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PHILOSOPHICAL STUDIES

By

G. E. MOORE, Litt.D.

_Hon. LL.D. (St. Andrews), F.B.A._

_Lecturer in Moral Science in the University of Cambridge
Author of "Principia Ethica"_

LONDON

ROUTLEDGE & KEGAN PAUL LTD

BROADWAY HOUSE: 68-74 CARTER LANE, E.C.4

1922

CONTENTS

     I.   THE REFUTATION OF IDEALISM
     II.  THE NATURE AND REALITY OF OBJECTS OF PERCEPTION
    III.  WILLIAM JAMES' "PRAGMATISM"
     IV.  HUME'S PHILOSOPHY
      V.  THE STATUS OF SENSE-DATA
     VI.  THE CONCEPTION  OF REALITY
    VII.  SOME JUDGMENTS OF PERCEPTION
   VIII.  THE CONCEPTION OF INTRINSIC VALUE
     IX.  EXTERNAL AND INTERNAL RELATIONS
      X.  THE NATURE OF MORAL PHILOSOPHY

_Those of the papers in this volume, which have been previously
published, originally appeared as follows_:--

I. "The Refutation of Idealism" in _Mind,_ N.S. Vol. xii, 1903.

II. "The Nature and Reality of Objects of Perception" in _Proceedings
of the Aristotelian Society,_ 1905-6.

III. "Professor James' 'Pragmatism'" in _Proceedings of the
Aristotelian Society,_ 1907-8.

IV. "Hume's Philosophy" in _The New Quarterly,_ November, 1909.

V. "The Status of Sense-Data" in _Proceedings of the Aristotelian
Society,_ 1913-14.

VI. "The Conception of Reality" in _Proceedings of the Aristotelian
Society,_ 1917-18.

VII. "Some Judgments of Perception" in _Proceedings of the Aristotelian
Society,_ 1918-19.

IX. "External and Internal Relations" in _Proceedings of the
Aristotelian Society,_ 1919-20.

PREFACE

All the papers contained in this volume, except the two ethical ones
(VIII and X), have been previously published; and of those which have
been previously published all, except that on "External and Internal
Relations" (IX), are here re-printed without change. They were written
at various dates between 1903 and 1921, and all are here printed in the
order in which they were written, except that VIII on "The Conception
of Intrinsic Value," which was written earlier than VI and VII, has
been moved out of its proper place in order to bring it nearer to IX
and X, to both of which it is closely related in subject.

All, except IV and X, were primarily intended for an audience
familiar with the writings of philosophers; but I hope that they may
nevertheless prove intelligible even to those who have read little or
no philosophy, since I make little use of technical terms, and, where I
have done so, have done my best to explain in ordinary language exactly
what I mean by them. The tone of X is somewhat different from that
of the rest, because it was written as a lecture for the _Leicester
Philosophical Society_, with regard to which I was informed that I must
not assume any previous acquaintance with philosophy in most of the
audience. It accordingly bears marks throughout of the kind of audience
for which it was intended.

An attentive reader will easily discover that some of the views
expressed in some of the papers are inconsistent with views expressed
in others. The fact is that some of the views expressed in some of the
earlier ones are views with which I no longer agree; and I feel that
some apology is needed for nevertheless republishing them exactly as
they stood. In all cases, except one, my excuse is that the mistaken
views in question are so embedded in the form and substance of the
papers in which they occur, that it would have been impossible to
correct them without practically substituting new papers for the old
ones; and that, in spite of these mistakes, the old papers, as they
stand, still seem to me, on the whole, to say things which are worth
saying in a form which, however defective it may be, I doubt my
own ability to improve upon. The only case in which I doubt whether
this excuse applies is that of the first paper--"The Refutation of
Idealism." This paper now appears to me to be very confused, as well
as to embody a good many down-right mistakes; so I am doubtful whether
I ought to have included it. But in this case I have another excuse:
namely that it is a paper to which a good many allusions have been made
by contemporary writers on philosophy; and I was told that, for some
readers at all events, it would be a convenience that it should be
re-printed along with the rest, if only for the sake of reference.

I said above that the only one of the previously published papers,
in which changes have been made, is IX on "External and Internal
Relations." In this case the changes are not due to any change in my
views, but to the fact that, in that part of the paper in which symbols
are used, I tried, when it was first published in the _Proceedings of
the Aristotelian Society,_ to use the symbols adopted by Whitehead and
Russell in _Principia Mathematica,_ and used them also without giving
an explanation of their meaning which would be sufficient for readers
not acquainted with that work. The symbols in question are symbols
which it is difficult for printers to reproduce; and I have, therefore,
thought it better, on this occasion, to use another set of symbols,
which seem to me to be adequate for the limited purpose I had in view.
I have tried to give an explanation of their meaning, which will
enable anyone to understand them; and I have taken the opportunity of
rewriting some of the parts of the paper in which they occur in a way
which will, I hope, make some points clearer than they originally were.

I have to thank the Committee of the Aristotelian Society for
permission to reprint the large number of papers (viz., II, III, V,
VI, VII and IX), which originally appeared in the _Proceedings_ of
that Society; and the Editor of the _New Quarterly_ for permission to
reprint the article on Hume's Philosophy (IV), which appeared in that
Journal in November, 1909.

G. E. MOORE.

CAMBRIDGE,

_January_, 1922.

Philosophical Studies

THE REFUTATION OF IDEALISM

Modern Idealism, if it asserts any general conclusion about the
universe at all, asserts that it is _spiritual._ There are two points
about this assertion to which I wish to call attention. These points
are that, whatever be its exact meaning, it is certainly meant to
assert (1) that the universe is very different indeed from what it
seems, and (2) that it has quite a large number of properties which it
does not seem to have. Chairs and tables and mountains _seem_ to be
very different from us; but, when the whole universe is declared to
be spiritual, it is certainly meant to assert that they are far more
like us than we think. The idealist means to assert that they are _in
some sense_ neither lifeless nor unconscious, as they certainly seem
to be; and I do not think his language is so grossly deceptive, but
that we may assume him to believe that they really are very different
indeed from what they seem. And secondly when he declares that they
are _spiritual,_ he means to include in that term quite a large number
of different properties. When the whole universe is declared to be
spiritual, it is meant not only that it is in some sense _conscious,_
but that it has what we recognise in ourselves as the _higher_ forms of
consciousness. That it is intelligent; that it is purposeful; that it
is not mechanical; all these different things are commonly asserted
of it. In general, it may be said, this phrase 'reality is spiritual'
excites and expresses the belief that the _whole_ universe possesses
_all the qualities_ the possession of which is held to make us so
superior to things which seem to be inanimate: at least, if it does not
possess exactly those which we possess, it possesses not one only, but
several others, which, by the same ethical standard, would be judged
equal to or better than our own. When we say it is _spiritual_ we mean
to say that it has quite a number of excellent qualities, different
from any which we commonly attribute either to stars or planets or to
cups and saucers.

Now why I mention these two points is that when engaged in the
intricacies of philosophic discussion, we are apt to overlook the
vastness of the difference between this idealistic view and the
ordinary view of the world, and to overlook the number of _different_
propositions which the idealist must prove. It is, I think, owing to
the vastness of this difference and owing to the number of different
excellences which Idealists attribute to the universe, that it seems
such an interesting and important question whether Idealism be true or
not. But, when we begin to argue about it, I think we are apt to forget
what a vast number of arguments this interesting question must involve:
we are apt to assume, that if one or two points be made on either side,
the whole case is won. I say this lest it should be thought that any of
the arguments which will be advanced in this paper would be sufficient
to disprove, or any refutation of them sufficient to prove, the truly
interesting and important proposition that reality is spiritual. For my
own part I wish it to be clearly understood that I do not suppose that
anything I shall say has the smallest tendency to prove that reality
is not spiritual: I do not believe it possible to refute a single one
of the many important propositions contained in the assertion that it
is so. Reality may be spiritual, for all I know; and I devoutly hope
it is. But I take 'Idealism' to be a wide term and to include not
only this interesting conclusion but a number of arguments which are
supposed to be, if not sufficient, at least _necessary,_ to prove it.
Indeed I take it that modern Idealists are chiefly distinguished by
certain arguments which they have in common. That reality is spiritual
has, I believe, been the tenet of many theologians; and yet, for
believing that alone, they should hardly be called Idealists. There
are besides, I believe, many persons, not improperly called Idealists,
who hold certain characteristic propositions, without venturing to
think them quite sufficient to prove so grand a conclusion. It is,
therefore, only with Idealistic _arguments_ that I am concerned; and
if any Idealist holds that _no_ argument is necessary to prove that
reality is spiritual, I shall certainly not have refuted him. I shall,
however, attack at least one argument, which, to the best of my belief,
is considered necessary to their position by _all_ Idealists. And
I wish to point out a certain advantage which this procedure gives
me--an advantage which justifies the assertion that, if my arguments
are sound, they will have refuted Idealism. If I can refute a single
proposition which is a necessary and essential step in all Idealistic
arguments, then, no matter how good the rest of these arguments may be,
I shall have proved that Idealists have _no reason whatever_ for their
conclusion.

Suppose we have a chain of argument which takes the form: Since A is
B, and B is C, and C is D, it follows A is D. In such an argument,
though 'B is C' and 'C is D' may both be perfectly true, yet if 'A
is B' be false, we have no more reason for asserting A is D than if
all three were false. It does not, indeed, follow that A is D is
false; nor does it follow that no other arguments would prove it to
be true. But it does follow that, so far as this argument goes, it is
the barest supposition, without the least bit of evidence. I propose
to attack a proposition which seems to me to stand in this relation
to the conclusion 'Reality is spiritual.' I do not propose to dispute
that 'Reality is spiritual;' I do not deny that there may be reasons
for thinking that it is: but I do propose to show that one reason upon
which, to the best of my judgment, all other arguments ever used by
Idealists depend is _false._ These other arguments may, for all I shall
say, be eminently ingenious and true; they are very many and various,
and different Idealists use the most different arguments to prove the
same most important conclusions. Some of these _may_ be sufficient to
prove that B is C and C is D; but if, as I shall try to show, their 'A
is B' is false the conclusion A is D remains a pleasant supposition.
I do not deny that to suggest pleasant and plausible suppositions may
be the proper function of philosophy: but I am assuming that the name
Idealism can only be properly applied where there is a certain amount
of argument, intended to be cogent.

The subject of this paper is, therefore, quite uninteresting. Even
if I prove my point, I shall have proved nothing about the Universe
in general. Upon the important question whether Reality is or is not
spiritual my argument will not have the remotest bearing. I shall only
attempt to arrive at the truth about a matter, which is in itself quite
trivial and insignificant, and from which, so far as I can see and
certainly so far as I shall say, no conclusions can be drawn about any
of the subjects about which we most want to know. The only importance
I can claim for the subject I shall investigate is that it seems to me
to be a matter upon which not Idealists only, but all philosophers and
psychologists also, have been in error, and from their erroneous view
of which they have inferred (validly or invalidly) their most striking
and interesting conclusions. And that it has even this importance I
cannot hope to prove. If it has this importance, it will indeed follow
that all the most striking results of philosophy--Sensationalism.
Agnosticism and Idealism alike--have, for all that has hitherto been
urged in their favour, no more foundation than the supposition that
a chimera lives in the moon. It will follow that, unless new reasons
never urged hitherto can be found, all the most important philosophic
doctrines have as little claim to assent as the most superstitious
beliefs of the lowest savages. Upon the question what we have _reason_
to believe in the most interesting matters, I do therefore think that
my results will have an important bearing; but I cannot too clearly
insist that upon the question whether these beliefs are true they will
have none whatever.

The trivial proposition which I propose to dispute is this: that _esse_
is _percipi._ This is a very ambiguous proposition, but, in some sense
or other, it has been very widely held. That it is, in some sense,
essential to Idealism, I must for the present merely assume. What I
propose to show is that, in all the senses ever given to it, it is
false.

But, first of all, it may be useful to point out briefly in what
relation I conceive it to stand to Idealistic arguments. That wherever
you can truly predicate _esse_ you can truly predicate _percipi_, in
some sense or other, is, I take it, a necessary step In all arguments,
properly to be called Idealistic, and, what is more, in all arguments
hitherto offered for the Idealistic conclusion. If _esse_ is
_percipi,_ this is at once equivalent to saying that whatever is, is
experienced; and this, again, is equivalent, in a sense, to saying that
whatever is, is something mental. But this is not the sense in which
the Idealist _conclusion_ must maintain that Reality is _mental._ The
Idealist _conclusion_ is that _esse_ is _percipere_; and hence, whether
_esse_ be _percipi_ or not, a further and different discussion is
needed to show whether or not it is also _percipere._ And again, even
if _esse_ be _percipere_, we need a vast quantity of further argument
to show that what has _esse_ has also those higher mental qualities
which are denoted by spiritual. This is why I said that the question
I should discuss, namely, whether or not _esse is percipi_, must be
utterly insufficient either to prove or to disprove that reality is
spiritual. But, on the other hand, I believe that every argument ever
used to show that reality is spiritual has inferred this (validly or
invalidly) from '_esse_ is _percipere'_ as one of its premisses; and
that this again has never been pretended to be proved except by use of
the premiss that _esse_ is _percipi._ The type of argument used for the
latter purpose is familiar enough. It is said that since whatever is,
is experienced, and since some things are which are not experienced by
the individual, these must at least form part of some experience. Or
again that, since an object necessarily implies a subject, and since
the whole world must be an object, we must conceive it to belong to
some subject or subjects, in the same sense in which whatever is the
object of our experience belongs to us. Or again, that, since thought
enters into the essence of all reality, we must conceive behind it, in
it, or as its essence, a spirit akin to ours, who think: that 'spirit
greets spirit' in its object. Into the validity of these inferences
I do not propose to enter: they obviously require a great deal of
discussion. I only desire to point out that, however correct they may
be, yet if _esse_ is not _percipi,_ they leave us as far from a proof
that reality is spiritual, as if they were all false too.

But now: Is _esse percipi?_ There are three very ambiguous terms in
this proposition, and I must begin by distinguishing the different
things that may be meant by some of them.

And first with regard to _percipi._ This term need not trouble us
long at present. It was, perhaps, originally used to mean 'sensation'
only; but I am not going to be so unfair to modern Idealists--the
only Idealists to whom the term should now be applied without
qualification--as to hold that, if they say _esse_ is _percipi_, they
mean by _percipi_ sensation only. On the contrary I quite agree with
them that, if _esse_ be _percipi_ at all, _percipi_ must be understood
to include not sensation only, but that other type of mental fact,
which is called 'thought '; and, whether _esse_ be _percipi_ or not, I
consider it to be the main service of the philosophic school, to which
modern Idealists belong, that they have insisted on distinguishing
'sensation' and 'thought' and on emphasising the importance of the
latter. Against Sensationalism and Empiricism they have maintained the
true view. But the distinction between sensation and thought need not
detain us here. For, in whatever respects they differ, they have at
least this in common, that they are both forms of consciousness or, to
use a term that seems to be more in fashion just now, they are both
ways of experiencing. Accordingly, whatever _esse_ is _percipi_ may
mean, it does _at least_ assert that whatever is, is _experienced._
And since what I wish to maintain is, that even this is untrue, the
question whether it be experienced by way of sensation or thought or
both is for my purpose quite irrelevant. If it be not experienced at
all, it cannot be either an object of thought or an object of sense.
It is only if being involves 'experience' that the question, whether
it involves sensation or thought or both, becomes important. I beg,
therefore, that _percipi_ may be understood, in what follows, to refer
merely to what is _common_ to sensation and thought. A very recent
article states the meaning of _esse_ is _percipi_ with all desirable
clearness in so far as _percipi_ is concerned.

'I will undertake to show,' says Mr. Taylor,[1] 'that what makes [any
piece of fact] real can be nothing but its presence as an inseparable
aspect of _a sentient experience_.' I am glad to think that Mr. Taylor
has been in time to supply me with so definite a statement that this
is the ultimate premiss of Idealism. My paper will at least refute
Mr. Taylor's Idealism, if it refutes anything at all: for I _shall_
undertake to show that what makes a thing real cannot possibly be its
presence as an inseparable aspect of a senient experience.

But Mr. Taylor's statement though clear, I think, with regard to
the meaning of _percipi_ is highly ambiguous in other respects. I
will leave it for the present to consider the next ambiguity in the
statement: _Esse_ is _percipi._ What does the copula mean? What can be
meant by saying that Esse _is_ percipi? There are just three meanings,
one or other of which such a statement _must_ have, if it is to be
true; and of these there is only one which it can have, if it is to
be important. (1) The statement may be meant to assert that the word
'esse' is used to signify nothing either more or less than the word
'percipi': that the two words are precise synonyms: that they are
merely different names for one and the same thing: that what is meant
by _esse_ is absolutely identical with what is meant by _percipi._
I think I need not prove that the principle _esse_ is _percipi_ is
_not_ thus intended merely to define a word; nor yet that, if it were,
it would be an extremely bad definition. But if it does _not_ mean
this, only two alternatives remain. The second is (2) that what is
meant by _esse,_ though not absolutely identical with what is meant by
_percipi_, yet _includes_ the latter as a _part_ of its meaning. If
this were the meaning of 'esse is percipi,' then to say that a thing
was real would not be the same thing as to say that it was experienced.
That it was _real_ would mean that it was experienced and _something
else besides_: 'being experienced' would be _analytically essential_
to reality, but would not be the whole meaning of the term. From the
fact that a thing was real we should be able to infer, by the law of
contradiction, that it was experienced; since the latter would be
_part_ of what is meant by the former. But, on the other hand, from the
fact a thing was experienced we should _not_ be able to infer that it
was real; since it would not follow from the fact that it had one of
the attributes essential to reality, that it _also_ had the other or
others. Now, if we understand _esse_ is _percipi_ in this second sense,
we must distinguish _three_ different things which it asserts. First of
all, it gives a definition of the word 'reality,' asserting that word
stands for a complex whole, of which what is meant by 'percipi' forms
a part. And secondly it asserts that 'being experienced' forms a part
of a certain whole. Both these propositions may be true, and at all
events I do not wish to dispute them. I do not, indeed, think that the
word 'reality' is commonly used to include 'percipi': but I do not wish
to argue about the meaning of words. And that many things which are
experienced are also something else--that to be experienced forms part
of certain wholes, is, of course, indisputable. But what I wish to
point out is, that neither of these propositions is of any importance,
unless we add to them a _third._ That 'real' is a convenient name for a
union of attributes which _sometimes_ occurs, it could not be worth any
one's while to assert: no inferences of any importance could be drawn
from such an assertion. Our principle could only mean that when a thing
happens to have _percipi_ as well as the other qualities included under
_esse,_ it has _percipi_: and we should never be able to _infer_ that
it was experienced, except from a proposition which already asserted
that it was both experienced and something else. Accordingly, if the
assertion that _percipi_ forms part of the whole meant by reality is
to have any importance, it must mean that the whole is organic, at
least in this sense, that the other constituent or constituents of it
_cannot_ occur without percipi, even if percipi can occur without them.
Let us call these other constituents _x._ The proposition that _esse_
includes _percipi,_ and that therefore from _esse percipi_ can be
inferred, can only be important if it is meant to assert that _percipi_
can be inferred from _x._ The only importance of the question whether
the whole _esse_ includes the part _percipi_ rests therefore on the
question whether the part _x_ is necessarily connected with the part
_percipi._ And this is (3) the third possible meaning of the assertion
_esse is percipi:_ and, as we now see, the only important one. _Esse_
is _percipi_ asserts that wherever you have _x_ you also have _percipi_
that whatever has the property _x_ also has the property that it is
_experienced._ And this being so, it will be convenient if, for the
future, I may be allowed to use the term '_esse_' to denote _x alone._
I do not wish thereby to beg the question whether what we commonly mean
by the word 'real' does or does not include _percipi_ as well as _x._ I
am quite content that my definition of 'esse' to denote _x_, should be
regarded merely as an arbitrary verbal definition. Whether it is so or
not, the only question of interest is whether from _x percipi_ can be
inferred, and I should prefer to be able to express this in the form:
can _percipi_ be inferred from _esse?_ Only let it be understood that
when I say _esse,_ that term will not for the future _include percipi_:
it denotes only that _x,_ which Idealists, perhaps rightly, include
_along with percipi_ under _their_ term _esse._ That there is such an
_x_ they must admit on pain of making the proposition an _absolute_
tautology; and that from this _x percipi_ can be inferred they must
admit, on pain of making it a perfectly barren analytic proposition.
Whether _x_ done should or should not be called _esse_ is not worth
a dispute: what is worth dispute is whether _percipi_ is necessarily
connected with _x._

We have therefore discovered the ambiguity of the copula in _esse_ is
_percipi,_ so far as to see that this principle asserts two distinct
terms to be so related, that whatever has the _one,_ which I call
_esse,_ has _also_ the property that it is experienced. It asserts a
necessary connexion between _esse_ on the one hand and _percipi_ on
the other; these two words denoting each a distinct term, and _esse_
denoting a term in which that denoted by _percipi_ is not included. We
have, then in _esse_ is _percipi,_ a _necessary synthetic_ proposition
which I have undertaken to refute. And I may say at once that,
understood as such, it cannot be refuted. If the Idealist chooses to
assert that it is merely a self-evident truth, I have only to say that
it does not appear to me to be so. But I believe that no Idealist ever
has maintained it to be so. Although this--that two distinct terms are
necessarily related--is the only sense which 'esse is percipi' can have
if it is to be true and important, it _can_ have another sense, if it
is to be an important falsehood. I believe that Idealists all hold this
important falsehood. They do not perceive that _Esse_ is _percipi_
must, if true, be _merely_ a self-evident synthetic truth: they either
identify with it or give as a reason for it another proposition which
must be false because it is self-contradictory. Unless they did so,
they would have to admit that it was a perfectly unfounded assumption;
and if they recognised that it was _unfounded,_ I do not think they
would maintain its truth to be evident. _Esse_ is _percipi,_ in the
sense I have found for it, _may_ indeed be true; I cannot, refute it:
but if this sense were clearly apprehended, no one, I think, would
_believe_ that it was true.

Idealists, we have seen, must assert that whatever is experienced,
is _necessarily_ so. And this doctrine they commonly express by
saying that 'the object of experience is inconceivable apart from the
subject.' I have hitherto been concerned with pointing out what meaning
this assertion must have, if it is to be an important truth. I now
propose to show that it may have an important meaning, which must be
false, because it is self-contradictory.

It is a well-known fact in the history of philosophy that _necessary_
truths in general, but especially those of which it is said that
the opposite is inconceivable, have been commonly supposed to be
_analytic,_ in the sense that the proposition denying them was
self-contradictory. It was in this way, commonly supposed, before Kant,
that many truths could be proved by the law of contradiction alone.
This is, therefore, a mistake which it is plainly easy for the best
philosophers to make. Even since Kant many have continued to assert
it; but I am aware that among those Idealists, who most properly
deserve the name, it has become more fashionable to assert that truths
are _both_ analytic and synthetic. Now with many of their reasons
for asserting this I am not concerned: it is possible that in some
connexions the assertion may bear a useful and true sense. But if we
understand 'analytic' in the sense just defined, namely, what is proved
by the law of contradiction _alone_, it is plain that, if 'synthetic'
means what is _not_ proved by this alone, no truth can be both analytic
and synthetic. Now it seems to me that those who do maintain truths to
be both, do nevertheless maintain that they are so in this as well as
in other senses. It is, indeed, extremely unlikely that so essential
a part of the historical meaning of 'analytic' and 'synthetic' should
have been entirely discarded, especially since we find no express
recognition that it is discarded. In that case it is fair to suppose
that modern Idealists have been influenced by the view that certain
truths can be proved by the law of contradiction alone. I admit they
also expressly declare that they can _not:_ but this is by no means
sufficient to prove that they do not also think they are; since it is
very easy to hold two mutually contradictory opinions. What I suggest
then is that Idealists hold the particular doctrine in question,
concerning the relation of subject and object in experience, because
they think it is an analytic truth in this restricted sense that it is
proved by the law of contradiction alone.

I am suggesting that the Idealist maintains that object and subject are
necessarily connected, mainly because he fails to see that they are
_distinct_, that they are _two,_ at all. When he thinks of 'yellow'
and when he thinks of the 'sensation of yellow,' he fails to see that
there is anything whatever in the latter which is not in the former.
This being so, to deny that yellow can ever _be_ apart from the
sensation of yellow is merely to deny that yellow can ever be other
than it is; since yellow and the sensation of yellow are absolutely
identical. To assert that yellow is necessarily an object of experience
is to assert that yellow is necessarily yellow--a purely identical
proposition, and therefore proved by the law of contradiction alone.
Of course, the proposition also implies that experience is, after all,
something distinct from yellow--else there would be no reason for
insisting that yellow is a sensation: and that the argument thus both
affirms and denies that yellow and sensation of yellow are distinct,
is what sufficiently refutes it. But this contradiction can easily
be overlooked, because though we are convinced, in other connexions,
that 'experience' does mean something and something most important,
yet we are never distinctly aware _what_ it means, and thus in every
particular case we do not notice its presence. The facts present
themselves as a kind of antinomy:

(1) Experience _is_ something unique and different from anything else;
(2) Experience of green is entirely indistinguishable from green; two
propositions which cannot both be true. Idealists, holding both, can
only take refuge in arguing from the one in some connexions and from
the other in others.

But I am well aware that there are many Idealists who would repel it
as an utterly unfounded charge that they fail to distinguish between
a sensation or idea and what I will call its object. And there are, I
admit, many who not only imply, as we all do, that green is distinct
from the sensation of green, but expressly insist upon the distinction
as an important part of their system. They would perhaps only assert
that the two form an inseparable unity. But I wish to point out that
many, who use this phrase, and who do admit the distinction, are not
thereby absolved from the charge that they deny it. For there is a
certain doctrine, very prevalent among philosophers nowadays, which by
a very simple reduction may be seen to assert that two distinct things
both are and are not distinct. A distinction is asserted; but it is
_also_ asserted that the things distinguished form an 'organic unity,'
But, forming such a unity, it is held, each would not be what it is
_apart from its relation to the other._ Hence to consider either by
itself is to make an _illegitimate abstraction._ The recognition that
there are 'organic unities' and 'illegitimate abstractions' in this
sense is regarded as one of the chief conquests of modern philosophy.
But what is the sense attached to these terms? An abstraction is
illegitimate, when and only when we attempt to assert of _a part_--of
something abstracted--that which is true only of the _whole_ to which
it belongs: and it may perhaps be useful to point out that this should
not be done. But the application actually made of this principle,
and what perhaps would be expressly acknowledged as its meaning, is
something much the reverse of useful. The principle is used to assert
that certain abstractions are _in all cases_ illegitimate; that
whenever you try to assert _anything whatever_ of that which is _part_
of an organic whole, what you assert can only be true of the whole.
And this principle, so far from being a useful truth, is necessarily
false. For if the whole can, nay _must,_ be substituted for the part
in all propositions and for all purposes, this can only be because the
whole is absolutely identical with the part. When, therefore, we are
told that green and the sensation of green are certainly distinct but
yet are not separable, or that it is an illegitimate abstraction to
consider the one apart from the other, what these provisos are used
to assert is, that though the two things are distinct yet you not
only can but must treat them as if they were not. Many philosophers,
therefore, when they admit a distinction, yet (following the lead
of Hegel) boldly assert their right, in a slightly more obscure form
of words, _also_ to deny it. The principle of organic unities, like
that of combined analysis and synthesis, is mainly used to defend the
practice of holding _both_ of two contradictory propositions, wherever
this may seem convenient. In this, as in other matters, Hegel's main
service to philosophy has consisted in giving a name to and erecting
into a principle, a type of fallacy to which experience had shown
philosophers, along with the rest of mankind, to be addicted. No wonder
that he has followers and admirers.

I have shown then, so far, that when the Idealist asserts the important
principle 'Esse is _percipi'_ he must, if it is to be true, mean by
this that: Whatever is experienced also _must_ be experienced. And
I have also shown that he _may_ identify with, or give as a reason
for, this proposition, one which must be false, because it is self
contradictory. But at this point I propose to make a complete break
in my argument. '_Esse_ is _percipi_,' we have seen, asserts of two
terms, as distinct from one another as 'green' and 'sweet,' that
whatever has the one has also the other: it asserts that 'being' and
'being experienced' are necessarily connected: that whatever _is_ is
_also_ experienced. And this, I admit, cannot be directly refuted.
But I believe it to be false; and I have asserted that anybody who
saw that '_esse_ and _percipi_' _were_ as distinct as 'green' and
'sweet' would be no more ready to believe that whatever _is_ is _also_
experienced, than to believe that whatever is green is also sweet. I
have asserted that no one would believe that '_esse_ is _percipi_'
if they saw how different _esse_ is from _percipi:_ but _this_ I
shall not try to prove. I have asserted that all who do believe that
'_esse_ is _percipi_' identify with it or take as a reason for it a
self-contradictory proposition: but this I shall not try to prove. I
shall only try to show that certain propositions which I assert to be
believed, are false. That they are believed, and that without this
belief '_esse_ is _percipi'_ would not be believed either, I must leave
without a proof.

I pass, then, from the uninteresting question 'Is _'esse percipi?'_ to
the still more uninteresting and apparently irrelevant question 'What
is a sensation or idea?'

We all know that the sensation of blue differs from that of green. But
it is plain that if both are _sensations_ they also have some point in
common. What is it that they have in common? And how is this common
element related to the points in which they differ?

I will call the common element 'consciousness' without yet attempting
to say what the thing I so call _is._ We have then in every sensation
two distinct terms, (1) 'consciousness,' in respect of which all
sensations are alike; and (2) something else, in respect of which one
sensation differs from another. It will be convenient if I may be
allowed to call this second term the 'object' of a sensation: this also
without yet attempting to say what I mean by the word.

We have then in every sensation two distinct elements, one which I call
consciousness, and another which I call the object of consciousness.
This must be so if the sensation of blue and the sensation of green,
though different in one respect, are alike in another: blue is one
object of sensation and green is another, and consciousness, which both
sensations have in common, is different from either.

But, further, sometimes the sensation of blue exists in my mind and
sometimes it does not; and knowing, as we now do, that the sensation of
blue includes two different elements, namely consciousness and blue,
the question arises whether, when the sensation of blue exists, it is
the consciousness which exists, or the blue which exists, or both.
And one point at least is plain: namely that these three alternatives
are all different from one another. So that, if any one tells us that
to say 'Blue exists' is the _same_ thing as to say that 'Both blue
and consciousness exist,' he makes a mistake and a self-contradictory
mistake.

But another point is also plain, namely, that when the sensation
exists, the consciousness, at least, certainly does exist; for when I
say that the sensations of blue and of green both exist, I certainly
mean that what is common to both and in virtue of which both are
called sensations, exists in each case. The only alternative left,
then, is that _either_ both exist or the consciousness exists alone.
If, therefore, any one tells us that the existence of blue is the same
thing as the existence of the sensation of blue he makes a mistake and
a self-contradictory mistake, for he asserts _either_ that blue is the
same thing as blue together with consciousness, _or_ that it is the
same thing as consciousness alone.

Accordingly to identify either "blue" or any other of what I have
called "_objects_" of sensation, with the corresponding sensation is
in every case, a self-contradictory error. It is to identify a part
either with the whole of which it is a part or else with the other part
of the same whole. If we are told that the assertion "Blue exists" is
_meaningless_ unless we mean by it that "The sensation of blue exists,"
we are told what is certainly false and self-contradictory. If we
are told that the existence of blue is inconceivable apart from the
existence of the sensation, the speaker _probably_ means to convey to
us, by this ambiguous expression, what is a self-contradictory error.
For we can and must conceive the existence of blue as something quite
distinct from the existence of the sensation. We can and must conceive
that blue might exist and yet the sensation of blue not exist. For my
own part I not only conceive this, but conceive it to be true. Either
therefore this terrific assertion of inconceivability means what is
false and self-contradictory or else it means only that _as a matter of
fact_ blue never can exist unless the sensation of it exists also.

And at this point I need not conceal my opinion that no philosopher
has ever yet succeeded in avoiding this self-contradictory error: that
the most striking results both of Idealism and of Agnosticism are only
obtained by identifying blue with the sensation of blue: that _esse_
is held to be _percipi,_ solely because _what is experienced_ is held
to be identical with _the experience of it._ That Berkeley and Mill
committed this error will, perhaps, be granted: that modern Idealists
make it will, I hope, appear more probable later. But that my opinion
is plausible, I will now offer two pieces of evidence. The first is
that language offers us no means of referring to such objects as "blue"
and "green" and "sweet," except by calling them sensations: it is an
obvious violation of language to call them "things" or "objects" or
"terms." And similarly we have no natural means of referring to such
objects as "causality" or "likeness" or "identity," except by calling
them "ideas" or "notions" or "conceptions." But it is hardly likely
that if philosophers had clearly distinguished in the past between a
sensation or idea and what I have called its object, there should have
been no separate name for the latter. They have always used the same
name for these two different "things" (if I may call them so): and
hence there is some probability that they have supposed these "things"
_not_ to be two and different, but one and the same. And, secondly,
there is a very good reason why they should have supposed so, in the
fact that when we refer to introspection and try to discover what the
sensation of blue is, it is very easy to suppose that we have before
us only a single term. The term "blue" is easy enough to distinguish,
but the other element which I have called "consciousness"--that which
sensation of blue has in common with sensation of green--is extremely
difficult to fix. That many people fail to distinguish it at all is
sufficiently shown by the fact that there are materialists. And, in
general, that which makes the sensation of blue a mental fact seems to
escape us: it seems, if I may use a metaphor, to be transparent--we
look through it and see nothing but the blue; we may be convinced that
there _is something_ but _what_ it is no philosopher, I think, has yet
clearly recognised.

But this was a digression. The point I had established so far was
that in every sensation or idea we must distinguish two elements,
(1) the "object," or that in which one differs from another; and (2)
"consciousness," or that which all have in common--that which makes
them sensations or mental facts. This being so, it followed that when
a sensation or idea exists, we have to choose between the alternatives
that either object alone, or consciousness alone, or both, exist;
and I showed that of these alternatives one, namely that the object
only exists, is excluded by the fact that what we mean to assert is
certainly the existence of a mental fact. There remains the question:
Do both exist? Or does the consciousness alone? And to this question
one answer has hitherto been given universally: That both exist.

This answer follows from the analysis hitherto accepted of the relation
of what I have called "object" to "consciousness" in any sensation or
idea. It is held that what I call the object is merely the "content" of
a sensation or idea. It is held that in each case we can distinguish
two elements and two only, (1) the fact that there is feeling or
experience, and (2) _what_ is felt or experienced; the sensation or
idea, it is said, forms a whole, in which we must distinguish two
"inseparable aspects," "content" and "existence." I shall try to show
that this analysis is false; and for that purpose I must ask what may
seem an extraordinary question: namely what is meant by saying that one
thing is "content" of another? It is not usual to ask this question;
the term is used as if everybody must understand it. But since I am
going to maintain that "blue" is _not_ the content of the sensation of
blue, and what is more important, that, even if it were this analysis
would leave out the most important element in the sensation of blue, it
is necessary that I should try to explain precisely what it is that I
shall deny.

What then is meant by saying that one thing is the "content" of
another? First of all I wish to point out that "blue" is rightly
and properly said to be part of the content of a blue flower. If,
therefore, we also assert that it is part of the content of the
sensation of blue, we assert that it has to the other parts (if any)
of this whole the same relation which it has to the other parts of
a blue flower--and we assert only this: we cannot mean to assert
that it has to the sensation of blue any relation which it does not
have to the blue flower. And we have seen that the sensation of blue
contains at least one other element beside blue--namely, what I call
"consciousness," which makes it a sensation. So far then as we assert
that blue is the content of the sensation, we assert that it has to
this "consciousness" the same relation which it has to the other parts
of a blue flower: we do assert this, and we assert no more than this.
Into the question what exactly the relation is between blue and a blue
flower in virtue of which we call the former part of its "content" I
do not propose to enter. It is sufficient for my purpose to point out
that it is the general relation most commonly meant when we talk of a
thing and its qualities; and that this relation is such that to say the
thing exists implies that the qualities also exist. The _content_ of
the thing is _what_ we assert to exist, when we assert _that_ the thing
exists.

When, therefore, blue is said to be part of the content of the
"sensation of blue," the latter is treated as if it were a whole
constituted in exactly the same way as any other "thing." The
"sensation of blue," on this view, differs from a blue bead or a blue
beard, in exactly the same way in which the two latter differ from one
another: the blue bead differs from the blue beard, in that while the
former contains glass, the latter contains hair; and the "sensation
of blue" differs from both in that, instead of glass or hair, it
contains consciousness. The relation of the blue to the consciousness
is conceived to be exactly the same as that of the blue to the glass or
hair: it is in all three cases the _quality_ of a _thing._

But I said just now that the sensation of blue was analysed into
"content" and "existence," and that blue was said to be _the_ content
of the idea of blue. There is an ambiguity in this and a possible
error, which I must note in passing. The term "content" may be used
in two senses. If we use "content" as equivalent to what Mr. Bradley
calls the "_what_"--if we mean by it the _whole_ of what is said to
exist, when the thing is said to exist, then blue is certainly not
_the_ content of the sensation of blue: part of the _content_ of the
sensation is, in this sense of the term, that other element which I
have called consciousness. The analysis of this sensation into the
"content" "blue," on the one hand, and mere existence on the other, is
therefore certainly false; in it we have again the self-contradictory
identification of "Blue exists" with "The sensation of blue exists,"
But there is another sense in which "blue" might properly be said to be
_the_ content of the sensation--namely, the sense in which "content,"
like _εἴδος_ is opposed to "substance" or "matter." For the element
"consciousness," being common to all sensations, may be and certainly
is regarded as in some sense their "substance," and by the "content"
of each is only meant that in respect of which one differs from
another. In this sense then "blue" might be said to be _the_ content
of the sensation; but, in that case, the analysis into "content" and
"existence" is, at least, misleading, since under "existence" must be
included "_what_ exists" in the sensation other than blue.

We have it, then, as a universally received opinion that blue is
related to the sensation or idea of blue, as its _content_, and
that this view, if it is to be true, must mean that blue is part of
_what_ is said to exist when we say that the sensation exists. To say
that the sensation exists is to say both that blue exists and that
"consciousness," whether we call it the substance of which blue is
_the_ content or call it another part of the content, exists too. Any
sensation or idea is a "_thing,_" and what I have called its object is
the quality of this thing. Such a "thing" is what we think of when we
think of a _mental image._ A mental image is conceived as if it were
related to that of which it is the image (if there be any such thing)
in exactly the same way as the image in a looking-glass is related to
that of which it is the reflection; in both cases there is identity
of content, and the image in the looking-glass differs from that
in the mind solely in respect of the fact that in the one case the
other constituent of the image is "glass" and in the other case it is
consciousness. If the image is of blue, it is not conceived that this
"content" has any relation to the consciousness but what it has to the
glass: it Is conceived _merely_ to be its _content._ And owing to the
fact that sensations and ideas are all considered to be _wholes_ of
this description--things in the mind--the question: What do we know?
is considered to be identical with the question: What reason have we
for supposing that there are things outside the mind _corresponding_ to
these that are inside it?

What I wish to point out is (1) that we have no reason for supposing
that there are such things as mental images at all--for supposing that
blue _is_ part of the content of the sensation of blue, and (2) that
even if there are mental images, no mental image and no sensation or
idea is _merely_ a thing of this kind: that 'blue,' even if it is
part of the content of the image or sensation or idea of blue, is
always _also_ related to it in quite another way, and that this other
relation, omitted in the traditional analysis, is the _only_ one which
makes the sensation of blue a mental fact at all.

The true analysis of a sensation or idea is as follows. The element
that is common to them all, and which I have called "consciousness,"
really _is_ consciousness. A sensation is, in reality, a case of
'knowing' or 'being aware of' or 'experiencing' something. When we
know that the sensation of blue exists, the fact we know is that
there exists an awareness of blue. And this awareness is not merely,
as we have hitherto seen it must be, itself something distinct and
unique, utterly different from blue: it also has a perfectly distinct
and unique relation to blue, a relation which is _not_ that of thing
or substance to content, nor of one part of content to another part
of content. This relation is just that which we mean in every case
by 'knowing.' To have in your mind 'knowledge' of blue, is _not_ to
have in your mind a 'thing' or 'image' of which blue is the content.
To be aware of the sensation of blue is _not_ to be aware of a
mental image--of a "thing," of which 'blue' and some other element
are constituent parts in the same sense in which blue and glass are
constituents of a blue bead. It is to be aware of an awareness of
blue; awareness being used, in both cases, in exactly the same sense.
This element, we have seen, is certainly neglected by the 'content'
theory: that theory entirely fails to express the fact that there is,
in the sensation of blue, this unique relation between blue and the
other constituent. And what I contend is that this omission is _not_
mere negligence of expression, but is due to the fact that though
philosophers have recognised that _something_ distinct is meant by
consciousness, they have never yet had a clear conception of _what_
that something is. They have not been able to hold _it_ and _blue_
before their minds and to compare them, in the same way in which they
can compare _blue_ and _green._ And this for the reason I gave above:
namely that the moment we try to fix our attention upon consciousness
and to see _what_, distinctly, it is, it seems to vanish: it seems as
if we had before us a mere emptiness. When we try to introspect the
sensation of blue, all we can see is the blue: the other element is
as if it were diaphanous. Yet it _can_ be distinguished if we look
attentively enough, and if we know that there is something to look for.
My main object in this paragraph has been to try to make the reader
_see_ it; but I fear I shall have succeeded very ill.

It being the case, then, that the sensation of blue includes in its
analysis, beside blue, _both_ a unique element 'awareness' _and_ a
unique relation of this element to blue, I can make plain what I meant
by asserting, as two distinct propositions, (1) that blue is probably
not part of the content of the sensation at all, and (2) that, even it
were, the sensation would nevertheless not be the sensation _of_ blue,
if blue had only this relation to it. The first hypothesis may now be
expressed by saying that, if it were true, then, when the sensation of
blue exists, there exists a _blue awareness_: offence may be taken at
the expression, but yet it expresses just what should be and is meant
by saying that blue is, in this case, a _content_ of consciousness
or experience. Whether or not, when I have the sensation of blue, my
consciousness or awareness is thus blue, my introspection does not
enable me to decide with certainty: I only see no reason for thinking
that it is. But whether it is or not, the point is unimportant, for
introspection _does_ enable me to decide that something else is also
true: namely that I am aware _of_ blue, and by this I mean, that my
awareness has to blue a quite different and distinct relation. It is
possible, I admit, that my awareness is blue _as well_ as being _of_
blue: but what I am quite sure of is that it is _of_ blue; that it has
to blue the simple and unique relation the existence of which alone
justifies us in distinguishing knowledge of a thing from the thing
known, indeed in distinguishing mind from matter. And this result I may
express by saying that what is called the _content_ of a sensation is
in very truth what I originally called it--the sensation's _object._

But, if all this be true, what follows?

Idealists admit that some things really exist of which they are not
aware: there are some things, they hold, which are not inseparable
aspects of _their_ experience, even if they be inseparable aspects of
some experience. They further hold that some of the things of which
they are sometimes aware do really exist, even when they are not aware
of them: they hold for instance that they are sometimes aware of other
minds, which continue to exist even when they are not aware of them.
They are, therefore, sometimes aware of something which is _not_ an
inseparable aspect of their own experience. They do _know some_ things
which are _not_ a mere part or content of their experience. And what
my analysis of sensation has been designed to show is, that whenever
I have a mere sensation or idea, the fact is that I am then aware of
something which is equally and in the same sense _not_ an inseparable
aspect of my experience. The awareness which I have maintained to be
included in sensation is the very same unique fact which constitutes
every kind of knowledge: "blue" is as much an object, and as little
a mere content, of my experience, when I experience it, as the most
exalted and independent real thing of which I am ever aware. There is,
therefore, no question of how we are to "get outside the circle of our
own ideas and sensations." Merely to have a sensation is already to
_be_ outside that circle. It is to know something which is as truly and
really _not_ a part of _my_ experience, as anything which I can ever
know.

Now I think I am not mistaken in asserting that the reason why
Idealists suppose that everything which _is_ must be an inseparable
aspect of some experience, is that they suppose some things, at least,
to be inseparable aspects of _their_ experience. And there is certainly
nothing which they are so firmly convinced to be an inseparable aspect
of their experience as what they call the _content_ of their ideas and
sensations. If, therefore, _this_ turns out in every case, whether it
be also the content or not, to be at least _not_ an inseparable aspect
of the experience of it, it will be readily admitted that nothing else
which _we_ experience ever is such an inseparable aspect. But if we
never experience anything but what is _not_ an inseparable aspect of
_that_ experience, how can we infer that anything whatever, let alone
_everything,_ is an inseparable aspect of _any_ experience? How utterly
unfounded is the assumption that "_esse_ is _percipi"_ appears in the
clearest light.

But further I think it may be seen that if the object of an Idealist's
sensation were, as he supposes, _not_ the object but merely the content
of that sensation, if, that is to say, it really were an inseparable
aspect of his experience, each Idealist could never be aware either of
himself or of any other real thing. For the relation of a sensation
to its object is certainly the same as that of any other instance of
experience to its object; and this, I think, is generally admitted even
by Idealists: they state as readily that _what_ is judged or thought or
perceived is the _content_ of that judgment or thought or perception,
as that blue Is the content of the sensation of blue. But, if so, then
when any Idealist thinks he is _aware_ of himself or of any one else,
this cannot really be the case. The fact Is, on his own theory, that
himself and that other person are in reality mere _contents_ of an
awareness, which is aware _of_ nothing whatever. All that can be said
is that there is an awareness in him, _with_ a certain content: it can
never be true that there is in him a consciousness _of_ anything. And
similarly he is never aware either of the fact that he exists or that
reality is spiritual. The real fact, which he describes in those terms,
is that his existence and the spirituality of reality are _contents_ of
an awareness, which is aware of nothing--certainly not, then, of it own
content.

And further if everything, of which he thinks he is aware, is in
reality merely a content of his own experience he has certainly no
_reason_ for holding that anything does exist except himself: it will,
of course, be possible that other persons do exist; solipsism will not
be necessarily true; but he cannot possibly infer from anything he
holds that it is not true. That he himself exists will of course follow
from his premiss that many things are contents of _his_ experience.
But since everything, of which he thinks himself aware, is in reality
merely an inseparable aspect of that awareness; this premiss allows no
inference that any of these contents, far less any other consciousness,
exists at all except as an inseparable aspect of his awareness, that
is, as part of himself.

Such, and not those which he takes to follow from it, are the
consequences which _do_ follow from the Idealist's supposition that the
object of an experience is in reality merely a content or inseparable
aspect of that experience. If, on the other hand, we clearly recognise
the nature of that peculiar relation which I have called "awareness of
anything"; if we see that _this_ is involved equally in the analysis
of _every_ experience--from the merest sensation to the most developed
perception or reflexion, and that _this_ is in fact the only essential
element in an experience--the only thing that is both common and
peculiar to all experiences--the only thing which gives us reason to
call any fact mental; if, further, we recognise that this awareness is
and must be in all cases of such a nature that its object, when we are
aware of it, is precisely what it would be, if we were not aware: then
it becomes plain that the existence of a table in space is related to
my experience of _it_ in precisely the same way as the existence of
my own experience is related to my experience of _that._ Of both we
are merely aware: if we are aware that the one exists, we are aware
in precisely the same sense that the other exists; and if it is true
that my experience can exist, even when I do not happen to be aware of
its existence, we have exactly the same reason for supposing that the
table can do so also. When, therefore, Berkeley, supposed that the only
thing of which I am directly aware is my own sensations and ideas, he
supposed what was false; and when Kant supposed that the objectivity of
things in space _consisted_ in the fact that they were "Vorstellungen"
having to one another different relations from those which the
same "Vorstellungen" have to one another in subjective experience,
he supposed what was equally false. I am as directly aware of the
existence of material things in space as of my own sensations; and
_what_ I am aware of with regard to each is exactly the same--namely
that in one case the material thing, and in the other case my sensation
does really exist. The question requiring to be asked about material
things is thus not: What reason have we for supposing that anything
exists _corresponding_ to our sensations? but: What reason have we for
supposing that material things do _not_ exist, since _their_ existence
has precisely the same evidence as that of our sensations? That either
exist _may_ be false; but if it is a reason for doubting the existence
of matter, that it is an inseparable aspect of our experience, the same
reasoning will prove conclusively that our experience does not exist
either, since that must also be an inseparable aspect of our experience
of _it._ The only _reasonable_ alternative to the admission that matter
exists _as well as_ spirit, is absolute Scepticism--that, as likely as
not _nothing_ exists at all. All other suppositions--the Agnostic's,
that something, at all events, does exist, as much as the Idealist's,
that spirit does--are, if we have no reason for believing in matter, as
baseless as the grossest superstitions.

[1] _International Journal of Ethics,_ October, 1902.

THE NATURE AND REALITY OF OBJECTS OF PERCEPTION

There are two beliefs in which almost all philosophers, and almost all
ordinary people are agreed. Almost everyone believes that he himself
and what he directly perceives do not constitute the whole of reality:
he believes that _something_ other than himself and what he directly
perceives _exists_ or is _real._ I do not mean to say that almost
everyone believes that what he directly perceives is real: I only mean
that he does believe that, whether what he directly perceives is real
or not, something other than it and other than himself certainly is so.
And not only does each of us thus agree in believing that _something_
other than himself and what he directly perceives is real: almost
everyone also believes that _among_ the real things, other than himself
and what he directly perceives, are other persons who have thoughts
and perceptions in some respects similar to his own. That most people
believe this I think I need scarcely try to show. But since a good many
philosophers may appear to have held views contradictory of this one, I
will briefly point out my reason for asserting that most philosophers,
even among those (if any) who have believed the contradictory of this,
have yet held this as well. Almost all philosophers tell us something
about the nature of _human_ knowledge and _human_ perception. They tell
us that _we_ perceive so and so; that the nature or origin of _our_
perceptions is such and such; or (as I have just been telling you) that
men in general have such and such beliefs. It might, indeed, be said
that we are not to interpret such language too strictly: that, though
a philosopher talks about _human_ knowledge and _our_ perceptions,
he only means to talk about his own. But in many cases a philosopher
will leave no doubt upon this point, by expressly assuming that there
are other perceptions, which differ in some respects from his own:
such, for instance, is the case when (as is so common nowadays) a
philosopher introduces psycho-genetic considerations into his arguments
--considerations concerning the nature of the perceptions of men who
existed before and at a much lower stage of culture than himself.
Any philosopher, who uses such arguments, obviously assumes that
perceptions other than his own have existed or been real. And even
those philosophers who think themselves justified in the conclusion
that neither their own perceptions nor any perceptions like theirs are
_ultimately_ real, would, I think admit, that _phenomenally_, at least,
they _are_ real, and are certainly _more_ real than some other things.

Almost everyone, then, does believe that some perceptions other than
his own, and which he himself does not directly perceive, are real; and
believing this, he believes that something other than himself and what
he directly perceives is real. But how do we know that anything exists
except our own perceptions, and what we directly perceive? How do we
know that there are any other people, who have perceptions in some
respects similar to our own?

I believe that these two questions express very exactly the nature of
the problem which it is my chief object, in this paper, to discuss.
When I say these words to you, they will at once suggest to your minds
the very question, to which I desire to find an answer; they will
convey to you the very same meaning which I have before my mind, when I
use the words. You will understand at once what question it is that I
mean to ask. But, for all that, the words which I have used are highly
ambiguous. If you begin to ask yourselves what I do mean by them, you
will find that there are several quite different things which I might
mean. And there is, I think, great danger of confusing these different
meanings with one another. I think that philosophers, when they have
asked this question in one sense, have often answered it in quite a
different sense; and yet have supposed that the answer which they have
given is an answer to the very same question which they originally
asked. It is precisely because there is this ambiguity--this danger of
confusion, in the words which I have used, that I have chosen to use
them. I wish to point out as clearly as I can, not only what I do mean
by them, but also some things which I do _not_ mean; and I wish to make
it clear that the questions which I do _not_ mean to ask, are different
questions from that which I do mean to ask.

I will take the second of my two questions, since there is in the other
an additional ambiguity to which I do not now wish to call attention.
My second question was: How do we know that there exist any other
people who have perceptions in some respects similar to our own? What
does this question mean?

Now I think you may have noticed that when you make a statement to
another person, and he answers "How do you know that that is so?" he
very often means to suggest that you do _not_ know it. And yet, though
he means to suggest that you do not _know_ it, he may not for a moment
wish to suggest that you do not _believe_ it, nor even that you have
not that degree or kind of conviction, which goes beyond mere belief,
and which may be taken to be essential to anything which can properly
be called knowledge. He does not mean to suggest for a moment that you
are saying something which you do not believe to be true, or even that
you are not thoroughly convinced of its truth. What he does mean to
suggest is that what you asserted was not _true_, even though you may
not only have believed it but felt sure that it was true. He suggests
that you don't _know_ it, in the sense that what you believe or feel
sure of is not true.

Now I point this out, not because I myself mean to suggest that we
don't know the existence of other persons, but merely in order to show
that the word "know" is sometimes used in a sense in which it is not
merely equivalent to "believe" or "feel sure of." When the question
"How do you _know_ that?" is asked, the questioner does not merely
mean to ask "how do you come to believe that, or to be convinced of
it?" He sometimes, and I think generally, means to ask a question with
regard to the _truth_, and not with regard to the _existence_ of your
belief. And similarly when I ask the question "How do we know that
other people exist?" I do _not_ mean to ask "How do we come to believe
in or be convinced of their existence?" I do not intend to discuss this
question _at all._ I shall not ask what _suggests_ to us our belief in
the existence of other persons or of an external world; I shall not
ask whether we arrive at it by inference or by "instinct" or in any
other manner, which ever has been or may be suggested: I shall discuss
no question of any kind whatever with regard to its origin, or cause,
or the way in which it arises. These psychological questions are _not_
what I propose to discuss. When I ask the question "How do we know that
other people exist?" I do _not_ mean:

"How does our belief in their existence arise?"

But if I do not mean this what do I mean P I have said that I mean
to ask a question with regard to the _truth_ of that belief; and the
particular question which I mean to ask might be expressed in the
words: _What reason have_ we for our belief in the existence of other
persons? But these are words which themselves need some explanation,
and I will try to give it.

In the first place, then, when I talk of "a reason," I mean _only_
a good reason and _not_ a bad one. A bad reason is, no doubt, a
reason, in one sense of the word; but I mean to use the word "reason"
exclusively in the sense in which it is equivalent to "good reason."
But what, then, is meant by a good reason for a belief? I think I can
express sufficiently accurately what I mean by it in this connection,
as follows:--A good reason for a belief is a proposition which is
true, and which would not be true unless the belief were also true. We
should, I think, commonly say that when a man knows such a proposition,
he has a good reason for his belief; and, when he knows no such
proposition, we should say that he has no reason for it. When he knows
such a proposition, we should say he knows something which is a reason
for thinking his belief to be true--something from which it _could_ be
validly inferred. And if, in answer to the question "How do you know
so and so?" he were to state such a proposition, we should, I think,
feel that he had answered the question which we meant to ask. Suppose,
for instance, in answer to the question "How do you know that?" he were
to say "I saw it in the _Times."_ Then, if we believed that he had
seen it in the _Times_, and also believed that it would not have been
in the _Times_, unless it had been true, we should admit that he had
answered our question. We should no longer doubt that he did _know_
what he asserted, we should no longer doubt that his belief was true.
But if, on the other hand, we believed that he had not seen it in the
_Times_--if, for instance, we had reason to believe that what he saw
was not the statement which he made, but some other statement which
he mistook for it; or if we believed that the kind of statement in
question was one with regard to which there was no presumption that,
being in the _Times_, it would be true: in _either_ of these cases
we should, I think, feel that he had _not_ answered our question. We
should still doubt whether what he had said was true. We should still
doubt whether he _knew_ what he asserted; and since a man cannot tell
you how he _knows_ a thing unless he does know that thing, we should
think that, though he might have told us truly how he _came to believe
it,_ he had certainly not told us how he _knew_ it. But though we
should thus hold that he had _not_ told us _how he knew_ what he had
asserted, and that he had given us no reason for believing it to be
true; we must yet admit that he had given us a reason in a sense--a
_bad_ reason, a reason which was no reason because it had no tendency
to show that what he believed was true; and we might also be perfectly
convinced that he had given us _the reason_ why he believed it--the
proposition by believing which he was induced also to believe his
original assertion.

I mean, then, by my question, "How do we know that other people
exist?" what, I believe, is ordinarily meant, namely, "What reason
have we for believing that they exist?" and by this again I mean, what
I also believe is ordinarily meant, namely, "What proposition do we
believe, which is both true itself and is also such that it would not
be true, unless other people existed?" And I hope it is plain that
this question, thus explained, is quite a different question from the
psychological question, which I said I did _not_ mean to ask--from the
question, "How does our belief in the existence of other people arise?"
My illustration, I hope, has made this plain. For I have pointed out
that we may quite well hold that a man has told us how a belief of
his arises, and even what was the reason which made him adopt that
belief, and yet may have failed to give us any _good reason_ for his
belief--any proposition which is both true itself, and also such that
the truth of his belief follows from it. And, indeed, it is plain that
if any one ever believes what is false, he is believing something for
which there _is_ no good reason, in the sense which I have explained,
and for which, therefore, he cannot possibly have a good reason; and
yet it plainly does not follow that his belief did not arise in anyway
whatever, nor even that he had no reason for it--no bad reason. It
is plain that false beliefs do arise in some way or other--they have
origins and causes: and many people who hold them _have_ bad reasons
for holding them--their belief does arise (by inference or otherwise)
from their belief in some other proposition, which is not itself true,
or else is not a _good_ reason for holding that, which they infer
from it, or which, in some other way, it induces them to believe. I
submit, therefore, that the question, "What good reason have we for
believing in the existence of other people?" is different from the
question, "How does that belief arise?" But when I say this, I must
not be misunderstood; I must not be understood to affirm that the
answer to both questions _may_ not, in a sense, be the same. I fully
admit that the very same fact, which suggests to us the belief in the
existence of other people, _may_ also be a good reason for believing
that they do exist. All that I maintain is that the question whether
it is a good reason for that belief is a different question from the
question whether it suggests that belief: if we assert that a certain
fact _both_ suggests our belief in the existence of other persons and
is _also_ a good reason for holding that belief, we are asserting two
different things and not one only. And hence, when I assert, as I shall
assert, that we _have_ a good reason for our belief in the existence
of other persons, I must not be understood also to assert either that
we infer the existence of other persons from this good reason, or that
our belief in that good reason suggests our belief in the existence
of other persons in any other way. It is plain, I think, that a man
may believe two true propositions, of which the one would not be true,
unless the other were true too, without, in any sense whatever, having
arrived at his belief in the one _from_ his belief in the other; and it
is plain, at all events, that the question whether his belief in the
one _did_ arise from his belief in the other, is a different question
from the question whether the truth of the one belief follows from the
truth of the other.

I hope, then, that I have made it a little clearer what I mean by the
question: "What reason have we for believing in the existence of other
people?" and that what I mean by it is at all events different from
what is meant by the question: "How does our belief in the existence of
other people arise?"

But I am sorry to say that I have not yet reached the end of my
explanations as to what my meaning is. I am afraid that the subject may
seem very tedious. I can assure you that I have found it excessively
tedious to try to make my meaning clear to myself. I have constantly
found that I was confusing one question with another, and that, where
I had thought I had a good reason for some assertion, I had in reality
no good reason. But I may perhaps remind you that this question, "How
do we know so and so?" "What reason have we for believing it?" is one
of which philosophy is full; and one to which the most various answers
have been given. Philosophy largely consists in giving reasons; and the
question what are good reasons for a particular conclusion and what are
bad, is one upon which philosophers have disagreed as much as on any
other question. For one and the same conclusion different philosophers
have given not only different, but incompatible, reasons; and
conversely different philosophers have maintained that one and the same
fact is a reason for incompatible conclusions. We are apt, I think,
sometimes to pay too little attention to this fact. When we have taken,
perhaps, no little pains to assure ourselves that our own reasoning
is correct, and especially when we know that a great many other
philosophers agree with us, we are apt to assume that the arguments
of those philosophers, who have come to a contradictory conclusion,
are scarcely worthy of serious consideration. And yet, I think, there
is scarcely a single reasoned conclusion in philosophy, as to which
we shall not find that some other philosopher, who has, so far as we
know, bestowed equal pains on his reasoning, and with equal ability,
has reached a conclusion incompatible with ours. We may be satisfied
that we are right, and we may, in fact, be so; but it is certain that
_both_ cannot be right: either our opponent or we must have mistaken
bad reasons for good. And this being so, however satisfied we may be
that it is not we who have done so, I think we should at least draw the
conclusion that it is by no means easy to avoid mistaking bad reasons
for good; and that no process, however laborious, which is in the least
likely to help us in avoiding this should be evaded. But it is at least
possible that one source of error lies in mistaking one kind of reason
for another--in supposing that, because there is, in one sense, a
reason for a given conclusion, there is also a reason in another, or
that because there is, in one sense, no reason for a given conclusion,
there is, therefore, no reason at all. I believe myself that this _is_
a very frequent source of error: but it is at least a possible one.
And where, as disagreements show, there certainly is error on one
side or the other, and reason, too, to suppose that the error is not
easy to detect, I think we should spare no pains in investigating any
source, from which it is even possible that the error may arise. For
these reasons I think I am perhaps doing right in trying to explain as
clearly as possible not only what reasons we have for believing in an
external world, but also in what sense I take them to be reasons.

I proceed, then with my explanation. And there is one thing, which, I
think my illustration has shown that I do _not_ mean. I have defined
a reason for a belief as a true proposition, which would not be true
unless the belief itself--what is believed--were also true; and I
have used, as synonymous with this form of words, the expressions: A
reason for a belief is a true proposition from which the truth of the
belief _follows_ from which it _could_ be _validly inferred._ Now these
expressions might suggest the idea that I mean to restrict the word
"reason," to what, in the strictest sense, might be called a _logical_
reason--to propositions from which the belief in question _follows,_
according to the rules of inference accepted by Formal Logic. But I
am _not_ using the words "follow," "validly inferred," in this narrow
sense; I do _not_ mean to restrict the words "reason for a belief"
to propositions from which the laws of Formal Logic state that the
belief could be deduced. The illustration which I gave is inconsistent
with this restricted meaning. I said that the fact that a statement
appeared in the _Times_ might be a good reason for believing that
that statement was true. And I am using the word "reason" in the wide
and popular sense, in which it really might be. If, for instance,
the _Times_ stated that the King was dead, we should think that was
a good reason for believing that the King was dead; we should think
that the _Times_ would not have made such a statement as that unless
the King really were dead. We should, indeed, not think that the
statement in the _Times_ rendered it absolutely _certain_ that the
King was dead. But it _is_ extremely unlikely that the _Times_ would
make a statement of this kind unless it were true; and, in that sense,
the fact of the statement appearing in the _Times_ would render it
_highly probable_--much more likely than not--that the King was dead.
And I wish it to be understood that I am using the words "reason for
a belief" in this extremely wide sense. When I look for a good reason
for our belief in the existence of other people, I shall not reject any
proposition merely on the ground that it only renders their existence
probable--only shows it to be more likely than not that they exist.
Provided that the proposition in question does render it _positively
probable_ that they exist, then, if it also conforms to the conditions
which I am about to mention, I shall call it a "good reason."

But it is not every proposition which renders it probable that
other people exist, which I shall consider to be a good answer to
my question. I have just explained that my meaning is wide in one
direction--in admitting _some_ propositions which render a belief
merely probable; but I have now to explain that it is restricted in
two other directions. I do mean to exclude certain propositions which
do render that belief probable. When I ask: What reason have _we_ for
believing in the existence of other people? a certain ambiguity is
introduced by the use of the plural "we." If each of several different
persons has a reason for believing that he himself exists, then it is
not merely probable, but certain, according to the rules of Formal
Logic, that, in a sense, _they_ "have a reason for believing" that
several people exist; each has a reason for believing that he himself
exists; and, therefore, all of them, taken together, have reasons for
supposing that several persons exist. If, therefore, I were asking
the question: What reason have _we_ for believing in the existence
of other persons? in this sense, it would follow that if each of us
has a reason for believing in his own existence, these reasons, taken
together, would be a reason for believing in the existence of all of
us. But I am not asking the question in this sense: it is plain that
this is not its natural sense. What I do mean to ask is: Does _each
single one_ of us know any proposition, which is a reason for believing
that _others_ exist? I am using "we," that is to say, in the sense
of "each of us." But again I do mean _each_ of us: I am not merely
asking whether some _one_ man knows a proposition which is a reason
for believing that other men exist. It would be possible that some
one man, or some few men, should know such a proposition, and yet the
rest know no such proposition. But I am not asking whether this is the
case. I am asking whether among propositions of the kind which (as we
commonly suppose) all or almost all men know, there is any which is a
reason for supposing that other men exist. And in asking this question
I am not begging the question by supposing that all men do exist. My
question might, I think, be put quite accurately as follows. There are
certain kinds of belief which, as we commonly suppose, all or almost
all men share. I describe this kind of belief as "our" beliefs, simply
as an easy way of pointing out which kind of belief I mean, but without
assuming that all men do share them. And I then ask: Supposing a
single man to have beliefs of this kind, which among them would be a
good reason for supposing that other men existed having like beliefs?

This, then, is the first restriction which I put upon the meaning
of my question. And it is, I think, a restriction which, in their
natural meaning, the words suggest. When we ask: What reason have
we for believing that other people exist? we naturally understand
that question to be equivalent to: What reason has _each_ of us for
that belief? And this question again is naturally equivalent to the
question: Which among the propositions that a single man believes, but
which are of the kind which (rightly or wrongly) we assume all men to
believe, are such that they would not be true unless some other person
than that man existed? But there is another restriction which, I think,
the words of my question also naturally suggest. If we were to ask
anyone the question: How do you know that you did see that statement
in the _Times_? and he were to answer "Because I did see it in the
_Times_ and in the _Standard_ too," we should not think that he had
given us a _reason_ for the belief that he saw it in the _Times._ We
should not think his answer a _reason_, because it asserts the very
thing for which we require a reason. And similarly when I ask: How
do we know that any thing or person exists, other than ourselves and
what we directly perceive? What reason have we for believing this? I
must naturally be understood to mean: What proposition, _other_ than
one which itself asserts or presupposes the existence of something
beyond ourselves and our own perceptions, is a reason for supposing
that such a thing exists? And this restriction obviously excludes an
immense number of propositions of a kind which all of us do believe. We
all of us believe an immense number of different propositions about
the existence of things which we do not directly perceive, and many
of these propositions are, in my sense, good reasons for believing in
the existence of still other things. The belief in the existence of a
statement in the _Times,_ when we have not seen that statement, may,
as I implied, be a good reason for believing that someone is dead. But
no such proposition can be a good answer to my question, because it
asserts the very kind of thing for which I require a reason: it asserts
the existence of something other than myself and what I directly
perceive. When I am asking: What reason have I for believing in the
existence of anything but myself, my own perceptions, and what I do
directly perceive? you would naturally understand me to mean: What
reason, _other than_ the existence of such a thing, have I for this
belief?

Each of us, then, we commonly assume, believes some true propositions,
which do not themselves assert the existence of anything other than
himself, his own perceptions, or what he directly perceives. Each of
us, for instance, believes that he himself has and has had certain
particular perceptions: and these propositions are propositions of
the kind I mean--propositions which do not themselves assert the
existence of anything _other than_ himself, his own perceptions,
and what he directly perceives: they are, I think, by no means the
only propositions of this kind, which most of us believe: but they
_are_ propositions of this kind. But, as I say, I am not assuming
that each of us--each of several different people--does believe
propositions of this kind. All that I assume is that at least one man
does believe some such propositions. And then I ask: Which among those
true propositions, which one man believes, are such that they would
probably not be true, unless some other man existed and had certain
particular perceptions? Which among them are such that it _follows_
(in the wide sense, which I have explained) from their truth, that it
is more likely than not that some other man has perceptions? This is
the meaning of my question, so far as I have hitherto explained it:
and I hope this meaning is quite clear. It is in this sense that I am
asking: What reason have we for believing that other people exist? How
do we know that they exist? This, indeed, is not _all_ that I mean by
that question: there is one other point--the most important one--which
remains to be explained. But this is _part_ of what I mean to ask; and
before I go on to explain what else I mean, I wish first to stop and
enquire what is the answer to this part of my question. What is the
answer to the question: Which among the true propositions, of a kind
which (as we commonly assume) each of us believes, and which do not
themselves assert the existence of anything other than that person
himself, his own perceptions, or what he directly perceives, are such
that they would probably not be true unless some other person existed,
who had perceptions in some respects similar to his own?

Now to this question the answer is very obvious. It is very obvious
that in this sense we have reasons for believing in the existence of
other persons, and also what some of those reasons are. But I wish
to make it quite plain that this is so: that in this sense one man
_has_ a reason for believing that another has certain perceptions. All
that I am asking you to grant, is, you see, that some of you would
not be having just those perceptions which you now have, unless I,
as I read this paper, were perceiving more or less black marks on a
more or less white ground; or that I on the other hand, should not
be having just those perceptions which I now have, unless some other
persons than myself were hearing the sounds of my voice. And I am
not asking you even to grant that this is certain--only that it is
positively probable--more likely than not. Surely it is very obvious
that this proposition is true. But I wish to make it quite clear
what would be the consequences of denying that any such propositions
are true--propositions which assert that the existence of certain
perceptions in one man are a reason for believing in the existence of
certain perceptions in another man--which assert that one man would
probably not have had just those perceptions which he did have, unless
some other man had had certain particular perceptions. It is plain, I
think, that, unless some such propositions are true, we have no more
reason for supposing that Alexander the Great ever saw an elephant,
than for supposing that Sindbad the Sailor saw a Roc; we have no more
reason for supposing that anybody saw Julius Caesar murdered in the
Senate House at Rome, than for supposing that somebody saw him carried
up to Heaven in a fiery chariot. It is plain, I think, that if we have
any reason at all for supposing that in all probability Alexander the
Great did see an elephant, and that in all probability no such person
as Sindbad the Sailor ever saw a Roc, part of that reason consists
in the assumption that some other person would probably not have had
just those perceptions which he did have, unless Alexander the Great
had seen an elephant, and unless Sindbad the Sailor had not seen a
Roc. And most philosophers, I think, are willing to admit that we have
some reason, in some sense or other, for such propositions as these.
They are willing to admit not only that some persons probably did see
Julius Caesar murdered in the Senate House; but also that some persons,
other than those who saw it, had and have _some reason_ for supposing
that some one else probably saw it. Some sceptical philosophers might,
indeed, deny both propositions; and to refute their views, I admit,
other arguments are needed than any which I shall bring forward in this
paper. But most philosophers will, I think, admit not only that facts,
for which there is, as we say, good historical evidence, are probably
true; but also that what we call good historical evidence really is
in some sense a good reason for thinking them true. Accordingly I am
going to assume that many propositions of the following kind are true.
Propositions, namely, which assert that one man would probably not
have certain perceptions which he does have, unless some other man had
certain particular perceptions. That some of you, for instance, would
probably not be having precisely the perceptions which you are having,
unless I were having the perception of more or less black marks on a
more or less white ground. And, in this sense, I say, we certainly have
reasons for supposing that other people have perceptions similar, in
some respects, to those which we sometimes have.

But when I said I was going to ask the question: What reason have we
for supposing that other people exist? you will certainly not have
thought that I merely meant to ask the question which I have just
answered. My words will have suggested to you something much more
important than merely this. When, for instance, I said that to the
question "How do you know that?" the answer "I saw it in the _Times"_
would be a satisfactory answer, you may have felt, as I felt, that it
would not in all circumstances be regarded as such. The person who
asked the question might, in some cases, fairly reply: "That is no
answer: how do you know that, because you saw a thing in the _Times_,
it is therefore true?" In other words he might ask fora _reason_ for
supposing that the occurrence of a particular statement in the _Times_
was a reason for supposing that statement true. And this is a question
to which we all believe that there may be an answer. We believe that,
with some kinds of statements which the _Times_ makes--some kinds of
statements with regard to Fiscal Policy for example--the fact that
the _Times_ makes them is no reason for supposing them to be true:
whereas with regard to other kinds of statements, which it makes, such
a statement, for instance, as that the King was dead, the fact that it
makes them _is_ a reason for supposing them true. We believe that there
are some kinds of statements, which it is very unlikely the _Times_
would make, unless they were true; and others which it is not at all
unlikely that the _Times_ might make, although they were not true. And
we believe that a reason might be given for distinguishing, in this
way, between the two different kinds of statement: for thinking that,
in some cases (on points, for instance, which, as we should say, are
not simple questions of fact) the _Times_ is fallible, whereas in other
cases, it is, though not absolutely infallible, very unlikely to state
what is not true.

Now it is precisely in this further sense that I wish to consider: what
reason have we for believing that certain particular things, other
than ourselves, our own perceptions, and what we directly perceive,
are real? I have asserted that I do have certain perceptions, which it
is very unlikely I should have, unless some other person had certain
particular perceptions; that, for instance, it is very unlikely I
should be having precisely those perceptions which I am now having
unless someone else were hearing the sound of my voice. And I now
wish to ask: What reason have I for supposing that this is unlikely?
What reason has any of us for supposing that any such proposition is
true? And I mean by "having a reason" precisely what I formerly meant.
I mean: What other proposition do I know, which would not be true,
unless my perception were connected with someone else's perception, in
the manner in which I asserted them to be connected? Here again I am
asking for _a good reason_; and am not asking a psychological question
with regard to origin. Here again I am not asking for a reason, in the
strict sense of Formal Logic; I am merely asking for a proposition
which would probably not be true, unless what I asserted were true.
Here again I am asking for some proposition of a kind which _each_ of
us believes; I am asking: What reason has _each_ of us for believing
that some of his perceptions are connected with particular perceptions
of other people in the manner I asserted?--for believing that he would
not have certain perceptions that he does have, unless some other
person had certain particular perceptions? And here again I am asking
for a _reason_--I am asking for some proposition _other_ than one
which itself asserts: When one man has a perception of such and such a
particular kind, it _is_ probable that another man has a perception or
thought of this or that other kind.

But what kind of reason can be given for believing a proposition of
this sort? For believing a proposition which asserts that, since one
particular thing exists, it is probable that another particular thing
also exists? One thing I think is plain, namely that we can have no
good reason for believing such a proposition, unless we have good
reason for believing some _generalisation._ It is commonly believed,
for instance, that certain so-called flint arrow-heads, which have been
discovered, were probably made by prehistoric men; and I think it is
plain that we have no reason for believing this unless we have reason
to suppose that objects which resemble these in certain particular
respects are _generally_ made by men--are _more often_ made by men
than by any other agency. Unless certain particular characteristics
which those arrow-heads have were characteristics which belonged at
least more frequently to articles of human manufacture than to any
articles not made by men, it would surely be just as likely as not
that these arrowheads were _not_ made by men--that they were, in fact
not arrow-heads. That is to say, unless we have reason to assert a
_generalisation_--the generalisation that objects of a certain kind
are _generally_ made by men, we have no reason to suppose that these
particular objects, which are of the kind in question, _were_ made
by men. And the same, so far as I can see, is true universally. If
we ever have any reason for asserting that, since one particular
thing exists, another probably exists or existed or will exist also
part of our reason, at least, must consist in reasons for asserting
some generalisation--for asserting that the existence of things of
a particular kind is, more often than not, accompanied or preceded
or followed by the existence of things of another particular kind.
It is, I think, sometimes assumed that an alternative to this theory
may be found in the theory that the existence of one kind of thing
"intrinsically points to," or is "intrinsically a sign or symbol of"
the existence of another thing. It is suggested that when a thing
which thus points to the existence of another thing exists, then it is
at least probable that the thing "pointed to" exists also. But this
theory, I think, offers no real alternative. For, in the first place,
when we say that the existence of one thing A is a "sign of" or "points
to" the existence of another thing B, we very commonly actually mean to
say that when a thing like A exists, a thing like B _generally_ exists
too. We may, no doubt, mean something else _too_; but this we do mean.
We say, for instance, that certain particular words, which we hear or
read, are a "sign" that somebody has thought of the particular things
which we call the meaning of those words. But we should certainly
hesitate to admit that the hearing or reading of certain words could be
called a "sign" of the existence of certain thoughts, unless it were
true that when those words are heard or read, the thoughts in question
_generally_ have existed. If when those words were heard or read, the
thoughts had generally _not_ existed, we should say that, in one sense
of the word at all events, the hearing of the words was _not_ a sign of
the existence of the thoughts. In this sense, therefore, to say that
the existence of A "points to" or "is a sign of" the existence of B is
actually to say that when A exists, B _generally_ exists also. But,
no doubt, the words "points to" "is a sign of" may be used in some
other sense: they may, for instance, mean only that the existence of A
_suggests_ in some way the belief that B exists. And in such a case we
certainly might know that the existence of A pointed to the existence
of B, without knowing that when A existed B generally existed also.
Let us suppose, then, that in some such sense A does "point to" the
existence of B; can this fact give us a reason for supposing it even
probable that B existed. Certainly it can, _provided_ it is true that
when A _does_ point to the existence of B, B _generally_ exists. But
surely it can do so, only on this condition. If when A _points_ to
the existence of B, B, nevertheless, does _not_ generally exist, then
surely the fact that A points to the existence of B can constitute no
probability that B does not exist: on the contrary it will then be
probable that, even though A "points to" the existence of B, B does
_not_ exist. We have, in fact, only substituted the generalisation that
A's _pointing to_ B is generally accompanied by the existence of B, for
the generalisation that A's _existence_ is generally accompanied by the
existence of B. If we are to have any reason for asserting that, when
A _points to_ or is a sign of the existence of B, B probably exists, we
must still have a reason for some generalisation--for a generalisation
which asserts that when one thing points to the existence of another,
that other _generally_ exists.

It is plain, then, I think, that if we are to find a reason for the
assertion that some particular perception of mine would probably not
exist, unless someone else were having or had had a perception of a
kind which I can name, we must find a reason for _some_ generalisation.
And it is also plain, I think, that in many cases of this kind the
generalisation must consist in an assertion that when one man has a
certain kind of perception, some other man generally has had some
other perception or belief. We assume, for instance, that when we hear
or read certain words, somebody besides ourselves has thought the
thoughts, which constitute the meaning of those words; and it is plain,
I think, that we have no reason for this assumption except one which
is also a reason for the assumption that when certain words are heard
or read, somebody generally has had certain thoughts. And my enquiry,
therefore, at least includes the enquiry: What reasons have we for such
generalisations as these? for generalisations which assert a connection
between the existence of a certain kind of perception in one man, and
that of a certain kind of perception or belief in another man?

And to this question, I think, but one answer can be given. If we
have any reason for such generalisations at all, some reason must
be given, in one way or another, by observation--by observation,
understood in the wide sense in which it includes "experiment." No
philosopher, I think, has ever failed to assume that observation does
give a reason for _some_ generalisations--for some propositions
which assert that when one kind of thing exists, another generally
exists or has existed in a certain relation to it. Even those who,
like Hume, imply that observation cannot give a _reason_ for anything,
yet constantly appeal to observation in support of generalisations of
their own. And even those who hold that observation can give no reason
for any generalisation about the relation of one man's perceptions to
another's, yet hold that it _can_ give a reason for generalisations
about the relation of some to others among a man's own perceptions.
It is, indeed, by no means agreed _how_ observation can give a reason
for any generalisation. Nobody knows what reason we have, if we have
any, for supposing that it can. But _that_ it can, everyone, I think,
assumes. I think, therefore, most philosophers will agree, that if we
can find any reason at all for generalisations of the kind in which
I am interested, a reason for _some_ of them at all events must be
found in observation. And what I propose to ask is: What reason can be
found in observation for even a single proposition of the kind I have
described? for a proposition which asserts that when one man has one
kind of perception, another man generally has or has had another.

But, when it is said that observation gives us a reason for
generalisations, two things may be meant neither of which I mean. In
the first place, we popularly use "observation" in a sense in which
we can be said to _observe_ the perceptions, feelings and thoughts
of other people: in which, therefore, we can be said to observe the
very things with regard to which I am asking what reason we have for
believing in their existence. But it is universally[1] agreed that
there is a sense in which no man can observe the perceptions, feelings
or thoughts of any other man. And it is to this strict sense that
I propose to confine the word. I shall use it in a sense, in which
we can certainly be said to observe nothing but ourselves, our own
perceptions, thoughts and feelings, and what we directly perceive. And
in the second place, it may be said that observations made by another
person may give _me_ a reason for believing some generalisation. And
it is certainly the case that for many of the generalisations in which
we all believe, if we have a reason in observation at all, it is not
in _our own_ observation that we have it: part of our reason, at all
events, lies in things which _other_ people have observed but which we
ourselves have not observed. But in asking this particular question,
I am not asking for reasons of this sort. The very question that I am
asking is: What reason has any one of us for supposing that any other
person whatever has ever made any observations? And just as, in the
first meaning which I gave to this question, it meant: What thing,
that any single man observes is such that it would probably not have
existed, unless some other man had made a particular observation?
So now I am asking: Which among the things, which _one single man
observes_, are such that they would probably not have existed, unless
it were true that some of them generally stood in certain relations to
observations of some other person? I am asking: Which among _my own_
observations give me a reason for supposing that some of them are of
a kind which are generally preceded or accompanied by observations
of other people? Which, for instance, among my own observations give
a good reason for the generalisation that when I hear certain words,
somebody else has generally had certain particular thoughts, or that
whenever anyone hears certain words, somebody else has generally had
the thoughts which constitute what we call the meaning of those words?
I am asking: Which among the vast series of observations, which any
one individual makes during his lifetime, give a good reason for
any generalisation _whatever_ of this kind--a generalisation which
asserts that some of them are generally preceded by certain thoughts,
perceptions or feelings in other persons? I quite admit that there
are some generalisations of this kind for which the observations of
_some_ particular men will _not_ give a reason. All that I ask is:
Is there even _one_ generalisation of this kind, for which the kind
of observations, which (as we commonly assume) each man, or nearly
every man does make, do give a reason? Among observations of the kind
which (as we commonly assume) are common to you and to me, do yours,
by themselves, give any reason for even _one_ such generalisation?
And do mine, by themselves, give any reason for even _one_ such
generalisation? And if they do, which, among these observations, is it
which do so?

My question is, then: What reason do my own observations give me, for
supposing that any perception whatever, which I have, would probably
not occur, unless some other person had a certain kind of perception?
What reason do my own observations give me for supposing, for instance,
that I should not be perceiving what I do now perceive, unless
someone were hearing the sound of my voice? What reason do your own
observations give you for supposing that you would not be perceiving
just what you are perceiving, unless I were perceiving more or less
black marks on a more or less white ground? The question does, I
think, appear to be a reasonable one; and most philosophers, I think,
have assumed that there is an answer to it. Yet it may be said that
there is no answer to it: that my own observations give me no reason
whatever for any single proposition of this kind. There are certain
philosophers (even apart from thorough sceptics, with whom, as I have
said, I am not now arguing) who have denied that they do. There are
certain philosophers who hold that nothing which any single one of
us observes or can observe, gives the slightest reason for supposing
that any of his own perceptions are generally connected with certain
perceptions in other people. There are philosophers who hold that the
only generalisations for which our own observations do give any warrant
are generalisations concerning the manner in which our own perceptions,
thoughts and feelings do and probably will succeed one another; and who
conclude that, this being so, we have no reason whatever for believing
in the existence of any other people. And these philosophers are, I
think, right in drawing this conclusion from this premiss. It does
not, indeed, follow from their premiss that we have not a reason in
the sense which I first explained, and in which, I insisted, it must
be admitted that we have a reason. It does not follow that some of our
perceptions _are_ not such as would probably not exist, unless some
other person had certain perceptions. But, as I have urged, when we
say that we have a reason for asserting the existence of something not
perceived, we commonly mean something more than this. We mean not only
that, since what we perceive does exist, the unperceived thing probably
exists too; we mean also that we have some reason for asserting this
connection between the perceived and the unperceived. And holding, as
we do, that no reason can be given for asserting such a connection,
except observation, we should say that, if observation gives no reason
for asserting it, we have _no_ reason for asserting it; and having no
reason for asserting this connection between the perceived and the
unperceived, we should say that we have none either for asserting the
even probable existence of the unperceived. This, I think, is what
we commonly mean by saying that we have no reason to believe in the
existence of a particular thing which we do not perceive. And hence,
I think, those philosophers who hold that our own observations give
us no reason whatever for any generalisation whatever concerning
the connection of any of them with those of other people, are quite
right in concluding that we have no reason to assert that any other
person ever did have any particular thought or perception whatever. I
think that the words of this conclusion, understood in their natural
meaning, express precisely what the premiss asserts. We need not,
indeed, conclude, as many of these philosophers are inclined to do,
that, because we have no reason for believing in the existence of other
people, it is therefore highly doubtful whether they do exist. The
philosophers who advocate this opinion commonly refute themselves by
assigning the existence of other people as part of their reason for
believing that it is very doubtful whether any other people exist. That
for which we have no reason may, nevertheless, be certainly true. And,
indeed, one of the philosophers who hold most clearly and expressly
that we do know not only the existence of other people but also that
of material objects, is also one of those who deny most emphatically
that our own observations can give any reason for believing either
in the one or in the other. I refer to Thomas Reid. Reid, indeed,
allows himself to use not only the word "observe," but even the word
"perceive," in that wide sense in which it might be said that we
observe or perceive the thoughts and feelings of others: and I think
that the fact that he uses the words in this sense, has misled him into
thinking that his view is more plausible and more in accordance with
Common Sense than it really is: by using the words in this sense he is
able to plead that "observation" really does give a reason for some of
those generalisations, for which Common Sense holds that "observation"
(in a narrower sense) does give a reason. But with regard to what we
observe or perceive, in the strict sense to which 1 am confining those
words, he asserts quite explicitly that it gives us no reason either
for believing in the existence of material objects or for believing
in the existence of other minds. Berkeley, he says, has proved
incontrovertibly that it gives us no reason for the one, and Hume that
it gives us no reason for the other.

Now these philosophers may be right in holding this. It may, perhaps,
be true that, in this sense, my own observations give me no reason
whatever for believing that any other person ever has or will perceive
anything like or unlike what I perceive. But I think it is desirable
we should realise how paradoxical are the consequences which must be
admitted, if this is true. It must then be admitted that the very
large part of our knowledge, which we suppose to have some basis in
experience, is by no means based upon experience, in the sense, and
to the extent, which we suppose. We do for instance, commonly suppose
that there is some basis in experience for the assertion that some
people, whom we call Germans, use one set of words to express much the
same meaning which we express by using a different set of words. But,
if this view be correct, we must admit that no person's experience
gives him any reason whatever for supposing that, when he hears certain
words, any one else has ever heard or thought of the same words, or
meant anything by them. The view admits, indeed, that I do know that
when I hear certain words, somebody else has generally had thoughts
more or less similar to those which I suppose him to have had: but it
denies that my own observations could ever give me the least reason
for supposing that this is so. It admits that my own observations may
give me reason for supposing that _if_ anyone has ever had perceptions
like mine in some respects, he will also have had other perceptions
like others of mine: but it denies that they give me any reason for
supposing that any one else has had a perception like one of mine. It
admits that my own observations may give me reason for supposing that
certain perceptions and thoughts in _one_ person (_if_ they exist) will
be followed or preceded by certain other perceptions and thoughts in
that person: but it denies that they give me any reason whatever for
_any_ similar generalisation concerning the connection of a certain
kind of perception in one person with a certain kind of perception in
another. It admits that I should not have certain perceptions, which
I do have, unless someone else had had certain other perceptions; but
it denies that my own observations can give me any reason for saying
so--for saying that I should not have had this perception, unless
someone else had had that. No observations of mine, it holds, can ever
render it probable that such a generalisation is true; no observation
of mine can ever confirm or verify such a generalisation. If we are to
say that any such generalisation whatever is based upon observation,
we can only mean, what Reid means, that it is based on a series of
assumptions. When I observe this particular thing, I assume that _that_
particular thing, which I do not observe, exists; when I observe
another particular thing, I again assume that a second particular
thing, which I do not observe, exists; when I observe a third
particular thing, I again assume that a third particular thing, which I
do not observe, exists. These assumed facts--the assumed fact that one
observation of mine is accompanied by the existence of one particular
kind of thing, and that another observation of mine is accompanied by
the existence of a different particular kind of thing, will then give
me a reason for different generalisations concerning the connection of
different perceptions of mine with different external objects--objects
which I do not perceive. But (it is maintained) nothing but a mass of
such assumptions will give me a reason for any such generalisation.

Now I think it must be admitted that there is something paradoxical
in such a view. I think it may be admitted that, in holding it, the
philosopher of Common Sense departs from Common Sense at least as far
in one direction as his opponents had done in another. But I think
that there is some excuse for those who hold it: I think that, in one
respect, they are more in the right than those who do not hold it--than
those who hold that my own observations do give me a reason for
believing in the existence of other people. For those who hold that my
observations do give me a reason, have, I believe, universally supposed
that the reason lies in a part of my observations, in which no such
reason is to be found. This is why I have chosen to ask the question:
_What_ reason do my observations give me for believing that any other
person has any particular perceptions or beliefs? I wish to consider
_which_ among the things which I observe will give such a reason. For
this is a question to which no answer, that I have ever seen, appears
to me to be correct. Those who have asked it have, so far as I know,
answered it _either_ by denying that my observations give me any reason
_or_ by pointing to a part of my observations, which, as it seems to
me, really do give none. Those who deny are, it seems to me, right in
holding that the reason given by those who affirm is no reason. And
their correct opinion on this point will, I think, partly serve to
explain their denial. They have supposed that if our observations give
us any reason at all for asserting the existence of other people, that
reason must lie where it has been supposed to lie by those who hold
that they do give a reason. And then, finding that this assigned reason
is no reason, they have assumed that there is no other.

I am proposing then to ask: Which among the observations, which I make,
and which (as we commonly suppose) are similar in kind to those which
all or almost all men make, will give a reason for supposing that the
existence of any of them is generally connected with the existence of
certain kinds of perception or belief in other people? And in order to
answer this question, it is obvious we must first consider two others.
We must consider, in the first place: Of what nature must observations
be, if they are to give a reason for any generalisation asserting that
the existence of one kind of thing is generally connected with that of
another? And we must consider in the second place: What kinds of things
do we observe?

Now to the first of these questions I am not going to attempt to give
a complete answer. The question concerning the rules of Inductive
Logic, which is the question at issue, is an immensely difficult and
intricate question. And I am not going to attempt to say, what kind of
observations are _sufficient_ to justify a generalisation. But it is
comparatively easy to point out that a certain kind of observations are
_necessary_ to justify a generalisation: and this is all that I propose
to do. I wish to point out certain conditions which observations must
satisfy, if they are to justify a generalisation; without in any way
implying that all observations which do satisfy these conditions,
_will_ justify a generalisation. The conditions, I shall mention, are
ones which are certainly _not_ sufficient to justify a generalisation;
but they are, I think, conditions, without which no generalisation can
be justified. If a particular kind of observations do _not_ satisfy
these conditions, we can say with certainty that those observations
give us _no_ reason for believing in the existence of other people;
though, with regard to observations which _do_ satisfy them, we shall
only be able to say that they _may_ give a reason.

What conditions, then, must observations satisfy, if they are to
justify a generalisation? Let us suppose that the generalisation to
be justified is one which asserts that the existence of a kind of
object, which we will call A, is generally preceded, accompanied, or
followed by the existence of a kind of object, which we call B. A, for
instance, might be the hearing of a certain word by one person, and B
the thought of that which we call the meaning of the word, in another
person; and the generalisation to be justified might be that when one
person hears a word, not spoken by himself, someone else has generally
thought of the meaning of that word. What must I have observed, if the
generalisation that the existence of A is generally preceded by the
existence of B, is to be justified by my observations? One first point,
I think, is plain. I must have observed both some object, which is in
some respects like A, and which I will call _α_, and also some object
in some respects like B which I will call _β_: I must have observed
both _α_ and _β_, and also I must have observed _β_ preceding _α._
This, at least, I must have observed. But I do not pretend to say _how_
like _α_ and _β_ must be to A and B; nor do I pretend to say how often
I must have observed _β_ preceding _α_, although it is generally held
that I must have observed this more than once. These are questions,
which would have to be discussed if we were trying to discover what
observations were _sufficient_ to justify the generalisation that the
existence of A is generally preceded by that of B. But I am only
trying to lay down the minimum which is _necessary_ to justify this
generalisation; and therefore I am content to say that we must have
observed something more or less like B preceding something more or less
like A, at least once.

But there is yet another minimum condition. If my observation of _β_
preceding _α_ is to justify the generalisation that the _existence_ of
A is generally preceded by the _existence_ of B, it is plain, I think,
that both the _β_ and the _α,_ which I observed, must have _existed_
or been _real_; and that also the existence of _β_ must _really_ have
preceded that of _α_. It is plain that if, when I observed _α_ and
_β_, _α_ existed but _β_ did not, this observation could give me no
reason to suppose that on another occasion when A existed, _β_ _would_
exist. Or again, if, when I observed _β_ preceding _α_, both _β_ and
_α_ existed, but the existence of _β_ did not _really_ precede that of
α, but, on the contrary, followed it, this observation could certainly
give me no reason to suppose that, in general, the existence of A was
_preceded_ by the existence of B. Indeed this condition that what is
observed must have been _real_ might be said to be included in the very
meaning of the word "observation." We should, in this connection, say
that we had _not_ observed _β_ preceding _α,_ unless _β_ and _α_ were
both real, and _β_ had really preceded _α._ If I say "I have _observed_
that, on one occasion, my hearing of the word 'moon' was followed by
my imagining a luminous silvery disc," I commonly mean to include in
my statement the assertion that I did, on that occasion, really hear
the word "moon," and really did have a visual image of a luminous
disc, and that my perception was really followed by my imagination.
If it were proved to me that this had not really happened, I should
admit that I had not really observed it. But though this condition
that, if observation is to give reason for a generalisation, what is
observed must be real, may thus be said to be implied in the very
word "observation," it was necessary for me to mention the condition
explicitly. It was necessary, because, as I shall presently show,
we do and must also use the word "observation" in a sense in which
the assertion "I observe A" by no means includes the assertion "A
exists"--in a sense in which it _may_ be true that though I did observe
A, yet A did _not_ exist.

But there is also, I think, a third necessary condition which is very
apt to be overlooked. It may, perhaps, be allowed that observation
gives some reason for the proposition that hens' eggs are generally
laid by hens. I do not mean to say that any one man's observation can
give a reason for this proposition: I do not assume either that it can
or that it cannot. Nor do I mean to make any assumption as to what
must be meant by the words "hens" and "eggs," if this proposition is
to be true. I am quite willing to allow for the moment that if it is
true at all, we must understand by "hens" and "eggs," objects very
unlike that which we directly observe, when we see a hen in a yard, or
an egg on the breakfast-table. I am willing to allow the possibility
that, as some Idealists would say, the proposition "Hens lay eggs" is
false, unless we mean by it: A certain kind of collection of spirits or
monads sometimes has a certain intelligible relation to another kind of
collection of spirits or monads. I am willing to allow the possibility
that, as Reid and some scientists would say, the proposition "Hens
lay eggs" is false, if we mean by it anything more than that: Certain
configurations of invisible material particles sometimes have a certain
spatio-temporal relation to another kind of configuration of invisible
material particles. Or again I am willing to allow, with certain
other philosophers, that we must, if it is to be true, interpret
this proposition as meaning that certain kinds of sensations have to
certain other kinds a relation which may be expressed by saying that
the one kind of sensations "lay" the other kind. Or again, as other
philosophers say, the proposition "Hens lay eggs" may possibly mean:
Certain sensations of mine _would_, under certain conditions, have to
certain other sensations of mine a relation which may be expressed by
saying that the one set would "lay" the other set. But whatever the
proposition "Hens' eggs are generally laid by hens" may _mean_, most
philosophers would, I think, allow that, in some sense or other, this
proposition was true. And they would also I think allow that we have
_some_ reason for it; and that _part_ of this reason at all events lies
in observation: they would allow that we should have no reason for it
unless certain things had been observed, which have been observed.
Few, I think, would say that the existence of an egg "intrinsically
points" to that of a hen, in such a sense that, even if we had had no
experience of any kind concerning the manner in which objects like eggs
are connected with animals like hens, the mere inspection of an egg
would justify the assertion: A hen has probably existed.

I assume, then, that objects having all the characteristics which
hens' eggs have (whatever these may be) are generally laid by hens
(whatever hens may be); and I assume that, if we have any reason
for this generalisation at all, observation gives us some reason
for it. But now, let us suppose that the only observations we had
made were those which we should commonly describe by saying that we
had seen a hen laying an egg. I do not say that any number of such
observations, by themselves, would be _sufficient_ to justify our
generalisation: I think it is plain that they would not. But let us
suppose, for the moment, that we had observed nothing else which bore