Hence his syllogism only proves that 
ideas are real things, and some real things are ideas ; 
which is true enough, but also consistent with other real 
things. Xow, corpuscular science proves bodies which 
are real things in the external world ; and, to infer them, 

CHAP, vi r. BERKELEY 223 


logic requires bodily data, wliicli are real things in the 
nervous system. Other real things, then, are known 
and perceived, besides ideas. 

Berkeley s idealism and we may add all Berkele- 
ianism is false, metaphysically, psychologically, and 
logically : 

1. His metaphysical theory of existence is false, 
because not all real things are sensible ideas whose sole 
cause is God ; but some realities are known to be 
physical causes. 

2. His psychological theory of immediate perception 
is false, because we immediately perceive neither sen 
sible ideas, nor sensations, nor the real things, but real 
physical effects, representing real physical causes. 

3. His logical theory of reasoning is false, because 
from the first he prefers imagination and memory of 
ideas to reasoning about causes, and reasoning synthe 
tically from hypotheses to reasoning analytically from 

Berkeley omitted nature, between sense and God. 
Starting from Locke s hypothesis of the objects of know 
ledge, he rejected discoveries of natural philosophy, 
when he ought to have preferred the latter to the former. 
He ought to have gone still further, and surrendered 
not only Locke s hypothesis of the objects, but also the 
hypothesis of Descartes that the data of knowledge are 
psychical ideas. When Newton had shown what could 
be done in natural philosophy, mental philosophy should 
have reformed its data to explain his discoveries. But 
how seldom philosophers realise that their theories of 
man ought to explain a Shakespeare, a Bacon, a Newton ! 
To infer the Newtonian philosophy, the senses of man 
must perceive, not ideas of qualities, but various parts 
of the physical substance of the nervous system sensibly 


qualified as durable, extended, moving, as well as sound 
ing, heated, coloured ; from which even an ordinary man 
infers insensible bodies, a scientific man their imper 
ceptible corpuscles and motions and laws. If all objects 
of human knowledge were ideas of spirit, man could 
infer nothing but spirit and ideas. But the antecedent 
is an hypothesis, for which Berkeley had no authority 
except Descartes and Locke : the consequent is false, 
being contradictory to corpuscular science : therefore, 
the antecedent hypothesis is also false, because from 
true premises it is not possible to . draw a false conclu 
sion. The real world includes, between the sensible 
and the supernatural, the natural world of insensible 
bodies and imperceptible corpuscles, which are physical 
objects of scientific knowledge inferrible only from 
physical data of human sense. Such is the answer of 
physical realism. 



IN answering the objections which might be made 
against his Principles, Berkeley refers to his Essay 
towards a New Theory of Vision as follows : 

Thirdly, it will be objected, that we see things 
actually without or at a distance from us, and which 
consequently do not exist in the mind, it being absurd 
that those things which are seen at the distance of 
several miles should be as near to us as our own 
thoughts. In answer to this, I desire it may be con 
sidered, that in a dream we do oft perceive things as 
existing at a great distance off, and yet for all that, 
those things are acknowledged to have their existence 
only in the mind. 

4 But for the fuller clearing of this point, it may be 
worth while to consider, how it is that we perceive dis 
tance and things placed at a distance by sight. For 
that we should in truth see external space, and bodies 
actually existing in it, some nearer, others farther off, 
seems to carry with it some opposition to what hath 
been said, of their existing nowhere without the mind. 
The consideration of this difficulty it was, that gave 
birth to my " Essay towards a New Theory of Vision," 
which was published not long since. Wherein it is shown 
that distance or outness is neither immediately of itself 
perceived by sight, nor yet apprehended or judged of 



by lines and angles, or anything that hath a necessary 
connexion with it : but that it is only suggested to our 
thoughts by certain visible ideas and sensations attend- 
in o- vision, which in their own nature have no manner 


or similitude or relation, either with distance, or things 
placed at a distance. But by a connexion taught us 
by experience, they come to signify and suggest them 
to us, after the same manner that words of any language 
suggest the ideas they are made to stand for. Insomuch 
that a man born blind, and afterwards made to see, 
would not, at first sight, think the things he saw, to be 
without his mind, or at any distance from him. See 
sect. xli. of the forementioned treatise. 

The ideas of sight and touch make two species, 
entirely distinct and heterogeneous. The former are 
marks and prognostics of the latter. That the proper 
objects of sight neither exist without the mind, nor are 
the images of external things, was shown even in that 
treatise. Though throughout the same, the contrary be 
supposed true of tangible objects : not that to suppose 
that vulgar error, was necessary for establishing the 
notions therein laid down ; but because it was beside my 
purpose to examine and refute it in a discourse concern 
ing vision. So that in strict truth the ideas of sight, 
when we apprehend by them distance, and things placed 
at a distance, do not suggest or mark out to us things 
actually existing at a distance, but only admonish us 
what ideas of touch will be imprinted in our minds at 
such and such distances of time, and in consequence of 
such and such actions. It is, I say, evident from what 
has been said in the foregoing parts of this treatise, and 
in section cxlvii. and elsewhere of the Essay concerning 
Vision, that visible ideas are the language whereby the 
governing spirit, on whom we depend, informs us what 


tangible ideas lie is about to imprint upon us, in case 
we excite this or that motion in our own bodies. But 
for a fuller information on this point, I refer to the 
Essay itself. l 

Here we find from Berkeley s own words that he 
had more than one object in writing the Theory of 
Vision. It is an essay half physical, half psychological, 
and this doubleness of purpose has ever since clung to 
the subject. On the one hand, he wanted to destroy 
the exaggerations introduced by mathematicians into 
optics, by showing that the eye is not fitted to see any 
thing, and therefore not any lines and angles, beyond 
itself; on the other hand, he wanted to support the 
idealistic theory, which he had already conceived, and 
shortly intended to publish in the Principles, by show 
ing that, whereas we do not see things without, we do see 
visible ideas and sensations. In its first purpose, the 
main thesis of the Theory of Vision is a great optical 
discovery, though exaggerated ; in its second purpose, 
it is an excellent disproof of intuitive realism, but no 
proof at all of psychological idealism. Perhaps no 
treatise has ever evinced such a singular compound of 
genius and confusion. The effect both of its truth and 
its falsity persists to this very day, especially in the 
hypothesis of local signs. 

What does Berkeley prove about the sense of vision ? 
He divides the subject into four parts distance, magni 
tude, situation, and the difference between sight and 
touch. 2 On the first point, he says that distance being 
a line directed endwise to the eye, it projects only one 

1 Princ. xlii.-xliv. 

2 Theory, i. Distance is discussed in i.-li. ; Magnitude, lii.-lxxxvii. ; 
Situation, Ixxxviii.-cxx. ; The difference between sight and touch, cxxi. 
to end. 

Q 2 


point in the fund of the eye, which point remains 
invariably the same, whether the distance be longer or 
shorter. l This proves, according to him, that we do 
not see distance at all, but really that we do not see 
remote distance, in depth or the third dimension, verti 
cally from the eye. As he says elsewhere, we see no 
solidity or profundity. 2 On the second point, he shows 
that we do not see the real magnitude, greater and 
smaller, of an external object. Thus, for instance, he 
very properly remarks, the very same quantity or 
visible extension, which in the figure of a tower doth 
suggest the idea of a great magnitude, shall in the figure 
of a man suggest the idea of much smaller magnitude. 3 
On the third point, he relies on the inverted image in 
vision to show that we do not see the real situation, as 
high and low, of external objects. On the fourth point, 
he makes the instructive remark that there is no vision 
of resistance, 4 and he has brought out more clearly 
than any of his predecessors that there is no one self 
same numerical extension perceived both by sight and 
touch, 5 and that 6 we never see and feel one and the 
same object. G 

This conclusion is the great stumbling-block to the 
ordinary man, who has so overlaid sense with inference, 
and, we may add, had so many visible pictures of his 
hand and other members visibly touching visible objects, 
all within his sense of vision, that he finds himself almost 
incapable, even when he becomes a philosopher, of 
realising to himself that he is really seeing one set of 
objects within the retina and feeling another within the 
tactile nerves, while he infers an external object in re- 

1 Theory, ii. ~ Ib. cxxxv., cliv. 

3 Ib. Ivii. 4 Ib. cxxxv. 

5 Ib. cxxi. 6 Ib. xlix. 


lation to both. Nevertheless, Berkeley verified the pre 
vious scientific discovery of the distinction between ex 
ternal and sensible objects by his new discovery of the 
invisibility of remote distance. Since we do not see 
distance in the third dimension from the eye, we cannot 
see, but only infer, a remote object. The visible object 
might, indeed, still be an object touching the eye ; but 
even this hypothesis is negatived by the further study 
of the nervous system. 

What did Berkeley not prove about the sense of 
vision ? On the very first point, while he proved that we 
do not see remote distance he did not prove that we do 
not see distance at all. He did not prove that we do 
not see a surface painted on the retina, with its distances. 
There are three dimensions of extension or space ; in 
each there is distance distance from point to point of 
a line, from line to line of a surface, from surface to 
surface of a solid : in each dimension the parts or places, 
which are distant, are out of one another. Now what 
he proved was that there is no vision of the third 
dimension, not that there is none of the other two ; that 
there is none of distance in depth, not that there is 
none of distance in length and width ; that there is none 
of outness in the external world, not that there is none 
of outness of parts on the surface painted on the retina ; 
that there is none of solid, not that there is none of 
superficial extension ; that there is none of distance 
endwise to the eye, not that there is none of space and 
its distances within the eye. In short, he concluded 
more than he proved. It is, lie says, I think, agreed 
by all, that distance, of itself and immediately, cannot 
be seen. 1 It is still agreed by present psychologists ; 
but we want something more than agreement to prove 

1 Tlicory, ii. 


that, because remote distance is not seen, therefore no 
distance can be seen. From what we have shown, he 
says, it is a manifest consequence that the ideas of a 
space, outness, and things placed at a distance, are not, 
strictly speaking, the object of sight ; they are not 
otherwise perceived by the eye than by the ear. l But 
he had proved only that we do not see external things 
placed at a distance and their outness in space. It still 
remained, and remains even now, to be proved that the 
space, the outnesses, and the distances, within the sur 
face of the picture painted on the retina, are not objects 
of sight. 

Therefore, he did not prove that we have no vision 
of space. He vacillated ; sometimes allowing, some 
times denying that the extended is visible, 2 and finally 
deciding that what we strictly see are not solids, nor 
yet plains variously coloured ; they are only diversity 
of colours. 3 But the same evidence, which proves that 
we do not see solid distance, proves that we do see a 
plain, with its superficial extension and the distances on 
its surface. There is, at this day, as he says himself, 
6 no one ignorant that the pictures of external objects 
are painted on the retina, or fund of the eye. 4 He began 
then with the external object and the retina. Very well ; 
but what is the external object, and what the retina? 
Both of them have surfaces. Undoubtedly the- former 
reflects what the mathematician abstracts as rays, but 
what the physicist knows to be undulations, which ulti 
mately impress the terminations of nervous fibres in the 
retina of the eye. We do not see the sides of these 
rays or undulations : hence we do not see distance in 
the third dimension. But we do see the imprints of 

1 Theory, xlvi. a Cf. ib. xliii., xlv.-xlvi., xlviii., civ. 

3 Ib. clviii. 4 Ib. Ixxxviii. 


their ends. Now, in the first place, the end of any wave 
of sether, however small, is a surface ; in the second 
place, the end of every single optic fibre is a surface ; 
thirdly, as a fact, no one undulation of aether ever 
reaches the eye alone ; and, fourthly, no one nervous 
fibre is excited alone, but the whole retinal surface by 
a whole undulatory surface of aether. Though, there 
fore, the visible picture painted on the retina by the 
external world is not itself solid, it is painted by 
the surface of one solid on the surface of another. 
Not remote distance, but superficial extension is 

It is unscientific in the extreme to arbitrarily select 
one part of the optical evidence and reject the rest, or to 
see through the mathematical abstractions of the line 
and the angle, and then to confuse mathematical points 
with the extended ends of physical objects. This is the 
mistake of Berkeley. He knows that the rays of light 
are not mathematical lines, yet he says at the opening 
and often repeats, what has been repeated after him 
again and again ad nauseam to the present day, that a 
point is presented to the retina. Nothing of the kind ; 
it is not a point, but, to say the very least, a physical 
ray s extended end, which is a surface, presented to the 
extended end of another physical object which is a 
surface, the end of a nervous fibre. There is, no doubt, 
a minimum visibile, which may be coextensive with the 
end of a nervous fibre ; but it is not a point, it is a 
surface. The whole point-to-point theory of vision is 
nothing but a mathematical abstraction converted into 
a physical reality. 

It is true that the retina itself may not be sensible ; 
but whatever part of the optic nerve or of the brain 
itself is first sensible, that part is a surface. It is true, 


again, that we have admitted a psychical element in 
sensation, but we can only interpret its object by con 
sciousness, observation, and reasoning. We have seen 
the verdict of the two latter evidences : every physical 
part without and within us has a surface. Now, what 
does consciousness of vision say ? Why, I cannot help 
being conscious that I am at this moment seeing an 
extended surface. I confuse this picture within, I 
admit, with what I infer without ; but the scientific 
distinction between the external and the sensible only 
shows that I was wrong in the supposition of the exter 
nality or remote distance of the sensible, not that I was 
wrong in being conscious that I see an extended sur 
face, a plain variously coloured. The whole evidence, 
scientific and conscious, is in favour of the visible 
object being like a painting, or still more like a picture 
in a camera obscura, flat to sense, inferred by a complex 
process of reasoning to represent an external solid, 
but confused, by a long-standing association, with the 
external solid itself. 

Again, on the second point, Berkeley proved that we 
do not see the real magnitude of an external object. 
That is no reason why we should not see the magnitude 
of the visible object impressed on the retina, nor why it 
also should not be a real magnitude, though distinct 
from external magnitude. On this point, again, he 
vacillated. First he admits a size of things seen, that 
they grow greater and smaller, and that there is not 
only a tangible but a visible magnitude ; then he says 
that visible extension, though immediately perceived, is 
nevertheless little taken notice of; and finally contends 
that the ideas of visible magnitude are equally fitted to 
bring into our minds the idea of small or great, or of 
no size at all of outward objects, like the words of a 


language. 1 The truth is, that we see an extended 
coloured plain, as we have already said. We are not 
able to alter its whole size on a single retina, because 
the whole retina is used at once ; and this is a great 
point of difference from touch, wherein we use a finger, 
a hand, or our whole body to touch at pleasure. The 
only variation we can get in the size of the whole 
picture is the difference of magnitude between the area 
of a single retina, and the whole field of vision covered 
by both eyes. Usually, however, both eyes are used at 
once, when the visible picture has a single fixed mag 
nitude. But the parts of it have very varying degrees 
of magnitude ; for example, the black spot made by a 
blot of ink covers a trifling amount of the retinal mag 
nitude, compared with that impressed by the white 
paper before me. Hence within a single visible magni 
tude, fixed on the retina, we see all sorts of sizes of the 
parts not behind but beside one another, some greater, 
others smaller, and therefore having various relations of 
size to the whole retinal picture. It is on this sensation 
of varying degrees of magnitude of the parts relatively 
to the fixed magnitude of the whole of the superficial 
picture on the retina, that the wonderful subtlety of the 
sense of sight is founded. In itself, this vision of magni 
tude within a magnitude carries us no further; but 
when allied with data of other senses, it becomes the 
basis of countless inferences about external size. For 
example, the sight of Snowdon, when I am in the open 
air, is smaller than the sight of my own room, when I 
am indoors ; but knowing in other ways the real size of 
Snowdon and of my room, I can from sight measure the 
relative sizes of parts of each in a way possible to no 
other sense. There is another element in the vision of 

1 Theory, xxviii., 1., liv., Ixi., Ixiv. 


size about which we must be careful. We see tlie 
magnitude of the parts relatively to the whole retinal 
magnitude. There are minima, beyond which this de 
duction of visible parts cannot go, supposed to be con 
nected with the distinction of nervous fibres. But, as I 
said before, a minimum visibile is not a point but an ex 
tended end, like the end of a pencil. Secondly, it is 
tempting, with Berkeley, to conclude that the minimum 
is always the same size in vision. 1 But it is not at all 
impossible that the parts impressed on adjacent nervous 
fibres may not be always visibly distinct. In looking at 
an object of a single colour, as a white leaf of a book, 
we do not so carefully distinguish small parts as when 
the object is very varied, as in reading the printed 
matter. The minimum, impressed on each fibre, may be 
always the same, and yet the minima, distinctly visible, 
greater or smaller according to the intensity and variety 
of the excitations. On the whole, then, there is a visible 
magnitude of the picture, always of the same size, deter 
mined by the retina ; visible parts, greater and smaller, 
in reference to the whole size ; minima visiUlia, beyond 
which vision cannot go, but to which, perhaps, it does 
not in every act of vision reach. 

On his third point, Berkeley proved that we do not 
see the real situations of external objects and, in especial, 
that we do not see which is up and which down, but 
an inverted image. He did not prove that sight sees 
no places in its inverted picture ; nor has any of the 
many philosophers, who have strangely attacked visible 
places, ever disproved them. Berkeley, as before, 
vacillated : he first denied them and then admitted 
them. He first says that a blind man returned to sight 
would not at first think that anything he saw was 

1 Theory, Ixxx. 


high or low, erect or inverted. l Afterwards, he says 
that we denominate any object of sight, high or low, in 
proportion as it is more or less distant from the visible 
earth. 2 The latter is the truth. In the visible flat 
extended picture, of a constant retinal magnitude, we 
not only see some parts greater and some smaller, but also 
some in one place, some in another, though all inverted. 
Nor is there any occasion to suppose that the image is 
ever re-inverted. It includes images of our own body 
and of the earth. From the data of touch, we infer 
that our feet are down towards the earth s centre, and our 
heads erect as away from it ; next, we find, over and 
over again, that these inferred objects, in this order, 
have in the visible picture various parts corresponding 
to them, in a corresponding order one part for the 
earth, another for our feet, another for our heads : con 
sequently, from this combined evidence of touch and 
sight, we do not see but infer that the part of the retinal 
image answering to the head represents up, and the part 
corresponding to the feet represents down, and so on 
with all other visible places. 

-Av-eL, R ^ ie fourth point, Berkeley proved that we do 
not see and feel the same object, and that the visible 
picture is numerically distinct from the tactile impres 
sion produced by the same external object; e.g. my 
retinal picture of the paper before me is in my optic 
nerve, my tactile impression in my nerves of touch. 
But he asked the further question whether they are also 
specifically distinct, or whether there is anything in 
common, or similar, in the visible object and the tangible 
object. After having, though in the vacillating manner 
already stated, admitted in the visible picture a visible 
extension, visible magnitude greater and smaller, and 

1 Theory, xcv, 2 Ib. cxi. 


visible situations high or low in relation to visible earth, 
he answered the question by denying that there is any 
thing common to sight and touch. \ The true answer is 
that his previous admissions were better than his final 
theory. Vision sees a picture visibly extended in the 
above-mentioned ways : touch feels a tangible imprint 
extended in the same ways. The visible and tangible 
objects, so far as the former is coloured and the latter 
heated, are dissimilar; so far as the former is in the 
optic and the latter in the tactile nerves they are not 
numerically the same ; but, so far as they are both ex 
tended, they are similar. Aristotle was right in dis 
tinguishing special and common sensibles, and in assign 
ing the extended both to sight and to touch. 1 Locke 
was right in repeating the distinction. 2 Berkeley was 
wrong as well as inconsistent in rejecting it. But his 
rejection has infected the whole subsequent course of 
the science of vision, the metaphysics of space, and the 
psychology of sense. 

Berkeley s theory contains a double paradox. In 
the first place, he supposed that we see no visibly ex 
tended object, when all he had proved is that we see 
no Visibly 7 remote object. He used the action of the 
external object on the retina, to prove that we do not 
see a line endwise, but a point ; and then discarded it 
when it would also prove that we do not see a point 
but a surface broadwise presented to the retina. 3 He 
had no definite idea of what is meant by distance. He 
evidently confused it at first with the third dimension 
of space. 4 Afterwards, he saw that there is a visible 
distance between interjacent visible points. 5 But he 
never fairly faced the fact that distance is the interval 

1 De Anima, ii. 6. 2 Locke, Essay, ii. 5. 

3 Theory, clvii. 4 Ib. ii. 5 Ib. cxii. 


between any places, that there is a distance in length 
and width, as well as in depth, and that, though distance 
in depth is invisible, distance in both the other dimen 
sions is visible. He coolly rejected the constant appeal 
of the geometer to visible figures. 1 He supposed a 
person without touch but with sight, and asked what 
kind of geometry he would produce ; a useless question, 
because man is an animal, and an animal without touch 
impossible. This supposititious seeing geometer would 
have certain limits, as Berkeley says : first, he would 
have no sense of a solid, 2 which requires distance in 
the third dimension ; secondly, he would have no sense 
of resistance, which requires touch. 3 He would, there 
fore, infer no external world. But he would have a 
sense of an extended plain with its distances, the mag 
nitudes of its parts, and the situations of its places. He 
would, therefore, see a plain, and on that plain the 
outnesses of the parts to one another, and their distances 
from one another in length and width. He would have 
a sense, not a science, of space. Yet Berkeley denied all 
these consequences of his previous admissions, assuming 
that an object presents a point endwise to the eye. In 
short, throughout the Essay, the same merit is con 
stantly vitiated by the same defect, the discovery of 
the invisibility of remote distance confused with the 
assumption of the invisibility of extended space. 

In the second place, he constantly asserts that what 
we strictly see are not solids, nor yet plains variously 
coloured ; they are only diversity of colours. 4 He then 
defies us to assign any similitude between the visible 
and the tangible, and concludes that the objects of 
vision are not similar to external objects, but mere 

1 Theory, cl. scq. 2 Ib. cliv. 3 Ib. cxxxv. 

4 Ib. xliii., Ixv., ciii., cxxix.-cxxx., cliii.-clviii. 


signs, like words ; so that the proper objects of vision 
constitute an universal language of the Author of 
nature. l Meanwhile, all he has proved is, that we 
do not see remote distance in the third dimension. 
Secondly, he has forgotten his constant admission that 
we see visible extension, visible magnitude, visible 
situations. Thirdly, he is plainly under the dominion 
of the abstraction of qualities. He says very truly that 
we can neither abstract the idea of visible extension 
from colour, nor that of colour from visible extension. 
But the extraordinary thing is, that he thinks this 
argument proves, not that we see something coloured 
and extended, but that we see colour, not extension. 2 
He is evidently under the dominion of this simple 
fallacy : colour is not extension ; what we see is colour ; 
therefore it is not extension. But in reality, though 
colour is not extension, what is coloured can be also 
extended ; what we see is a picture at once coloured and 
extended, and that is the reason why we cannot separate 
colour and visible extension, but only attend the more 
to colour, or the more to visible extension in the self 
same picture.* Hence, the visible object is not an 
arbitrary sign, but similar to the tangible object felt, 
and, we may add, to the external object inferred, in 
extension. / The visible figure in geometry is not, in 
deed, the object of the science, but it is the best illus 
tration of the object to the sense and imagination of the 
geometer. The visible object is not like a word, and 
vision not like a language, which may or may not be 
like what is signified, but the former is the sensible 
object, and the latter the sense, most correspondent to 
the extended external world, though not the most 
direct way of inferring it. In short, vision sees the 

1 Theory, cxlvii. ; cf. li., Ixiv.-lxv.. cxliii. 2 Ib. cxxx. 


visibly extended, touch feels the tangibly extended, 
reason infers the externally extended; and all three 
objects are similar, though not the same, in extension. 

So far, we have seen how brilliant, and how delu 
sive, was Berkeley s discovery of the invisibility of 
remote distance, in its physical aspect. But, as we 
said above, he wrote the Theory of Vision also in a 
psychological interest. He certainly proved in it that 
we_ do not see an object at a distance; and it is a 
curious problem that, after this discovery, the intuitive 
realists should have advanced their hypothesis that we 
immediately perceive the external world. The reason 
is that Berkeley buried his discovery under such a heap 
of errors, that we can hardly be surprised if the truth 
for a time lay hid. He found out that we do not see * 
depth, and confirmed the theory that we do not see 
anything without. But he also proceeded to infer that 
we do not see visible space, but only various colours. 
Not content with this double paradox, he proceeded to 
another, which was indeed a main object of the Essay ; 
namely, that we see only visible ideas, visible ideas of 
colours. There is no better instance of the extraordinary 
way in which the assumption of idealism is made in books 
of philosophy, than its sudden appearance in the Theory 
of Vision. After he has concerned himself with the 
external objects, and the rays of light, and the retina 
of the eye, we suddenly find ourselves transplanted into 
quite a new world with the words : It is evident that 
when the mind perceives any idea, not immediately and 
of itself, it must be by the means of some other idea. l 

The invisibility of distance in the third dimension 
proves that we do not see external objects at a distance 
from the eye. The propagation of undulations to the 

1 Theory, ix. 


retina and the consequent nervous motion prove that 
we do not see external objects at all. But neither 
evidence proves that we see something not merely 
within ourselves, but also within our minds, or that the 
visible object is a visible idea. Berkeley, however, falls 
into this ordinary idealistic non sequitur, without any 
evidence, either physical or psychological, throughout 
the Theory of Vision. For instance, he says that c a 
man born blind, being made to see, would, at first, have 
no idea of distance by sight ; the sun and stars, the 
remotest objects as well as the nearer, would all seem 
to be in his eye, or rather in his mind. l Similarly, 
lie assumes it as agreed on all hands that colours are 
not without the mind, from which, of course, it 
would follow that neither is visible extension. 2 He 
even uses the mere assumption that what is in the eye 
is in the mind to argue that, as the objects of sight 
do not exist without the mind, the pictures painted on 
the bottom of the eye are not the pictures of external 
objects ! 3 Meanwhile, the evidences, which are all 
drawn from the way in which external objects affect 
the retina, prove that there is a variously coloured 
picture produced in the camera obscura of the eye upon 
the retina, but prove absolutely nothing at all about 
visible ideas within the mind. 

Let us now shortly resume what Berkeley proved 
and did not prove about vision as a sense. We see no 
remote distance, no real magnitude, and no real situa 
tions of external objects ; no solidity, no resistance, no 
protrusion ; no outness of the world in external space : 
this is what he proved. He vacillated about visible 
extension, and finally concluded, but did not prove, that 
6 what we strictly see are not solids, nor yet plains 

1 Theory, xli. ; cf. xcv. 2 Ib. xliii. 3 Ib. cxvii. 


variously coloured ; they are only diversity of colours. 
Nor did he prove that the visible object is not on the 
retina, nor in the optic nerve, but is a visible idea in 
the mind : this is a petitio principii committed very early 
in the Essay. l Consequently, he did not prove that 
vision is a universal language, and that visible objects are, 
like words, mere signs of extended objects without being 
extended. The same optical evidence, which proves 
that we do not see remote distance endwise, proves 
that we do see the extended imprinted broadwise on the 
retina of our eyes. The visible picture, with distances 
not endwise but broadwise, magnitudes of parts, and 
situations of places, though numerically different, is 
specifically similar to the tangible imprint, and to the 
inferred original of both, in physical extension. 

But while Berkeley s psychological interest was en 
ticing him to resolve optical effects into visible ideas, 
his physical discovery was at the same time forcing 
him to recognise external objects to cause them. At 
the very outset he admits the existence of a distance 
projecting an effect on the eye. 2 In the sequel, he 
allows that the object which exists without the mind 
and is at a distance is different from the visible object, 3 
the former remaining the same while the latter alters 
according to the remoteness of the eye from the external 
object. He talks of our advancing forward to it so 
many paces or miles. 4 He considers that it affects not 
only our bodies but even our minds. We regard, he 
says, the objects that environ us in proportion as they 
are adapted to benefit or injure our own bodies, and 
thereby produce in our minds the sensations of pleasure 
and pain. 5 No realist requires more admissions. Given 
only the eye, and all the universe follows, bathed through- 

1 Theory, ix. - Ib. ii. 3 Ib. Iv. 4 Ib. xlv. 5 Ib. lix. 



out its mass and its molecules in that light which is re 
flected from external bodies on the retina of the eye. 
Optics requires external bodies to reflect and a sentient 
body to receive light. As soon as Berkeley becomes a 
natural philosopher, he deserts the pure idealism of 
his Principles, and admits between God and the ideas 
within our minds the intervention of unthinking objects 
projecting effects on the retina and causing visible ideas. 

Nevertheless, he proceeded to misinterpret the ex 
ternal object. In the Principles, with much consist 
ency though with no truth, he emphatically denies that 
any sensible object, any primary or secondary quality, 
is anything but an idea within the mind. But in the 
Essay, while he thought that visible objects are 
ideas within the mind, he identified the external and 
the tangible, and supposed that tangible objects exist 
without the mind./ For, says he, all visible things 
are equally in t]*e mind, and take up no part of the 
external space ; and consequently are equidistant from 
any tangible thing, which exists without the mind. l 
This view, which is entirely inconsistent with the 
idealism of the Principles, is curiously like intuitive 
realism. But even if it were possible that colour and 
extension could be wholly separated in this manner, at 
any rate the identification of tangible and external ex 
tension is a confusion of effect and cause. Eeally, the 
externally extended object is the common original of 
the visible and the tangible objects, both of which are 
within ourselves. 

Berkeley s identification of the external and the 
tangible led him into two false consequences. In the 
first place, it led him to deny any common cause of 
sight and touch. It is a mistake, he says, to think 

1 Theory, cxi. ; cf. Iv. 


tlie same thing affects both sight and touch. If the 
same angle or square which is the object of touch be 
also the object of vision, what should hinder the blind 
man, at first sight, from knowing it ? It is true that 
the square felt and the square seen are not the same : 
one is in the tactile, the other in the optic nerves. It 
is true, also, that a blind man, when first restored to 
sight, would have a difficulty in comparing them. But 
this is no proof, and it is not true, that the external 
square object which causes the tangible square is 
different from the square which causes the visible square. 
Trafalgar Square is one object, though it is one thing to 
look at it and another to walk round it. It is the same 
crystal which presses the hand and dazzles the eye of 
the natural philosopher, though the modes of motion, 
by which it gravitates towards the hand, and by 
which it reflects undulations towards the eye, are 
different. Otherwise, science would be impossible, for 
it would never be concerned with one and the same 
object. Secondly, the identification of the external 
and the tangible led Berkeley into a paradoxical theory 
of the object of geometry. He proved, in the end of 
the Theory of Vision, that neither abstract nor 
visible extension makes the object of geometry. 2 But, 
by a false disjunctive judgment, he thought himself 
entitled to conclude that the object of geometry is there 
fore tangible extension. This conclusion entailed the 
corollary that a geometrical square is really a tangible 
square, and is not even represented by a visible square, 
which, according to him, has four parts rather than four 
sides. 3 But who ever heard of a geometer feeling a square 
rather than looking at one ? Through his confusion of 
the external and the tangible, Berkeley has entirely 

1 Theory, cxxxvi. 2 Ib. clix. s Cf. ib. cxli.-cxlii. 

K 2 


overlooked tlie real square of the geometer, which is 
neither an abstract idea nor visible nor tangible, but an 
object of reasoning, capable of being partially repre 
sented by a tangible square, much better by a visible 
square, but perfectly by neither. In elementary geo 
metry, a geometrical figure is better represented by 
sight than by touch ; even sight fails adequately to 
represent more complicated figures, such as a chiliagon, 
while in the geometry of infinites a polygon with infinite 
sides is a pure object of reasoning. 

But Berkeley s confusion of external and tangible 
objects needs no further criticism, for having published 
it in 1709, he retracted it in 17] 0. In his Essay 
towards a New Theory of Vision, it was put forward 
as the explanation of the external object, considered by 
geometry, and required by optics. In his Principles, 1 
he calls it himself a vulgar error. But he at once flew 
to the opposite error, and confused the tangible object 
with a tangible idea ; falsely identifying the physical 
with the psychical, and logically but falsely resigning 
the external object altogether. At the same time, he 
insinuated that this oscillation between intuitive realism 
and psychological idealism made no difference. In 
reality, it spoilt his theory of external objects in both 
books. In the Essay, his confusion of the external 
and tangible concealed from him that the external 
object is the common original of touch and of vision, 
distinct from the objects of both. In the Principles, 
his confusion of the tangible, as well as the visible, 
with ideas made him omit the external object altogether. 
Although the object at a distance directing a line end 
wise to the eye had been the foundation of his discovery 
of the invisibility of remote distance, he now proceeded, 

1 Princ. xliv., quoted at the beginning of this chapter. 


in defiance of the science of optics, to make visible as 
well as tangible ideas effects of the governing spirit, 
with not a single word about external objects without 
our minds. At the price of the physical truth of 
the Essay he saved the psychological idealism of the 

Berkeley, in the Principles, is a logical idealist ; 
but Berkeley, in his works, is, like Locke, two philo 
sophers in one. On the one hand, take the Theory of 
Vision. Here he is Locke, with his admissions. In 
the same somewhat half-hearted way he recognises the 
external objects of science : he has an undercurrent of 
ontology : he is a cosmothetic idealist in visible ideas 
which he supposes to be projected by external objects, 
and an intuitive realist in tangible objects which he 
supposes to be externally felt, as Locke, after limiting 
sensation to ideas, had supposed primary qualities with 
out to be objects of a kind of bastard sensation. On the 
other hand, take the Principles of Human Knowledge. 
Here he is Locke, reduced to logic. He sees that mind 
and ideas end in mind and ideas, and that if, as Locke 
himself had at first said, ideas are all the objects of 
knowledge, then, as Locke ought to have concluded, 
not unthinking body but the Divine Mind is the only 
external cause. 

But Berkeley s optics were superior to his psychology. 
We must appeal from the Principles to the Theory 
of Vision. There is, says he in the latter treatise, no 
one ignorant that the pictures of external objects are 
painted on the retina or fund of the eye. l Then, 
these external objects are not tangible, nor visible, 
nor sensible at all, but are causes of sensible objects, 
or, as Berkeley would say, of ideas. Not all objects 

1 Theory, Ixxxviii. 


of knowledge, then, are sensible ideas. Again, these 
external objects, whose pictures are painted on the 
retina, are not God, and yet are causes of sensible 
effects. God, then, is not the sole cause. In short, 
optics require, between God and our ideas, an intervening 
nature. The scientific admissions of the Theory of 
Vision are sufficient to destroy the pure idealism of 
the Principles of Human Knowledge. 

Besides the optical discovery of the invisibility of 
remote distance, the psychological hypothesis that we 
see visible ideas, and the ontological recognition of the 
existence of an extended world without the mind falsely 
confused with the tangible object, the Theory of 
Vision finally contains a logical speculation on the 
origin from vision of our knowledge of the extended 
beyond vision. Like the main thesis, this speculation 
contains much that is true, and especially that we do 
not see but infer an external world. It is also most 
suggestive, and in fact was the first hint of the hypo 
thesis that association may be an account of, or rather 
a substitute for, the origin of knowledge. But it does 
not in the least explain the knowledge of extended 
objects in the external world, required by optics and 
admitted by Berkeley. We must not be led away by 
the appearance of simplicity, but keep steadily before 
us the known facts to be explained, and by them test 
the hypothesis. 

We do not see remote distance : we do judge and 
infer it from sight : this is the essential truth in Ber 
keley s theory. 1 The question is, how this judgment and 
inference are made. He answers that when the mind 
perceives any idea not immediately and of itself, it must 
be by the means of some other idea : 2 distance, then, 

1 Theory, iii. 3 IL. ix. 



is suggested to the mind by the mediation of some 
other idea, which is itself perceived in the act of seeing. 1 
He finds three ideas, which arise according to the 
different distances of objects : the first, the lessening or 
widening the intervals between the pupils of our eyes, 
attended with a sensation ; 2 the second, the more or 
less confused appearance ; the third, the prevention of 
this confusion by straining the eye, with its sensation. 3 
These are the ideas which he thinks will suggest the 
idea of the distance of the external object : not that 
there is any natural or necessary connection of those 
ideas with distance, but that there is an habitual or cus 
tomary connection between these ideas and the idea of 
distance. 4 

This process implies that the idea of distance itself 
has been acquired in some other way. This way, 
according to Berkeley, is touch combined with motion, 
lie gives the whole process in the following passage : 
Having of a long time experienced certain ideas 
perceivable by touch, as distance, tangible figure, and 
solidity, to have been connected with certain ideas of 
sight, I do upon perceiving those ideas of sight, forth 
with conclude what tangible ideas are, by the wonted 
ordinary course of nature, like to follow. Looking at 
an object I perceive a certain visible figure and colour, 5 
with some degree of faintness and other circumstances, 
which from what I have formerly observed, determine 
me to think, that if I advance forward so many paces 
or miles, I shall be affected with such and such ideas of 
touch. G 

This process, by which visible ideas suggest tangible 

1 Theory, xvi. 3 Ib. xvi. 3 Ib. xxvii. 

4 Cf. ib. xxviii. with the above sections. 

Note this admission of visible figure as well as colour. to Ib. xlr. 

PART ir. 


ideas of distance, is what is ordinarily called association. 
Berkeley describes this operation with great clear 
ness. < That one idea, he says, may suggest another 
to the mind, it will suffice that they have been observed 
to go together, without any demonstration of the ne 
cessity of their co-existence, or without so much as 
knowing what it is that makes them so co-exist. J There 
is such an operation, and its recognition was not new 
in philosophy. Plato and Aristotle, Hobbes and Locke 
were aware of it. Aristotle, for instance, says that we 
recollect from what is similar -or contrary or con 
tiguous. 2 But what was new in Berkeley s Theory of 
Vision was the hypothesis, afterwards developed by 
Hume, that this process of recovering ideas is some 
times the analysis of what we call knowing objects. The 
ordinary man, when he uses his eyes, supposes that he 
knows, nay sees, that there is an external object at a 
distance from him. Berkeley tells him that he is really 
letting visible ideas suggest to him tangible ideas of 
(^stance ; that is all. 

There is a negative value in Berkeley s analysis. It 
is greatly superior to the ordinary supposition that we 
see a distant object. Berkeley, though he exaggerated 
when he said that we do not see any distances at all, 
showed conclusively that we do not see but infer a 
distant object in the external world. It is also 
superior to the supposition of Descartes and others 3 
that we infer the distance of objects from the angles 
they make with our eyes. Berkeley disposed of this 
jmmour of making one see by geometry/ when he 
showed that the lines and angles between the external 
objects and the eyes are as invisible as the external 

1 Theory, xxv. 2 D e Mem. 2 = 451 B, 18-20. 

3 Theory, iv. not 


objects themselves. 1 Mathematical opticians had fallen 
into the blunder of supposing that lines and angles, 
known only to themselves by science, are sensible data 
which ordinary men use in vision to infer an external 

There is also positive information in Berkeley s 
analysis. It contributed some new truths on the senses. 
In the first place, about sight ; he did not indeed show 
that there is no vision of space, but he did show that 
it is in a way unnecessary. He called attention to the 
scientific observation of the misfortune of the blind, 
who have no eyes, yet feel and infer space. Again, his 
remark, that no resistance is perceived by sight, con 
tains the true reason why from sight alone we could 
not infer an external world, and therefore must appeal 
to touch and motion. Lastly, though it is not the case, 
it is possible that sight might, like hearing, or, at any 
rate, like language, contain no apprehension of extension, 
and yet enable us, when combined with a sense of exten 
sion, to infer an extended object. On the whole, he has 
not shown that the visible object is not an extended 
picture ; but he has shown that, whatever the visible 
object is, we can know an extended object in the 
external world without it, and not by it alone. 

Secondly, he has the great merit of having hinted, 
however imperfectly, at what is now called the muscular 
sense. When he speaks of the motion of his body 
which is perceivable by touch, 2 though he may be ex 
aggerating its connection with touch, he is recognising a 
sense of motion. He also saw that in vision there is 
something more than seeing. What he calls lessening 
or widening the intervals between the pupils, which is 
attended with a sensation, is the convergence or diver- 

1 Theory, iv., xii., lii.-liii. 2 Ib. xlv. 


gence of tlie optic axes by the internal and external 
recti muscles, with their muscular sense. When he 
speaks of the confused appearance caused by objects 
brought too close to the eye, and of preventing 
the appearances growing more confused by straining 
the eye, and of its sensation, 1 he is pointing towards 
the increase of the convexity of the crystalline lens, for 
the more rapid convergence of rays from near objects to 
the retina, by the action of the ciliary muscle, with its 
muscular sense. He also refers to the movements of 
the eyes up and down, to the right and left, which are 
performed by the four recti muscles. 2 In none of these 
cases did he analyse the muscular movements or assign 
them a distinct muscular sense. Nevertheless, he called 
attention to movement, to the sense of movement in 
touch, and to the sense of some kind of action in sight, 
connected with the knowledge of extension. 

At the same time, these great achievements are 
quite consistent with equally great blunders about our 
senses, of which there are two, at opposite extremes. 
On the one hand, he underrates the efficacy of vision 
when he tends to confine it to visible ideas of colour ; 
on the other hand, he exaggerates the efficacy of touch 
when he tends to extend it to external objects. Eeally, 
the former is the vision of the extended in the optic 
nerves, the latter is the feeling of the extended in the 
tactile nerves. However, these errors do not touch the 
exact question before us. Whatever else it may be, 
the object of vision is certainly not the external object 
at a remote distance. Now, the question is whether, 
when we say that there is such an external object, cor 
responding to what we see, we are only letting visible 
ideas suggest tangible ideas of remote distance. 

1 Theory, xxi.-xxvii. * Ib. xcvii.- xcviii. 


111 solving this problem, two concessions must be at 
once made. In the first place, from vision, being no 
sense of resistance, we do not infer the external world 
directly, but only indirectly through touch and motion. 
Secondly, visible ideas do suggest tangible ideas, and 
other ideas also for that matter, by the customary tie 
of association, which is a real fact of human nature. 
But we must also ask ourselves whether this suggestion 
is all that happens. If so, we should only have the 
ideas ; we should not infer that, over and above the 
ideas, the object seen corresponds to an extended object 
in the external world. For example, at this moment, 
my vision of the white would suggest my tangible idea 
of the extended ; but I should not infer, as I really do, 
that over and above the tangible idea there is an ex 
tended paper in an external world, corresponding 
both to. the object of touch and the object of sight. 
Berkeley substituted the suggestion of ideas for the 
inference of external objects. 

Even in the c Theory of Vision, in spite of having 
admitted the existence of the external object, and its 
action on the retina, Berkeley partly accepted the 
consequence. Sitting in my study, he says, I hear 
a coach drive along the street ; I look through the 
casement and see it ; I walk out and enter into it ; thus 
common speech wou d incline one to think, I heard, saw, 
and touch d the same thing, to wit, the coach. It is 
nevertheless certain, the ideas intermitted by each sense 
are widely different, and distinct from each other ; but 
having been observed constantly to go together, they 
are spoken of as one and the same thing. 1 Similarly, 
he afterwards says that, though the objects are different, 
as they are called by the same name, he will, to avoid 

1 Theory, xlvi. 


tediousness and singularity of speech, speak of them as 
belonging to one and the same thing. 1 

Now, it is quite true that the audible, visible, and 
tangible are different objects, and also that, if nothing 
happened except that ideas of the audible and visible sug 
gested ideas of the tangible, no real identification could 
take place. But something further does take place. In 
the first place, when I hear something sounding in my 
auditory, see something coloured in my optic, and feel 
something hard in my tactile nerves, and have often ex 
perienced these sensible objects in a similar order, I infer 
that there is one external object, which is the common 
original of these sensible objects on any given occasion. 
Secondly, I call this common original by one and the 
same name, coach, because I infer it to be one thing. 
It is true that I have an habitual tendency to confuse the 
one external object with the several and different audi 
tory, visible and tangible objects within me. But it is 
not true that there is no identity but an identity of 
name. There is an identical external object, the coach, 
which I infer, and which I can disengage from the con 
fusion with its different sensible results, by means of 
science. Now, if the auditory, visible and tangible 
objects had been mere ideas in my mind, and if these 
ideas merely suggested one another, I could never have 
inferred the one external object, and it is most im 
probable that I should have even called the different 
ideas by one name. But I do infer one external object, 
and am justified by optics and other sciences connected 
with the senses. Therefore, in the first place, the pro 
cess of this inference of one external object cannot be a 
mere suggestion of different ideas ; and secondly, the 
data of this inference of an external object cannot be 

1 Theory, Iv. 


auditory, visible and tangible ideas. In reality, from 
physical data in the several nerves, I infer one physical 
coach, and give it, not them, one name. 

In the Theory of Vision, however, Berkeley did 
not fully realise the consequence of reducing the infer 
ence of external objects to the suggestion of tangible 
ideas, because he combined this association of ideas 
with an intuitive touch of external objects. Hence, 
later on, he says of a man, that when he has by 
experience learned the connexion there is between 
the several ideas of sight and touch, he will be able, 
by the perception he has of the situation of visible 
things in respect of one another, to make a sudden 
and true estimate of the situation of outward tangible 
things, corresponding to them. And thus it is, he 
shall perceive by sight the situation of external 
objects, which do not properly fall under that sense. l 
Such an estimate would require the impossible iden 
tification of tangible ideas, tangible objects, and out 
ward things. But, in the first place, touch does not 
feel the outward thing. Secondly, a visible idea 
suggests a tangible idea, but not a tangible object. 
Thirdly, what we really do is to estimate the situation 
not of a tangible idea, nor of a tangible object, but of 
an outward thing corresponding on the one hand to the 
tangible, on the other hand to the visible, object within 
ourselves. We cannot bolster up the association of 
ideas by an intuitive touch of outward things. 

In the Principles, when he had retracted the con 
fusion of the external and the tangible, and the intuitive 
touch of the external, the consequence of supposing 
that the inference from vision is nothing but an associa 
tion of ideas came out in its simple nakedness. He 

1 Ib. xcix. 


then saw that, in this case, ideas of sight only admonish 
us what ideas of touch will be imprinted on our minds, 
and do not mark out to us things actually existing at a 
distance. 1 I freely admit that Berkeley was right in 
retracting the tangible intuition of the external world, 
and that if we start with visible ideas, and by the 
suggestion of ideas let these visible suggest tangible 
ideas, and have no tangible intuition of extended 
objects in the external world, we shall begin and end 
in ideas. But we do not end in ideas. His own optics 
require that we know external objects, and that no one 
is ignorant of their painting pictures on the retina of 
the eye. His hypothesis of the suggestion of ideas does 
not account for the knowledge of their causes. It is, 
therefore, false. 

The cause of Berkeley s error was that neglect of 
logical inference which made its appearance in the 
Second Book of Locke s Essay, and led to the postpone 
ment of reasoning to all kinds of lesser powers. Like 
Locke, Berkeley was aware of the difference between 
association and reasoning. 2 But, like Locke, he kept in 
the background, and to the last, reasoning, the one power 
which will be heard and will not wait. Hence, in the 
Principles, he supposes that ideas suggest ideas, until 
reason at last infers a God. Hence, in the Theory of 
Vision, he substitutes for inference a false touch of out 
ward things and an imperfect suggestion by visible of 
tangible ideas. He overlooks in both the human, though 
complex, inference of an external extended object 
which causes both sight and touch. 

The Theory of Vision contains the discoveries of 

1 Princ. xliv., quoted at the beginning of this chapter. 

2 Cf. Locke, Essay, ii. 33, 13 ; Berkeley, The Theory of Visual 
Language Vindicated, 42. 


the invisibility of remote distance, and of the combina 
tion of sight and touch with a sense of motion. It is 
a very good answer to those who say that we see the 
external world ; though even they could retort on 
Berkeley that he says himself that we feel it. It is no 
answer to those who say that we know the external 
world. It is a good answer to those who say that we 
infer it directly from sight by lines and angles, or by 
any other direct inference, from sight, which feels no re - 
sistance. But it is no answer to those who say that we 
infer an external extended world first from the resistance 
felt in the senses of touch and motion, and then from 
the correspondence in extension between inferred, tan 
gible, and visible objects. Finally, Berkeley s Theory 
of Vision contains two fundamental errors of omis 
sion : the first, that there is no vision of an extended 
object within ; the second, no inference of an extended 
object without, common to our senses of sight and 




THE academical or sceptical philosophy of Hume admits 
of being summarised as follows. All the perceptions 
of the mind are impressions and thoughts or ideas. 1 
All our ideas or more feeble perceptions are copies of 
our impressions or more lively ones. 2 Association is a 
principle of * connection which, by resemblance, con 
tiguity or causation, on the appearance of a perception 
suggests thoughts or ideas. 3 All the objects of human 
reason or inquiry may naturally be divided into two 
kinds, to wit, Relations of Ideas and Matters of Fact. Of 
the former kind are the sciences of geometry, algebra, 
and arithmetic, and, in short, every affirmation which 
is either intuitively or demonstratively certain. 4 The 
origin of our beliefs, i.e. vivid ideas, of matters of 
fact, is experience of a constant conjunction of impres 
sions, and association which, from this constant con 
junction, begets such a connection in the imagination 
that, on the appearance of the antecedent, we have the 
idea, i.e. belief, of the consequent and of their connection 
as cause and effect. 5 The mind lias never anything 
present to it but the perceptions, and cannot possibly 
reach any experience of their connection with objects. 
The supposition of such a connection is, therefore, with- 

1 Inquiry, 2. 2 Ib. 3 Ib. 3. 

4 Ib. 4. 5 Ib. 4-7, esp. 7, Part II. 

CHAP. ix. HUME 257 

out any foundation in reasoning. 1 The great subverter 
of Pyrrhonism, or the excessive principles of scepticism, 
is action. 2 There is, indeed, a more mitigated scepticism, 
or academical philosophy, which may be both durable 
and useful, and which may, in part, be the result of this 
Pyrrhonism or excessive scepticism, when its undistin 
guished doubts are, in some measure, corrected by 
common sense and reflection. 3 

The point of this academical philosophy is that man 
has the faculties to receive impressions and conceive 
ideas or thoughts ; and by association to make vivid 
ideas of causation, which are his only beliefs on 
matters of fact ; but not by reasoning to infer exter 
nal objects. Plume published it twice over, first in the 
Treatise of Human Nature, afterwards in the Inquiry 
concerning Human Understanding. The earlier work is 
more elaborate, containing in the First Part a fuller 
discussion of the origin of ideas, modelled on the Second 
Book of Locke s Essay, but w r ith the stress laid on asso 
ciation ; in the Second Part, a theory of the apprehen 
sions of time and space, which hardly appears at all in 
the later work ; in the Third Part, a longer but less 
elegant exposition of his theory of association as the 
origin of the belief in causation ; and in the Fourth 
Part, a long discussion of the apprehension of objects, 
answering to the last section of the Inquiry, but com 
prising a sceptical theory of substances, both material 
and thinking, which he afterwards omitted but by no 
means retracted in his later work. Since the Treatise 
was published when the author was a young man of 
twenty-seven, the Inquiry ten years later in the prime 
of life, the impartial critic must dwell mainly on the more 

1 Inquiry, 12, Part I. ~ Ib. 12, Part II. 

3 Ib. 12, Part III. 


mature work ; especially as in his account of My own 
Life Hume says himself, I had been guilty of a very 
usual indiscretion in going to the press too early a 
useful warning to youthful philosophers. Nevertheless, 
the essence of both Treatise and Inquiry is the same : 
it is a reduction of man to mere perceptions. Berkeley 
had attacked natural science : it remained for Hume to 
attack the human intellect. But we must take care not 
to be argued out of our wits. 

Hume s philosophy is founded on the following 
distinction of perceptions into impressions and ideas, 
which he identifies with thoughts : 

Here, therefore, we may divide all the perceptions 
of the mind into two classes or species, which are 
distinguished by their different degrees of force and 
vivacity. The less forcible and lively are commonly 
denominated thoughts or ideas. The other species want 
a name in our language, and in most others ; I suppose, 
because it was not requisite for any, but philosophical 
purposes, to rank them under a general term or appella 
tion. Let us, therefore, use a little freedom and call 
them impressions ; employing that word in a sense some 
what different from the usual. By the term impres 
sions, then, I mean all our more lively perceptions, 
where we hear, or see, or feel, or love, or hate, or 
desire, or will. And impressions are distinguished from 
ideas, which are the less lively perceptions, of which we 
are conscious, when we reflect on any of those sensa 
tions or movements above mentioned. l 

The distinction between impressions and ideas is an 
important discovery, or rather re-discovery. Aristotle 
had, in the De Anima, carefully distinguished between 
cesthemata, or the objects in sense when an external ob 
ject is present, and phantasmata, or their relics in the 

1 Inquiry, 2. 

CHAP. ix. HUME 259 

imagination when the external object is absent. But, 
as we have already seen, Descartes afterwards confused 
the object of sensation and conception under the name 
idea, and Locke and Berkeley had followed him. So 
long as it was admitted that some external object is 
also known, this confusion had no very serious conse 
quences ; for the reduction of sense to a purely psy 
chical object at all was a far more fundamental error 
than the reduction of this psychical object to an idea. 
But when it began to be doubted whether any external 
object could be known, it then became a serious ques 
tion, how we can distinguish an adventitious idea im 
printed on the senses from a fictitious idea generated by 
the imagination. 

Berkeley felt this difficulty, 1 and got over it partly 
by supposing that adventitious are more vivid than 
factitious ideas, but mainly by his theory that the 
former are directly inspired by God. Now, Hume 
doubted our knowledge of any cause of our per- 
ceptions^ natural or spiritual. Moreover, he saw that 
the word idea seems to be commonly taken in a very 
loose sense by Locke and others, as standing for any of 
our perceptions, our sensations and passions, as well as 
thoughts. 2 In these circumstances, he revived the 
ancient distinction of cesthema and phantasma under 
the new names impression and idea, yet without 
resorting either to matter or to God. As he says in the 
Treatise, By the term of " impression," I would not be 
understood to express the manner in which our lively 
ideas are produced in the soul, but merely the percep 
tions themselves. 3 Consequently he had to look out for 
some fresh criterion to distinguish the thing as well as 
the term, and found it in the liveliness of an impres- 

1 Princ. xxxiii. ~ Inquiry, 2, note. 3 Treatise, i. 1, note. 

s 2 


sion as contrasted with an idea. In the Bhetoric, 
Aristotle had described, without meaning to define, 
imagination as a kind of weak sense. 1 Hobbes had 
exalted this description into a definition Imagination 
being (to define it) conception remaining, and by little 
and little decaying from and after the Act of Sense! 2 
Berkeley had made faintness a partial test of an idea of 
imagination : Hume exalted it into the sole criterion, 
and committed himself to the consequences. The 
most lively thought, says he, is still inferior to the 
dullest sensation. 

The hypothesis that there is no more distinction 
between sense and imagination than between vivid and 
faint perceptions, or states of consciousness, as they 
now call them, has become a favourite with modern 
idealists, simply because they have destroyed the real 
criterion afforded by the presence and absence of exter 
nal objects. But there is a difference in kind between 
sense and imagination, of which different degrees of 
force and vivacity furnish no adequate criterion. The 
faintest impressions would be undistinguishable from 
the most vivid ideas. This objection Hume had noticed 
himself in the Treatise, and tried to evade it : 

The common degrees of these are easily distin 
guished : though it is not impossible but, in particular 
instances, they may very nearly approach to each other. 
Thus, in sleep, in -a fever, in madness, or in any very 
violent emotions of soul, our ideas may approach to our 
impressions : as, on the other hand, it sometimes hap 
pens that our impressions are so faint and low, that we 
cannot distinguish them from our ideas. But, notwith 
standing this near resemblance in a few instances, they 

1 Ar. Ehet. i. 11 = 1370 A, 28. 

2 Hobbes, Human Nature, chap. iii. 1. 

CHAP. ix. HUME 261 

are in general so very different, that no one can make a 
scruple to rank them under distinct heads, and assign 
to each a peculiar name to mark the difference. * 

The conclusion of this passage exhibits a common 
practice of trying to get round a contradictory instance. 
It is true that, on the whole, the livelier would be dis 
tinct from the fainter perceptions, but there would still 
be a margin between the lively and the faint, which, in 
the absence of any other criterion, it would be arbitrary 
to place among either impressions or ideas. But there 
is a still more fatal objection : some ideas are livelier 
than impressions, and would have, by the bare criterion 
of lively and faint, to change places with them. Yet 
Hume, to save his theory, has to say that c all ideas, 
especially abstract ones, are naturally faint and ob 
scure, while all sensations, either outward or inward, 
are strong and vivid. 2 But abstract ideas of mathe 
maticians are often brighter tfrarftheir concrete impres 
sions, as in the case of the mathematician who in a fit 
of abstraction held the egg in his hand while he boiled 
his watch. Ideas of men in disease are often so vivid 
as to be mistaken for impressions. The artistic imagina 
tion is sometimes stronger than ordinary sensation, as 
Handel, on being asked how he wrote the Hallelujah 
Chorus, said, I did see all heaven before me, and the 
great God Himself. 

This superior vividness of imagination is finely de 
scribed by Addison : 

Words, when well chosen, have so great a force in 
them, that a description often gives us more lively ideas 
than the sight of things themselves. The reader finds a 
scene drawn in stronger colours, and painted more to 
the life in his imagination, by the help of words, than 

1 Treatise, i. 1. 2 Inquiry, 2. 


by an actual survey of the scene which they describe. 
In this case the poet seems to get the better of nature ; 
he takes, indeed, the landskip after her, but gives it 
more vigorous touches, heightens its beauty, and so en 
livens the whole piece, that the images which flow from 
the objects themselves appear weak and faint, in com 
parison of those that come from the expressions. l 

Hume, in distinguishing impressions and ideas, 
rightly restored the word idea to its original sense, 
from which Descartes had perverted it in making it 
stand for all our perceptions. But he tried to put new 
wine into old bottles. The Aristotelian distinction of 
impressions and ideas does not accord with Hume s 
distinctions of vivid and faint perceptions, and can only 
be explained by the Aristotelian criterion of the pre 
sence and absence of an external object, which was 
repugnant to Hume s philosophy. Sensation is the ap 
prehension of an object presented to the senses repre 
senting an external object; while hallucination, or 
subjective sensation, is a similar apprehension pro 
duced by pressure on a sensory nerve : imagination is 
the apprehension of an idea representing a sensible 
object or something similar to it and inferred from it. 
But the presentations of sense are often less vivid than 
the afterthoughts of fancy. 

Hume s second point is the empirical doctrine that 
impressions are the originals of all our ideas, which, as 
before, he identifies with our thoughts : 

But though our thought seems to possess this 
unbounded liberty, we shall find, upon a nearer exami 
nation, that it is really confined within very narrow 
limits, and that all this creative power of the mind 
amounts to no more than the faculty of compounding, 

1 Spectator, No. 416. 



transposing, augmenting, or diminishing the materials 
afforded us by the senses and experience. When we 
think of a golden mountain, we only join two consistent 
ideas, gold and mountain, with which we were formerly 
acquainted. A virtuous horse we can conceive ; be 
cause, from our own feeling, we can conceive virtue ; 
and this we may unite to the figure and shape of a 
horse, which is an animal familiar to us. In short, all 
the materials of thinking are derived either from our 
outward or inward sentiments : the mixture and com 
position of these belongs alone to the mind and will : 
or, to express myself in philosophical language, all our 
ideas *or more feeble perceptions are copies of our im 
pressions or more lively ones. l 

The conclusion of this passage is a neat summary of 
the argument in the Second Book of Locke s Essay. 
Sense is the source of ideas, however indirect the process 
of their formation. Locke had disposed of innate ideas. 2 
As Hume puts it, all our impressions are innate, and our 
ideas not innate, 3 meaning that the former are intuitive 
and the latter derivative. But when we are told that 
all our ideas are copies, direct or indirect, of our im 
pressions, several questions present themselves. First, 
what are those impressions which have to be the ori 
ginals of all ideas ? Secondly, what are the processes 
which enable us to copy the original impressions ? 
Thirdly, what are the ideas and thoughts which we are 
able to reach ? We shall have to ask ourselves about our 
impressions, our processes, our ideas, and our thoughts. 

What are impressions ? It is surprising how little 
Hume condescends to tell us on this subject, incom 
parably the most important in his philosophy. In the 
Treatise he says that the examination of our sensations 

1 Inquiry, 2. Cf. Treatise, iii. 14. 3 Inquiry, 2. note. 


belongs more to anatomists and natural philosophers 
than to moral ; and, therefore, shall not at present be 
entered upon. l It never is entered upon in the 
Treatise ; and in the Inquiry all that is said on the sub 
ject is that impressions are more vivid than ideas, that 
they are the origin of ideas, that there are impressions 
of sensation and impressions of reflection, and that in 
all cases the mind has never anything present to it 
but perceptions, which are either impressions or ideas. 
We are left to gather that the sensible object of the 
impression, being a mere quality not distinct from the 
operation, is, in short, the impression itself. Bare ab 
stract impressions are the data of Hume s empiricism. 
j But it is one thing to admit that knowledge begins with 
\sense, another to assume that it begins with a sense of 
1 impressions. 

When we reflect that these impressions are deliber 
ately stated to be the premises of all our conclusions by 
a philosopher who truly says that 4 one mistake is the 
necessary parent of another, the omission of an exami 
nation of sensation strikes us with the greatest surprise. 
But when we consider that all the idealists have taken 
their data of sense with the same coolness, the wonder 
ceases. As, to begin with, Descartes had attempted no 
formal proof that a soul must perceive ideas, while 
Locke and Berkeley simply accepted the hypothesis 
that it does perceive ideas, so Hume assumed that the 
mind has never anything present to it but perceptions, 
and so, after him, Kant begged that the matter of sense, 
and Mill begged that the information which the senses 
give us concerning objects, is our sensations. 2 

1 Treatise, i. 2. 

2 Of. Hume, Inquiry, 12 ; Kant, Critique (ed. Hartenstein, pp. 83, 
55-6; Meiklejohn s translation, Bohn), pp. 1, 21; Mill, Examination of 
Hamilton s Philosophy, chap. ii. 



111 order to correct Hume s theory of impressions, 
and his followers theory of sensation, it is necessary to 
repeat, what we have already proved, that sense appre 
hends neither itself nor abstractions. It is, in the first 
place, always an operation of a subject apprehending 
an object, internal, but not identical with the operation. 
Secondly, its object is always a qualified substance, 
internal but not resolvable into abstract qualities. 
Thirdly, when it is outer sense, sensation, and sensi 
tive observation, the substance apprehended is the ner 
vous substance sensibly qualified in different parts as 
coloured, heated, &c. Fourthly, when it is inner sense, 
consciousness and conscious reflection, the substance 
apprehended is the thinking subject, body and soul. 
An impression without a substantial subject and object 
is an abstraction, never perceived, never known, with 
difficulty made an object of attention. A man is a sub 
stantial subject impressed with a substantial object, and 
can be conscious of himself being so impressed, as well 
as conceiving, reasoning, and performing other opera 

Hume s theory of impressions, when corrected by 
being converted from the abstract into the concrete, 
contains the valuable point, too often neglected, that, 
even without judgment, a man s simple sensation of the 
white, or the hot, is a beginning of knowledge, and no 
mere abstraction. Nay, as we saw in the first part of 
this essay, we can even trace knowledge to a still simpler 
origin. I begin to know when I feel pained or pleased ; 
not, be it remembered, when there is pain or pleasure, 
which are afterthoughts. My first act of knowledge is 
having a simple feeling in the concrete : my second act 
of knowledge is having a simple sensation of a sensible 
obiect in the concrete. 


There are two ways of criticising Hume s theory of 
impressions. The wrong criticism is to accept it as a 
complete account of sensation, conclude that pure sensa 
tion is an abstraction which never occurs in conscious 
ness, and yet assume these very abstractions to be the 
elements of a psychological synthesis. 1 Those who take 
this view are too much tarred with the brush of Hume. 
A pure sensation, or impression in Hume s terminology, 
is an abstraction ; but so far from being an element of 
knowledge, it is a subsequent result of concentration on 
the mere operation of knowing, to the neglect of sub 
ject and object, and is only put for the real elements of 
knowledge by a convenient form of speech. The right 
criticism is to point out that Hume substituted the after- 
abstraction of sensation for the data of sense and the 
elements of knowledge, which are always a substantial 
subject sensibly perceiving substantial objects within 
the nervous system and consciously perceiving himself. 
There is no such a thing in rerum naturd as an im 
pression and a consciousness, which are merely ab 
stracted post rem, but there is such a thing as man 
impressed with an object and man conscious of himself. 
Sensation and consciousness, in this concrete shape, are, 
moreover, not only the real elements of knowledge, but 
are themselves knowledge ; for, as Aristotle saw, though 
sense is not science (eVioTT?/^), on the other hand it is 
knowledge (y^oicris). 

Next, we come to the association of ideas, thus de 
scribed by Hume : 

It is evident that there is a principle of connection 
between the different thoughts or ideas of the mind, and 
that, in their appearance to the memory or imagination, 

1 Cf. Wundt, Pliysiologisclie Psychologic, ii. 196. 



they introduce each other with a certain degree of 
method and regularity. 1 

He also assigned three principles of connection among 
ideas, namely, resemblance, contiguity in time or place, 
and cause or effect ; for example, a picture leads our 
thoughts to the original ; the mention of one apartment 
in a building suggests a discourse concerning the others ; 
and if we think of a wound, we can scarcely forbear 
reflecting on the pain which follows it. 2 Such is the 
association of ideas on these three principles ; a pro 
cess, which Hume did not exactly substitute for all 
reasoning, for he regarded mathematics as intuitive and 
demonstrative, and founded morals on sympathy and 
reason ; but which he did make the substitute for 
reason in all matters of causation, the organ of natural 
philosophy, and, after sense, the main origin of our 
ideas, which in the passage just quoted are, for the 
third time, identified with our thoughts. 

Association of ideas is a vera causa : this is the 
great advantage of Hume over Kant. We are conscious 
that when we have been sensible of two objects together, 
and have a sensation or idea of one, we, in consequence, 
have the idea of the other: we are not conscious that 
we have an a priori idea, or any other apprehension of 
an object which we have not apprehended beforehand, 
either immediately or mediately. The simplest way, in 
which this conscious suggestion of ideas acts, is when 


simple feelings or sensations and their ideas introduce the 
ideas of one another. That is not a bad instance given 
by Hume ; the idea of a wound suggests the idea of 
pain. The conditions of such a simple sensitive associa 
tion, as we may name it, are, first, simple feelings or 
sensations occurring together ; secondly, their being 

* Inquiry, 3. 2 Ib. 


repeated together ; thirdly, imagination, or the power of 
conceiving ideas; fourthly, the appearance of one of 
the feelings or sensations, or of one of their ideas ; and 
finally, the association itself, which consists in the con 
sequent introduction of the idea of the other feeling or 
sensible object. 

A question may, indeed, be raised, which is evaded 
by Hume and by many of his disciples. Need we only 
have had the original impressions together, or must 
we have also perceived their relation, or the relation 
of their objects? For example, must we have been 
sensible not only of the wound and of the pain, but also 
that the wound was cause of the pain, before it would 
suggest the idea of the pain ? Hume, starting as he 
did from simple impressions, would no doubt have 
answered this question in the negative. He would pro 
bably have been right ; and, moreover, he was aware of 
the reason, which is the anatomical connection of the 
parts of the nervous system, 1 though how, if everything 
we know is perceptions, he could know about the nervous 
system, which is the material cause of these perceptions, 
he did not vouchsafe to explain. The unconscious con 
nection of nervous centres, e.g. between those which 
control the contraction of the iris and those which act 
on the ciliary muscle to increase the convexity of the 
crystalline lens in the eye, the facts of automatic action 
in general, and those of unconscious cerebration in par 
ticular, make it exceedingly probable, notwithstanding 
the difficulty of isolating such a fact in consciousness, 
that when a connection has been set up between ner 
vous centres, through two simple sensations repeatedly 
occurring together, then the occurrence of one will, by 
an association founded on the nervous connection, in- 

1 Treatise, ii. 5 ; cf. Locke, Essay, ii. 33, 6. 

x. HUME 1^09 

troduce the idea of the other, without our having ever 
perceived that the two sensations or their sensible 
objects were connected. In accordance also with that 
gradation of animal faculties first noticed by Aristotle, 
it is not at all improbable that some animals, which 
have got beyond feeling and simple sensation to the 
phantasy of imagination, may possess this simple sensi 
tive association of ideas, which also, through the power 
of ideas over passions and passions over movements, 
may be the guide of their lives. 

It is a very different question how far simple sensa 
tion, ideation, and association would carry a man on the 
path of rational life. All association of ideas is an act 
of reproductive imagination. It merely reproduces the 
idea of something already known somehow or other. 
We shall find, in the sequel, that as knowledge widens 
association widens with it. But at present we are deal 
ing with the simplest kind of association from simple 
sensations, which is also the only kind which Hume 
formally recognises. Now, his doctrine is that when we 
have had simple impressions together, ideas are their 
copies, and association introduces these ideas by the 
laws of connection among the impressions. This can 
only mean that association reproduces the idea of an 
object already sensible ; for example, if having been 
hurt I felt pain, being hurt again will reproduce the 
idea of the previously felt pain. 

An idea of a previously felt pain is quite a different 
thing from the idea of a similar pain not yet felt ; the 
former represents a previous impression, the latter a 
future impression ; the former is an object of simple 
reproductive, the latter of simple productive imagina 
tion. Now, simple sensitive association reproduces in 
the present the idea of a particular pain already actually 


felt ill the past ; but neither Hume nor any of his dis 
ciples has shown that it will perform the very different 
operation of producing the similar but new idea of a 
similar but new pain to be possibly felt in the future. 
j Here is the limit of association : it always reproduces 
the idea of something already apprehended ; never pro 
duces the idea of something not yet apprehended. I 
have been hurt and felt pain : I am now hurt ; I imagine 
the ideas of previous pain when I was hurt ; I also 
imagine the idea of a pain now to follow the hurt, but 
not yet felt. Association reproduces the former ideas ; 
and why ? Because the particular impressions, of 
which the particular ideas are copies, have occurred 
together. But this reproductive act will not of itself 
produce the latter idea, the impression of which has 
never occurred at all. Association from simple im 
pression reproduces particular ideas of particular ob 
jects previously sensible : it does not produce a particu 
lar idea even of a single particular object, not yet sen 
sible ; a fortiori, it is powerless to generate a general 

Hume s critic must constantly keep before him the 
question Is all the reasoning of the natural philosopher 
nothing but a reproduction of sensible ideas by simple 
association ? This question brings us to Hume s main 
point, that while all mathematical reasoning is a process 
from intuition through demonstration to relations of 
ideas, all reasoning about facts is a process from ex 
perience of constant conjunction of impressions through 
association to ideas, i.e. beliefs, of cause and effect. The 
discussion of this complicated theory compels the con 
sideration of many points : belief or judgment and reason 
ing or inference, intuition and demonstration, causation 
and our knowledge of cause and effect. Judgment and 

CHAP. ix. HUME 271 

reasoning alone almost require a logic. I propose to 
confine myself to these, leaving the remaining points 
for subsequent discussion. We must not leave the most 
precious of all man s gifts to be stolen from him without 
striking a blow. What was wanted, and is still a de 
sideratum, is, not a Critique of Pure Eeason, but a 
Vindication of Logical Reasoning. 

Nature, says Hume, by an absolute and uncon 
trollable necessity, has determined us to judge, as well 
as breathe and feel. l He saw the importance of judg 
ment or belief. He also set himself, both in the Treatise 
and in the Inquiry, 2 to examine more accurately the 
nature of this belief. But in both cases he adopted the 
same extraordinary paradox, that, as impression is only a 
more vivid perception than an idea, so a belief is only a 
more vivid idea than a fiction. I say that belief is no 
thing but a more vivid, lively, forcible, firm, steady con 
ception of an object than what the imagination alone is 
ever able to attain : such is Hume s definition of belief. 3 

Why did he fall into this extraordinary confusion of 
simple and complex apprehension, of conception and 
judgment, of an idea and a belief? Because, wanting 
to derive all beliefs from association, and being aware 
that association terminates in ideas, there was nothing 
for it but to reduce beliefs to vivid ideas. He cut his 
coat according to his cloth in a thoroughly iderjhstic 
style of tailoring. Whenever, he says, any object 
is presented to the memory or senses, i^Jmmediately. 
by the force of custom, carries the imagination to con 
ceive that object which is usually conjoined to it ; and 
this conception is attended with a feeling or^sentiment 
different from the loose reveries of the fancy. In this 

1 Treatise, iv. 1. 2 Ib. iii. 7 ; Inquiry, 5. 

3 Inquiry, 5, Part II. 


consists the whole nature of belief. l All he really 
shows is that, if association is the origin, of beliefs, they 
would be mere ideas ; but he does not prove^that they 
are so. It was to prepare for this confusion of concep 
tion and belief, that he had said first tjb^all percep- 
tipns__axfi impressions and ideas or thoughts, thatT all 
ideas or thoughts are copies of impressions, and that 
association is a principle of connection of ideas or 
thoughts ; as if all thought were ideas and ideas our 
only thoughts ! 

Judgment, or belief, is, like conception, an appre 
hension, but not like it in being the apprehension of an 
idea ; nor can any accumulation of epithets added to a 
conception make it a judgment. Judgment is the 
apprehension of a relation. Hume entirely missed this 
point, by which judgment is differentiated from all con 
ception whatever. He was, no doubt, much deceived 
by the conceptualistic theory of relation in Locke s 
Essay. But Locke, though he had confused relations 
with their ideas in the Second Book, changed his key 
when he came to the Fourth Book, and regarded judg 
ments as perceptions of the agreement and disagreement 
of ideas, without resolving these relations into ideas, as 
strict consistency would have demanded. It should be 
noticed that this differentia of judgment holds even 
when the things related are ideas ; when I judge that a 
dragon is a serpent breathing flame, I have only ideas of 
a dragon and of such a fiery serpent, but I judge that 
the ideas actually have the relation of identity, which I 
can express in a proposition by the copula, is. Locke, 
then, might at least have taught Hume thajL .ajudgment 
perceives, not mere ideas, but^ the_agreement _and dis 
agreement^ of ideas. But, as usual, the Second Book 

1 Inquiry, 5, Part II. 

CHAP. ix. HUME 273 

attracted philosophers to the neglect of the Fourth 
Book of Locke s Essay. 

But though Locke s theory of judgment is wider 
than Hume s, it is not adequate ; not all judgments 
apprehend relations of ideas ; for some judgments appre 
hend relations of sensible objects. This point has been 
excellently made by Mill, the logician of the school of 
Locke and Hume, in his Logic, when he says that 

has for itsjsubject the facts 


themselves, though a previous mental conception of the 
facts is au indispensable condition. When I say that 
fire causes heaT,~ do I mean that my idea of fire causes 
my idea of heat ? No ; I mean that the natural pheno 
menon, fire, causes the natural phenomenon, heat. 
When I mean to assert anything respecting ideas, I give 
them their proper name ; I call them ideas ; as when I 
say that a child s idea of a battle is unlike the reality. l 
Hence, Mill s Logic recognises judgments of relations 
between phenomena as well as between ideas, from 
which the founder of the modern distinction of im 
pressions and ideas could hardly have escaped. Not 
that even Mill s analysis is adequate. In the first place, 
Mill s list of judgments is incomplete; there are judg 
ments of relations between sensible objects, between 
ideas, between insensible, and between imperceptible 
objects, judgments of sense, of conception, of inferential 
perception, and of transcendental inference ; secondly, 
even if, so far as judgments are premises, conceptions 
may be their conditions, so far as they are conclusions, 
the judgment is often the condition of the conception, 
as when we infer a corpuscle, and then conceive it. 
But for our present purpose it is sufficient that, as Mill 
sa} T s, there are judgments of relations between phaeno- 

1 Mil], Logic, i. 5, 1 ; cf. also Exam, of Hamilton s Phil. chap, xviii. 



mena, sensible objects, the objects of simple impressions. 
Such a judgment is not an apprehension of a relation 
of ideas, much less an idea of a relation. 

It would not be difficult to distinguish judgments 
from ideas by Hume s admissions. In the first place, 
he recognises relations, reducing them in the Treatise 1 
to seven general heads : resemblance, identity, those of 
space and time, quantity or number, degrees of quality, 
contrariety, and cause or effect ; and, in both Treatise 
and Inquiry, admitting the relations of resemblance, 
contiguity, and sequence of impressions, on which asso 
ciation is founded. There are, then, relations to be 
judged. Secondly, he held that mathematics are con 
cerned with relations of ideas, and unwarily admits 
Locke s doctrine that a mathematical proposition ex 
presses a relation. 2 Thirdly, and most curiously, in the 
very chapter in which he had defined belief as an idea 
made vivid by association, he goes on to allow that, 
when a picture introduces the idea of a friend, the 
association presupposes a belief in the friend s exist 
ence. We may observe, says he, that in these pheno 
mena the belief of the correlative object is always 
presupposed ; without which the relation would have 
no effect. The influence of the picture supposes that we 
believe our friend to have once existed. What can this 
belief in a friend s existence be, according to Hume, 
except Mill s apprehension of a relation of phenomena 
or impressions? And are not there such beliefs, not 
only of existence, but also of the other relations of 
phenomena, mentioned by Mill coexistence, sequence, 
resemblance, even if not of causation ? 

Hume would, perhaps, reply that we have a vivid 
idea of the relation between our friend and his exist- 

1 Treatise, i. 5. 2 Inquiry, 4. 

CHAP. ix. HUME 275 

ence, in which the belief consists. It is true that we 
have such an idea. But, in truth and in Hume s philo 
sophy, this idea must be copied from an impression ; 
there must, therefore, be a prior impression of the re 
lation between our friend and his existence, in which 
the belief consists. We first judge of a relation and 
then conceive the idea of it, in consequence of the 
judgment an important source, by the way, of complex 
ideas of relation. 

If the judgment were merged in the mere idea of 
the relation, it could not be distinguished from fictitious 
ideas of relation. Hume, indeed, tries to distinguish 
ideas of the judgment from fictions of the imagination 
by his usual criterion of vivacity, contending, for in 
stance, that these ideas take faster hold of my mind 
than ideas of an enchanted castle. l This may be true 
ofWalpole s Castle of Otranto. But Hume wrote before 
the appearance of Scott s historical romances, after 
which he could not have failed to see that the mere 
idea of a relation in belief is often very inferior in 
vivacity to the idea of a relation in fiction. There are 
few scenes in history so vividly painted in my imagina 
tion as my idea of Quentin Durward conducting the 
Countess Isabelle out of France to Liege, and from 
Liege into Burgundy. But, in spite of the force of the 
idea, I do not believe in the relation, and why not? 
Because I do not judge or apprehend that the relation 
ever occurred, and only conceive the idea of it in 
imagination, stimulated by the genius of Sir Walter 

Belief, then, is not conception : a judgment is not 
an idea, but the apprehension of a relation. Now, what 
is the relation of judgments to association? According 

1 Inquiry, 5 ; cf. Treatise, iii. 7. 

T 2 


to Hume, all of them are its results ; only, however, if 
they are nothing but ideas, because the association of 
ideas terminates in ideas. Well, as no judgment is an 
idea, not one judgment, not even one which apprehends 
a relation of ideas, is a result of association, which 
never can give an apprehension of a relation. Secondly, 
a judgment which apprehends a relation of sensible ob 
jects, such as, I am hurt and feel pained, cannot be an 
effect of association, because the judgment signifies, in 
Hume s language, a relation of two impressions, w T hile 
in association, even when that which suggests is an im 
pression, that which is suggested is an idea, and because 
the judgment is prior to any association in which one 
of the two impressions suggests the idea of the other. 
Thirdly, those judgments which apprehend relations of 
objects not now in sense are not results of association, 
because they are not ideas, and are not concerned with 

Hence association is not an adequate origin of 
memory and expectation, which are judgments of the 
past and of the future. Memory, according to Hume, is 
a more vivid idea. But ideas of fancy are often more 
vivid than those of memory. Memory contains an 
idea, but it is a judgment that the idea represents a 
previously apprehended object. Now association can 
reproduce the idea, but not produce the judgment of 
memory. Still less is expectation a result of associa 
tion. It contains an idea, but is a judgment that the 
object will or may be apprehended. When the idea 
represents an object already apprehended, as in the 
case of memory, association reproduces the idea, but 
does not produce the judgment of the object expected. 
When, as in expectation, the idea represents an object 
similar to previously apprehended objects, but not itself 


HUME 277 

yet apprehended, association does not even produce the 
idea of the expected object ; for, as we found before, 
association only reproduces ideas. History and predic 
tion are not results of association, because they consist 
of judgments, because their objects have never been in 
sense, because their ideas are ideas of insensible objects. 
A fortiori, science, an apprehension of laws, or similar 
relations between an indefinite number of insensible 
objects, cannot be a result of association. The associ 
ation of ideas could not make us conceive the idea, 
much less judge that the cities of the plain once existed, 
which we never saw ; nor that the earth will one day 
be too cold for habitation, when we shall not be alive 
to see that day ; nor that all fluids propagate their 
motions equally in all directions, which we judge to 
be universal, but cannot perceive, nor conceive univer 
sally. The association of ideas does not produce the 
judgments of history, prediction, and science. In short, 
judgments are apprehensions of present relations in 
objects of sense, of past relations in memory and his 
tory, of future relations in expectation and prediction, 
of universal relations in science, which, not being ideas, 
are not results of association, but of sense and reasoning. 
Association of ideas reproduces an idea : it does not 
produce an idea : it neither produces nor reproduces a 
belief. How, then, do we get these beliefs or judg 
ments? That is the whole question. How does judg 
ment apprehend present relations of objects in sense ? 
That is the first and fundamental question, never faced 
by Hume. I have admitted that, when his abstractions 
have been interpreted, he was right in saying that we 
have simple impressions in the sense of simply feeling 
pleased and pained, simply perceiving sensible objects, 
the white, the hot, &c., and simply being conscious of 


ourselves operating, feeling, seeing, touching, &c. These 
are simple acts of knowledge. A simple sensation re 
quires, indeed, a subject apprehending an object, and 
must not be resolved into a mere abstraction. It does 
not follow that it contains a conscious judgment of the 
relation of subject and object, as some philosophers 
suppose. It requires also to be different from other 
sensations, in accordance with the principle of Hobbes 
Idem sentire et non sentire ad idem recidunt. It does 
not follow that it contains a sense of discrimination. 
When light is presented to my retina, by simple sensa 
tion, I see a visible object in my optic nerve, without 
judging its relation to myself, or to other sensible objects, 
and so far as I see it, know it. But though I have 
simple sensations or, as Hume calls them, impressions, 
without judgment, yet I also judge of the relations of 
sensible objects. Hume rightly recognised simple sensa 
tion, wrongly ignored sensitive judgment. 

The source of sensitive judgment is synthetic sense. 
Unless I actually had a sense of the succession of being 
hurt and being pained I could not judge that the 
succession occurred. Moreover, there is a synthetic 
sense of other relations, on which sensitive judgment 
is founded, of the relations enumerated in Hume s 
6 Treatise, of the relations regarded in his Inquiry as 
necessary to association, of the relations truly regarded 
by Mill in his Logic as part of the very import of a 
judgment and a proposition. Hume should have dis 
tinguished two kinds of impressions, simple and syn 
thetic ; impressions of sensible objects and impressions 
of relations of objects. Like simple tastes and smells, 
or feelings of pleasure and pain, as Professor Huxley 
says, they are ultimate irresolvable facts of conscious 
experience ; and, if we follow the principle of Hume s 


HUME 279 

nomenclature, they must be called impressions of rela 
tion. But it must be remembered that they differ from 
the other impressions, as requiring the pre-existence of 
at least two of the latter. l In this way, when two sen 
sible objects are presented to us, we are sensible of their 
succession, their coexistence, their similarity, and so 

The first point to notice about this sense of a rela 
tion is, that as the sensible objects, so the sensible rela 
tions, are not external but internal, yet not psychical. 
When I feel a tangible effect in my tactile nerves, pro 
duced by laying my arms on a table containing paper, 
cloth, pens, &c,, I feel several tangible objects coexisting 
with one another within my tactile nerves. Secondly, 
this sense of a relation is as presentative as any simple 
sense, and does not construct relations but apprehends 
them, when they are present, between the sensible ob 
jects. In a word, the immediate apprehension of a re 
lation is not a psychological synthesis of abstract sensa 
tions, but a synthetic sense of sensible objects. In the 
books of idealists, sensation is an abstraction from a 
substantial subject perceiving a substantial object of 
sense ; and synthesis is a second abstraction, founded on 
the first, from the receptivity of a sensible relation. But 
in reality there are two apprehensions by a subject of 
sensible objects, both equally sensitive ; first, simple 
sensations of particular objects, and secondly, synthetic 
sensations of particular relations of particular objects. 
There are also two kinds of experience : the first, a sum 
of simple sensations, e.g. of being pained ; the second, 
a sum of synthetic sensations, e.g. of being pained at 
repeated blows in a fight. 

Curiously enough, Hume over and over again men- 

1 Professor Huxley, Hume, chap. ii. 



lions instances of synthetic sense and synthetic ex 
perience intervening between impression and associ 
ation, yet without formal acknowledgment. In the 
Treatise, he says that when both the objects are 
present to the senses along with the relation, we call 
this perception rather than reasoning ; nor is there in 
this case any exercise of the thought, or any action, 
properly speaking, but a mere passive admission of the 
impressions through the organs of sensation. l Again, 
in speaking of the data of the idea of causation, he 
says : The nature of experience is this : We remem 
ber to have had frequent instances of the existence of 
one species of objects ; and also remember, that the 
individuals of another species of objects have always 
attended them, and have existed in a regular order of 
contiguity and succession with regard to them. Thus 
we remember to have seen that species of object we call 
flame, and to have felt that species of sensation we call 
heat. We likewise call to mind their constant conjunc 
tion in all instances. 2 In the Inquiry we find pas 
sages close together, one implying synthetic sense 

followed by another implying synthetic experience : 

Suppose a person, though endowed with the strongest 
faculties of reason and reflection, to be brought on a 
sudden into this world ; he would, indeed, immediately 
observe a continual succession of objects and one event 
following another. . . . Suppose again that he has 
acquired more experience, and has lived so long in the 
world as to have observed similar objects or events to be 
constantly conjoined together ; what is the consequence 
of this experience ? He immediately infers the exist 
ence of one object from the appearance of the other. 3 

1 Treatise, iii. 2. 2 Ib> ^ 6 . cf . 8> 

3 Inquiry, 5, Part I. 


HUME 281 

Similarly, in a well-known passage, lie says : All 
events seem entirely loose and separate. One event 
follows another, but we never can observe any tie 
between them. They seem conjoined, but never con 
nected! l Whatever Hume may say about impressions, 
he constantly admits an immediate observation and ex 
perience of any relations, short of connection ; when he 
says that events seem loose and separate, he does not 
mean that they seem quite isolated ; and he allows a 
power of apprehending constant conjunction, though 
without causation, prior to association. How then 
could he refuse to call this sensitive apprehension of a 
relation belief, or contend that such a sensitive belief is 
a result of association ? 

Thus we find that belief or judgment is not an idea, 
but an apprehension of a relation ; and not a result of 
association, but originally derived from a synthetic sense 
of relations. What are the consequences? In the 
first place, synthetic sense and judgment are not asso 
ciations, because the objects related are both sensible ; 
neither is an idea ; and one does not suggest the other, 
but their relation is presented. Secondly, synthetic 
sense, experience, and judgment having apprehended a 
relation in particular instances, cause a complex idea of 
the relation ; thus forming a source of ideas unnoticed 
by Locke and his followers. Thirdly, although simple 
sensations and experiences sometimes, by the anatomical 
connection of their nervous centres, without any judg 
ment of their relation, produce an association of ideas ; 
nevertheless, in an animal capable of judgment, it more 
frequently happens that synthetic sense, experience, and 
judgment apprehend the relation of the sensible objects, 
and cause an association of the ideas of the objects and 

1 Inquiry, 7, Part II. 


of their relation, which I propose to call synthetic sen 
sitive association. In these cases, so far from associa 
tion producing belief, belief produces association. For 
example, I judge that one object follows another in my 
senses, and when one appears again, I consequently 
have not only the idea of the other, but also the idea of 
their sequence, which I could not get from simple sensi 
tive association. Here, perhaps, is another stopping 
place in animal intelligence. Fourthly, synthetic sense 
and experience of relations, being the sources of sensi 
tive and empirical judgments without association, supply 
the original evidences of reasoning without association. 
The want of a formal recognition of synthetic sense, at 
the very time he was accumulating instances of its 
action, concealed from Hume the true sources of reason 
ing, and its independence of association. 

The problem of inference or reasoning hinges on two 
questions ; the origin of new judgments, and the origin 
of new ideas. We have achieved some of the data for 
solving this problem ; by showing that we have judg 
ments of synthetic sense to start with, that no judgment 
is an idea, and that association, in reproducing ideas of 
objects already sensible, does not produce an idea of an 
object not yet sensible, and does not produce a judgment 
at all. These data of themselves indicate a difference 
between the association of ideas and the inference of 
judgments, and also point to an origin of ideas other than 
association. Eeason starts directly from judgments of 
synthetic sense, and, without passing through associa 
tion, infers judgments, issuing in rational ideas. 

Man, says Hume, is a reasonable being ; and, as 
such, receives from science his proper food and nourish 
ment. 1 Hume did not deny reasoning, nor resolve it 

1 Inquiry, 1. 


HUME 283 

all into association. He had no general theory on the 
subject ; and this is one of the weaknesses of his philo 
sophy. But he admitted, in mathematics, a species of 
reasoning, not only distinct from association, but even 
consisting of demonstration from intuition. However, in 
spite of his distinction of impressions and ideas, in the 
spirit of Locke, he thought that this mathematical 
reasoning is limited to the relation of ideas. The point 
of his polemic against reason was that it never reaches 
matters of fact. He wanted to prove that judgments 
of fact, being mere ideas, are mere products of associa 
tion. He failed, because judgments are not ideas, 
because association does not produce ideas much less 
judgments, and because reasoning from sensitive judg 
ments produces rational judgments of fact, and rational 
ideas. In this part of his philosophy he shows a re 
markable spirit of inquiry, and as remarkable a power 
of missing the point of difference between one operation 
and another. 

All conclusions about facts, he thought, are about 
cause and effect, all conclusions about cause and effect 
are from experience. What, he asks, is the founda 
tion of all conclusions from experience ? I want, he 
says, to learn the foundation of this inference. l All 
inferences from experience, therefore, are effects of 
custom, not of reasoning : 2 this is the starting-point of 
his answer. All our reasonings concerning matters of 
fact are founded on a species of analogy, which leads us 
to expect from any cause the same events which we have 
observed to result from similar causes : 3 this is his in 
terpretation of customary inference. This interpretation 
was required for his main point, that customary infer- 

1 Inquiry, 4, Part II. 2 Ib. 5, Part I. 

3 Ib. 9 ; cf. 5, Part I. 


ence is the same as the association of ideas ; for analogy 
supplies the inference most like the association of ideas. 
When a sword, he says, is levelled at my breast, does 
not the idea of wound and pain strike me more strongly 
than when a glass of wine is presented to me, even 
though by accident this idea should occur after the 
appearance of the latter object? But what is there in 
this whole matter to cause such a strong conception, 
except only a present object and a customary transition 
to the idea of another object, which we have been 
accustomed to conjoin with the former? This is the 
whole operation of the mind in all our conclusions 
concerning matter of fact and existence. l That is, 
judgments are strong conceptions, and inferences are 
analogies, which are associations of ideas. 

Analogous inference is like synthetic association in 
data. Both start w^ith the same synthetic experience, 
which, in Hume s example, is 

Swords levelled at me have already pained me ; 

This sword is like previous swords. 

This synthetic experience sets up three processes : (1) 
this sword, being like previous swords, reproduces the 
idea of having been already pained ; (2) the combina 
tion of the two sensitive judgments produces the new 
judgment that this sword may possibly pain me ; and 
(3) this new judgment produces the idea of being 
possibly pained. Of these processes, the first is associa 
tion of ideas, the second is analogous inference, the 
third is analogous conception. Now, analogous infer 
ence is further like synthetic association in process. 
Both are customary processes in obedience to certain 
laws ; the laws of association, and the law of analogy. 

1 Inquiry, 4, Part II. 

CHAP. ix. HUME 285 

The law of analogy is expressed in logic as a general 
axiom thus : what is related in experience to particu 
lars in experience is possibly related to other particulars 
like them in experience. This axiom, however, does not 
appear in the premises of the inference, but as the laws 
of association are laws we spontaneously obey in repro 
ducing ideas, so the law of analogy is the spontaneous 
law which, without knowing it, we obey in inferring 
from particular to particular judgment. It is after 
wards discovered by logicians, and then is expressed as 
the law of the form of analogous inference ; but it would 
be a sad confusion to suppose that because logicians know 
it everybody who uses analogy knows it. The axiom 
of analogy is a mechanical law of analogous inference ; 
and the man who has not studied logic infers from the 
above-stated premises that a sword may pain him, not 
by reasoning from the axiom as a major premise, but 
by the habit of using it as a mechanical law. The 
nearest animals to man probably infer by the very same 
habit of analogy, as Hume and Mill after him have re 
marked. We have already suggested that some animals, 
after the lowest stage of mere feeling and the stage of 

o O O 

mere sense, may stop at simple sensitive association, 
while others may rise to synthetic sensitive association. 
Perhaps the analogous inference, which we are now 
describing, is the highest limit of brute reasoning. 
Finally, analogous inference is like synthetic association, 
not only in data and process, but also in result. Both 
end in particulars. 

Where, then, is the difference ? One ends in an 
idea of the past, the other in a judgment of the 
possible. The association of ideas terminates in an 
idea of having been previously pained ; the analogous 
inference concludes with a judgment that this sword 


may now possibly pain me. As a judgment is not an 
idea, so there must be something different in the processes 
which produce the one and the other. The difference 
consists in the laws which the processes habitually 
use : association, acting by the laws of the reproduction 
of ideas from resemblance, contiguity and sequence, 
&c., analogous inference by the law of the analogous 
production of a particular judgment : what is related in 
experience to particulars in experience is possibly re 
lated to other particulars like those in experience. 
Finally, besides terminating in a judgment, analogous 
inference produces another effect, to which association 
is incompetent; the conception of an idea of being 
possibly pained, which is not to be confused, as Associa- 
tionists confuse it, with the idea of having been formerly 
pained. This further operation I propose to call analo 
gous conception. It is an important operation. Thus, 
having by analogy inferred that Mars, being like the 
earth, may be inhabited, my analogous conception 
pictures an idea of Martial men. If I mistake not, 
analogous conception comes much nearer than associa 
tion to the productive imagination of art. Analogous 
inference, then, is custom, but not association. Asso 
ciation is customary reproduction of ideas ; analogous 
inference is customary inference from particular to par 
ticular judgment; and analogous conception is the 
conception in the productive imagination of an idea of 
a new particular inferred by analogy. 

Hume s reduction of inference from experience to 
association breaks down at the very first touch of logic. 
It would not be worth while to pursue the subject, had 
he not made an audacious attack on induction, reducing 
it to analogy, in order to identify it with association. 
Moreover, a similar attempt appears in Mill s reduction 

CHAP. ix. HUME 287 

of induction to inference from particular to particular, 1 
though in a much more half-hearted fashion, partly be 
cause he does not in his Logic further identify analogy 
with association, and partly because, immediately and in 
the sequel, he proceeds to treat induction in quite a differ 
ent manner. We shall find that induction is not analo 
gous inference, much less association of ideas. We must 
retrace our steps from Mill, through Hume, to Bacon, 
who says : Aut enim defertur judicium ab experimentis 
ad experimenta ; aut ab experimentis ad axiomata, quas 
et ipsa nova experimenta designent ; 2 and to Aristotle, 
who, as if foreseeing logical scepticism, warns us that 
6 inference by example is neither as particular to general, 
nor as general to particular, but as particular to 
particular. 3 

Induction is not analogy, because the aim of induc 
tion is to arrive at a general judgment. By analogy 
we infer, not a general but a particular conclusion : by 
induction we infer not a particular but a general con 
clusion. Hence induction does not contain the very 
point of analogical inference, the analogy itself. To 
judge that a particular sword is like previous swords is 
necessary, if we wanT to reason about that one in par 
ticular, but not if we want to conclude generally that 
all swords whatever are painful, when levelled at one s 
breast. It is true that there is a point in common be 
tween the two processes the judgment that sVords 
levelled at me have already pained me, which is also 
present in synthetic association. But the difference is 
that, when a similar sword is levelled at me, by associa 
tion I reproduce the idea of having been formerly 

1 Mill, Logic, ii. 3, 7. 

2 Bacon, De Aug. Scient. v. 2 (p. 622 ; ed. Ellis & Spedding) ; cf. Nov. 
Ory. i. 103. 

3 Ar. Prior. An. ii. 24 = 69, A 13-15. 


pained, and by analogical inference I infer that tins 

sword may pain me again ; while, without a similar 

sword being present, by induction I conclude generally 

that all swords, levelled at me, would be painful. As- 

! sociation ends in a particular idea, and analogy in a 

| particular judgment. Induction ends, not in particulars, 

but in a general judgment, beyond the reach both of 

association and of analogy. 

There is, however, a difficulty in the superior claims 
of induction, which did not escape Hume s inquiring 
mind. How do we go from the particulars of experi 
ence to the general conclusion of inference, from many 
to all ; for in the vast majority of cases we cannot 
experience all ? In the first place, particulars, which 
at once prompt us to association and analogy, do not 
justify logical induction. In order to draw a general 
conclusion, we must not rest content with this or that 
particular, but accumulate instances of three kinds, as 
Bacon showed : instances of presence or agreement, of 
absence or difference in similar circumstances, of com 
parative degrees or concomitant variations. 1 Secondly, 
even then, we have only experience, albeit scientific, of 
many, not of all. There may, in the remaining instances 
not experienced, be an exception. Mox enim prod- 
ibit, says Leibnitz, qui negabit ob peculiarem quandam 
rationem in aliis nondum tentatis veram esse. 2 There 
is a leap in induction from various members to the 
whole class, from the particulars to the general, from 
many swords to all. How do we effect this leap ? 
By the axiom of generality : things so related as to be 
always present, absent, and varying together in experi 
ence are, with a probability proportionate to the extent 
of the experience in time, place, and circumstance, so 

1 Nov. Org. ii. 11 scq. 2 Leibnitz, DC Stilo Fliilosopliico Nizolii, xxxji. 

CHAP. ix. HUME 289 

related in all similar cases. This is the law of the form 
of induction, distinguishing it from association and 
analogy by the power of inferring a general judgment, 
leaving it indeed a probable inference, yet with an 
approximate certainty continually tending to absolute 

Three mistakes are often made about this axiom of 
generality : first, it is stated most carelessly, as if it 
were simply that what is true of many things of a class 
belongs to the rest, omitting both the scientific cha 
racter of the experience and the problematic character 
of the conclusion ; secondly, it is frequently confined to 
laws of causation, omitting inductions of coexistence, 
&c. ; thirdly, it is often regarded as if it were known to 
all men who induce, as an assumption involved in every 
case of induction, and even as a major premise convert 
ing induction into deduction. The first and second 
mistakes I have just corrected by attempting a more 
precise and general statement of the axiom. The third 
mistake is really too absurd; overlooking, as it does, 
that men, from time immemorial, however primitive, 
have made, and at the present day, however savage, 
do make inductions without dreaming of the axiom; 
while Aristotle, the founder himself of the lo^ic of in 
duction, even contradicted the law of uniformity by 
holding that nature has only a uniform tendency, and 
that there are exceptions to universality caused by 
accident inherent in matter. 1 

This false view of the axiom of generality, by 
which it is made a supposition involved in induction, 
gave Hume his opportunity: he saw that it would 
involve us in a circle. To endeavour, therefore, 
says he, < the proof of this last supposition by pro- 

1 Cf. Ar. Met. E. 2 = 1027 A, 5-15. 



bable arguments, or arguments regarding existence, 
must be evidently going in a circle, and taking that for 
granted which is the very point in question. l This 
difficulty has been often felt : we require an induction 
to found the axiom, which is nevertheless supposed to be 
the assumption involved in all induction. To surmount 
it, some resort to the theory that the axiom is a priori, 
though many, including Aristotle, have not even believed 
it. This was not the alternative of Hume, whose plan 
was to surrender universality, and renounce the inductive 
inference from particular to general judgments, in favour 
of the analogical inference from particular to particular 
judgment, which he falsely, as we have seen, reduced 
to association from particular impressions to particular 
ideas : 

What, then, is the conclusion of the whole matter ? 
A simple one ; though, it must be confessed, pretty 
remote from the common theories of philosophy. All 
belief of matter of fact or real existence is derived 
merely from some present object to the memory or 
senses, and a customary conjunction between that and 
some other object; or, in other words, having found, 
in many instances, that any two kinds of objects, flame 
and heat, snow and cold, have always been conjoined 
together : if flame or snow be presented anew to the 
senses, the mind is carried by custom to expect heat or 
cold, and to believe that such a quality does exist, and 
will discover itself upon a nearer approach. 2 

Hume was right in rejecting a quasi-inductive de 
duction from the supposition of generality. It does 
not follow that induction becomes mere analogy, still 
less association. Such an alternative is inadequate to 
the extent of general reasoning. Moreover, if induction 

1 Inquiry, 4. ~ Ib. 5, Tart I. 

CHAP. ix. HUME 991 

were analogous inference and association, the analogy 
must always be present, as Hume was well aware. 
Wherever he mentions his analysis, he admits that 
the analogous object is present, about which the in 
ference is made. In the instance above, flame analo 
gous to previous flames has to be presented anew to the 
senses, in order that we may expect its heat, and snow, 
analogous to previous snows, in order that we may ex 
pect its cold. In the instance of the sword, having 
experienced that swords levelled at us have been pain 
ful, I again experience that another sword is present, 
in order to infer that this particular sword is painful. 
If a new particular, similar to previous particulars, were 
not present in the premises, how could analogy infer 
an attribute of that particular in the conclusion, or 
association use it to introduce an idea? Now, this 
condition, though essential to association and analogy, 
is unnecessary, or rather completely extraneous, to in 
duction. Having experienced the relations of former 
particulars, without any new particular being present, 
it infers that all flame is hot, all snow is cold, all sword? 
levelled at one s breast are painful. 

We must find some other alternative, then, which 
neither surrenders the inference of generality nor makes 
the axiom of generality a supposition antecedent to 
induction, whether by an inductive circle or by a priori 
mysticism. We have already chosen such an alternative 
in explaining analogous inference : it is also applicable 
to induction. As the axiom of analogy is the law of the 
form, without being a premise, of analogical inference, 
so the axiom of generality is the law of the form, without 
being a premise, of induction ; a law not known, but 
mechanically and spontaneously obeyed by the ordinary 
man. and only afterwards discovered by logicians. The 

TJ -2 


reason why we induce from some flame is hot, some 
snow is cold, some sword-thrusts are painful, is because 
we have accumulated so many instances, in which the 
related objects have been present, absent and varying 
together in our synthetic experience, that, by the law of 
generality acting on us without our knowing it, we 
cannot but infer general judgments that all flame is hot, 
all snow is cold, all sword-thrusts are painful. 

Induction, then, like analogy, is the inference of a 
judgment; but is distinguished from analogy, because 
it proceeds from such an experience as will enable it 
by the law of generality to infer a general judgment. 
Induction, like association, is not a deduction from the 
law of its form, but a customary process by that law. 
But its custom is not association. First, association is 
a reproduction of past ideas, induction an inference of 
general judgments ; secondly, in order to suggest an 
idea, synthetic association contents itself with experience 
of any relation of objects ; but in order to produce a 
general judgment, induction logically requires experi 
ence of a relation of objects, present, absent and vary 
ing together ; thirdly, the form of association is governed 
by the spontaneous laws of the reproduction of ideas, 
the form of induction by the equally spontaneous but 
different law of generality. Finally, association and in 
duction differ not only in themselves, their experience, 
and their laws, but also in their result on conception : 
association produces no new idea of a particular, much 
less a general idea ; induction, having inferred a uni 
formity, produces what we may call an inductive idea 
of the uniformity, e.g. of the heat of flame in general, 
of the cold of snow in general, of the painfulness of 
sword- thrusts in general. 

Deduction from induction must be discarded by 

CHAP. ix. HUME 293 

every philosopher such as Hume, who resolves induc 
tion into analogy, because, in that case, the inference 
from particular to particular usurps the double function 
at once of the inference from particular to general, and 
of the inference from general to particular. Suppose, as 
Mill would say in imitation of Hume, this universal type 
of all inference : swords have been painful ; this sword is 
like previous swords ; therefore it is or may be painful. 
Then there is nothing left for the double process up to 
the general judgment about swords as a whole class, 
and down to a particular judgment about a sword not 
previously known. Accordingly, Hume banished reason 
ing, by which he meant deduction, entirely from em 
pirical conclusions ; and Mill declared syllogism to be 
no inference, regarding the double inference from par 
ticulars through a generality to a new particular as an 
unnecessary circuit. 1 

But induction and deduction are integral and 
complementary parts of a double process of inference, 
from particular to general, from general to particular. 
As we have seen, induction is not analogy ; it begins 
with particulars, but ends, not with a new particular, but 
with a general judgment about a class. Deduction from 
induction, or empirical deduction, as we may call it, com 
pletes the double process : it combines the general judg 
ment with a particular judgment, that a new particular 
belongs to this class, and infers that what belongs to the 
class belongs to the new particular. Empirical deduc 
tion differs from analogy in starting, not directly from 
particulars, but from a general judgment, given by 
induction ; it differs from induction, not only in using 
this general judgment as major premise, but in adding 
a minor, and drawing a particular or less general con- 

1 Mill, Logic, ii. 3. 


elusion. It may be called the complement of induction, 
needed to convert generalities into particulars, and 
bring the double process of general reasoning to a 
particular conclusion, like that of analogy, but reached 
through a generality. 

Deduction, as discovered by Aristotle, and disen 
gaged from the mere schematism of Galen and later 
logicians, consists of three orders or figures. They are 
three different ways of thinking. Sometimes I want to 
prove or disprove by means of a class ; for example, 
belonging to the class of magnitudes whose angles are 
equal to those of a perpendicular falling on a straight 
line, proves that a triangle has its angles equal to two 
right angles : this is the first figure or order of deductive 
thinking. Sometimes I want to disprove by means of a 
difference ; for example, as a demagogue differs from a 
statesman in being a truckler, he is not a statesman : 
this is the second order of deductive thinking, the figure 
of difference. Sometimes I want to prove by an instance 
or disprove by an exception ; for example, the genius 
of Nelson is sufficient to prove what Englishmen were 
capable of at the beginning of this century : this is the 
third order of deductive thinking, the figure of instance. 
Each of these figures has its own axiom ; that of the 
first being the dictum de omni et nullo, discovered by 
Aristotle ; those of the second and third being respec 
tively the dictum de diverse, and the dictum de exemplo 
et excepto, discovered by Lambert. 1 

I have a purpose in calling attention to these three 
axioms of the three orders of deductive reasoning. They 
are necessary laws of deduction ; yet they are not in the 
premises. Moreover, as men, in deducing conclusions, 
know nothing about them, they have not already been 

1 Lambert, Neues Organon, i. 4, 232. 


HUME 295 

acquired by a previous induction, still less are appre 
hended a priori. They are not presupposed, but used. 
What is the explanation? Precisely the explanation 
already given for the law of analogy and the law of 
generality. They are spontaneous laws used by every 
deducer, but discovered afterwards by the logician. 
Hence they never appear in a syllogism, being not its 
premises, but the laws of its form, each of the three 
dicta being the law of its own order of deductive think 
ing. As Aristotle said, the nature of a syllogism is 
not premised in a syllogism. 1 

Deduction would not be an inference, if it were not 
an advance in knowledge ; but it is an advance in 
knowledge. If induction were founded on a complete 
examination of all members of the class, there would be 
no occasion for deduction. But usually we only examine 
some members, from which induction leaps, by the 
axiom of generality, to the class ; and this very fact is 
what, according to Mill, makes induction an inference : 
we need only know some, not all particular men, to say 
that all men are mortal. Hence there is, so to speak, a 
generality about induction which only says that every 
body who may be a man is mortal : it does not, and 
cannot, enumerate every particular man. The con 
sequence is that the subsequent process of deduction, 
which, by combining the generality in the major premise 
with a new particular in the minor, enables us to dis 
cover that a particular object, which we never appre 
hended before to be a man, is mortal, must be an. 
advance in knowledge, and therefore a process of 

Mill would reply that, in this case, we are committing 
a petitio prindpii by adducing in proof of a particular 

1 Ar. Post. An. ii. G = 92 A, 11. 



a general judgment which presupposes it. This objec 
tion can only mean that the general judgment, all men 
are mortal, ought to have been inductively proved by 
examining all men : otherwise it does not presuppose 
every particular man. But, according to his own show 
ing, the general judgment is not to be proved by every 
particular : therefore it does not presuppose every par 
ticular, but only the original particulars of induction ; 
and therefore the process, which adds to the general 
judgment a new particular, is not using a general judg 
ment which presupposes that new particular, and is not 
a petitio principii. Mill made the beauty of induction 
the vice of syllogism : he first says that only some par 
ticulars are presupposed to induce a universal, and 
then that the universal presupposes every particular to 
deduce a particular. Eeally, the justification of induc 
tion is the justification of deduction from induction. 
Induction from many of the particulars concludes all in 
general : deduction adds the rest of the particulars. 

Mill was deceived by another mistake : he thought 
the inference was over when we get to the general judg 
ment, and the remainder is deciphering our notes. But 
the major premise is as powerless without the minor 
premise as the minor without the major. < It is evi 
dent, as Aristotle says, c that a syllogism consists of 
two premises, and no more ; for three terms make two 
premises. ] We therefore require two sets of notes in 
order to decipher a conclusion, and their combination 
in the two premises is the essence of syllogism. Mill 
was further deceived by writing down two simple pre 
mises, and thinking that, as the syllogism consists in 
drawing the conclusion, which is contained in the pre 
mises, it does not advance our knowledge. But a 

1 Ar. Pr. An. i. 25 = 42 A, 32 3. 

CHAP. ix. HUME 297 

syllogism does not consist in merely drawing a conclu 
sion ; and, when you have written down the two 
premises, the essence of syllogism is over : the difficulty 
is in combining the premises, and although the syllogism 
does not discover each premise, it does combine the 
two. So important an act is this, that, as Aristotle 
says, a man may know that all B is A and all C is B, 
and yet think that C is not A ; e.g. that every mule is 
barren, and this is a mule, and yet think it is going 
to foal, through not considering each of the two premises 
in combination. l 

Syllogism, then, from induction is an inference, 
because it is an advance in knowledge by adding par 
ticulars not contemplated in induction ; a legitimate 
inference, because it presupposes only the particulars 
contemplated in experience, and the indefinite generality 
inferred by induction, but not the new particular it is 
about to prove ; a complex inference, which consists 
neither in merely interpreting a major premise, nor in 
merely drawing a conclusion, but in a new combination 
of premises, or a direct comparison of two things with a 
third thing, so as to draw an indirect conclusion about 
their relation. In order to express the essence of syllo 
gism as a process of inference, I propose to define it : a 
combination of two premises so as to produce a conclu 
sion, not presupposed in either separately, though con 
tained in their combination. Hume s theory of inference 
is inadequate, because it ignores this process of reason 
ing from experience and induction ; and Mill s is false, 
because it ignores the combination of premises, which 
produces a new conclusion, advancing our knowledge. 

There are two ways of inferring from particular to 
particular ; directly by analogy, and indirectly through 

1 M o-vvdfwp&v TO naff (Kartpov. Ar. Pr. ii. 21 = 67 A, 33-7. 


a generality by induction and deduction. Mill, follow 
ing Hume, confuses them. The mortality of John, 
Thomas, and others, he says, < is, after all, the whole 
evidence we have for the mortality of the Duke of Wel 
lington. Not one iota is added to the proof by inter 
polating a general proposition. l Why, he asks, should 
we not take the shortest cut ? We often do : we go, 
like brutes, from particular to particular. But Mill 
himself gives a very good reason why we should not ; 
that to pass through a general proposition is a security 
for good reasoning. 2 Now, surely the aim of every 
honest man is, not reasoning, but good reasoning ; and 
logic is the art of reasoning well. We must avoid the 
shortest cut and go round the circuit of induction and 
deduction to rational truth, as we must avoid the broad 
and choose the narrow path to eternal life. We may be 
sure also that there is something more than usual in 
a security for good reasoning. That something more is 
the evidence of induction. We saw that we want less 
evidence for association and for analogy, which begin 
directly after experience, than for induction, which 
requires experience to be accumulated and sifted, by 
finding things present, absent, and vary ing together, so as 
to bring into operation the law of generality, by which 
we spontaneously induce a general judgment. In order 
to deduce a new particular we must have apprehended 
not only the original particulars, but also that they are 
sufficient to authorise a general judgment, which is the 
same thing as inferring it. The beauty of induction is 
the virtue of the syllogism. It is because analogy has 
not, induction has, sufficient evidence to infer a general 
judgment, that syllogism from induction is a security 
for o-ood reasoning. I do not say that this security is 

1 Mill, Logic, ii. 3, 3. 2 Ib. ii. 3, 8. 

CHAP. ix. HUME 299 

more than general probability. But analogy lias not 
this general probability: it varies, indeed, in proba 
bility, but directly its evidence guarantees general 
probability, analogy becomes induction followed by 
deduction. Induction is the inference of general pro 
bability and empirical deduction the inference from 
general probability ; and the probability of the double 
process, induction and deduction, varies, according to 
the original synthetic experience, from uncertainty to 
approximate certainty. 

Few modern logicians seem to have a sense of the 
enormous importance of syllogism or deduction. They 
do not feel the indefiniteness of the subject of a general 
judgment, which signifies all whatever they may be I 
do not know, the consequent imperfection of induction 
without deduction, and the necessity of syllogism to give 
defmiteness to our inferences from experience beyond 
experience. It is but little use knowing that when the 
earth intervenes between the sun and the moon there 
will be an eclipse, unless we are prepared to combine 
this mere generality with minor premises stating when 
the earth will be in this position. It is by deduction 
that we go back to the distant past: for example, 
nations which have words in common, expressing a 
degree of civilisation, too many to be explained by 
nature, chance, or communication, lived together up 
to that degree of civilisation ; the Greeks and Eomans 
had a multitude of words in common up to the stage of 
settled agriculture ; therefore they lived together to that 
point. It is by deduction we dive into the imper 
ceptible present : for example, perceptible bodies elastic 
and compressible have parts and pores ; solid bodies are 
elastic and compressible ; therefore they consist of parts 
and pores, though imperceptible. It is by deduction that 



we predict the future : for example, a planet deflected 
from the path prescribed by its gravitation to the sun 
gravitates to another planet in the direction of deflec 
tion ; Uranus was found so to deflect ; therefore, a new 
planet was predicted in the direction of deflection, and 
the new planet, Neptune, was afterwards discovered in 
that direction. Inferences of this kind are sometimes 
analogical, but they are often deductive, and they are 
so whenever induction has established a general judg 
ment. They are sometimes confused with induction, 
as when Mill calls the discoverer of a murderer by 
circumstantial evidence induction. 1 But when such an 
inference is not analogy it is deductive, because it con 
tains, besides the circumstances in the minor premises, 
a number of major premises judging such circumstances 
to be signs of murder, and a particular conclusion infer 
ring a murderer. 

Empirical deduction, like analogical and inductive 
inferences, is not association, and for the same reason ; 
it ends, not in conception, but in judgment. Even 
syllogism is a customary inference ; but its custom is 
not an association of ideas, but a habit of inferring 
judgments by the three laws of the three figures. Asso 
ciation, even of the more developed kind which starts 
from synthetic experience, gets as far as reproducing 
the ideas of the objects in that synthetic experience, 
and there stops. At that point we have not even got at 
the beginning of deduction : induction intervenes to 
infer the general judgment, which, as we have seen, is 
no result of association. Empirical deduction, then, 
begins with this general judgment, which at once dis 
tinguishes it from all sensitive synthetic association. 
It proceeds frequently to ask synthetic experience for a 

1 Mill, Logic, iii. 14, 7. 

CHAP. ix. HUME 3Q1 

minor premise, e.g. this is a sword ; and thus returns to 
the arena of association. But association deals with 
this new particular merely to reproduce ideas of former 
pains already apprehended by experience, analogy, and 
induction. Syllogism goes on to infer a new particular 
judgment that this sword will also prove painful. 

Nor is this all the difference : we must not deceive 
ourselves by taking too simple an instance. Through 
the power of general judgments we at last deduce par 
ticulars not only beyond sense, but insensible and im 
perceptible to us, e.g. the existence of insensible particles 
or corpuscles of solid bodies. Association, from the pre 
mises of this deduction and before deduction has drawn 
the conclusion, will reproduce only the ideas of the 
parts of bodies previously known : without deduction it 
will not enable me either to judge that the particular 
bodies in the minor premise consist of parts, or to con 
ceive ideas of their particular parts. Deduction, on the 
other hand, proceeds to draw the conclusion and then 
conceive the idea. Not association of ideas, but deduc 
tion, produces the judgment of the existence, and through 
this judgment the deductive conception of the idea, of 
a corpuscle. 

Hume, in the Treatise, said : I form an idea of 
Borne, which I neither see nor remember, but which is 
connected with such impressions as I remember to have 
received from the conversation and books of travellers 
and historians. ... All this, and everything else which 
I believe, are nothing but ideas. l This inadequate ac 
count of my knowledge of Borne goes further than could 
be justified by Hume, but not so far as is justified by 
history. Association of itself would not even give me 
an idea of Borne, which I have never seen ; history 

1 Hume, Treatise, iii. 9. 


infers the judgment that Rome has existed, perhaps 
from the time of Romulus, certainly since the transition 
from the monarchy to the republic. If association of 
ideas were substituted for deduction, on being told 
that there is a city like London and other cities I have 
experienced, I could only reproduce my particular 
idea of London, my particular ideas of other cities in 
my experience, and, with induction, my general idea 
of cities : I could not produce a new- particular idea 
of Rome beyond my experience. But deduction from 
the conversation and books of travellers and historians 
enables me to produce a belief that Rome exists, and 
has existed for centuries, which is not an idea, and, 
moreover, besides the belief, an inferential idea of 
the eternal city in my productive imagination. De 
duction is not association of ideas, because it directly 
produces deductive judgments about the existence, and 
indirectly deductive ideas ; of objects beyond sense, such 
as the danger of a sword which has not yet hurt me ; 
of insensible objects, such as historic Rome ; of imper 
ceptible objects, such as a physical corpuscle. 

Hume, having falsely identified ideas with thoughts, 
and resolved beliefs into ideas, could allow only one 
succession of thoughts, the succession of ideas. But 
judgments are not ideas but apprehensions of relations, 
inferences are not successions of ideas, but successions 
of judgments, and rational judgments are thoughts 
which are not ideas. From synthetic sense, which 
produces our first judgments of relations, there arise 
two streams of thought, synthetic association, which is 
a succession of ideas, and reasoning or a succession of 
judgments. These two streams flow together, yet dis 
tinctly ; but the stream of reasoning is the main river 
of human thinking, compared with which the stream of 

CHAP. ix. HUME 303 

association is a mere rivulet. Hume and his followers 
are like those explorers of the sources of the Nile who 
have taken a mere tributary for the main river. 

Inference and association are alike, not only so far 
as both start from synthetic sense and experience, but 
also in both being involuntary, spontaneous, custo 
mary. Impressions involuntarily suggest ideas, though 
we also recall them by voluntary reminiscence ; nor can 
we help inferring judgments, though we also reason 
voluntarily. Association and inference both sponta 
neously use laws, neither inductively nor a priori, but 
mechanically and without knowing it : as the laws of 
association, by resemblance, contiguity, succession, &c., 
are spontaneously used to introduce ideas, so is the 
law of analogy spontaneously used to infer from par 
ticular to particular judgment, the law of generality to 
infer a general judgment, the laws of the three figures 
to infer from general to particular judgments. The ex 
planation is probably the same in all cases, namely, the 
evolution of an habitual tendency by the action of nature 
on our organs without our knowing it. Again, analogy 
and induction are not deductions from the laws of their 
forms, but independent inferences from experience ; nay, 
deduction itself is not a deduction from the laws of its 
forms or figures, but from major and minor premises : 
all three processes of inference use their laws to pro 
duce judgments as habitually as association uses its 
laws to reproduce ideas. But because inference is an 
inevitable, spontaneous, customary use of laws, it is not 
on that account to be confused with association. 

Hume made two very great blunders about inference : 
he confused custom with association, and limited reason 
ing to deduction, or rather demonstration. But not all 
custom is association : there are habits of conceivin^, 


of judging, of acting ; and analogy, induction, and de 
duction are habits of judging by inference, not habits 
of conceiving by association. Again, all inference is 
reasoning, because it advances from judgment to judg 
ment ; reasoning does not begin with demonstration 
from axioms ; and there are three kinds of reasoning, all 
ultimately founded on judgments of synthetic sense, all 
inevitable, spontaneous and customary inferences bylaws 
of their forms, used without being known, except to the 
science of logic : these three types of inference are 
analogical, inductive and deductive reasoning. 

Seasoning is an instinct. The premises are acquired 
from experience, and the conclusion is inferred ; but the 
process of inferring is instinctive. It was probably 
gradually acquired by the action of natural uniformity 
on our organs : but it is used without presupposing any 
axiom of natural uniformity as a major premise. This 
instinctiveness of reason escapes the notice of philoso 
phers and even of logicians. Hume, for example, post 
poned reasoning to association, because it is slow, be 
cause it does not appear during the first years of infancy, 
because it is liable to error, and because nature has im 
planted in us the instinct of association. 1 But, in the 
first place, nothing is more rapid than reasoning, which 
goes through its trains of judgment as quickly as asso 
ciation through its trains of ideas ; secondly, it is an 
adult prejudice to suppose that young infants are not 
reasoning, because they are not talking, when they are 
far better occupied in the sensible and rational discovery 
of an internal and external world ; thirdly, reasoning is 
liable to error, but association has no perception of truth; 
fourthly, if association is an instinct, so is reasoning, 
each spontaneously using its laws to proceed from expe- 

1 Inquiry, 5. 

CHAP. ix. HUME 305 

rience, but the former to ideas, the latter to judgments. 
So closely related are the instincts of association and 
reasoning, yet so different, that, if association were not 
the vaguest term in the vague vocabulary of mental 
philosophy, I should have proposed to distinguish the 
two successions of thought as the association of ideas 
and the association of judgments. 

Hume allowed the psychology of association to 
blind him to the logic of reasoning. The consequence 
was that he missed the whole origin of rational judg 
ments and of rational ideas ; thus defeating his own 
object, which was to find the causes of ideas. The 
origin of ideas is in reality a very complicated problem, 
inseparable from that of judgments. We must distin 
guish productive and reproductive conception. The 
sources of productive conception, which we have 
reached so far, are simple sensations of sensible objects 
producing sensible ideas, synthetic sense and judgment 
of sensible relations producing ideas of relations, and 
reasoning to rational judgments producing rational 
conceptions; moreover, we have distinguished three 
kinds of rational conception, answering to three kinds 
of inference analogous, inductive and deductive ; and, 
finally, deductive conception produces ideas not only of 
the relation in the conclusion but of the insensible ob 
jects of that relation, e.g. the idea of corpuscles as well 
as of their cohesion. Eeproductive conception has two 
main sources, both obeying the same laws voluntary 
recollection (am/^o-t?), analysed by Aristotle, 1 and 
involuntary association, analysed by Hume ; who pro 
ceeded to elevate a mere reproduction of ideas into a 
substitute for the inference of judgments, and, when it 
does not produce ideas at all, and is only one way of 

1 Ar. De Mem. ii. 


reproducing them, positively made it the sole source of 
all belief in matters of fact. What a contrast there is 
between the analytic genius of Aristotle, giving each 
operation its due place, and the exaggerated scepticism 
of Hume, exalting the weakest over the strongest force 
in man s composition ! 

Hume invariably speaks as if all association of ideas 
were of one kind ; so usually do his followers. It is 
because they have become enamoured of one power to 
the neglect of the rest. This kind I have ventured to 
call simple sensitive association, because it starts with 
simple sensation and experience. But I have shown 
that Hume covertly introduces another kind, which I 
have called synthetic sensitive association, because it 
starts with synthetic sense and experience. To this 
sort belongs the association used by him to explain the 
apprehension of causation ; a process which, starting 
from the sense of sequence, and passing through the 
experience of constant conjunction, ends by the ante 
cedent introducing the idea of the consequent, which 
he falsely supposed to be our judgment of a cause 
producing an effect. But, now that I have analysed 
reasoning, I am prepared to take a further step and 
say that reasoning, though never association, is the 
foundation of a third kind of association, which I 
shall call rational association. When we have by 
any kind of inference inferred a relation, and by any 
kind of rational conception produced the ideas repre 
senting the relation and its objects, then, and not till 
then, rational association will enable us to reproduce 
the ideas by its own laws. Thus the contempla 
tion of eye, which suggests to the ordinary man 
the idea of love or war, will to the optician repro 
duce the rational ideas of aether, of undulation, of 

CHAP. ix. HUME 307 

reflection and refraction. But it would be mere con 
fusion to merge the reasoning by which he dis 
covered these facts in the association of the ideas, 
when the rational conception of the ideas intervenes 
between the rational inference and the rational asso 
ciation. The optician first by reasoning judges the 
existence of asther and its motions, then rationally 
conceives what ideas of them he can, and finally is 
reminded of them by association. Most associations 
are post-rational. 

The inference at the bottom of rational association 
will be found to solve many unsolved problems. One 
is the solubility of association. If we depended on as 
sociation alone, an association acquired by a constant 
experience could only be dissolved by one acquired by 
a still more constant experience. But, as a fact, a 
single instance will destroy the strongest association : 
when the idea of the proverbial whiteness of swans was 
dispelled by the discovery of a black swan, it was 
reason which dissolved the association. Another pro 
blem is the origin of complex ideas of substance. The 
theory of Associationists is that, having by sensation 
acquired together the ideas of yellowness from sight, 
smoothness from touch, sweetness from taste, association 
recalls these ideas so constantly as to form one complex 
idea of an orange. In this analysis the main elements 
of the simple ideas, and the process between them and 
the complex idea, are omitted. By sight we already see 
a yellow, by touch a smooth, by taste a sweet substance ; 
hence the simple ideas of substances ; by reasoning, we 
infer that all these correspond in our senses to one 
complex substance outside, represented by the yellow 
in sight, the smooth in touch, the sweet in taste ; and, 
having thus inferred an external orange, we form a 

x 2 


rational complex idea of it, which we then reproduce, 
not produce, by rational association. 

Another and somewhat different kind of problem is 
the origin of fictitious ideas, of the ideas of art, and of 
ideals. Hume truly said that an idea, such as that of 
a golden mountain, is ultimately made out of im 
pressions, but falsely thought that it is produced by 
sensitive association, which by itself could only repro 
duce the sensible ideas of gold and of mountain. The 
reasoning of the possible intervenes. We infer that as 
a mountain is made of one material it might be made 
of another, and having judged the possibility, analogi 
cally conceive the idea of a golden mountain, which is 
only reproduced by association. Sometimes we infer 
the possibility of more, sometimes of less, than sense per 
ceives ; hence we multiply man and horse into centaur, 
or diminish man into ghost. Sometimes we infer the 
possibility of something better than ordinary, as Homer 
did Achilles; sometimes worse, as Shakespeare did 
Caliban. But in artistic idealisation there is always an 
inference of possibility, which is the foundation of all 
ideal conception. It is quite the same in philosophical 
ideals. Plato thought of yhe possibility of men be 
coming angels before he conceived his ideal state. 

The final and most difficult problem is the influence 
of the association of ideas beyond ideas. Locke started 
this general problem in the Essay. The following is an 
often quoted instance from his chapter on Association : 

6 The ideas of goblins and uprights have really no 
more to do with darkness than light ; yet let but a 
foolish maid inculcate these often on the mind of a 
child, and raise them there together, possibly he shall 
never be able to separate them again so long as he 
lives ; but darkness shall ever afterwards bring with it 


HUME 809 

these frightful ideas, and they shall be so joined that 
he can no more bear the one than the other. l 

Locke did not make so much of this effect of asso 
ciation as the followers of Hume, who often suppose 
that the association of the ideas of ghosts and the dark 
produces a belief which produces a fear. But the fear 
often follows the idea, without the belief. There are in 
reality two different cases, in one of which there is no 
belief, in the other a belief, but not caused by the asso 
ciation of ideas. In simple sensitive association, where 
there has been no judgment of the relation of a ghost 
with the dark, the idea of the dark mechanically recalls 
the idea of the ghost, and this the idea of pain which is 
sufficient to generate fear. In synthetic sensitive asso 
ciation, where there has been a judgment that a ghost 
appears in the dark arising from a child s belief in the 
narratives of its nurse, the association of ideas is accom 
panied by a belief that a ghost may possibly appear, 
which, however, does not arise from the association of 
ideas, but by parallel inference from the same judgment 
as that which produces the association. Sometimes this 
judgment of possibility may arise, even when the person 
is sceptical about the actuality of ghosts. Still more 
often it is a vague inference of some dreadful possibility, 
because the dark is mysterious to man. 

Whenever, then, the association of ideas is of a 
simple kind, which has not arisen from a judgment, it 
is powerless to produce one ; and whenever it is ac 
companied by a judgment, they are joint effects of an 
original judgment, which produces on the one hand an 
inference at least of possibility, and on the other hand 
an association of ideas. At the same time there is an 
effect of association on belief, like the effect of volition.. 

1 Essay, ii. 33, 10. 


These two reproductive causes of ideas, by constantly 
promoting the same idea, challenge our attention not 
only to the idea but also to the parallel judgments. 
Thus a person, who constantly cherishes the idea of 
being wiser than others, will at last come to think he is 
so, not however from the association itself, but because 
Ids attention is thereby called towards the evidences 
which infer his superiority, and away from those which 
disprove it. 

Hume s empirical theory consists in three proposi 
tions : (1) All perceptions are impressions and ideas or 
thoughts ; (2) All ideas or thoughts are copies of 
impressions ; (3) Association of ideas is the origin of 
all beliefs of facts, that is, ideas or thoughts. But it is 
one thing to assert an empirical theory in general, and 
another to fill in its details. Impressions, as Hume de 
scribed them, are not by the process of association, as 
Hume described it, the origin of ideas, which are not, 
as Hume described them, all our thoughts. In the 
first place, the simplest sensation is merely an abstract 
attribute of a substantial subject apprehending a sub 
stantial object, and the simplest reflection an abstract 
attribute of that substantial subject apprehending him 
self. Secondly, sense is not only simple but synthetic ; 
and synthetic sense is the immediate origin of sensitive 
judgment, which is not an idea, but the immediate appre 
hension of a relation of sensible objects. Thirdly, associa 
tion is a reproduction, but it is not a production, of ideas, 
still less of beliefs, which are not ideas but judgments 
ultimately based on synthetic sense. Fourthly, reasoning 
is not an association of ideas, but of judgments ; and 
there are three types of inference analogical, inductive, 
and deductive all starting from synthetic sense, and by 
their own laws instinctively inferring rational judgments 


HUME 311 

which are not impressions nor ideas, yet are thoughts. 
Fifthly, the productive origin of ideas is simple sense 
forming the first ideas of qualified substances, synthetic 
sense forming the first ideas of relation, and reasoning 
analogical, inductive and deductive, which forms ideas 
not only of what is inferred to be actual, but also of 
what is inferred to be possible, fictitious, ideal : the re 
productive origin of ideas is passive association and 
active volition. Sixthly, there are three species of as 
sociation, simple and synthetic sensitive association, and 
rational association. A philosopher who, like Hume, 
does not understand reasoning, cannot understand ideas 
and their association. Logic is necessary to psychology. 
Empirical philosophy must comprise reason. If all 
knowledge is from experience, it is certainly not ac 
quired by association. 

Hume concludes his Inquiry with his Academical 
Philosophy. 1 He starts with what he calls the instinct 
by which men c suppose the very images presented by 
the senses to be the external objects ; on which he 
makes the following comment: 

But this universal and primary opinion of all men 
is soon destroyed by the slightest philosophy, which 
teaches us that nothing can ever be present to the 
mind but an image or perception, and that the senses 
are only the inlets through which these images are 
conveyed without being able to produce any immediate 
intercourse between the mind and the object. 

This most instructive passage shows, first, that ideal 
ism has a real advantage over intuitive realism, which 
falsely accepts the perception of an external object, 
and secondly, that idealists tend to beg that the repre 
sentative image perceived is a perception by confusing 

1 Inquiry, 12. 



the object with the operation of sense. Idealism is the 
scientific truth that sensible objects are effects on 
the senses, misinterpreted into the hypothesis that they 
are c perceptions in the mind, as Hume calls them in 
the same paragraph, without evidence. 

Having now got himself into a self-made difficulty 
about the data of sense, he proceeds to torture himself 
with the following question : 

By what argument can it be proved that the per 
ceptions of the mind must be caused by external objects, 
entirely different from them, though resembling them 
(if that be possible), and could not arise either from the 
energy of the mind itself, or from the suggestion of 
some invisible and unknown spirit, or from some other 
cause unknown to us ? 

This question is put with the logical power of 
Berkeley, and is answered with even more logic : 

It is a question of fact, whether the perceptions of 
the senses be produced by external objects resembling 
them : how shall this question be determined ? By 
experience, surely, as all other questions of a like 
nature. But here experience is, and must be, entirely 
silent. The mind has never anything present to it but 
the perceptions, and cannot possibly reach any experi 
ence of their connection with objects. The supposition 
of such a connection is, therefore, without any founda 
tion in reasoning. 

The fallacy of this argument consists in the assump 
tion with which it begins. Eeally, we are conscious of 
perceptions, or rather of ourselves perceiving ; but we 
perceive not perceptions, but sensible objects, and not 
in the mind, but in the nervous system ; and from these 
physical objects within we infer physical objects with 
out, different individually, but specifically similar to the 

CHAP. ix. HUME 313 

sensible objects from which they are inferred. But 
though Hume s data were false, his conclusions were 
logical. If all that we perceived were perceptions, they 
would be entirely different from external objects ; and 
experience, being confined to perceptions, would have 
no data to prove anything at all about objects, internal 
or external. Moreover, if the data both of sensitive 
and reflective perception w r ere perceptions, qualities as 
ideas of sensation, and operations as ideas of reflection, 
as Locke and Berkeley formally stated, we should only 
be able to infer perceptions. Hume has the best of the 
logic when he refuses to follow either Locke in sup 
posing matter, or Berkeley in supposing mind, seeing 
that neither of these philosophers allowed matter and 
mind in the data. of sensation and reflection, when they 
were delivering themselves ex cathedra on the subject of 
sensible data. As Hume afterwards says, nothing re 
mains but a certain unknown, inexplicable something, 
?,s the cause of our perceptions. Such is the false 
though logical end of Hume s speculative philosophy. 

He proceeds illogically to correct himself of his 
Pyrrhonism by the old view of the Academy that c all 
human life must perish, were his principles universally 
and steadily to prevail, which is no answer to the 
Pyrrhonist or to Berkeley, who would immediately 
resolve our bodies, our clothes, our food, our estates, 
into perceptions. But Hume valued common life too 
highly, and natural philosophy too little. We are not 
committed to the dilemma of thinking in one way and 
living in another. The answer to his mitigated scepti 
cism or academical philosophy is the physical dis 
coveries of natural philosophy. If, indeed, the objects 
of perception were perceptions, we should never infer 
anything but perceptions, with an unknown, inex- 


plicable something. But natural philosophy has dis 
covered imperceptible objects, substances qualified, 
causing and receiving motions, in accordance with uni 
versal laws, and ultimately causing our perceptions. 
Therefore, it is neither true that knowledge ends in an 
unknown something, nor that the objects of perception 
are perceptions, from which imperceptible objects of 
science could not have been inferred. The slightest 
philosophy teaches us that what is present to sense is an 
image, but not that this image is a perception. Simple 
sense perceives an object, internal but physical ; syn 
thetic sense and experience perceive the relations of 
these physical objects within, and reason infers the 
relations and existence of physical objects without. 

Hume s philosophy is a deductio ad absurdum of 
idealistic hypotheses. It is what was sure to follow if 
Locke and Berkeley were taken at their word, no re 
gard being paid to their admissions. As soon as the 
Cartesian consciousness of the thinking subject had 
been forgotten, all the data of sense were reduced by 
Locke and Berkeley to ideas, qualities as ideas of sen 
sation, and operations as ideas of reflection ; and the 
objects of understanding were logically inferred to be 
also ideas. Locke illogically admitted the supposition 
of substances, material and thinking ; Berkeley dog 
matically asserted the existence of mind as gathered from 
its effects ; and both ended by admitting the conscious 
ness of one s own existence. Berkeley saw the incon 
sequence of Locke s supposition of material substance 
beyond mere ideas of sensation, but he did not see 
that he was with equal inconsequence introducing 
mind, soul, spirit, directly after mere ideas of reflection. 
Hume acutely detected the half measures of Berkeley, 
but took the wrong alternative. Instead of going be- 

CHAP. ix. HUME 315 

hind both Locke and Berkeley to show that both sensa 
tion and reflection perceive qualified substances, he 
banished the thinking to the limbo of the material 
substance, and rigidly confined us to the abstract per 
ceptions which form the sum of the data of perception 
by the confession of both his predecessors. This con 
clusion is argued out in the Treatise on the following 
text : We have no perfect idea of anything but of a 
perception. A substance is entirely different from a 
perception. We have therefore no idea of a substance. l 
This logical syllogism, of which however the major is 
quite false, is applied both to material and thinking 
substance, in the Treatise. In the Inquiry, he became 
silent on this point ; but ignorance of substance is a 
necessary consequence from the perception of percep 
tions, which is common to both books. 

Hume may be said to have gathered the ideal theory 
of perception into a focus which reveals to us its errors. 
The supposition that sensible objects are psychical 
operations deprives us of objects and physical objects 
within, from which to infer physical objects without. 
The supposition that sensible objects are qualities and 
operations deprives us of the sense and inference of 
substances ; of the sensation and inference of material 
substances, and of the consciousness and inference of 
thinking substances, partly physical, partly psychical. 
On every side he paraded the mere logic of idealism. 
He was particularly attracted by Berkeley s philosophy ; 
for instance, by the theory of general ideas, and of 
primary and secondary qualities. Berkeley s hypothesis, 
in the Principles, of the inactivity of ideas, antici 
pated Hume s scepticism about power in causation ; 
while, in the c Theory of Vision, the hypothesis that 

1 Treatise, iv. 5. 


visible ideas suggest tangible ideas, without any inference 
of an external object common to touch and vision, gave 
the first hint for Hume s substitution of association for 
reasoning. Hume s scepticism is the dark shadow of 
Berkeley s theosophy, giving us the logical warning 
if no matter, then no spirit, and no God. He had no 
suspicion that Berkeley s so-called principles were hypo 
theses, any more than modern idealists have. Hence he 
says of Berkeley s arguments that they admit of no 
answer, and produce no conviction 1 

Here Hume missed an opportunity, such as seldom 
falls to the lot of a philosopher. Instead of being 
merely logical from the original hypotheses of his pre 
decessors, he ought to have used their subsequent 
admissions for a new departure in philosophy. He 
should have returned to the Cartesian consciousness of 
a thinking subject. He should have shown that both 
Locke and Berkeley, after beginning with a reflection of 
mere ideas of operations, admitted at last a direct con 
sciousness of one s own existence. He should have 
pointed out that this means a reflective consciousness 
of oneself as a thinking substance, and have similarly 
recognised sensations of qualified substances within 
oneself. From these data, together with the synthetic 
sense of relations, he could have proceeded to explain 
our inferences of external substances bodies, thinkers, 
God. But he preferred not to answer his predecessors, 
to stick to the idealistic last, and to work on nothing 
but impressions of sensation and reflection. 

To this scepticism about sense Hume added a scepti 
cism about reason. Logic, through the process of being 
made into text-books for education, has been too much 
schematised. For example, Aristotle distinguished 

1 Inquiry, 12, Part I., note. 

CHAP. ix. HUME 317 

simple from complex apprehension, 1 and names from 
propositions, 2 but did not co-ordinate reasoning with the 
two other apprehensions. St. Thomas Aquinas schema- 
tistically added reasoning as a third operation. 3 The 
moderns, by co-ordinating the three operations, have 
tended to lose sight of the process of reasoning at the 
back of conception and judgment, and many modern 
logicians speak as if there were three independent pro 
cesses, conducted quite independently, each with its 
own independent laws. But reasoning is a process from 
judgment to judgment, producing new conceptions. 
Again, the conceptualistic view of logic intensified 
the mischief, by regarding judgment as apprehending, 
and therefore reasoning as inferring, relations of ideas. 
At the same time, Descartes exaggerated the power of 
ideas over knowledge. 

These causes produced the exaggerated attention to 
ideas and their origin, their arbitrariness, and the post 
ponement of reasoning in Locke s Essay and Berkeley s 
Principles. The disease came to a head in Hume s 
works. In the first part of his Treatise, which is 
directly modelled on Locke s Second Book, Hume takes 
as his problem the mere origin of ideas. In the course 
of the same work he animadverts on the distinction of 
acts of the understanding into conception, judgment 
and reasoning, and the definitions given of them. Con 
ception, he says, is defined to be the simple survey of 
one or more ideas ; judgment to be the separating or 
uniting of different ideas ; reasoning to be the separating 
or uniting of different ideas by the interposition of 
others. 4 But his animadversions on these purely con 
ceptualistic definitions only end in his reducing all these 

1 Ar. DC An. iii. 0. - Id. PeriJtcrm, i. 

3 Aquinas in Perilierm, i. 4 Treatise, iii. 7, note. 


acts to conceptions. Hence liis resolution of judgment 
or belief into a vivid conception or idea, from which 
the substitution of association of ideas for inference of 
judgments immediately follows. The answer is that 
judgment is an apprehension of relations, beginning 
with the synthetic sense of the relations of sensible 
objects, and reasoning an inference from sensitive to 
rational judgments, culminating in the laws or uniform 
relations of insensible objects. Judgment is not an 
idea ; reasoning not an association of ideas. 

Hume was misled by psychological idealism and 
conceptualistic logic. Hence his scepticism about sense 
and reason. His philosophy, after all, is only the most 
conspicuous instance of four idealistic faults : the con 
fusion of the operation and the object of sense, the in 
vention of all sorts of out-of-the-way sources of ideas 
which are all the time due to sense and inference, the 
postponement of reasoning, and the conceptualistic 
supposition that conception, judgment, and reasoning 
are all equally concerned with ideas, j The proper cor 
rective is the study of Aristotle s Organon, Bacon s 
Novum Organum, and Newton s Principia. The 
fame of Cicero, says Hume, flourishes at present ; but 
that of Aristotle is utterly decayed. Deservedly did 
Aristotle s fame decay in natural philosophy. But his 
logic of reasoning, widened by Bacon s theory of induc 
tion and Newton s explanatory method, is necessary to 
all mental philosophy. Logical reasoning from ade 
quate data of sense is the main origin of knowledge, 
and of ideas, and of their association. 



KANT S Critique of Pure Eeason l begins by assuming 
Hume s theory of impressions : 

That all our knowledge begins with experience 
there can be no doubt ; for how should the faculty of 
knowledge be awakened into exercise otherwise than 
by means of objects which affect our senses, and partly 
of themselves produce representations, partly rouse our 
power of understanding into activity, to compare, to 
combine, or to separate these, and so to convert the 
raw material of our sensory impressions into a know 
ledge of objects, which is called experience ? In 
respect of time, therefore, no knowledge of ours is 
antecedent to experience, and all begins with it. 

This passage contains the truth, which I have all 
along admitted to lie at the foundation of psychological 
idealism ; that sense perceives not external things in 
themselves, but internal images representing them in 
our senses. But, like his predecessors, Kant went on 
to corrupt this truth by two assumptions. On the 
one hand, he supposed the operation of sense to be 
purely psychical ; on the other hand, he confounded the 
representative image with the operation of represent a- 

1 Critique of Pure Reason, ed. Hartenstein, p. 33 = Meiklejohn s 
translation (Bohn), p. 1. 

Ueberweg s summary of the Critique of Pure Eeason is printed in 
an Appendix at the end of this essay. 


tj on a confusion constantly favoured by tlie vague 
abstractions of modern languages, in which representa 
tion means indiscriminately both the operation of repre 
senting and the representative object, sensation and 
the sensible, or, in Aristotelian language, cesthesis and 

Hence, he started with the assumption that the 
matter of sense is nothing but its own representations, 
which do not exist out of the mind, and are not sensibly 
apprehended as objects. 1 This mere assumption vitiates 
the whole work ; for, of course, if there is no sense of 
objects within, reason cannot infer objects without, 
and, to know objects, we must find some other origin 
of knowledge. Hence, also, in the absence of adequate 
data of inference, sense and reason are displaced and 
divorced from one another by the intervention of an. 
independent understanding, on which the main stress 
is laid. Hence, finally, as understanding can act only 
on sensible representations, which are not sufficient data 
for a rational inference of external objects, knowledge 
is limited to sensible representations converted by 
understanding into objects of experience, or phenomena 
of the mind. This would have been tolerable, if Kant 
had started by proving that sense only apprehends its 
own representations. But he did not even make it a 
question. It never occurred to him that touch and 
vision are operations, but the hot felt and the red 
seen objects. He straightway begged that there is no 
such distinction in sense, and founded the Critique 
on a petitio principii. Why ? Because, uncritically, he 
accepted the hypothesis, that the matter of sense is 
impressions, from Hume. 

1 Cf. Hart. 111-20, 347 = Meik. 77-86, 307. 


Of all the many errors of psychological idealism the 
worst is its sequacity. Even critical idealism begins by 
being uncritical. Kant seemed to delight in assuming 
as data the unproved assumptions of his predecessors, 
which have been already criticised in this essay. From 
Descartes he accepted the confusion of subject and 
soul, the imaginary power of eliciting ideas, and the 
supposed psychical object of sense ; and from Locke the 
deduction that all objects of understanding are psj-chical, 
the hypothesis that outer sense is concerned with mere 
qualities and inner sense with mere operations, the 
neglect of logical reasoning, the consequent deduction 
of the false conclusion that relations are a work of 
understanding, and the unexplained supposition of an 
unknown thing as cause of the data of sense. After 
Berkeley, Kant surrendered the inconsequent deduction 
by Descartes, and the inconsistent admission by Locke, 
of a knowledge of physical objects, and accepted the 
logical conclusion that the objects of human knowledge, 
with all their qualities, primary as well as secondary, 
are psychical objects of perception, and the consequent 
but false identification of the perceptible and the real, 
so far as known. 

But Hume was Kant s main authority. They rightly 
agreed in rejecting Berkeley s dogmatism about the ex 
istence of mind and the non-existence of matter, and in 
the revival of the real distinction made by Aristotle 
between sensation and conception, in Hume s termin 
ology between impression and idea, in Kant s between 
intuition and conception. Along with these merits, 
the critic, without a word of criticism, accepted 
from the sceptic the extraordinary mass of paradoxes 
about sense and the sensible, by which idealism had 
become scepticism. What men call sensible objects, 



and believe to be external, what we have found to be 
internal but not psychical objects, are supposed by 
Hume and Kant to be not only internal but in the mind, 
not objects distinct from the operation of sensation or 
sensory representation, as Kant would say, not sub 
stantial, nor including any sensible relation of cause 
and effect; in a word, impressions, nothing more. 
Critical or transcendental idealism, and all the many 
idealisms which have sprung from it, exist only under 
the shadow and protection of Hume s scepticism ; for 
all of them, without exception, start with a sense of 
sensations, which has no authority except idealistic 
hypothesis ending in Hume s paradox of impressions. 
But we must go behind both Hume and Kant for the 
data of sense. 

Kant even went beyond Hume s scepticism about 
the matter, which the senses receive from without, 
The sceptic had doubted a sense of anything spatial or 
temporal, and had denied a sense of connection ; but, 
however informally, he allowed a sense of conjunction. 
His critic, taking him at his word when he put forward 
mere impressions as the data of sense, proceeded, logi 
cally but falsely, to separate space and time from the 
matter of sense, to obliterate the last trace of sensible 
relation, and to reduce the matter of sense to sensible 
representations or impressions, only lasting for an in 
stant. Moreover, Kant was the author of the paradox 
that the apprehension of the apparent manifold is 
always successive, and the manifold of appearances is 
always successively produced in the mind, 1 not allow 
ing that even coexistence is sensible. According to 
him, the matter of sense received from, without is 

1 Critique of Pure Bcason, ed. Hartenstcin, p. 175 - Meiklejolm s 
translation (Bohn), pp. 142-43. 


nothing but a manifold or aggregate of unrelated im 
pressions, a mere play of representations, 1 a rhapsody 
of perceptions. 2 One wonders at last that he did not 
say at once that nothing is sensible. Meanwhile, this 
emasculation of the senses is not a result of any in 
dependent examination, but simply the last step in the 
imitation of one idealist by another. Yet it is necessary 
to the argument of the Critique. It is because the 
matter of sense is presupposed to be mere impression 
that our knowledge of objects is supposed to be due to 
a priori sources. In short, Kant attempted a criticism 
of pure reason without a previous criticism of the 
matter of sense. After what I have said in this essay, 
not against one but against all these idealistic assump 
tions, I cannot be expected to enter even the vestibule 
of this uncritical philosophy. 

The opening of the Introduction to the Critique 
carries us insensibly back to the last section of Hume s 
4 Inquiry : The mind, says Hume, has never any 
thing present to it but the perceptions, and cannot 
possibly reach any experience of their connection with 
objects. 3 Hence we see the resemblance and difference 
between the two philosophers. Both agree that the 
senses perceive impressions or representations. But 
the point of Hume s philosophy is : given impressions, 
we have not the faculties to experience objects of any 
kind. The point of Kant s philosophy is : given repre 
sentations, the objects of knowledge require faculties to 
convert the raw material of our sensory impressions 
into a knowledge of objects called experience. The 
difference, however, is by no means so great as it 
appears at first sight ; for Hume and Kant alike begin 

1 Hart. 178 = Mcik. 145. 2 Hart. 152 - Meik. 118. 

* Inquiry, 12, Tart I. 

T 2 


by assuming that the matter of sense is mere impres 
sions, and end by denying a knowledge of objects beyond 

How, then, from sensible representations, supposed 
to be the matter of sense, do we arrive at a knowledge 
of objects ? The answer of Kant immediately follows 
the opening passage of the Introduction : 

But, though all our knowledge begins with expe 
rience, it by no means follows that all arises out of expe 
rience. For it could well be that even our empirical 
knowledge is a compound of that which we receive 
through impressions, and that which our own power of 
knowledge (merely occasioned by sensible impressions) 
supplies from itself, an addition which we cannot dis 
tinguish from the original element given by sense, till 
long practice has made us attentive to, and skilful in 
separating it. It is, therefore, at least a question which 
requires close investigation, and is not to be answered 
at first sight ; whether there exist a knowledge alto 
gether independent of experience, and even of all im 
pressions of sense ? Knowledge of this kind is called 
a priori, in contradistinction to empirical knowledge, 
which has its sources a posteriori, that is, in experience. l 

By a priori, as he proceeds to explain, he does not 
mean merely deductive from the results of previous 
experience, though this, or rather deductive from the 
prior cause to the posterior effect, was the usual mean 
ing of the phrase : what he calls knowledge a priori is 
absolutely independent of experience. 2 It is nearly 
related to what Descartes called innate. But the 
novelty of Kant s theory is that even sense and expe 
rience contain a priori forms. Given that mere repre 
sentations are the matter of sense received from with- 

1 Hart. 33 = Meik. 1. ~ Ib. 34 - Meik. 2. 


out, sense requires a priori forms or pure intuitions of 
space and time to receive representations in outer and 
inner sense ; understanding requires a priori forms of 
thought, pure notions, or categories, to convert repre 
sentations into a perception and experience of objects ; 
and reason requires us to conceive a priori ideas beyond 
objects of sense, understanding, perception, experience, 
knowledge, but cannot enable us speculatively to know 
the unconditioned objects of those ideas. The Kantian 
a priori theory differs from the Cartesian theory of 
innate ideas by the assertion of a priori forms in 
empirical knowledge and by the denial of a knowledge 
through a priori ideas beyond experience. 

I remarked in the first part of this essay that every 
theory of the origin of knowledge is an hypothesis, which 
must be tested by direct and indirect evidence ; and 
that the indirect evidence must comprise both explana 
tion of the known facts and elimination of other hypo 
theses ; while of all things what must be avoided is 
synthetical hypothesis, which, starting from the sup 
posed verity of putative principles, arbitrarily dictates 
and denies facts. It will be our task to apply these 
logical rules to Kant s a priori theory, comparing it 
with other theories of the origin of knowledge, as occa 
sion may arise. In the treatment of this subject it is 
too often supposed that the alternative lies between 
Hume and Kant, and that an empirical origin of know 
ledge means association, from which the only refuge is 
transcendentalism. I shall avoid this danger, thinking 
that in philosophy, as elsewhere, this is a pretty sale 
rule : when opposite parties quarrel with one another 
more hotly than usual, the truth lurks elsewhere. 
Moreover, I have shown in the last chapter, first, that 
sense is a very different thing from mere impression, 


and, secondly, that the empirical association of ideas is 
quite different from, and insignificant compared with, 
the empirical inference of judgments and the conse 
quent conception of ideas, analogical, inductive, and 
deductive ; so that there are at least two empirical 
theories of the origin of knowledge and ideas, which 
we may distinguish as the imaginative and the inferen 
tial. Lastly, I pointed out that there are laws which 
our operations mechanically obey without knowing 
them, even in reasoning itself. It is evident that causce 
cognoscendi are of a very complicated nature. The 
choice does not lie between Hume and Kant. 

Transcendentalism has no direct evidence. It sup 
poses what may be called, perhaps, a self-informing 
power, what Cudworth called a potential omniformity 
of the mind. But, however we name it, it is a power 
.of which one is not conscious. In this respect it is 
inferior to all forms of empiricism, which assume only 
conscious powers, such as sense, imagination, associa 
tion, memory, judgment, and reasoning. Kant, on the 
other hand, supposes a power of adding a priori to 
a posteriori elements for reasons of his own, not on 
account of, but rather in spite of, consciousness. I am 
not conscious, for example, when I put my hand on the 
table, that I apprehend something a posteriori as hard, 
and a priori as extended : rather, I seem, as Berkeley 
said, to be feeling the primary quality of extension 
inseparably united with the secondary quality of hard 
ness. Moreover, there is an absence of any anatomical 
evidence for a self-informing power. Where is its ner 
vous organ ? Not the brain in particular, which is the 
general organ of sense, reasoning, will ; not the nervous 
system as hereditarily adapted to perform its operations, 
for quick is not a priori apprehension. When Kant 


says that we know because we have an a priori power, 
it is suspiciously like saying we know because we have 
an occult power of knowing. Direct evidence, how 
ever, is not absolutely necessary, and it may be urged 
perhaps that the a priori stands on the same footing 
as the aethereal hypothesis. But there is a decisive 
difference. ^Ether is supposed to be moving according 
to the known laws of motion of all bodies. But accord 
ing to what laws does the supposed self-informing 
power act ? The only laws at all like it are those of 
pure fancy, which supplements the adventitious by the 
fictitious. But the laws of fancy will not suit the a 
priori hypothesis, which demands not fiction but know 
ledge. The peculiarity of transcendentalism is that it 
supposes a power and supposes it to obey laws of its 
own. It is what Mill would call an hypothesis of both 
cause and law. 1 

Transcendentalism really stands and falls on the 
indirect evidence that the objects of knowledge cannot 
be otherwise explained. Kant appeals, in the first place, 
to necessary judgments. As experience examines only 
many instances and not all, induction can conclude 
only comparative universality, which is, after all, open 
to exception. Necessity and strict universality, he 
concludes,, are, therefore, sure signs of a knowledge 
a priori! 2 Now there are, according to him, necessary 
judgments; for example, any proposition in mathema 
tics, and the necessary connection of cause and effect in 
the ordinary use of understanding. These necessary 
judgments, then, will be not inductive but a priori. 
Secondly, he argues that not only in judgments, but 
even in universal conceptions, an a priori origin some 
times discovers itself; take away from the empirical 

1 Mill, Logic, in. 14. 2 Hart. 35 = Meik. 3. 


conception of a body everything empirical, it disappears, 
but the space it occupied remains ; take away from the 
empirical universal conception of any object its em 
pirical qualities, substance remains. 1 Thirdly, he points 
to universal conceptions, which have no object corre 
sponding in experience, but belong to a suprasensible 
sphere, where experience can, as he thinks, give no 
guidance. These unavoidable problems of pure reason 
itself are, he says, God, Freedom, and Immortality. 2 

These three arguments for the a priori are stated in 
the Introduction, and are the gist of the Critique. 
They have a common point : they all refer to objects, 
supposed to require an a priori or self-informing power! 
But the first appeals to necessary judgments about 
objects of science, the second to objects of common ex 
perience, and the third to objects beyond all experience 
in a^suprasensible world. Again, the first challenges 
the limits of induction, the second the limits of sense, 
the third the limits of experience. To answer them 
we have to ask ourselves, indeed, whether induction 
sense, and experience are so limited ; but also, whether, 
in each case, our apprehensions of the objects are 
a priori. It should be noticed that there are always 
two different questions to be answered, before we can 
draw the transcendental conclusion; there is the 
question what is not, and the question what is, the 
origin of our knowledge and ideas. The negative 
criticism of a given aspect of empiricism is not always 
a positive proof of transcendentalism. 

The three arguments require different answers. The 
first is the most plausible. Induction is only probable ; 
necessary judgments therefore are not merely inductive. 
But it does not follow that they are therefore a priori ; 

1 nart.36 = Meik.4. * Ib. 37 = Meik. 4. 


on the contrary, as we shall presently find, they are 
analytical judgments a posteriori. The second argument 
depends, not on the logical limits of induction, but on 
Hume s hypothesis of the limits of sense, uncritically 
adopted by Kant. But sense is not limited to repre 
sentations ; it perceives the extended, as we found in 
examining Berkeley s < Theory of Vision, and substance, 
as we found in discussing Locke s Essay ; whatever 
extended substance is in experience is previously in 
sense, and what is not in sense is inferred by logical 
reasoning from sense. The third argument depend^s on 
the kind of experience which would be possible, if it 
were made out of representations by a priori notions of 
understanding, and were, therefore, confined to sensible 
phenomena, as Kant supposes. In that case, there 
would be no logical reasoning from experience of 
phenomena to non-phenomenal objects. But sense, 
outer and inner, apprehends internal but substantial 
objects, unthinking and thinking ; experience is the sum 
of sense ; and, not sense and experience, but logical 
reasoning from them infers a posteriori similar "sub 
stantial objects beyond experience ; God, nature made, 
and man made, saved, and raised by Him. The whole 
| Critique is a depreciation of sense and reason ; for, 
if a philosopher denies the objects of sense, he destroys 
the data of reason. Finally, to close this preliminary 
sketch, even if we could give no positive answer to 
Kant, we could at all events not accept his theory, 
which confessedly limits our inferences of necessary 
truths and extended substances to mere phenomena, 
and our apprehension of God, freedom, and immortality 
to bare ideas. He, at any rate, does not explain the 
power, the extent, the grasp, of human reason, because 
he has no adequate data of reasoning. 


Of the three indirect arguments, which constitute 
the proof of transcendentalism, the first is further de 
veloped in the Introduction, and required throughout 
the sequel of the Critique. It was derived from 
Leibnitz, who, in the Avant-propos of the Nouveaux 
Essais, had argued that necessary truths, especially 
in pure mathematics, though they are occasioned by 
the senses, do not depend on their evidence, but are 
innate. 1 Hume had, moreover, called attention to the 
belief in the supposed necessary connection of cause 
and effect, which he had explained away by experi 
ence and association. Stimulated by the problem 
of Hume, and prepared by the theory of Leibnitz, 
Kant extended the hypothesis of an a priori origin of 
necessary judgments from mathematics to natural 
philosophy, with the special view of solving thereby 
the problem of causation. At the same time, he did 
more than extend the a priori theory ; he alterec^ its 
character. Leibnitz had held an a priori analytical 
theory of necessity, and thought that necessary truths 
are innate in the sense of an analysis of our con 
ceptions. Kant, agreeing that they are not inductive 
but a priori, added the novel supposition that they 
are not analytical but synthetical, and therefore pro 
posed the question: How are synthetical judgments 
a priori possible ? 

At the present day, it is frequently supposed that 
the question of necessary truths depends on a choice 
between two synthetical theories, the a priori view of 
Kant and the a posteriori view of Mill. Kant, in his 
day, was at all events free from this defect. He knew 
that he had to deal with Leibnitz as well as empiricists, 
and directed his theory, so far as synthetical against 

1 Leibnitz, Opera (ed. Erdmann), 195 A, 209 B. 


the former, and, so far as a priori against the latter. 
There are, therefore, at least three alternatives about 
necessary truths : that they are synthetical a posteriori ; 
that they are synthetical a priori ; that they are analy 
tical a priori. There is one more alternative : they are 
analytical a posteriori. 

Having, in imitation of Leibnitz, eliminated the in 
ductive theory, Kant proceeded to eliminate the analy 
tical a priori theory of Leibnitz, in order to establish 
his own conclusion that necessary truths are synthetical 
a priori judgments. An analytical judgment he defines 
as one which analyses a subject into its constituent 
notions, e.g. all bodies are extended ; while a synthetical 
judgment is one which adds a predicate to our notion of 
the subject, e.g. all bodies are heavy. 1 Then he contends 
that, though some necessary judgments are analytical, 
all necessary principles are synthetical. He begins with 
pure mathematics. From arithmetic, having selected the 
sum 7 + 5 = 12, he points out that the universal con 
ception of twelve is by no means thought by thinking 
the union of seven and five. Pure geometry seemed to 
him to contain the judgment, that a straight line is the 
shortest between two points, which, as he contended, is 
synthetical, because the notion of straight contains 
nothing of magnitude, but only a quality, and the 
notion of shortest is added to, not extracted from, the 
notion of a straight line. 2 Xatural science (Pkysica) 
contains synthetical judgments a priori as principles in 
itself; 3 this is his next point. Finally, he concludes 
that metaphysics, at least as regards its end, consists 
of merely synthetical propositions a priori ; and asks 
the question, How are synthetical judgments a priori 

1 Hart. 40 - Meik. 7. 2 Ib. 43 -4 = Meik. 10. 

3 Ib. 44 = Meik. 11. 


possible? He even commits himself to the extra 
ordinary paradox that the solution of this problem 
must determine whether metaphysics is to stand or 
fall. 1 

Now, to resume his w T hole argument from necessary 
to synthetical a priori judgments : necessary judgments 
are not inductive ; they are, therefore, a priori : but 
there are necessary judgments, e.g. in mathematics and 
natural philosophy ; they are, therefore, not inductive, 
but a priori : again, they may be analytical or syntheti 
cal ; now, analytical judgments are analyses of a subject 
into its conceptions, and, though some necessary judg 
ments a priori are of this kind, necessary principles, 
e.g. in mathematics and natural philosophy, being 
a priori additions of a predicate to a subject, are not 
analytical but synthetical a priori. Such is the in 
genious reasoning by which Kant tried to eliminate, first, 
the inductive, and, secondly, the analytical theories of 
the origin of necessary truths. It opens up a number 
of questions ; but, as it admits the existence of ana 
lytical judgments, and we have not as yet looked into 
this aspect of analysis, our first anxiety must be to dis 
cover what is the nature and value of analytical judg 
ment, and what its limit. 

Aristotle laid the foundation of the distinction 
between analytical and synthetical judgments by his 
investigations about simple and complex being and 
intelligence (W^cris), about the axioms of being and 
knowing, about the self-evident principles of demon 
stration. In the Metaphysics he discussed, as axioms 
of being, the principles of contradiction and excluded 
middle, 2 and distinguished simple and complex being, 
remarking that things simple (TO, aavvOeTa), such as a 

1 Hart. 45 = Meik. 12, a Met. r. 3 seq. 


unit, are objects about which we may be ignorant, but 
not deceived, and either understand them altogether "or 
not at all ; whereas about a combination, such as wood 
being white, we may make propositions either true or 
false. 1 In the I)e Anima, after distinguishing simple 
and complex intelligence, he contended that the simple 
apprehension of the essence of a thing is always true, 
while the complex apprehension of something merely 
belonging to it may be either true or false, e.g. a white 
thing may or may not be a man. 2 In the Posterior 
Analytics he insists that the principles of demonstration 
must be necessary, that is, self-evident, 3 that the axioms 
of being, though principles, are not the actual premises, 4 
and that the principles of demonstration are acquired 
by a gradual process of sense, memory, experience, 
induction, and are recognised by intellect (vovs\ of 
which the obvious function is to apprehend their ne 
cessity. 5 

I do not commit myself to the whole of this theory 
of the self-evident principles of demonstration. Aris 
totle did not successfully explain the power of intellect 
to apprehend the self-evident, and, though he founded 
the constituents, did not actually recognise the analytical 
judgment. Especially I take exception to his doctrine 
that the apprehension of an essence or definition is 
always true. There are really two ways of arriving 
at definitions, one of which I take to be on the whole 
that described by Aristotle, and exemplified in the 
simple definitions of mathematics ; but the other is far 
more complicated, being an accumulation of facts, 
followed by an explanatory hypothesis of essence ; a 
way which is exemplified in the explanation of the 

1 Met. O. 10. - DC An. \\i. 6. 3 Post. An. i. 46. 

4 Ib. i. 11. 5 Ib. ii. 19. 


foots of heat and light by defining them as undula 
tions of aether. The omission of this second process 
is a great blot in Aristotle s logic of science, which 
is too much modelled on mathematics. It made him, 
as Bacon remarked, fly to principles, think all scientific 
principles simple and self-evident, and all science de 
monstrative, or deductive from the self-evident, Hence 
his anticipation of nature in natural philosophy ; for 
example, his hypothesis that heat is a primary quality 
of matter whose nature is simple and self-evident; 
whereas it is a secondary quality, whose nature has 
been discovered only after an indirect process of ac 
cumulating its properties, and then explaining them by 
sethereal motion. But at the bottom of these exaggera 
tions Aristotle was the discoverer of a great truth. There 
are self-evident truths about things, simple not synthetic, 
in accordance with the principles of contradiction and 
excluded middle, yet not deduced from them, discovered 
a posteriori, but recognised by some power of intellect, 
and forming principles of demonstration. Aristotle s is 
a realistic theory of self-evident truths. It has, more 
over, exercised an immense influence on modern philo 
sophy, though it has become corrupted by conceptualism 
and nominalism. 

Even empirical philosophers admit self-evident truths, 
and some of them even adopt the analytical theory of 
mathematics. Among the conceptualists, Locke, at the 
beginning of the Fourth Book of his Essay, recognised 
self-evidence under the name of c intuitive knowledge, 
which perceives the agreement or disagreement of ideas 
bv themselves, e.g. that white is not black, that a circle 
is not a triangle, that three are more than two and 
equal to one and two ; he admitted that intuition is the 
most certain kind of knowledge, and the foundation of 


demonstration, 1 in mathematics. But he gave no proof 
that it is limited to ideas, nor any explanation of its 
operation. Similarly, Hume in the Treatise admits 
intuition. No one, says he, can once doubt hut 
existence and non-existence destroy each other, and 
are perfectly incompatible and contrary." 2 In the 
1 Inquiry he regards pure mathematics as consisting 
of propositions, which express relations of ideas, either 
intuitively or demonstratively certain, and discoverable 
by the mere operation of thought. 3 The conclusions, 
says he, which it draws from considering one circle 
are the same which it would form upon surveying all the 
circles in the universe. 4 But he confined the self- 
evident and demonstrative to mathematics. 6 He 
adopted from Locke the analytical theory of mathema 
tics in a conceptualistic form, but neither of them 
proved that self-evident truths express merely relations 
of ideas. Mill differed on this subject from them in 
two respects. In the first place, he adopted, from 
Hobbes, a nominalistic view of self-evidence, regarding 
all self-evident, analytical, identical, essential proposi 
tions as purely verbal, stating the meaning of a name 
but giving no information about a thing. 6 Secondly, 
he attempted to banish the self-evident entirely from 
science, and went to a pitch of scepticism of which even 
Hume hardly dreamt, by reducing mathematical neces 
sity to probability, resulting from induction and asso 
ciation. In this respect he at the same time departed 
from Hobbes, who had taken up the extraordinary posi 
tion that, while self-evident propositions are merely 
nominal, they are principles of science, which would 
make truth and falsity purely arbitrary. Meanwhile, 

1 Essay, iv. 2, 1. Treatise, iii. 1. 3 Inquiry, 4. 

4 Ib. 5. * Cf. ib. 12, Tart III. 6 Mill, Logic, i. G, 4. 


Mill s nominalism did not rid him of self-evident pro 
positions. He allowed that they are such as every 
one assented to without proof the moment he compre 
hended the meaning of the words. 1 Moreover, he 
admitted the original inconceivability of a direct 
contradiction, 2 without, however, seeing that it is a 
negative instance entirely disproving the reduction of 
all necessity to association. 

There are, therefore, three theories of self-evidence, 
all admitting the self-evident : the realistic theory of 
Aristotle, the conceptualistic of Locke and Hume, and 
the nominalistic of Hobbes and Mill; and there are 
two theories among modern empiricists about necessary 
truths in mathematics, the older empiricists holding them 
to be self-evident, while Mill thinks them mere results 
of induction and association. But before going any 
further, we must first say something about Leibnitz, 
whose views about self-evidence, and the self-evident 
character of the necessary truths of mathematics, were 
the immediate occasion of Kant s distinction of analy 
tical and synthetical judgments a priori. 

Leibnitz, being, even more than Locke, under the 
influence of Descartes, adopted the conceptualistic 
theory that self-evident truths are founded on ideas. 
But his originality appeared in his attempt for the first 
time to explain in detail how we apprehend their neces 
sity. In opposition to Locke s criticism, Leibnitz con 
tended for innate ideas, in the form that, on the 
occasion of sensation, the mind by reflection finds 
certain ideas in itself, and for innate principles formed 
out of these innate ideas. The axiom of identity, that 
which is is, of difference, that which is the same thing 
is not different, of contradiction, it is impossible that a 

1 Mill, Logic, i. 6, 4. - Examination of Hamilton s Phil, chap vi. 


tiling should be and not be at the same time, were re 
garded by him as innate identical principles, from which 
we deduce propositions such as, sweet is not bitter, and 
a square is not a circle. To the objection that men 
make such propositions without knowing the principles, 
he answers that they are like the majors suppressed in 
enthymemes. Finally, he regarded arithmetic and 
geometry as purely innate, consisting of necessary prin 
ciples analysing our innate ideas by the principles of 
identity, difference, &C. 1 

Hence Kant s theory of analytical judgments. Ac 
cording to him, an analytical judgment is obtained 
a priori from an analysis of a conception by means of 
the principle of contradiction, which he regards as the 
supreme principle a priori of all analytical judgments. 2 
From Leibnitz he adopted the conceptualistic theory of 
the nature, and the a priori theory of the origin, of an 
analytical judgment. But he differed from his prede 
cessor in thinking that the necessary principles of 
mathematics are not included among such analytical 
judgments, but are synthetical judgments a priori. 
We have, therefore, now to find a way, if we can, 
through a host of disputes, and to ask ourselves about 
the nature, origin, and limits of analytical judgments. 
Are they concerned with names, conceptions, or things? 
Are they a priori or a posteriori ? Are they necessary 
principles ? 

To begin with the last point, mathematicians evi 
dently use some analytical premises. The axiom, the 
whole is greater than its part, is confessedly an analytical 
judgment, which, according to Mill, would state the 
meaning of the name, and according to Leibnitz and 

1 Leibnitz, Nouveaiix Essais, i. 1 (Opera, p. 2,04 scq. ed. Erdmann). 

2 Hart. 148-50 - Meik. 115-7. 


Kant, the analysis of the conception, of a whole. Now, 
to take one instance out of many, it is used as a major 
premise in Euclid I. 7, twice over to prove that an angle 
is greater than an angle contained in it. Again, Kant 
confesses that the axioms of equality are analytical, 1 and 
the first of them is the major premise of the very first 
proposition in Euclid, while the third is the basis of the 
fifth proposition. The way of getting out of this ob 
jection in the Critique is exceedingly lame. Kant, 
having to admit the use of these analytical judgments 
in geometry, maintains that they serve only for the 
chain of method, and not as principles. 2 But in 
Euclid I. 7 the axiom, the whole is greater than its 
part, is used as a primary major premise, and, when it 
is combined with a minor premise, stating that a given 
angle is a whole of which the contained angle is a part, 
it produces the conclusion that the given angle is 
greater than the contained angle. A confessedly ana 
lytical axiom then is a primary major premise in a 
geometrical deduction ; and it is a mere affair of words 
whether it is called a principle or not. 

Analytical judgments, being scientific principles, in 
the sense of primary premises in mathematical reason 
ing, are not mere analyses of conceptions, nor meanings 
of names. Both Kant and Mill admit that mathematical 
truths apply beyond conceptions and names to sensa 
tions or phenomena, which they regard as facts, while 
mechanics and all mixed mathematics prove that they 
apply to the minutest particles, beyond our sensations, 
conceptions, and names. But if any premise in a 
mathematical deduction were about conceptions or 
names, it would be a fallacy to conclude about any 
thing else. The demonstration in Euclid I. 7 would be 

1 Hart. 157-Meik. 124. 2 Hart. 44 = Meik. 11. 


a paralogism with a quaternio terminorum, if it stood in 
this form : the conception or the name, whole, is the 
conception or the name, of something greater than its 
part ; but the angle ACD is a whole, of which the 
angle BCD is a part ; and therefore, the angle ACD 
is greater than the angle BCD. The conception or 
the name would never prove that an actual whole in 
cludes its part, even among phenomena, much less that 
a whole body is greater than its particles. Since, then, 
this and other analytical axioms are principles, which 
enable us to come to conclusions beyond conceptions and 
names, they must themselves be concerned with some 
thing more than conceptions and names. That something 
more would, according to Kant and Mill, have to be 
phenomena ; but really, it includes insensible things 
beyond. The axiom of totality enables me, as I look at 
this paper and its ink-marks, to infer that the whole 
coloured surface must be greater than any one of its 
black parts ; and it also enables science to infer that a 
whole drop of water must be greater than any one of 
its imperceptible particles. Every whole in the universe 
is a case of this analytical law. Hence the conceptu- 
alistic and nominalistic theories of analytic judgments 
are miserably narrow ; for analytical judgments are 
principles of sensible and of insensible objects. We 
must return to Aristotle s realism of the self-evident. 

The conceptualistic and nominalistic theories of 
analytical judgments have each its peculiar error. The 
former theory was caused by the Cartesian confusion of 
the sensible and conceivable. Since the objects of sense 
were supposed to be concerned with ideas, it followed 
that analytical judgments, requiring no new experience, 
could not go beyond our ideas. We have destroyed 
this error from the foundation by separating sensible 

z 2 


objects from ideas. The latter theory, as it exists in 
Mill s Logic, is founded on a false disjunction. He 
supposes that all propositions are either verbal or real, 
and finding that analytical judgments, often expressing 
the meaning of a name, are verbal, concludes that they 
are not real. But the division of propositions into 
verbal and real is defective. A verbal is not necessarily 
opposed to a real proposition, a predicate does not cease 
to be a characteristic of a thing by becoming the meaning 
of a name, and there are some propositions which are 
verbal and real, such as all bodies are extended, the whole 
is greater than its part. Mill pokes fun at such a propo 
sition as Omnis homo est rationalis, which expresses part 
of the meaning of the name, man. But does that pre 
vent men from being rational ? Again, his remark that 
analytical judgments convey no information about the 
thing, betrays a sad ignorance of human nature ; for most 
men s simple apprehensions are miserably confused, as 
you may find by asking them what is a substance, an 
attribute, a body, a unit, a whole, a circle ; and one of 
the main uses of analytical judgments is to make a con 
fused apprehension distinct by dividing it into a subject 
and the predicates contained in it. In short, the division 
into analytical and synthetical does not correspond to 
the imperfect distinction of verbal and real ; analytical 
judgments are sometimes about names, sometimes about 
conceptions, but also sometimes about objects distinct 
from both ; and these latter are real. Sometimes the 
same analytical judgment is at once real, notional, and 
verbal, e.g. the whole is, is conceived, and means, that 
which is the sum of its parts. 

So far, then, we have ascertained that analytical 
judgments, such as the whole is greater than its part, 
are principles of science, and are accordingly not. 


limited to names and conceptions, but are concerned 
with sensible and insensible objects of science. Our 
next step must be to find their origin. Mill has no 
theory on the subject. Leibnitz and Kant have a theory, 
the common point of which is that we deduce the 
analysis of our conceptions from the principle of con 
tradiction a priori. 1 As Kant merely followed Leibnitz 
in this respect, it will be best to criticise the original 
authority, in accordance with the method of this essay, 
which always contemplates the discovery of idealistic 
errors at their first source. 

Descartes had, as we found, a confused notion of 
an innate power discovering ideas in ourselves, which 
Locke showed to be nothing but inner sense or reflec 
tion. It is an extraordinary thing that in the Nou- 
veaux Essais, which is an elaborate criticism of Locke s 
Essay, Leibnitz knew Locke s theory of reflection, 
and yet coolly repeats that the ideas derived from it 
are innate, without taking any notice of the sensible and 
presentative origin of such ideas from inner sense. 
Perhaps, he says, our able author will not be entirely 
removed from my sentiments ; for, after having employed 
all his first book in rejecting innate lights, taken in a 
certain sense, he avows at the commencement of the 
second and in the sequel, that ideas which have not their 
origin from sensation come from reflection. Now re 
flection is nothing but attention to that which is in us, 
and the senses do not give us that which we already 
possess. This being so, can it be denied that there is 
much that is innate since we are innate, so to speak, to 
ourselves ; and that there is in us Being, Unity, Sub 
stance, Duration, Change, Action, Perception, Pleasure, 

1 Hart. 39-42, 148-50 = Meik. 79, 115-17. 


and a thousand other objects of our intellectual ideas ? l 
Locke s answer would have been simple and conclusive. 
Admitting that we derive all these ideas, except that 
of substance, by attention to what is in us, which is 
reflection and not sensation, he had shown that this 
reflection is a sense, which notices our being, unity, 
&c., only because they are there to be noticed, and are 
presented to it, precisely as sensation notices white or 
hot when presented. To call these results of inner sense 
innate is to confuse the intuitive and presentative with 
the a priori and elicited. 

Leibnitz made a second mistake about innate ideas, 
in which Locke himself perhaps encouraged him. He 
put ideas down to reflection which are not confined to 
it. The correction of this mistake is of consequence, 
because Locke s exaggeration of the sphere of reflection, 
and the conversion of its ideas by Leibnitz into innate 
ideas, gave occasion to Kant s hypothesis that time is 
the mere form of inner sense and similar errors. Now, in 
the list of ideas quoted above, and supposed by Leibnitz 
to be innate, perception and pleasure are pure data of 
reflection, but being and unity belong to all data of 
sense, and to all things. Not being confined to reflec 
tion, they are not innate ideas, in the Leibnitzian 
meaning of this phrase. He made the same mistake 
about numbers, which he supposed to be purely innate 
ideas, giving rise to innate truths. 2 But, as the very 
hairs of our heads, so are the data of sense, and the 
particles of matter, all numbered. His theory, there 
fore, that number and its truths are innate, because 
they are results of reflection, is not adequate to our 
knowledge of universal number. 

To come now to the bearing of the theory of innate 

1 Leib. Opera (ed. Erdmann), 196 A. 2 Ib. 210 A, 212 A. 


ideas on the origin of analytical judgments. If analytical 
judgments were formed out of ideas, they would be 
concerned with ideas, and, as we have already found, 
they would not in that case be applied to the sensible 
and insensible beyond ideas, and therefore could not be 
principles of science. But Leibnitz admitted, or rather 
contended, that they are the principles of science. It 
follows that an analytical judgment, such as a square is 
not a circle, cannot be formed, as Leibnitz thought, 
purely from innate ideas, because it is applicable to 
sense. In fact, it was the adoption of this theory of 
analytical judgments from Leibnitz that made Kant 
refuse to analytical judgments the title of principles. 
But the right alternative would have been to conclude 
that, since analytical judgments are universal principles 
of science beyond conceptions, they are not derived 
from mere conceptions. 

But the most fundamental error of Leibnitz, which 
Kant shared with him, was the supposed deduction 
of analytical judgments from metaphysical principles 
a priori. Leibnitz supposed that, in order to say a 
square is not a circle, or bitter is not sweet, we must 
already be in possession of the general axioms, A is A, A 
is not non-A, A is not B, and so forth, which are there 
fore innate principles of analytical judgments. It is 
better to have no theory than a bad one ; and Locke, 
though he did not probe the origin of an analytical 
judgment, such as white is not black, at all events 
divined that it cannot be derived by deduction from 
principles, because men make such judgments in entire 
ignorance of the principles. Who perceives not, he 
asks, that a child certainly knows that a stranger is 
not its mother : that its sucking-bottle is not the rod, 



long before lie knows that tis impossible for the same 
thing to be, and not to be ? l 

Leibnitz replies that one founds oneself on these 
general maxims, as one founds oneself on the majors, 
which are suppressed in reasoning by enthymemes. 2 
But in an enthymeme we apprehend the major in 
thought and suppress it in speech, usually because 
the hearer will supply it himself, though sometimes be 
cause we know it to be doubtful, and hope that it will 
escape his notice ; moreover, we recognise the major 
when expressed. On the other hand, it can hardly be 
maintained that a young child apprehends but sup 
presses the principle of contradiction : and it is cer 
tainly false that he would recognise it when expressed. 
It needs a considerable education to recognise such 
principles ; and, indeed, they were rejected over and 
over again by philosophers until the genius of Aristotle 
established their metaphysical formulas. That same 
genius established them without exaggerating them. 
He pointed out that the principle of contradiction is 
a condition, but not a premise of any deduction, unless 
it has been denied in a particular case. 3 Leibnitz, on 
the other hand, and Kant after him, fell into the error 
of confusing the man with the metaphysician, when 
they supposed that we deduce analytical judgments 
from the principle of contradiction a priori. 

It does not follow that we must commit ourselves 
wholly to Locke s view about the principle of con 
tradiction. This and similar axioms put us in a kind 
of dilemma. On the one hand, Locke shows that they 
are not known a priori ; on the other, Leibnitz as 
clearly shows that they are required to make any 

1 Locke, Essay, iv. 7, 9. 2 Opera (ed. Era.), 211 A. 

3 Ar. Post. An. i. 11. 


analytical judgment. The way out of this difficulty 
may be found by combining the hint of Aristotle, 
that they are conditions, not premises, with the last 
chapter, in which I pointed out that the laws of asso 
ciation, and the axioms obeyed by reasoning, analogical, 
inductive and deductive, are not premises of associa 
tion and reasoning. Now, as, when the sight of a 
dog recalls the idea of his master, I use the law of 
association by contiguity ; as, when I reason from the 
earth to Mars, I use the axiom of analogy ; as, when I 
reason from dead men to the mortality of man, I use the 
axiom of uniformity ; as, when I reason in the first 
figure, I use the dictum de omni, in the second the dic 
tum de diverso, in the third the dictum de exemplo ; but 
in no case deduce either my idea in association, or 
my judgment in reasoning, from the law, axiom, or dic 
tum which governs the process ; so do I use the axioms 
of identity, difference, contradiction, &c., when I make 
an analytical judgment, such as the whole is greater 
than its part, or white is not black, or a square is not 
a circle ; but I do not deduce any of these analytical 
judgments from these axioms, which are the sponta 
neous laws of the form of analytical judgments, not 
known premises to deduce them a priori. 

The arguments of Leibnitz prove this and no more. 
He admitted that they are not universally known, but 
rejoined that one employs them without envisaging 
them expressly, that they are necessary as muscles 
and tendons are necessary to walk, and that they are 
like veins in marble before they are discovered. 1 But 
these arguments and analogies only prove, not that 
the principle of contradiction and similar axioms are 
innate major premises, but that they are laws which 

1 Opera (ed. Erd.), 207 B, 211 B, 213 A. 


regulate the operation of analytical judgment. The 
ordinary man knows nothing about them : the meta 
physician has often denied them, Plato only caught 
glimpses of them, and they were never extended to the 
whole universe of being and thinking, until Aristotle . 
established them. In metaphysics, indeed, they are 
themselves analytical judgments, and are a justifica 
tion of the self-evidence of other analytical judgments, 
but in ordinary thinking they are laws spontaneously 
governing analysis, without being known. 

If, then, we frame analytical judgments not from, 
but only by, the axioms of identity, &c., from what 
source do we derive them? Ultimately, by general 
reasoning from sense, inductive and deductive. The 
axioms alone, even if they were known a priori, would 
be powerless : as it is, being only used, they are not 
even major premises. Without sense and reasoning, 
we should never know of anything being one and 
many, whole and part, white or black, sweet or bitter, 
square or round, or solid. By general reasoning we 
infer that there are classes of these objects, and also 
that a body moves its places in time, that a solid 
body is of three dimensions, that things are one and 
many, that a whole thing is greater than its parts. It 
is thus we get the content of all our general judgments. 
But I have confessed that induction and deduction from 
induction are only probable. How, then, do we pass 
from the probability of general reasoning to the neces 
sity of analytical judgment? By the perfection of 
rational abstraction. 

There is another power in man, discovered by 
Aristotle abstraction. Abstraction has already been 
mentioned in this essay. I have admitted, in the 
chapter on Locke, that abstraction from sense may 



conceive general ideas ; and in the chapter on Berkeley, 
that abstraction is a kind of attention, which does not 
form a merely abstract general idea. I have con 
tended, against Locke and Berkeley alike, that it forms 
a general idea of a miscellaneous assemblage of similar 
individuals. But, without reasoning, such abstraction 
is limited merely to a general idea of sensible objects ; 
it is general, not universal. I added that there is a 
rational abstraction, such that, when reasoning infers 
a class of objects, e.g. of corpuscles, and rational con 
ception forms a general idea of them, abstraction is 
capable of attending to them. Now, because it is at 
tention, abstraction is not limited to ideas, but attends 
also to their objects. We may attend to names, to 
ideas, and to objects of sense and reason ; and it is no 
easier to attend to ideas than it is to objects. Abstrac 
tion, like other powers, has suffered at the hands of 
modern conceptualists. 

Abstraction, as Aristotle was aware, neglects the 
other characteristics of a complex object for the purpose 
of isolating one characteristic, or rather the object as so 
characterised. For example, there is no such thing as 
a whole ; but we can neglect the other characteristics 
of an object, which is, among other things, a whole, 
and attend to it so far as it is a whole. Hence we often 
use the formula, as a whole, or qua whole the 
Latin qua being a translation of the Aristotelian "ry ." 
The value of this operation, which the moderns ridi 
cule as metaphysicians but use as men, is that we get 
rid of the complexity of general reasoning, and are 
able, by attention, to isolate a simple kind of ob 
ject ; and all abstract sciences take advantage of this 
isolation. Now, not in all cases, but in those objects 
which are peculiarly susceptible of isolation, there is a 


PART 11. 

further effect: we are able so far to isolate a simple 
kind of object, that we get rid of the synthesis of 
general reasoning, attend to a simple object in its com 
pleteness, and apprehend its nature or essence. Thus, 
general reasoning infers that a whole thing is greater 
than its part ; but this conclusion is liable to exceptions, 
for the thing may be absolutely simple, in which case 
it has no part to be exceeded by the whole. Again, 
general reasoning infers that one thing is undivided in 
quantity ; but, if it is a complex body, it is also many 
corpuscles in quantity, divided from one another. But 
by rational abstraction we are so far able to isolate the 
wholeness of a thing as to apprehend a thing qua whole 
as that which is nothing but a sum of its parts ; and so 
far able to isolate the unity of a thing as to apprehend 
a thing qua one as the undivided in quantity, and 
nothing more. 

This perfect abstraction is the foundation of exact 
science. The perfect abstractions of arithmetic have 
just been given. In the same way in geometry, 
general reasoning tells us that bodies are extended in 
three dimensions, but perfect abstraction is required 
to isolate the solidity of body and apprehend body qud 
solid as that which is long, broad, and deep, and nothing 
more. Similarly, in abstract mechanics, it is not till we 
have regarded a body qud moving as simply changing 
place during time, and not as possessing any particular 
structure, that we can strictly apply to it the laws of 
motion. There is, then, in exact sciences, a perfect 
abstraction, not a priori, but founded on general reason 
ing, inductive and deductive, from sense, consisting of 
attention, not to an abstract idea, but to a simple object 
in the abstract, and the apprehension of its nature, to 
the neglect of its synthesis with other characteristics or 


with other objects. This power is sometimes called 
intuition. But it is not intuitive any more than a priori. 
It requires sense, general reasoning, and rational ab 
straction ; nor is this rational abstraction always perfect ; 
but when it is perfect it is a simple apprehension of 
the nature of the object. 

An analytical judgment is one which divides a 
simple object of perfect abstraction into subject and 
predicate. When we have thus got the entire content 
from general reasoning, and have abstracted simple 
objects, an affirmative analytical judgment simply 
divides the same simple object into subject and predi 
cate by, not from, the principle of identity a thino- is 
the same as itself. This operation must be carefully 
guarded from misapprehension : there is no mystery 
about it. In the first place, it is not merely concerned 
with a common name, nor with an abstract idea, but 
with an object in the abstract, discovered by reasoning, 
isolated by perfect abstraction, and divided into subject 
and predicate by analysis. Secondly, it is not, as 
usually described, an analysis of the subject of the 
judgment into the predicate, which would deprive the 
latter of its content, but an analysis of the simple object 
isolated by perfect abstraction into subject and predi 
cate, as the object and its nature. Thirdly, it adds 
nothing to the abstraction, but, as the abstraction iso 
lates the simple object from the synthesis of general 
reasoning, so the analysis divides this simple object into 
subject and predicate. For example, having discovered 
that things which are wholes contain their parts, and 
having by perfect abstraction isolated a thing qud whole 
as merely a sum of its parts, the analytical judgment 
simply asserts this result of perfect abstraction in the 
form of a judgment, for the purpose of making demon- 


strations from it. Indeed, Aristotle was not wrong in 
saying that there is a simple apprehension of simple 
objects, though he ought to have added the analytical 
judgment, because it is as a judgment that the appre 
hension becomes a principle of demonstration. Fourthly, 
the analytical judgment is made spontaneously by the 
principle of identity, which is the law of its form, but 
not deduced from the principle as a premise. It has 
nothing a priori about it, being derived from sense and 
general reasoning, through perfect abstraction, by ana 
lysis, adding nothing but the division into subject and 
predicate, not independent of experience, but only re 
quiring no new experience ; in short, a priori only in 
the old sense of indirectly a posteriori. 

A negative analytical judgment is of the same kind, but 
one decree more complicated. General reasoning from 
sense infers that white objects are not black, that sweet 
objects are not bitter, that square objects are not round, 
and so forth. Perfect abstraction isolates the different 
objects and causes a simple apprehension of their 
natures as different. In the case of simple objects of 
sense, such as sensibly white and sensibly black, perfect 
abstraction is applicable, because the objects are so 
simple, and the abstraction simply apprehends the sen 
sibly white as containing nothing black, and rice versa. 
In the case of other objects, such as things which are 
square or round, the abstraction, to become perfect, 
requires the neglect of many extraneous circumstances, 
in order to apprehend a thing qua square containing 
nothing round, and vice versa. A negative analytical 
judgment, thereupon, divides the objects differentiated 
in the abstract as subject and predicate of a negative 
judgment, a sensible object qua white is never black, a 
thins qud square is never round. Its principle is that 


of difference, that which is the same thing is not different, 
or two different things are not the same, or, in its more 
developed form, the principle of contradiction. But 
this law of the form of a negative analytical judgment 
is not an a priori major premise from which any 
analytical judgment is deduced, except in metaphysics 
and logic as sciences. 

Perfect abstraction and analytical judgments are not 
unlimited. Quantitative objects are more capable of 
abstract isolation than qualitative, in the narrow sense 
of this word. Perhaps no precise limit can be marked 
out, but we may lay down the general rules, that with 
the power of isolating a simple kind of object and 
apprehending its nature, abstraction ceases to be perfect, 
and, when perfect abstraction fails, analytical judgment 
is no longer possible. Thus we can perfectly abstract 
a thing qua whole, and judge analytically that so far 
it is greater than its part ; perfectly abstract the sensibly 
white from the sensibly black, and judge analytically 
that so far one is not the other. On the other hand, 
when we come to so complicated an object as external 
light, we can no longer apprehend in isolation what 
light is as light, but must accumulate its facts and infer 
that its nature is undulative by the method of explana 
tion. Hence two origins of definition : perfect abstrac 
tion in exact science, explanation of properties in other 
sciences. An abstract science is one which attends to 
an object, so far as characterised in some particular 
manner : an exact science is one in which this abstract 
attention is perfect. 

An analytical is the same as a self-evident judgment, 
and its necessity is self-evidence. If all other tilings 
are possible, it is at least impossible that a thing should 
not be the same as itself, or be the same as something 


different. Not metaphysics but perfect abstraction 
gives this internal necessity to analytical judgments. 
But metaphysics justifies it by analysing the analytical 
axioms of identity and difference, and affords a technical 
description, by which, if we are asked why a whole, 
for example, is greater than its part, we can answer 
because a thing qua whole is the same as the sum of 
its parts, because otherwise it would not be a whole, 
and because to deny it would be a contradiction in 
terms. But such a deduction is purely metaphysical. 
Nor is it a valid objection that the ordinary man could 
not apprehend the necessity of his analytical judgments 
unless he knows the axioms, for he is in the same 
position about ordinary deduction, where he plainly 
knows the logical necessity of the inference, without 
knowing the axioms which it requires. Analytical 
judgments, then, are self-evident, without being deduced 
a priori from their axioms. 

This self-evidence has several special characteristics. 
In the first place, we have no apprehension of it till 
we apprehend the objects, but directly we apprehend 
them in the abstract we at once accept the analytical 
judgment. Hence it is that there are many men, and 
even nations, who have never heard of the very judg 
ments which to others are self-evident, The former 
have not, the latter have, performed the necessary 
abstraction. A man who has not thought of a thing as 
a whole has no acquaintance with the judgment, the 
whole is greater than its part ; no sooner has he thought 
of it qua whole, than he asks for no proof of the axiom. 
The analytical theory of principles is the only one 
which accounts for this extreme contrast between 
ignorance and certainty. Secondly, self-evidence gives 
to analytical judgments a universal applicability. They 


are not liable to the difficulty of synthesis, that an 
exception may be found to the combination of two kinds 
of objects ; a difficulty which, Kant confesses, applies even 
to a priori synthesis beyond objects of experience. In 
an analytical judgment there is only one kind of ob 
ject, which must be the same as itself and different from 
other things, wherever it is found. Thus the synthe 
tical judgment, a whole thing is greater than its part, 
is liable to the exception that a thing may sometimes 
have no parts ; but the analytical judgment, a thing so 
far as it is a whole is greater than its part, can have no 
exception, because qua whole it is only a sum of parts. 
Thirdly, self-evidence makes analytical judgments con 
vertible or coextensive ; so long as a thing is a whole it 
is greater than its part, and as soon as it ceases to be 
greater than its part it ceases to be a whole. We can 
even say that such a judgment is of eternal application ; 
for, even if things ceased to be wholes, it would still be 
true that they would be greater than their parts if there 
were wholes. Hence, there could not be another world 
in which a whole would not be greater than its part, 
for it could not be a whole ; nor can any really self- 
evident or analytical judgment be reversed. 

Such is the outline of a realistic theory of self- 
evident analytical judgments a posteriori, of which the 
points are, first, that such judgments are not always 
about names and conceptions, but also about objects of 
sense and reason ; secondly, that we discover the objects 
by general reasoning from sense, by perfect abstraction 
apprehend a simple kind of object, and analyse it into 
subject and predicate by, not from, the principles of 
identity and difference, or contradiction, a posteriori ; 
thirdly, that analytical judgments are self-evident to 
one who has abstracted the objects, universal without 

A A 


exception, and convertible ; and, fourthly, that analy 
tical judgments about objects of reason in the abstract 
are sometimes principles of science. 

As analytical principles are self-evident, conclusions 
logically deduced from them are necessary, though not 
self-evident, and the process of deduction from self- 
evident principles is demonstrative. There are two 
kinds of necessary truths : self-evident principles and 
demonstrative conclusions. Again, there are two kinds 
of deduction, which may be distinguished as empirical 
and demonstrative, provided we remember that demon 
stration is indirectly empirical. In the last chapter we 
discussed empirical deduction from induction, which, 
though formally necessary, is materially only as pro 
bable as the induction on which it is founded. In the 
present chapter we have added that deduction is not 
always limited by the probabilities of induction, but, 
when mediated by perfect abstraction, and starting 
from analytical self-evident principles a posteriori, is 
demonstrative of necessary conclusions. There are, 
therefore, two kinds of knowledge : one consisting 
of induction and deduction, combined together in cir 
cumstantial evidence, with various degrees of proba 
bility up to approximate certainty ; while the other starts 
in the same manner, but by the perfect abstraction of 
a simple, non-synthetic object, such as a thing qua 
whole, a body qua solid, a body qua moving, &c., 
obtains self-evident analytical judgments, from which 
deduction demonstrates conclusions, materially as well 
as formally necessary. The former is science ; but the 
latter is exact science. 

Kant in the Critique, and Mill in his Logic, both 
recognised analytical judgments and their self-evidence, 
but the former was deceived by conceptualism and the 


latter by nominalism, and accordingly both fell into the 
common error of excluding analytical judgments from 
principles of science. In order to answer them, we 
have only to remember that the axiom, the whole is 
greater than its part, is confessedly an analytical judg 
ment, and certainly a primary major premise in mathe 
matical demonstrations. Hence it is not a mere analysis 
of conceptions, still less the mere meaning of a name. 
It is the analysis of an object of general reasoning iso 
lated by a perfect abstraction of a thing qud whole as 
a sum of its parts. This analytical a posteriori axiom, 
being a real principle, is a sufficient contradictory in 
stance to destroy both the theory in Kant s Critique 
that all mathematical principles are synthetical a priori, 
and the synthetical a posteriori theory in Mill s Logic. 
Major est vis instantice negativce. 

We found that Kant starts his argument by the 
position that necessity and strict universality are not 
inductive. This position is common ground. After and 
beyond induction, Aristotle introduced an intelligent 
understanding of principles, purposely to explain their 
necessity. Neque tamen, says Bacon, etiam in uni- 
versalibus istis propositionibus exactam aut absolutam 
affirmationem vel abnegationem requirimus. 1 Newton, in 
the fourth Eegula Philosophandi, with which he opens 
the Third Book of the Principia, acknowledges that in 
duction is only valid donee alia occurrerint phenomena. 
Similarly, all that Mill contends is that whatever has 
been found true in innumerable instances, and never found 
to be false in any, we are safe in acting on as universal 
provisionally until an undoubted exception appears ; 
provided the nature of the case be such that a real 
exception could scarcely have escaped notice. More- 

1 Nov. Org. ii. 33. 2 Mill, Logic, iii. 21, 4. 

A A 2 


over, it is patent, from the limitation of human expe 
rience to some instances out of all, that the induction of 
all must end in probability, however great. 

The difference between Kant and Mill begins with 
the contention of the latter that there are no truths 
more necessary than those mere probabilities of induc 
tion which seem necessary to us only through insepar 
able association. But, in the first place, Mill is not true to 
his own position, because, as we saw before, he acknow 
ledges the original inconceivability of a contradiction ; 
though, like other philosophers, he passes lightly over 
this negative instance destructive of his theory that 
association is the origin of all ideas of necessity. 
Secondly, he ought to have gone further than mere 
inconceivability. Analytical principles of science are 
such that the contradictory is not only inconceivable in 
idea but impossible in belief, because it is incredible 
that a thing should not be the same as itself. Now 
Mill admits, on the one hand, that the impossible is 
different from the inconceivable, and, on the other 
hand, that association is limited to the inconceivable. 
As, then, association is no origin of principles, whose 
contradictions are impossible, and as self-evident ana 
lytical judgments are such principles, it follows that 
their necessity cannot be due to association of ideas. 
Moreover, if the axiom, the whole is greater than its 
part, were a synthetical a posteriori judgment, dis 
covered by mere induction, with a mere idea of necessity 
due to association, there would be two ideas, one of 
which would suggest the other ; but there is only one 
idea of one kind of object which is analytically judged 
to be identically a whole and greater than its part, 
Association, in fact, is no origin of the real and iden 
tical necessity of an analytical principle, which is self- 


evident. There are, then, necessary truths of which 
the opposites are neither mere improbabilities of in 
duction nor mere inconceivabilities of association, but 
incredible impossibilities of existence ; namely, self- 
evident analytical judgments. 

Kant then was right in repeating after Leibnitz that 
there are necessary judgments in the sciences ; thereby 
he eliminated their synthetical a posteriori origin. But 
he did not thereby eliminate their analytical a posteriori 
origin. Necessity and strict universality are, there 
fore, says he, sure signs of a knowledge a priori 
That therefore is a rash word. Baculus stat in 
angulo ; ergo pluit. There is another alternative. 
Because the necessary is not inductive, it does not follow 
that it is straightway a priori. Necessity is a soluble 
and not an infallible sign, because there is another source 
of necessity, namely, self-evident analytical judgments a 
posteriori. But Kant was misled by Leibnitz into think 
ing that analytical judgments were a priori. Hence 
his non sequitur from the inductive to the a priori. 
Hence also the importance of showing, as I have 
attempted to do, that analytical judgments are a pos 
teriori, real, and necessary principles. It is to found a 
theory of necessity without mysticism. 

Kant, in fact, eliminated analytical judgments from 
the position of scientific principles, only in the concep- 
tualistic a priori shape into which, under Cartesian 
influences, they had been thrown by Leibnitz. He did 
not eliminate them in the realistic a posteriori light in 
which they were rightly regarded by Aristotle. Not 
all necessary truths are a priori, because self-evident 
necessary truths are a posteriori. Not all necessary 
principles of science are synthetical judgments a priori, 
because some analytical judgments a posteriori are 


necessary principles of science. The analytical axioms, 
the whole is greater than the part, if equals be added 
to equals the wholes are equal, if equals be taken from 
equals the remainders are equal, have a reality in 
things, and an a posteriori origin, and a position among 
Euclid s principle* 2 , which contradict the fundamental 
hypothesis of Kant s Critique, that all necessary 
principles of science are synthetical judgments a priori. 

Kant might reply that, though some analytical 
judgments may be principles, they do not carry us far ; 
and that most principles at all events are synthetical 
judgments a priori ; such as 7 + 5 = 12 in arithmetic, 
and a straight line is the shortest between two points. 
But Kant was, to say the least of it, unfortunate in 
his instances. The proposition, 7 + 5 are 12, is not an 
arithmetical principle, but a demonstrative conclusion ; 
and the shortest distance between two points is so far 
from being the geometrical definition of a straight line 
that it is not geometrical at all, being merely that 
property of a straight line which is of most importance 
in mechanics. 

The definition of a straight line would require an 
investigation of space and geometry. I will only remark 
at present that Euclid s definition is at all events geome 
trical, and it is unsatisfactory only because he attempted 
to define a line without a superficies, committing a 
blunder common with systematisers of previous dis 
coveries, that of beginning too synthetically. A point 
is only definable by abstraction from a line ; and simi 
larly, a line from a surface, a surface from a solid, in 
the manner indicated, though not completely developed, 
by Dr. Simson in his Notes to the First Book of Euclid. 
A straight line also requires this analytical treatment. 
It has been for centuries perfectly abstracted ; but, as 


often happens, it has been over-abstracted, and will 
never be successfully denned until it is analytically 
approached from its place in a superficies. But arith 
metic comes before geometry : a unit is simpler than 
a point, a number than a magnitude. As Aristotle 
remarked, and Comte repeated, a science from fewer 
data precedes a science which adds more. 1 Accordingly, 
the question of necessary truths ought to be contested 
in the simpler and more universal science of arithmetic. 

The arithmetical principle concerned with the number 
12 is 11 + 1, which is its sole and sufficient definition. 
If we were to take 7 + 5 for a definition, 12 would have 
infinite definitions by the addition and subtraction of 
other numbers, none of which would be of any further 
use, because to use a number in a sum we must know 
out of what number it is formed by the addition of a 
unit. In the case of 12, 11 is that number which by 
the addition of 1 makes 12, as 10 is the number which 
by the addition of 1 makes 11, and so on till we come 
back to 1 + 1 are 2. All those arithmetical principles, 
which are definitions of numbers, are founded on the 
units added together ; as the Greeks knew perfectly 
well when they said that the unit is the origin of num 
ber, and number is multitude composed of units. 2 

The discovery of abstract numbers is a good instance 
of the process of abstraction and analysis I have been 
describing in this chapter. By sense and reason we find 
that objects are one and many and wholes, among other 
of their attributes, and infer that one object is always 
undivided, many are divided into units, and a whole is 
greater than its part. We thus discover truths of num 
ber. But how do we apprehend their necessity ? By 
perfect, abstraction we isolate an object ^a one asundi- 

] Ar. Post. An.i. 27. Eucl. VII. Def. 2. 


vided in quantity, objects qua two as one -\ one, &c., &c. 
Tliis abstraction is necessary to the science of arithmetic. 
As Plato, though lie did not understand abstraction, 
long ago pointed out, 1 concrete units are not altogether 
undivided ; a man, for example, is many in his members 
and only one on the whole ; but an arithmetical unit is 
absolutely undivided. Why ? Simply because the thing 
as divided is neglected, and attended to only as undi 
vided, by perfect abstraction. On this abstraction of 
the unit, not as a mere conception, but as a simple 
object of attention, we have, not a priori, but by a 
posteriori analysis, the analytical judgment, which is 
the definition of a unit : not, be it remarked, the con 
tingent proposition, one thing is the undivided in 
quantity, which is not always true ; but a thing qua 
one is the undivided in quantity, which is self-evidently 
necessary. So far as a thing is one, it is undivided in 
quantity, and so far as it is divided in quantity, it is no 
longer one. This analytical definition is the foundation 
of all arithmetical definitions, all of which are merely 
analyses of numbers into units ; thus 1 + 1 are 2 ; 2 + 1 
are 3, and so forth ; every one of which are analytical 
definitions. Hence, though 7 + 5 is not, 11 + 1 is, the 
analytical definition of 12. All things, qua 11 + 1 are 12, 
and qud 12 are 11 + 1. 

Mill, indeed, contends that there is a difference 
between 2 + 1 and 3, because three pebbles in two 
separate parcels, and three pebbles in one parcel, do 
not make the same impression on our senses. 2 But he 
overlooks the fact that, when three pebbles are in two 
separate parcels, if they give us the impression 2 + 1, 
this is the impression 3 without any comparison with 
three pebbles in one parcel ; and conversely, when three 

1 Plato, Eep. vii. 525 D-G B. 2 Mill, Logic, ii. 6, 2. 


pebbles are in one parcel, if they give us the impression 
3, this is the impression 2 * 1, without any comparison 
with three pebbles in two parcels. We do not require two 
sets of three objects each to count 2 and 1 are 3. The 
truth is that he was deceived by the formula 2 + 1 = 3, 
in which, for mere convenience, we apply to number the 
geometrical sign for equality of two magnitudes ; but 
we must not allow this mere symbol to make us think 
that we are always comparing different quantities on 
each side of it; in arithmetic, equality means identity, 
and the correct arithmetical formula is 2 + 1 are 3. 

Kant, on the other hand, did not even take the 
definition of the number 12, which, as we have seen, is 

11 + 1, but one of its many properties, 7 + 5. He rightly 
says that the proposition, 7 + 5 are 12, is not analytical : 

12 is not the selfsame thing as 7 + 5, because it is 
8 + 4, &c. But this proposition, though not analytical, 
is also not a principle, but a demonstrative conclusion 
from principles which are analytical, the definition of 
the unit and the definitions of the numbers up to 12, as 
11 4 1 ; and we are able from these analytical to demon 
strate synthetical judgments, by that combination which 
we found in the last chapter to be the essence of syllogism 
or deduction. Kant s attempt to prove that the prin 
ciples of arithmetical demonstration are not analytical 
by the instance 7 + 5 are 12, is an ignoratio elenchi, be 
cause this proposition is not a principle, but a demon 
strative conclusion from analytical principles, including 
11 + 1 are 12. 

It is curious what a cursory attention is paid to 
arithmetic in Kant s Critique and Mill s Logic. But by 
looking a little more closely into this most fundamental 
of all special sciences, we have found that it contains 
analytical principles a posteriori both in the axiom, the 



whole is greater than its part, and in its definitions. 
Thus we can destroy both the synthetical theories. On 
the one hand, as these principles, being self-evident, 
are such that the contradictory is impossible, Mill is 
wrong in reducing arithmetic to the mere probability of 
induction and association. He quotes, indeed, with 
approval a supposition that there might be a world, 
in which, whenever two pairs of things are contem 
plated together, a fifth thing is brought within con 
templation, and the result to the mind of contemplating 
two two s would be to count five. 1 But it is absurd 
to suppose minds contemplating a fifth thing without 
counting it in the enumeration, and yet to end the sum, 
as if they had counted it, with the number 5. Either 
one would count the fifth thing, in which case the sum 
would be 2 + 2 + 1 are 5, or one would not, in which 
case the sum would be 2 + 2 are 4. There can be no 
world in which the result to the mind of contemplating 
two two s would be to count five, because 2 + 2 are de- 
monstrably 4, and 4 + 1 are identically the same as 5. 
On the other hand, as necessary arithmetical principles 
are a posteriori analytical judgments, we cannot follow 
Kant in passing from the synthetical a posteriori to the 
a priori synthetical theory ; for a definition, such as 
11 + 1 are 12, is discovered by empirical reasoning, and 
by perfect abstraction and analysis becomes a self-evi 
dent principle, whereby 7 + 5 is 12 are demonstrated. 

Finally, if we were to surrender entirely the analy 
tical a posteriori origin of necessary truths, yet the 
synthetical a priori origin is an untenable hypothesis, 
because it does not explain the facts. Let us take for 
granted the Kantian series of arguments : the neces 
sary is not inductive, therefore it is a priori ; there are 

1 Examination of Hamilton s Philoso2)Jiy, chap. vi. note. 


necessary principles in the sciences, therefore they are 
a priori ; analytical judgments are merely a priori ana 
lyses of conceptions, but principles of science are true 
beyond conceptions, therefore they are never analytical 
judgments : but if they are neither synthetical a poste 
riori, nor analytical a priori, all principles of science are 
synthetical a priori. Now, everywhere throughout the 
Critique, Kant confesses that the a priori is contri 
buted by mind to mental representations, and that the 
data of mental representations, without which the a 
priori is mere conception, are sensations, which the a 
priori converts into objects of knowledge. Hence he 
concludes that perception, experience, understanding, 
reasoning, knowledge, science are all confined to 
sensible representations informed by a priori elements. 
Hence, according to him, necessary principles of science, 
being synthetical a priori, are necessary within, but 
impossible without, the sphere of sense and experience. 
Kant everywhere accepts this consequence : synthetical 
principles a priori are necessary, and apply, only within 
the limits of phenomena. 1 

This corollary of transcendentalism maybe illustrated 
by its application to arithmetic. According to Kant, 
arithmetic will contain analytical a priori axioms - 
for example, the whole is greater than its part which, 
however, will not be principles ; and synthetical prin 
ciples a priori, an example of which will be 7 + 5 are 12 
He did not, indeed, leave a satisfactory theory of the 
place of number in his system. There is a sentence in 
the Critique 2 in which he says that number is no 
thing but the unity of the synthesis of the manifold of 
a homogeneous intuition in general, gained by my gene- 

1 Hart. 57, 152-3, 208 = Meik. 44, 119, 177. 
2 Hart. 144 = Meik. 110. 


rating time itself in the apprehension of the intuition ; 
that is, apparently, by generating a successive addition 
of units in time. The same view is confirmed by a passage 
in the c Prolegomena to all Future Metaphysics. Geo 
metry, says he, is based upon the pure intuition of 
space. Arithmetic accomplishes its concept of number 
by the successive addition of unities in time. 1 This, 
however, is a conclusion so paradoxical, that we may 
in charity suppose him to concede that we also apprehend 
contiguous units in space. But even so, space and time 
alike are regarded by him merely as a priori forms of 
sense and of sensible phenomena. Moreover, the cate 
gories, schemata, and principles of quantity are all 
confined by him to phenomena. The consequence is 
that number is strictly limited to phenomena, and even 
the synthetical principles a priori of arithmetic are re 
garded by Kant himself as necessarily true of phenomena 
of sense, and no more. Hence his extraordinary state 
ments, numerus est quantitas phenomenon, and 
ceternitas, necessitas, phenomena, &c. 2 

But is it true that the laws of number are limited 
to the phenomena of sense ? The very first definitions 
of Newton s Principia disprove such a narrow theory. 
The quantity of matter is the measure of the same 
arising from its density and magnitude conjointly : this 
is the first definition, which is immediately illustrated by 
the arithmetical proposition that air of a double density 
in a double space is quadruple, in a triple space sex 
tuple, while this quantity of matter is identified with 
its mass. The quantity of motion is the measure of 
the same arising from the velocity and quantity of 
matter conjointly : this is the second definition, which 

1 Prolegomena (translated by Mahaffy), p. 45. 
2 Hart. 146 = Meik. 113. 


is again elucidated by the arithmetical illustration, that 
in a body, double in quantity, motion with equal velocity 
is double, with double velocity quadruple. If, now, 
arithmetic were limited to the phenomena of sense, the 
laws of mass and motion would either have to be limited 
to the phenomena of sense, or, beyond the phenomena 
of sense, contain no quantity of matter or of motion, no 
measure, no numerical proportion ; both of which alter 
natives are absurd. 

The truth is that the laws of mass and motion carry 
us far beyond the phenomena of sense into a 11011- 
phsenomenal yet scientific world of material particles, 
and carry the laws of arithmetic with them. The law 
of gravitation is a law of motion by numerical propor 
tion. All the particles of matter gravitate to one an 
other with a force directly as their mass, and inversely 
to the square of the distance ; on the one hand, this 
gravitation is inferred to be in numerical proportion 
both to the quantity of matter and to the distances of 
the particles; on the other hand, every particle of 
matter in the universe is inferred to gravitate with this 
numerical proportion, in times, places, and circumstances, 
wholly inaccessible to any possible senses of living 
beings. In the laws too of the structures and motions of 
imperceptible particles, all the definitions and axioms 
of arithmetic are employed. For example, in a drop of 
water, every thousand of the imperceptible particles 
with another particle makes one thousand and one, and 
is a whole including every one of these particles as parts. 
In rebus enim, says Bacon, qiue per numeros 
transiguiitur, tarn facile quis posuerit aut cogitaverit 
milleiiarium, quam imum ; aut millesimam partem 
unius, quam uimni integrum. l As Mill remarks, the 

1 Bacon, Nov. Org. ii. 8. 


great agent for transforming experimental into deductive 
sciences is the science of number. 1 We can neither 
allow that these deductive sciences, which measure the 
structures and motions of imperceptible particles, are 
limited to phenomena of sense, nor that there is any 
measure of quantity available except number. 

But we need not go beyond the Critique itself to see 
the impossibility of limiting number, the quantitative 
categories of unity plurality and totality, and arith 
metical principles, to phenomena. One of the points 
of the Critique is that God is not a phenomenon. 
But God is one. Therefore unity is not limited to phe 
nomena. Kant also assures us that we have a unity of 
apperception, an identical self, which is supposed by 
him to be not a phenomenon, but that which unites 
phenomena. Lest we should suppose that these objec 
tions prove only unity and not number beyond phe 
nomena, he distinguishes for us the human understand 
ing with its unity of apperception to combine sensible 
representations from the divine understanding, which 
does not require it. 2 There are, therefore, according 
to Kant, who was innocent of the Hegelian identifica 
tion of similars and confusion of divine and human, 
two understandings, the divine and the human, numeri 
cally different, yet neither a phenomenon. God, he 
also tells us, does not make a whole with the world ; 
there are, therefore, three things God, the world, and 
human understanding ; none of them phenomena. 

All things are at least numbered, whether they be 
material or spiritual ; hence the dispute, whether Kant 
ought to have made number belong to space or to time, 
is completely beside the mark, for it belongs to every 
thing whatever. It is impossible, therefore, to confine 

1 Mill, Logic, ii. 4, 7. 2 Hart. 119, 123 = Meik. 85, 89. 


number, arithmetic, or arithmetical necessity to phe 
nomena of sense. What is the consequence ? Not all 
necessary principles are limited to phenomena. Con 
sequently, again, they cannot be synthetical judgments 
a priori, which, on Kant s own confession, would limit 
them to phenomena. In other words, the synthetical 
a priori theory does not account for arithmetical neces 
sity, the simplest and best instance of scientific neces 
sity, beyond phenomena in an imperceptible world. 

Arithmetical principles apply to everything what 
ever. After all, there is only one theory which can 
account for this absolute universality of arithmetic, which 
counts subjects as well as sensations, men, bodies, cor 
puscles, and God Himself. There is not one arithmetical 
judgment limited to phenomena any more than to ideas. 
Now, this could not be, if they were analytical a priori, 
which would limit them to ideas, nor synthetical a pos 
teriori, which would make them contingent, nor syn 
thetical a priori, which would make them necessary 
only within the limits of phenomena. But it can be, 
if they are analytical a posteriori judgments about 
simple objects of reasoning in the abstract. Either, 
then, this theory must be accepted, or some new theory 
found. But where ? 

When we look back on the whole discussion of this 
difficult subject, we shall find that there is no evidence 
for the Kantian hypothesis of a priori synthetical judg 
ments, as the origin of necessary truths, except its 
advantage over the synthetical a posteriori and the 
analytical a priori theories. It has no direct evidence, 
either from consciousness or from anatomy, and it is 
not only that we are unconscious of a priori necessity, 
but that we are unconscious of any a priori power, or 
of anything like it. In indirect evidence it also fails. It 


does not attempt to eliminate an analytical a posteriori 
theory, although such a theory, as I have shown, can 
Teadily be developed from the works of Aristotle. But 
what filially condemns it, and makes it quite impossible, 
is its confessed inability to explain even the logical in 
ference, much more the scientific knowledge, of neces 
sary truths beyond the phenomena of sense ; when, as 
a matter of fact, in all the sciences, and not only in 
mechanics and all natural philosophy, but also in psy 
chology and theology itself, insensible and impercep 
tible objects are logically inferred and known to obey the 
necessary laws of unity, plurality, and totality. Every 
thing known is one ; not everything a phenomenon. 

What makes so many philosophers at this moment 
cling to an hypothesis so utterly wanting in verification, 
elimination, and explanation? Partly, no doubt, its 
superiority to the hypothesis of Mill. But two blacks 
do not make a white ; and it makes little difference 
whether we say that association makes us necessarily 
conceive, or a priori synthesis necessarily believe, the 
necessity of principles within the phenomena of sense, 
when the real question is how we infer their necessity 
in insensible and imperceptible nature, and in the super 
natural world. Partly, it is thought that the Kantian 
theory of necessity must be accepted, because other 
parts of the Critique seem to support religion. But 
we must beware of building the house of religion on 
the sand ; and religion can hardly be supported by a 
philosophy, which makes it a fallacy to say that God 
is one. The main cause of the popularity of Kant s 
philosophy, however, seems to be founded on the vague 
use of the term phenomena, which suggests to the 
unwary all the facts in heaven and earth, sensible, in 
sensible, and imperceptible. But this is not what Kant 


meant, nor what lie could mean, by phenomena, and 
it would be a sad pity to rest the reputation of a 
philosophy on an equivocation. 

As Leibnitz before him spoke of phenomena sive 
apparitiones quae in mente mea existunt, l so Kant 
always speaks of them as sensible representations which 
cannot exist out of our mind ; opposing them to nou- 
mena, or things of which we must form ideas, but 
which as objects are unknown. He was aware that his 
philosophy compelled him to make these sensible repre 
sentations the limit of knowledge, not merely because 
they are the matter of sense, but also because a priori 
forms of mind cannot be valid beyond a posteriori data 
of mind. Moreover, as we find from the Preface to the 
Second Edition, 2 he looked upon it as one of the ad 
vantages of his Critique of Pure Eeason, so to limit 
speculative knowledge to phenomena that we can have 
knowledge of no object as a thing in itself, but only so 
far as it is an object of sensory intuition, i.e. as manifes 
tation, because thereby he thought to make room for a 
practical proof of the freedom of the will beyond the 
area of phenomena. 

Kant, then, in limiting all speculative knowledge to 
phenomena, meant that necessary truths, being synthe 
tical judgments a priori, are only necessary about the 
a priori forms of sensible representations and about 
sensible representations converted into objects of know 
ledge by these a priori forms. Such a limitation to 
things of sense, Sinnenwesen, phenomena, is far too 
narrow, because arithmetical necessity applies to every 
imperceptible object of logical reasoning and scientific 
knowledge. His fundamental position, that necessity is 

1 Leibnitz, Op. (ed. Erdmann), p. 442, A. 

2 Hart. 22 scq. = Meik. xxxii. scq. 

B B 


an infallible sign of a priori knowledge, must be tra 
versed by this still more fundamental position : imper- 
ceptibility is an infallible sign of a logical inference and 
a scientific knowledge which is neither phenomenal nor 
a priori. 

Kant s Critique of Pure Eeason is a conspicuous 
instance of the failure of the synthetic method, and 
indeed of the impossibility of carrying it out con 
sistently. He supposes himself to use the origin of 
knowledge to determine the limits of the objects known. 
Accordingly, on this synthetic method, he begins with 
sense, at once begs a sense of sensible representations, 
and thus founds his philosophy on an hypothesis which 
dictates the conclusion that knowledge is limited to 
phenomena. On the other hand, every one of his main 
arguments takes a premise from the other end of know 
ledge, its objects, and, by an analytic method, uses the 
objects to infer an a priori origin of knowledge. Thus, 
in the Introduction, necessary truths about objects of 
science are used to deduce the theory of synthetic 
judgments a priori-, in the Transcendental ^Esthetic, 
from their known properties space and time are inferred 
to be a priori forms of sense ; in the Transcendental 
Analytic, a definition of the objects of knowledge is used 
to prove that they contain a priori categories of under 
standing. Nor is this all. Having taken as much about 
an object as he wants for his a priori theory, Kant then, 
by his synthetic method, uses his a priori theory to dis 
pose of the rest of the object. Thus, he argues that 
necessity requires synthetical judgments a priori, which 
again prove necessity phenomenal ; that the properties 
of time and space require a priori forms of sense, which 
again prove time and space phenomenal ; that known 
objects require a priori categories, e.g. substance and 


cause, wliicli again prove known objects, e.g. substances 
and causes, phenomenal. 1 

The Critique is a perpetual see-saw between two 
methods ; the professed from the origin to the objects, 
and the concealed from the objects to the origin of 
knowledge. It is first synthetical, then analytical, and 
finally synthetical. It assumes as a principle that the 
matter of sense is representations. But this synthetic 
beginning would not justify transcendentalism. It then 
argues that the objects of knowledge require a priori 
elements. Now, this analytical procedure gives trans 
cendentalism a momentary plausibility. It finally con 
tends that a posteriori representations converted into 
objects by a priori elements are the objects of experience, 
and that all objects of logical inference and knowledge 
are phenomena. But this synthetical ending brings 
transcendentalism into conflict with a characteristic 
of the objects of knowledge, omitted in the analysis ; 
namely, that they are not limited to phenomena. It is 
as if a natural philosopher should show that the theory 
of emission explains reflection and refraction, and then 
deny the interference of polarised light. So Kant 
shows that the a priori theory explains the necessity 
of synthetical truths, and then denies their universal 
applicability ; shows that it explains the properties of 
time and space in, and then denies them beyond, sense ; 
shows that it explains the experience of objects, and then 
denies the knowledge of objects beyond experience. 
He arbitrarily appeals to some of the characteristics, 
but neglects the insensibility, of objects of science. His 
whole method is ad placitum. He makes origin and 
objects, objects and origin, origin and objects, recipro 
cally determine one another, in a perpetual circle. 

1 Hart. 22, 80, 123-4, 133-4, &c. = Meik. xxxiii. 44, 90, 100, &c. 

B B 2 


The analytic method, used consistently, makes com 
plete havoc of the Critique. Tempus, spatium, 
locus, et motus sunt omnibus notissima. Notandum 
tamen, quod vulgus quantitates hasce non aliter quam 
ex relatione ad sensibilia concipiat. 1 In this passage, 
Newton points out that the limitation of the objects of 
science to the sensible is a vulgar error. Yet it is 
a constant error of mental philosophers, who think that, 
when they have considered only objects of sense, they 
have solved the secret of the scientific universe. It 
was the very error of Kant when he called time and 
space forms of /sense, and therefore limited motion to 
sense ; when hettnunciated the extraordinary series of 
paradoxes : numerics est quantitas phenomenon, sensatio 
realitas phenomenon, constans et perdurabile rerum 
substantia phenomenon, ceternitas, necessitas, pheno 
mena, &c. 2 ; when he concluded that whatever is known 
is a phenomenon, and what is not a phenomenon can be 
conceived by pure reason, but neither inferred by logical 
reason nor scientifically known. This philosophy, sccun- 
dum sensum, was an hypothetical corollary from the 
theory that all objects of experience are sensible repre 
sentations informed by a priori intuitions and notions of 
mind. But as certainly it is false, because it cannot 
explain a millionth, nor even an infinitesimal, part of 
the insensible objects of science. 

Let us return from the Critique of Pure Eeason 
to the Philosophie Naturalis Principia Mathematical 
and enlarge our thoughts, not to the immensity of the 
unknown, but to the extent of the objects of science, 
such as was made known by Newton, 

Felix, qui potuit rerum cognoscere causas. 

Insensible corpuscles of matter are scientifically inferred 

1 Newton, Principia, Def. Scholium. ~ Hart. 146-Meik. 113. 


to be each one, many and numbered, and to obey the 
necessary laws of number ; to be in insensible time and 
space, and to obey the necessary laws of magnitude ; to 
be insensible substances, and move according to the laws 
of motion ; to be insensible causes of insensible motions, 
and to be insensible causes of sensible objects. They 
are actual, but they are not actual phenomena of sense, 
but insensible external causes of internal sensible ef 
fects. Nor, being actual, are they possible phenomena ; 
for possible, which are not actual, phenomena are 
nothing at present, whereas the insensible particles of a 
drop of water, now gravitating towards my hand, are 
actual at present, real because causal of effects in my 
senses, and at the same time not only insensible but 
imperceptible ; so far from possibilities, impossibilities of 
sensation ; yet actual objects of science. The irresistible 
conclusion of this consistent and thorough appeal to 
the objects of knowledge, is that not all of them are 
phenomena, actual or possible, but far the larger part 
non-phsenomenal, noumenal in the sense of rationally 
inferred, known things in themselves, as apart from our 
senses, though not as apart from their relations to one 

The weight of natural philosophy is destined to 
destroy all that mental philosophy of the present day 
which begins from a sense of sensations, even if it 
makes a vain effort to recover its false start by catching 
at the shadow of a priori mysticism. When Kant pro 
poses to convert sensible representations of minds into 
objects of knowledge by a priori intuitions and notions 
of minds, he all the more limits scientific inference to 
phenomena. But, as we have just seen, the objects of 
scientific inference include insensible and imperceptible 
things, which are not phenomena, actual or possible. 



Therefore, in the first place, the Critique is incredibly 
narrow and absolutely false in limiting scientific infer 
ence to phenomena, actual and possible ; and secondly, 
the data of scientific inference cannot be sensible re 
presentations, even sublimated by a priori forms, which 
all the more surely would condemn science to the nar 
row limits of phenomena. 

Finally, we must apply consistent analysis to the 
Kantian arguments in detail. Thus, if necessary truths 
were synthetical judgments a priori, they would be 
limited to phenomena ; but science extends them to 
all particles of matter ; therefore, they are not limited 
to phenomena, and therefore are not synthetical judg 
ments a priori. Secondly, if time and space were such 
as to be necessarily a priori forms of sense, they would 
be limited to phenomena ; but science infers that they 
are forms of every particle of matter in the universe ; 
therefore, they are not limited to phenomena, and 
therefore they are not a priori forms of sense. Thirdly, 
if objects were such as to require a priori categories of 
substance and cause, they would be limited to phe 
nomenal substances and causes ; but science infers that 
all particles of matter are substantial bodies, causing 
and receiving motions, acting and reacting on one an 
other, inert until moved or resisted by one another, 
and, among countless effects, producing sensible objects 
in us ; therefore, objects scientifically inferred are not 
phenomenal substances and causes, and, therefore, sub 
stance and cause are not a priori categories. In short, 
objects of scientific inference are not phenomena, and 
could not be inferred from a posteriori sensations con 
verted into objects by a priori forms. Critical idealism 
is a false philosophy, both of the limits and of the origin 
of knowledge. 



The one beacon of the present day is scientific dis 
covery and invention : it was lighted by the principles 
of the Newtonian philosophy. But though natural philo 
sophy will reveal to us nature, and provide us external 
goods, it will not alone produce philosophical wisdom 
or constitute essential happiness. What we want is 
principles in general philosophy. When such princi 
ples have been found, it will be discovered that there 
was a time when the details of nature were not so well 
known, but the general relation of God, nature, and man 
was much better understood than at present. We may 
laugh at the want of knowledge, but we must never 
forget the wisdom of the ancients. The stream of 
human discovery has been like a river, part of which 
escapes into marshes, while the main channel flows on 
into the sea : so philosophy, the perennial sources of 
which are to be found in Greek philosophy and sciences, 
speculative and practical, has in modern times been 
partly diverted into the marshes of idealism, while the 
main stream has expanded into the natural philosophy 
of Copernicus and Kepler, Bacon and Galileo, Descartes 
and Newton, and perpetually issues in discoveries and 

Can we bring mental philosophy back into the main 
stream of discovery ? We can, by using the discoveries 
of natural philosophy as objects of science to discover 
the data of sense. Idealism has failed because it has 
used a wrong method, and begun at an unknown be 
ginning. It has taken psychical data of sense for prin 
ciples, which are really hypotheses, and has used them 
to dictate the objects of knowledge. As it has found 
new difficulties, it has feigned new hypotheses, until it 
has culminated in the absolute idealism of Hegel, who, 
by heaping hypothesis on hypothesis, sensible repre- 



sentations, a priori categories, one spiritual subject 
in God and all men, of which nature is a system of 
objective thoughts compiled a system of philosophy 
which is as cumbrous a mass of hypotheses as the 
Ptolemaic system of astronomy. But the truth is, that, 
like the old hypothesis of planetary circles round the 
earth, the modern idealistic hypothesis of a sense of 
psychical data, whether called ideas or impressions, 
representations or sensations, is a false beginning, and 
could never lead to scientific knowledge. 

Modern astronomers succeeded by reversing the 
method of astronomy. They gave up reasoning synthe 
tically from hypotheses of planetary circles to the de 
tails of planetary motion, and began with the planetary 
motions as facts. Copernicus found that the planets 
, move round the sun, and Kepler that they move not in 
circles but in ellipses: proceeding from these facts, 
Newton inquired analytically what simple motions were 
required to explain such elliptical motions : this was the 
analytical method which ended in Newton s discovery 
of astronomical principles. In the same way mental 
philosophy should reverse its method. Instead of reason 
ing synthetically from hypotheses of sensible data to 
what objects we can and must know, we should find 
what we do infer and know in the sciences, and then 
inquire analytically what sensible data are required to 
explain our inference and science. In this way, and no 
other, as Newton by an analysis of elliptical motions 
discovered the principles of astronomy, so may we by 
an analysis of the objects of scientific reasoning dis 
cover the principles of mental philosophy. 

There is one characteristic of objects scientific, 
which is at once a positive instance to bring us to 
principles of mental philosophy, and a negative instance 


to destroy all psychological idealism : it is the insen 
sibility of corpuscles. Corpuscles, insensible and imper 
ceptible substances in time and space, moving according 
to laws of motion, are physical objects of science, 
requiring physical data of sense. On the one hand, 
V consider this analytical deduction destructively. In 
/ ilrcH-ka^glace, it follows that these insensible and 
(imperceptible objects of scientific inference are not 
Sensible ideas, not perceptions, not phenomena, nor 
unknown things. This consequence destroys the ideal 
isms of Berkeley, Hume, and Kant. Secondly, these in 
sensible and imperceptible objects of scientific inference 
could not be logically inferred from ideas, nor from im 
pressions, nor from sensible representations converted into 
phenomenal objects by a priori forms. This destroys 
the idealisms I have examined, from Descartes to Kant. 
Nor could they be inferred from any sense of sensations, 
however elaborated. This destroys the idealisms of 
our own day. On the other hand, consider this analy 
tical deduction constructively. These insensible and 
imperceptible objects of scientific inference require a 
sense, from which reason may infer them by parity of 
reasoning. Hence, in the first place, sense is simple and 
synthetic ; perceiving substantial objects, which are 
internal but physical, durable, extended, and related 
to one another, within our nervous systems. Secondly, 
reason infers similar objects and relations in external 
nature. There are three types of inference, analogical, 
inductive and deductive, each mechanically obeying its 
own laws, and primarily from judgments of synthetic 
sense inferring judgments about objects insensible and 
imperceptible. General reasoning, inductive and de 
ductive, used circumstantially, produces a knowledge 
and science with an approximate always tending to 


an absolute certainty. After sense and general reasoning, 
perfect abstraction by attention, mechanically obeying 
the laws of identity and difference, makes us apprehend 
a kind of object as simply the same with itself, and 
frame analytical judgments of what it must be and not 
be, in the abstract. These analytical judgments are self- 
evident principles of demonstration, producing exact 
science, but a posteriori. This is a general outline of 
the analytical philosophy attempted in this essay. 

Among many difficulties, which may occur to 
others, I anticipate three main lines of objection to this 
essay. In the first place, it may be thought that, what 
ever value physical realism may have in dealing with 
nature as an object of scientific knowledge, idealism 
retains an advantage of its own in its treatment of man 
as a spiritual subject. On the contrary, against Des 
cartes and all his followers, but from the consilience of 
consciousness, observation, and reasoning about myself, 
I contend that man is an organism, partly body and 
partly soul; who knows of himself, on the one hand, 
that he is an animal, inhabiting the surface of no very 
large planet in a considerable solar system, which is 
only one among countless stellar worlds, in a stupen 
dous immeasurable universe ; and, on the other hand, 
that, infinitesimally little as he is in himself, by sense 
and reason he is great, in his knowledge and power 
over nature, which make him like even to God. But, 
reasonable as is this realistic, but not materialistic, con 
clusion, the idealists more and more tend to the hypo 
thesis, that man is a purely psychical self, while his 
own body is not an integral part of himself, as subject, 
but is one among all other known bodies, which, as 
objects, are either all alike inferred from, or all alike 
identical with, his sensations or thoughts in general. 


Now, the former of these alternatives leaves out half 
the man ; the latter inverts man and nature ; while 
both idealistic theories of personal identity, by draw 
ing the line of self at spirit, or between soul and body 
instead of between man and nature, contradict the con 
silience of consciousness, observation, and reasoning : 
a combined evidence not to be parted, because man 
is a complex being, mainly imperceptible to himself, 
who by night falls asleep and becomes oblivious of his 
being, by day does not remember his infancy, never 
can remember nor as yet be conscious of his future 
career, and, therefore, is not aware of his personal iden 
tity throughout life by retentive consciousness alone. 
Why, then, does modern thought tend towards idealistic 
spiritualism ? Partly from a want of simplicity and a 
certain vanity of man, who in his rationality would 
fain forget he is an animal ; mainly from a confusion 
of idealism and spiritualism with Christianity. But we 
have the best possible authority on the Christian doc 
trine of man himself: the words of Christ incarnate. 
And He said unto them, why are ye troubled? and 
wherefore do reasonings arise in your heart? See 
My hands and My feet, that it is 1 Myself : handle Me, 
and see; for a spirit hath not flesh and bones, as ye 
behold Me having. l 

Secondly, it will be doubted whether my general 
theory can be worked out in detail. I feel the full 
force of this difficulty. When this essay was mapped 
out it was to include many more details. Starting from 
Newton s < Principia, I had hoped to include a theory, 
long cherished, that the properties of time and space, 
enunciated by him in the Scholium to the Definitions, 
can only be explained by defining time and space as 

1 St. Luke xxiv. 38-39 (Revised Version). 


the continuance and continuity of tlie universe, the 
former being the continual duration, the latter the 
continuous extension, of the universe as one substance 
including many substances, from a star to an atom. 
From the same starting-point, I hoped to show that a 
necessary physical cause of motion is any body which 
displaces or resists any other body, as demonstratively 
following from the impenetrability of matter, by which 
two bodies cannot at the same time occupy the same 
place in space, and that again from the analytical judg 
ment that a body as solid is extended in three dimen 
sions. Moreover, I had hoped to apply the analytical 
a posteriori theory of necessity to geometry by starting 
from the definition of a solid. I have also written 
chapters, which are in print, on possible phenomena, 
and on actual realities, in order to show at length that 
scientific objects cannot be resolved into the former. 
These were to be followed by a discussion of ideas, 
including a criticism of Hegelianism, written but not 
printed. I have in print chapters on touch and on 
vision, directed against the doctrines of local signs, 
further developing the views in my criticism of Berke 
ley s Theory of Vision, and also based on the argu 
ment that a sense of place is necessary to a sense of 
motion. Finally, I meant to have revived the logic of 
a method, which appears in Aristotle, but has fallen 
out of logic. I mean the analytical deduction from 
effect to cause, which appears to me to be the com 
monest method of science, because man knows facts 
before and better than causes. But seeing that all 
these matters would have made at least another volume, 
and fearful of becoming tedious, I also felt that I had 
already claimed as much attention as could be hoped 
bv an untried author. 


Thirdly, it will be said that I have exaggerated the 
power of sense. This is a difficulty I do not feel or 
allow. The emasculation of sense, which is the most 
fundamental defect of modern philosophy, is a result of 
a bygone anatomy. It was formerly thought that the 
five senses were inlets, passages, or pores through which 
sensible effects were received within us, according to 
some, to the heart, according to others, to the head. 
In these circumstances, it was excusable to suppose 
that such poverty-stricken organs contributed nothing 
but isolated data, which the soul worked up within into 
all sorts of relations. But all that is changed now. It 
has been discovered that the senses are highly compli 
cated nervous structures ending in the brain, that the 
brain is an integral organ of sense as well as of reason, 
and that the whole nervous system has been for count 
less generations hereditarily modified by its operations, 
and, on the whole, better adapted to perform more and 
more complex operations. Since these discoveries, I 
submit that there is no bar to supposing that so wondrous 
a sensitive structure, as a brain and a system of sensory 
nerves has become, is an organ of simple and synthetic 
sense of objects and relations, internal and physical, 
as I have suggested. But I do not merely rely on 

My main trust is in the philosophy of science. 
Science proves the power of man to know nature. But 
logic also proves the weakness of mere reason, which, 
without adequate data of sense, is consistency, not 
science. Eeason cannot logically infer insensible objects 
and relations in external nature, unless there are sensible 
objects and relations in our internal nature for sense 
to perceive. Hence, to provide adequate data for the 
parity of reasoning, I suppose a simple and synthetic 


sense of physical objects and relations within the ner 
vous system. I hope, by this means, to have done 
what I could to physic two diseases of modern idealism 
the separation of reason from nature, and the divorce 
of reason from sense. The real problem of philosophy 
is not how to form ideas, nor how to escape from them 
to things ; it is not to start with sensations, and ask 
how much, by association, we can conceive but not 
know, nor how much, by a priori elements, we can 
know, of mere phenomena. What are the adequate 
data of sense, and what the logical processes of reason- 
ing, which enable science to infer an insensible and im- 
perceptible world. These are the questions for psycho 
logy and Icgic to ask about sense and reason. Itaque, 
in the words of Bacon, ex harum facultatum, Experi- 
mentalis scilicet et Eationalis, arctiore et sanctiore 
foedere (quod adhuc factum non est) bene sperandum 
est. : 

1 Nov. Org. i. 95. 



By the critique of the reason Kant understands the exami 
nation of the origin, extent, and limits of human knowledge. 
Pure reason is his name for reason independent of all experience. 
The * Critique of the Pure Reason subjects the pure speculative 
reason to a critical scrutiny. Kant holds that this scrutiny must 
precede all other philosophical procedures. Kant terms every 
philosophy, which transcends the . sphere of experience without 
having previously justified this act by an examination of the faculty 
of knowledge, a form of Dogmatism ; the philosophical limita 
tion of knowledge to experience he calls Empiricism ; philoso 
phical doubt as to all knowledge transcending experience, in so 
far as this doubt is grounded on the insufficiency of all existing 
attempts at demonstration, and not on an examination of the 
human faculty of knowledge in general, is termed by him ! 
cism, and his own philosophy, which makes all further philosophis 
incr dependent on the result of such an examination, Criticism. 
Criticism is < transcendental philosophy or transcendental idealism 
in so far as it inquires into and then denies the possibility of i 
transcendent knowledge, i.e. of knowledge respecting what lies 
beyond the range of experience. 

Kant sets out in his critique of the reason with a twof 
division of judgments (in particular, of categorical judgments). 
With reference to the relation of the predicate to the subject, he 
divides them into analytical or elucidating judgments -where the 
predicate can be found in the conception of the subject by simple 
analysis of the latter or is identical with it (in which latter case t 
analytical judgment is an identical one) -and synthcti 

i Ucbcrwcg s Hist, of Phil. (English Trans.), vol. ii. pp. 154 58 122). 


cative judgments where the predicate is not contained in the 
concept of the subject, but is added to it. The principle of analy 
tical judgments is the principle of identity and contradiction ; a 
synthetic judgment, on the contrary, cannot be formed from the 
conception of its subject on the basis of this principle alone. Kant 
further discriminates, with reference to their origin as parts of 
human knowledge, between judgments a priori and judgments a 
posteriori ; by the latter he understands judgments of experience, 
but by judgments a priori, in the absolute sense, those which 
are completely independent of all experience, and in the relative sense, 
those which are based indirectly on experience, or in which the concep 
tions employed, though not derived immediately from experience, are 
deduced from others that were so derived. As absolute judgments 
a priori Kant regards all those which have the marks of necessity 
and strict universality, assuming (what he does not prove, but 
simply posits as self-evident, although his whole system depends 
upon it) that necessity and strict universality are derivable from 
no combination of experiences, but only independently of all ex 
perience. All analytical judgments are judgments a priori ; for 
although the subject-conception may have been obtained through 
experience, yet to its analysis, from which the judgment results, no 
further experience is necessary. Synthetic judgments, on the con 
trary, fall into two classes. If the synthesis of the predicate with 
the subject is effected by the aid of experience, the judgment is 
synthetic a posteriori ; if it is effected apart from all experience, it 
is synthetic a priori. Kant holds the existence of judgments of 
the latter class to be undeniable ; for among the judgments whicli 
are recognised as strictly universal and apodictical, and which are 
consequently, according to Kant s assumption, judgments a priori, 
he finds judgments which must at the same time be admitted to be 
synthetic. Among these belong, first of all, most mathematical 
judgments. Some of the fundamental judgments of arithmetic 
(e.y. a=a) are, indeed, according to Kant, of an analytical nature ; 
but the rest of them, together with all geometrical judgments, arc. 
in his view, synthetic, and, since they have the marks of strict 
universality and necessity, are synthetic judgments a priori. The 
same character pertains, according to Kant, to the most general 
propositions of physics, such as, for example, that in all the changes 
of the material world the quantity of matter remains unchanged. 
These propositions are known to be true apart from all experience, 
since they are universal and apodictical judgments ; and yet they 
are not obtained through a mere analysis of the conceptions of their 
subjects, for the predicate adds something to those conceptions. In 

APPENDIX ;; s - 

liko manner, finally, are all metaphysical principles, at least in their 
tendency, synthetic judgments a priori, e.g. the principle that 
every event must have a cause. And if the principles of meta 
physics are not altogether incontrovertible, yet those of mathematics 
at least are established beyond all dispute. There exist, therefore 
concludes Kant, synthetic judgments a priori or judgments of the 
pure reason. The fundamental question of his Critique becomes, 
then : How are synthetic judgments a priori possible ? 

The answer given is : Synthetic judgments ^ jmm are possible, 
because man brings to the material of knowledge, which he acquires 
empirically in virtue of his receptivity, certain pure forms of know 
ledge, which he himself creates in virtue of his spontaneity and 
independently of all experience, and into which lie fits all given 
material. These forms, which are the conditions of the possibility 
of all experience, are at the same time the conditions of the possi 
bility of the objects of experience, because whatever is to be an 
object for me, must take 011 the forms through which the Ego, my 
original consciousness, or the transcendental unity of apperception, 
shapes all that is presented to it ; they have, therefore, objective 
validity in a synthetic judgment a priori. But the objects, with 
reference to which they possess this validity, are not the things-in- 
themselves or transcendental objects, i.e. objects as they are in 
themselves, apart from our mode of conceiving them ; they are only 
the empirical objects or the phenomena which exist in our conscious 
ness in the form of mental representations. The things-in-them- 
selves are unknowable for man. Only a creative, divine mind, that 
gives them reality at the same time that it thinks them, can have 
power truly to know them. Things-in-themselves do not conform 
themselves to the forms of human knowledge, because the human 
consciousness is not creative, because human perception is not free 
from subjective elements, is not intellectual intuition. Nor do 
the forms of human knowledge conform themselves to things-in-them- 
selves ; otherwise all our knowledge would be empirical and without 
necessity and strict universality. But all empirical objects, since 
they are only representations in our minds, do conform themselves 
to the forms of human knowledge. Hence we can know empirical 
objects or phenomena, but only these. All valid a priori knowledge 
has respect only to phenomena, hence to objects of real or possible 

The forms of knowledge are forms either of intuition or of 
thought. The Transcendental ^Esthetic treats of the former, the 
Transcendental Logic of the latter. 

The forms of intuition are space and time. Space is the form 

C C 


of external sensibility, time is the form of internal and indirectly 
of external sensibility. On the a priori nature of space depends 
the possibility of geometrical and on the a priori nature of time 
depends the possibility of arithmetical judgments. Things-in-them- 
selves or transcendental objects are related neither to space nor to 
time ; all co-existence and succession are only in phenomenal 
objects, and consequently only in the perceiving Subject. 

The forms of thought are the twelve categories or original con 
ceptions of the understanding, on which all the forms of our judg 
ments are conditioned. They are : unity, plurality, totality, 
reality, negation, limitation, substantiality, causality, reciprocal 
action, possibility, existence, necessity. On their a priori nature 
depends the validity of the most general judgments, which lie at the 
foundation of all empirical knowledge. The things-in-themselves or 
transcendental objects have neither unity nor plurality ; they are not 
substances, nor are they subject to the causal relation, or to any of 
the categories ; the categories are applicable only to the phenomenal 
objects which are in our consciousness. 

The reason strives to rise above and beyond the sphere of the 
understanding, which is confined to the finite and conditioned, to 
the unconditioned. It forms the idea of the soul, as a substance 
which ever endures ; of the world, as an unlimited causal series ; 
and of God, as the absolute substance and union of all perfections, 
or as the most perfect being. Since these ideas relate to objects 
which lie beyond the range of all possible experience, they have no 
theoretic validity ; if the latter is claimed for them (in dogmatic 
metaphysics) this is simply the result of a misleading logic founded 
on appearances, or of dialectic. The psychological paralogism con 
founds the unity of the I which can never be conceived as a pre 
dicate, but only and always as a subject with the simplicity and 
absolute permanence of a psychical substance. Cosmology leads to 
antinomies, whose mutually contradictory members are each equally 
susceptible of indirect demonstration, if the reality of space, time 
and the categories be presupposed, but which with the refutation of 
this supposition cease to exist. Rational theology, in seeking by the 
ontological, cosmological, and physico- theological arguments to prove 
the existence of God, becomes involved in a series of sophistications. 
Still these ideas of the reason are in two respects of value : (1) theo 
retically, when viewed not as constitutive principles through which 
a real knowledge of things-in-themselves can be obtained, but as 
regulative principles, which affirm that, however far empirical in 
vestigation may at any time have advanced, the sphere of objects of 
possible experience can never be regarded as fully exhausted, but that 


there will always be room for further investigation ; (2) practically, 
in so far as they render conceivable suppositions, to which the 
practical reason conducts with moral necessity. 

In the Metaphysical Principles of Physics/ Kant seeks, by 
reducing matter to forces, to justify a dynamical explanation of 




t ** 


JUK 1 5 1930 

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