In the following pages I have confined myself in the main to those
problems of philosophy in regard to which I thought it possible to say
something positive and constructive, since merely negative criticism
seemed out of place. For this reason, theory of knowledge occupies a
larger space than metaphysics in the present volume, and some topics
much discussed by philosophers are treated very briefly, if at all.
I have derived valuable assistance from unpublished writings of
G. E. Moore and J. M. Keynes: from the former, as regards the
relations of sense-data to physical objects, and from the latter as
regards probability and induction. I have also profited greatly by
the criticisms and suggestions of Professor Gilbert Murray.
1912
CHAPTER I
APPEARANCE AND REALITY
Is there any knowledge in the world which is so certain that no
reasonable man could doubt it? This question, which at first sight
might not seem difficult, is really one of the most difficult that can
be asked. When we have realized the obstacles in the way of a
straightforward and confident answer, we shall be well launched on the
study of philosophy--for philosophy is merely the attempt to answer
such ultimate questions, not carelessly and dogmatically, as we do in
ordinary life and even in the sciences, but critically, after
exploring all that makes such questions puzzling, and after realizing
all the vagueness and confusion that underlie our ordinary ideas.
In daily life, we assume as certain many things which, on a closer
scrutiny, are found to be so full of apparent contradictions that only
a great amount of thought enables us to know what it is that we really
may believe. In the search for certainty, it is natural to begin with
our present experiences, and in some sense, no doubt, knowledge is to
be derived from them. But any statement as to what it is that our
immediate experiences make us know is very likely to be wrong. It
seems to me that I am now sitting in a chair, at a table of a certain
shape, on which I see sheets of paper with writing or print. By
turning my head I see out of the window buildings and clouds and the
sun. I believe that the sun is about ninety-three million miles from
the earth; that it is a hot globe many times bigger than the earth;
that, owing to the earth's rotation, it rises every morning, and will
continue to do so for an indefinite time in the future. I believe
that, if any other normal person comes into my room, he will see the
same chairs and tables and books and papers as I see, and that the
table which I see is the same as the table which I feel pressing
against my arm. All this seems to be so evident as to be hardly worth
stating, except in answer to a man who doubts whether I know anything.
Yet all this may be reasonably doubted, and all of it requires much
careful discussion before we can be sure that we have stated it in a
form that is wholly true.
To make our difficulties plain, let us concentrate attention on the
table. To the eye it is oblong, brown and shiny, to the touch it is
smooth and cool and hard; when I tap it, it gives out a wooden sound.
Any one else who sees and feels and hears the table will agree with
this description, so that it might seem as if no difficulty would
arise; but as soon as we try to be more precise our troubles begin.
Although I believe that the table is 'really' of the same colour all
over, the parts that reflect the light look much brighter than the
other parts, and some parts look white because of reflected light. I
know that, if I move, the parts that reflect the light will be
different, so that the apparent distribution of colours on the table
will change. It follows that if several people are looking at the
table at the same moment, no two of them will see exactly the same
distribution of colours, because no two can see it from exactly the
same point of view, and any change in the point of view makes some
change in the way the light is reflected.
For most practical purposes these differences are unimportant, but to
the painter they are all-important: the painter has to unlearn the
habit of thinking that things seem to have the colour which common
sense says they 'really' have, and to learn the habit of seeing things
as they appear. Here we have already the beginning of one of the
distinctions that cause most trouble in philosophy--the distinction
between 'appearance' and 'reality', between what things seem to be and
what they are. The painter wants to know what things seem to be, the
practical man and the philosopher want to know what they are; but the
philosopher's wish to know this is stronger than the practical man's,
and is more troubled by knowledge as to the difficulties of answering
the question.
To return to the table. It is evident from what we have found, that
there is no colour which pre-eminently appears to be _the_ colour of
the table, or even of any one particular part of the table--it appears
to be of different colours from different points of view, and there is
no reason for regarding some of these as more really its colour than
others. And we know that even from a given point of view the colour
will seem different by artificial light, or to a colour-blind man, or
to a man wearing blue spectacles, while in the dark there will be no
colour at all, though to touch and hearing the table will be
unchanged. This colour is not something which is inherent in the
table, but something depending upon the table and the spectator and
the way the light falls on the table. When, in ordinary life, we
speak of _the_ colour of the table, we only mean the sort of colour
which it will seem to have to a normal spectator from an ordinary
point of view under usual conditions of light. But the other colours
which appear under other conditions have just as good a right to be
considered real; and therefore, to avoid favouritism, we are compelled
to deny that, in itself, the table has any one particular colour.
The same thing applies to the texture. With the naked eye one can see
the grain, but otherwise the table looks smooth and even. If we
looked at it through a microscope, we should see roughnesses and hills
and valleys, and all sorts of differences that are imperceptible to
the naked eye. Which of these is the 'real' table? We are naturally
tempted to say that what we see through the microscope is more real,
but that in turn would be changed by a still more powerful microscope.
If, then, we cannot trust what we see with the naked eye, why should
we trust what we see through a microscope? Thus, again, the
confidence in our senses with which we began deserts us.
The shape of the table is no better. We are all in the habit of
judging as to the 'real' shapes of things, and we do this so
unreflectingly that we come to think we actually see the real shapes.
But, in fact, as we all have to learn if we try to draw, a given thing
looks different in shape from every different point of view. If our
table is 'really' rectangular, it will look, from almost all points of
view, as if it had two acute angles and two obtuse angles. If
opposite sides are parallel, they will look as if they converged to a
point away from the spectator; if they are of equal length, they will
look as if the nearer side were longer. All these things are not
commonly noticed in looking at a table, because experience has taught
us to construct the 'real' shape from the apparent shape, and the
'real' shape is what interests us as practical men. But the 'real'
shape is not what we see; it is something inferred from what we see.
And what we see is constantly changing in shape as we move about the
room; so that here again the senses seem not to give us the truth
about the table itself, but only about the appearance of the table.
Similar difficulties arise when we consider the sense of touch. It is
true that the table always gives us a sensation of hardness, and we
feel that it resists pressure. But the sensation we obtain depends
upon how hard we press the table and also upon what part of the body
we press with; thus the various sensations due to various pressures or
various parts of the body cannot be supposed to reveal _directly_ any
definite property of the table, but at most to be _signs_ of some
property which perhaps _causes_ all the sensations, but is not
actually apparent in any of them. And the same applies still more
obviously to the sounds which can be elicited by rapping the table.
Thus it becomes evident that the real table, if there is one, is not
the same as what we immediately experience by sight or touch or
hearing. The real table, if there is one, is not _immediately_ known
to us at all, but must be an inference from what is immediately known.
Hence, two very difficult questions at once arise; namely, (1) Is
there a real table at all? (2) If so, what sort of object can it be?
It will help us in considering these questions to have a few simple
terms of which the meaning is definite and clear. Let us give the
name of 'sense-data' to the things that are immediately known in
sensation: such things as colours, sounds, smells, hardnesses,
roughnesses, and so on. We shall give the name 'sensation' to the
experience of being immediately aware of these things. Thus, whenever
we see a colour, we have a sensation _of_ the colour, but the colour
itself is a sense-datum, not a sensation. The colour is that _of_
which we are immediately aware, and the awareness itself is the
sensation. It is plain that if we are to know anything about the
table, it must be by means of the sense-data--brown colour, oblong
shape, smoothness, etc.--which we associate with the table; but, for
the reasons which have been given, we cannot say that the table is the
sense-data, or even that the sense-data are directly properties of the
table. Thus a problem arises as to the relation of the sense-data to
the real table, supposing there is such a thing.
The real table, if it exists, we will call a 'physical object'. Thus
we have to consider the relation of sense-data to physical objects.
The collection of all physical objects is called 'matter'. Thus our
two questions may be re-stated as follows: (1) Is there any such thing
as matter? (2) If so, what is its nature?
The philosopher who first brought prominently forward the reasons for
regarding the immediate objects of our senses as not existing
independently of us was Bishop Berkeley (1685-1753). His _Three
Dialogues between Hylas and Philonous, in Opposition to Sceptics and
Atheists_, undertake to prove that there is no such thing as matter at
all, and that the world consists of nothing but minds and their ideas.
Hylas has hitherto believed in matter, but he is no match for
Philonous, who mercilessly drives him into contradictions and
paradoxes, and makes his own denial of matter seem, in the end, as if
it were almost common sense. The arguments employed are of very
different value: some are important and sound, others are confused or
quibbling. But Berkeley retains the merit of having shown that the
existence of matter is capable of being denied without absurdity, and
that if there are any things that exist independently of us they
cannot be the immediate objects of our sensations.
There are two different questions involved when we ask whether matter
exists, and it is important to keep them clear. We commonly mean by
'matter' something which is opposed to 'mind', something which we
think of as occupying space and as radically incapable of any sort of
thought or consciousness. It is chiefly in this sense that Berkeley
denies matter; that is to say, he does not deny that the sense-data
which we commonly take as signs of the existence of the table are
really signs of the existence of _something_ independent of us, but he
does deny that this something is non-mental, that it is neither mind
nor ideas entertained by some mind. He admits that there must be
something which continues to exist when we go out of the room or shut
our eyes, and that what we call seeing the table does really give us
reason for believing in something which persists even when we are not
seeing it. But he thinks that this something cannot be radically
different in nature from what we see, and cannot be independent of
seeing altogether, though it must be independent of _our_ seeing. He
is thus led to regard the 'real' table as an idea in the mind of God.
Such an idea has the required permanence and independence of
ourselves, without being--as matter would otherwise be--something
quite unknowable, in the sense that we can only infer it, and can
never be directly and immediately aware of it.
Other philosophers since Berkeley have also held that, although the
table does not depend for its existence upon being seen by me, it does
depend upon being seen (or otherwise apprehended in sensation) by
_some_ mind--not necessarily the mind of God, but more often the whole
collective mind of the universe. This they hold, as Berkeley does,
chiefly because they think there can be nothing real--or at any rate
nothing known to be real except minds and their thoughts and feelings.
We might state the argument by which they support their view in some
such way as this: 'Whatever can be thought of is an idea in the mind
of the person thinking of it; therefore nothing can be thought of
except ideas in minds; therefore anything else is inconceivable, and
what is inconceivable cannot exist.'
Such an argument, in my opinion, is fallacious; and of course those
who advance it do not put it so shortly or so crudely. But whether
valid or not, the argument has been very widely advanced in one form
or another; and very many philosophers, perhaps a majority, have held
that there is nothing real except minds and their ideas. Such
philosophers are called 'idealists'. When they come to explaining
matter, they either say, like Berkeley, that matter is really nothing
but a collection of ideas, or they say, like Leibniz (1646-1716), that
what appears as matter is really a collection of more or less
rudimentary minds.
But these philosophers, though they deny matter as opposed to mind,
nevertheless, in another sense, admit matter. It will be remembered
that we asked two questions; namely, (1) Is there a real table at all?
(2) If so, what sort of object can it be? Now both Berkeley and
Leibniz admit that there is a real table, but Berkeley says it is
certain ideas in the mind of God, and Leibniz says it is a colony of
souls. Thus both of them answer our first question in the
affirmative, and only diverge from the views of ordinary mortals in
their answer to our second question. In fact, almost all philosophers
seem to be agreed that there is a real table: they almost all agree
that, however much our sense-data--colour, shape, smoothness,
etc.--may depend upon us, yet their occurrence is a sign of something
existing independently of us, something differing, perhaps, completely
from our sense-data, and yet to be regarded as causing those
sense-data whenever we are in a suitable relation to the real table.
Now obviously this point in which the philosophers are agreed--the
view that there _is_ a real table, whatever its nature may be--is
vitally important, and it will be worth while to consider what reasons
there are for accepting this view before we go on to the further
question as to the nature of the real table. Our next chapter,
therefore, will be concerned with the reasons for supposing that there
is a real table at all.
Before we go farther it will be well to consider for a moment what it
is that we have discovered so far. It has appeared that, if we take
any common object of the sort that is supposed to be known by the
senses, what the senses _immediately_ tell us is not the truth about
the object as it is apart from us, but only the truth about certain
sense-data which, so far as we can see, depend upon the relations
between us and the object. Thus what we directly see and feel is
merely 'appearance', which we believe to be a sign of some 'reality'
behind. But if the reality is not what appears, have we any means of
knowing whether there is any reality at all? And if so, have we any
means of finding out what it is like?
Such questions are bewildering, and it is difficult to know that even
the strangest hypotheses may not be true. Thus our familiar table,
which has roused but the slightest thoughts in us hitherto, has become
a problem full of surprising possibilities. The one thing we know
about it is that it is not what it seems. Beyond this modest result,
so far, we have the most complete liberty of conjecture. Leibniz
tells us it is a community of souls: Berkeley tells us it is an idea
in the mind of God; sober science, scarcely less wonderful, tells us
it is a vast collection of electric charges in violent motion.
Among these surprising possibilities, doubt suggests that perhaps
there is no table at all. Philosophy, if it cannot _answer_ so many
questions as we could wish, has at least the power of _asking_
questions which increase the interest of the world, and show the
strangeness and wonder lying just below the surface even in the
commonest things of daily life.
Is there any knowledge in the world which is so certain that no
reasonable man could doubt it? This question, which at first sight
might not seem difficult, is really one of the most difficult that can
be asked. When we have realized the obstacles in the way of a
straightforward and confident answer, we shall be well launched on the
study of philosophy--for philosophy is merely the attempt to answer
such ultimate questions, not carelessly and dogmatically, as we do in
ordinary life and even in the sciences, but critically, after
exploring all that makes such questions puzzling, and after realizing
all the vagueness and confusion that underlie our ordinary ideas.
In daily life, we assume as certain many things which, on a closer
scrutiny, are found to be so full of apparent contradictions that only
a great amount of thought enables us to know what it is that we really
may believe. In the search for certainty, it is natural to begin with
our present experiences, and in some sense, no doubt, knowledge is to
be derived from them. But any statement as to what it is that our
immediate experiences make us know is very likely to be wrong. It
seems to me that I am now sitting in a chair, at a table of a certain
shape, on which I see sheets of paper with writing or print. By
turning my head I see out of the window buildings and clouds and the
sun. I believe that the sun is about ninety-three million miles from
the earth; that it is a hot globe many times bigger than the earth;
that, owing to the earth's rotation, it rises every morning, and will
continue to do so for an indefinite time in the future. I believe
that, if any other normal person comes into my room, he will see the
same chairs and tables and books and papers as I see, and that the
table which I see is the same as the table which I feel pressing
against my arm. All this seems to be so evident as to be hardly worth
stating, except in answer to a man who doubts whether I know anything.
Yet all this may be reasonably doubted, and all of it requires much
careful discussion before we can be sure that we have stated it in a
form that is wholly true.
To make our difficulties plain, let us concentrate attention on the
table. To the eye it is oblong, brown and shiny, to the touch it is
smooth and cool and hard; when I tap it, it gives out a wooden sound.
Any one else who sees and feels and hears the table will agree with
this description, so that it might seem as if no difficulty would
arise; but as soon as we try to be more precise our troubles begin.
Although I believe that the table is 'really' of the same colour all
over, the parts that reflect the light look much brighter than the
other parts, and some parts look white because of reflected light. I
know that, if I move, the parts that reflect the light will be
different, so that the apparent distribution of colours on the table
will change. It follows that if several people are looking at the
table at the same moment, no two of them will see exactly the same
distribution of colours, because no two can see it from exactly the
same point of view, and any change in the point of view makes some
change in the way the light is reflected.
For most practical purposes these differences are unimportant, but to
the painter they are all-important: the painter has to unlearn the
habit of thinking that things seem to have the colour which common
sense says they 'really' have, and to learn the habit of seeing things
as they appear. Here we have already the beginning of one of the
distinctions that cause most trouble in philosophy--the distinction
between 'appearance' and 'reality', between what things seem to be and
what they are. The painter wants to know what things seem to be, the
practical man and the philosopher want to know what they are; but the
philosopher's wish to know this is stronger than the practical man's,
and is more troubled by knowledge as to the difficulties of answering
the question.
To return to the table. It is evident from what we have found, that
there is no colour which pre-eminently appears to be _the_ colour of
the table, or even of any one particular part of the table--it appears
to be of different colours from different points of view, and there is
no reason for regarding some of these as more really its colour than
others. And we know that even from a given point of view the colour
will seem different by artificial light, or to a colour-blind man, or
to a man wearing blue spectacles, while in the dark there will be no
colour at all, though to touch and hearing the table will be
unchanged. This colour is not something which is inherent in the
table, but something depending upon the table and the spectator and
the way the light falls on the table. When, in ordinary life, we
speak of _the_ colour of the table, we only mean the sort of colour
which it will seem to have to a normal spectator from an ordinary
point of view under usual conditions of light. But the other colours
which appear under other conditions have just as good a right to be
considered real; and therefore, to avoid favouritism, we are compelled
to deny that, in itself, the table has any one particular colour.
The same thing applies to the texture. With the naked eye one can see
the grain, but otherwise the table looks smooth and even. If we
looked at it through a microscope, we should see roughnesses and hills
and valleys, and all sorts of differences that are imperceptible to
the naked eye. Which of these is the 'real' table? We are naturally
tempted to say that what we see through the microscope is more real,
but that in turn would be changed by a still more powerful microscope.
If, then, we cannot trust what we see with the naked eye, why should
we trust what we see through a microscope? Thus, again, the
confidence in our senses with which we began deserts us.
The shape of the table is no better. We are all in the habit of
judging as to the 'real' shapes of things, and we do this so
unreflectingly that we come to think we actually see the real shapes.
But, in fact, as we all have to learn if we try to draw, a given thing
looks different in shape from every different point of view. If our
table is 'really' rectangular, it will look, from almost all points of
view, as if it had two acute angles and two obtuse angles. If
opposite sides are parallel, they will look as if they converged to a
point away from the spectator; if they are of equal length, they will
look as if the nearer side were longer. All these things are not
commonly noticed in looking at a table, because experience has taught
us to construct the 'real' shape from the apparent shape, and the
'real' shape is what interests us as practical men. But the 'real'
shape is not what we see; it is something inferred from what we see.
And what we see is constantly changing in shape as we move about the
room; so that here again the senses seem not to give us the truth
about the table itself, but only about the appearance of the table.
Similar difficulties arise when we consider the sense of touch. It is
true that the table always gives us a sensation of hardness, and we
feel that it resists pressure. But the sensation we obtain depends
upon how hard we press the table and also upon what part of the body
we press with; thus the various sensations due to various pressures or
various parts of the body cannot be supposed to reveal _directly_ any
definite property of the table, but at most to be _signs_ of some
property which perhaps _causes_ all the sensations, but is not
actually apparent in any of them. And the same applies still more
obviously to the sounds which can be elicited by rapping the table.
Thus it becomes evident that the real table, if there is one, is not
the same as what we immediately experience by sight or touch or
hearing. The real table, if there is one, is not _immediately_ known
to us at all, but must be an inference from what is immediately known.
Hence, two very difficult questions at once arise; namely, (1) Is
there a real table at all? (2) If so, what sort of object can it be?
It will help us in considering these questions to have a few simple
terms of which the meaning is definite and clear. Let us give the
name of 'sense-data' to the things that are immediately known in
sensation: such things as colours, sounds, smells, hardnesses,
roughnesses, and so on. We shall give the name 'sensation' to the
experience of being immediately aware of these things. Thus, whenever
we see a colour, we have a sensation _of_ the colour, but the colour
itself is a sense-datum, not a sensation. The colour is that _of_
which we are immediately aware, and the awareness itself is the
sensation. It is plain that if we are to know anything about the
table, it must be by means of the sense-data--brown colour, oblong
shape, smoothness, etc.--which we associate with the table; but, for
the reasons which have been given, we cannot say that the table is the
sense-data, or even that the sense-data are directly properties of the
table. Thus a problem arises as to the relation of the sense-data to
the real table, supposing there is such a thing.
The real table, if it exists, we will call a 'physical object'. Thus
we have to consider the relation of sense-data to physical objects.
The collection of all physical objects is called 'matter'. Thus our
two questions may be re-stated as follows: (1) Is there any such thing
as matter? (2) If so, what is its nature?
The philosopher who first brought prominently forward the reasons for
regarding the immediate objects of our senses as not existing
independently of us was Bishop Berkeley (1685-1753). His _Three
Dialogues between Hylas and Philonous, in Opposition to Sceptics and
Atheists_, undertake to prove that there is no such thing as matter at
all, and that the world consists of nothing but minds and their ideas.
Hylas has hitherto believed in matter, but he is no match for
Philonous, who mercilessly drives him into contradictions and
paradoxes, and makes his own denial of matter seem, in the end, as if
it were almost common sense. The arguments employed are of very
different value: some are important and sound, others are confused or
quibbling. But Berkeley retains the merit of having shown that the
existence of matter is capable of being denied without absurdity, and
that if there are any things that exist independently of us they
cannot be the immediate objects of our sensations.
There are two different questions involved when we ask whether matter
exists, and it is important to keep them clear. We commonly mean by
'matter' something which is opposed to 'mind', something which we
think of as occupying space and as radically incapable of any sort of
thought or consciousness. It is chiefly in this sense that Berkeley
denies matter; that is to say, he does not deny that the sense-data
which we commonly take as signs of the existence of the table are
really signs of the existence of _something_ independent of us, but he
does deny that this something is non-mental, that it is neither mind
nor ideas entertained by some mind. He admits that there must be
something which continues to exist when we go out of the room or shut
our eyes, and that what we call seeing the table does really give us
reason for believing in something which persists even when we are not
seeing it. But he thinks that this something cannot be radically
different in nature from what we see, and cannot be independent of
seeing altogether, though it must be independent of _our_ seeing. He
is thus led to regard the 'real' table as an idea in the mind of God.
Such an idea has the required permanence and independence of
ourselves, without being--as matter would otherwise be--something
quite unknowable, in the sense that we can only infer it, and can
never be directly and immediately aware of it.
Other philosophers since Berkeley have also held that, although the
table does not depend for its existence upon being seen by me, it does
depend upon being seen (or otherwise apprehended in sensation) by
_some_ mind--not necessarily the mind of God, but more often the whole
collective mind of the universe. This they hold, as Berkeley does,
chiefly because they think there can be nothing real--or at any rate
nothing known to be real except minds and their thoughts and feelings.
We might state the argument by which they support their view in some
such way as this: 'Whatever can be thought of is an idea in the mind
of the person thinking of it; therefore nothing can be thought of
except ideas in minds; therefore anything else is inconceivable, and
what is inconceivable cannot exist.'
Such an argument, in my opinion, is fallacious; and of course those
who advance it do not put it so shortly or so crudely. But whether
valid or not, the argument has been very widely advanced in one form
or another; and very many philosophers, perhaps a majority, have held
that there is nothing real except minds and their ideas. Such
philosophers are called 'idealists'. When they come to explaining
matter, they either say, like Berkeley, that matter is really nothing
but a collection of ideas, or they say, like Leibniz (1646-1716), that
what appears as matter is really a collection of more or less
rudimentary minds.
But these philosophers, though they deny matter as opposed to mind,
nevertheless, in another sense, admit matter. It will be remembered
that we asked two questions; namely, (1) Is there a real table at all?
(2) If so, what sort of object can it be? Now both Berkeley and
Leibniz admit that there is a real table, but Berkeley says it is
certain ideas in the mind of God, and Leibniz says it is a colony of
souls. Thus both of them answer our first question in the
affirmative, and only diverge from the views of ordinary mortals in
their answer to our second question. In fact, almost all philosophers
seem to be agreed that there is a real table: they almost all agree
that, however much our sense-data--colour, shape, smoothness,
etc.--may depend upon us, yet their occurrence is a sign of something
existing independently of us, something differing, perhaps, completely
from our sense-data, and yet to be regarded as causing those
sense-data whenever we are in a suitable relation to the real table.
Now obviously this point in which the philosophers are agreed--the
view that there _is_ a real table, whatever its nature may be--is
vitally important, and it will be worth while to consider what reasons
there are for accepting this view before we go on to the further
question as to the nature of the real table. Our next chapter,
therefore, will be concerned with the reasons for supposing that there
is a real table at all.
Before we go farther it will be well to consider for a moment what it
is that we have discovered so far. It has appeared that, if we take
any common object of the sort that is supposed to be known by the
senses, what the senses _immediately_ tell us is not the truth about
the object as it is apart from us, but only the truth about certain
sense-data which, so far as we can see, depend upon the relations
between us and the object. Thus what we directly see and feel is
merely 'appearance', which we believe to be a sign of some 'reality'
behind. But if the reality is not what appears, have we any means of
knowing whether there is any reality at all? And if so, have we any
means of finding out what it is like?
Such questions are bewildering, and it is difficult to know that even
the strangest hypotheses may not be true. Thus our familiar table,
which has roused but the slightest thoughts in us hitherto, has become
a problem full of surprising possibilities. The one thing we know
about it is that it is not what it seems. Beyond this modest result,
so far, we have the most complete liberty of conjecture. Leibniz
tells us it is a community of souls: Berkeley tells us it is an idea
in the mind of God; sober science, scarcely less wonderful, tells us
it is a vast collection of electric charges in violent motion.
Among these surprising possibilities, doubt suggests that perhaps
there is no table at all. Philosophy, if it cannot _answer_ so many
questions as we could wish, has at least the power of _asking_
questions which increase the interest of the world, and show the
strangeness and wonder lying just below the surface even in the
commonest things of daily life.
CHAPTER II
THE EXISTENCE OF MATTER
In this chapter we have to ask ourselves whether, in any sense at all,
there is such a thing as matter. Is there a table which has a certain
intrinsic nature, and continues to exist when I am not looking, or is
the table merely a product of my imagination, a dream-table in a very
prolonged dream? This question is of the greatest importance. For if
we cannot be sure of the independent existence of objects, we cannot
be sure of the independent existence of other people's bodies, and
therefore still less of other people's minds, since we have no grounds
for believing in their minds except such as are derived from observing
their bodies. Thus if we cannot be sure of the independent existence
of objects, we shall be left alone in a desert--it may be that the
whole outer world is nothing but a dream, and that we alone exist.
This is an uncomfortable possibility; but although it cannot be
strictly proved to be false, there is not the slightest reason to
suppose that it is true. In this chapter we have to see why this is
the case.
Before we embark upon doubtful matters, let us try to find some more
or less fixed point from which to start. Although we are doubting the
physical existence of the table, we are not doubting the existence of
the sense-data which made us think there was a table; we are not
doubting that, while we look, a certain colour and shape appear to us,
and while we press, a certain sensation of hardness is experienced by
us. All this, which is psychological, we are not calling in question.
In fact, whatever else may be doubtful, some at least of our immediate
experiences seem absolutely certain.
Descartes (1596-1650), the founder of modern philosophy, invented a
method which may still be used with profit--the method of systematic
doubt. He determined that he would believe nothing which he did not
see quite clearly and distinctly to be true. Whatever he could bring
himself to doubt, he would doubt, until he saw reason for not doubting
it. By applying this method he gradually became convinced that the
only existence of which he could be _quite_ certain was his own. He
imagined a deceitful demon, who presented unreal things to his senses
in a perpetual phantasmagoria; it might be very improbable that such a
demon existed, but still it was possible, and therefore doubt
concerning things perceived by the senses was possible.
But doubt concerning his own existence was not possible, for if he did
not exist, no demon could deceive him. If he doubted, he must exist;
if he had any experiences whatever, he must exist. Thus his own
existence was an absolute certainty to him. 'I think, therefore I
am,' he said (_Cogito, ergo sum_); and on the basis of this certainty
he set to work to build up again the world of knowledge which his
doubt had laid in ruins. By inventing the method of doubt, and by
showing that subjective things are the most certain, Descartes
performed a great service to philosophy, and one which makes him still
useful to all students of the subject.
But some care is needed in using Descartes' argument. 'I think,
therefore I am' says rather more than is strictly certain. It might
seem as though we were quite sure of being the same person to-day as
we were yesterday, and this is no doubt true in some sense. But the
real Self is as hard to arrive at as the real table, and does not seem
to have that absolute, convincing certainty that belongs to particular
experiences. When I look at my table and see a certain brown colour,
what is quite certain at once is not '_I_ am seeing a brown colour',
but rather, 'a brown colour is being seen'. This of course involves
something (or somebody) which (or who) sees the brown colour; but it
does not of itself involve that more or less permanent person whom we
call 'I'. So far as immediate certainty goes, it might be that the
something which sees the brown colour is quite momentary, and not the
same as the something which has some different experience the next
moment.
Thus it is our particular thoughts and feelings that have primitive
certainty. And this applies to dreams and hallucinations as well as
to normal perceptions: when we dream or see a ghost, we certainly do
have the sensations we think we have, but for various reasons it is
held that no physical object corresponds to these sensations. Thus
the certainty of our knowledge of our own experiences does not have to
be limited in any way to allow for exceptional cases. Here,
therefore, we have, for what it is worth, a solid basis from which to
begin our pursuit of knowledge.
The problem we have to consider is this: Granted that we are certain
of our own sense-data, have we any reason for regarding them as signs
of the existence of something else, which we can call the physical
object? When we have enumerated all the sense-data which we should
naturally regard as connected with the table, have we said all there
is to say about the table, or is there still something else--something
not a sense-datum, something which persists when we go out of the
room? Common sense unhesitatingly answers that there is. What can be
bought and sold and pushed about and have a cloth laid on it, and so
on, cannot be a _mere_ collection of sense-data. If the cloth
completely hides the table, we shall derive no sense-data from the
table, and therefore, if the table were merely sense-data, it would
have ceased to exist, and the cloth would be suspended in empty air,
resting, by a miracle, in the place where the table formerly was.
This seems plainly absurd; but whoever wishes to become a philosopher
must learn not to be frightened by absurdities.
One great reason why it is felt that we must secure a physical object
in addition to the sense-data, is that we want the same object for
different people. When ten people are sitting round a dinner-table,
it seems preposterous to maintain that they are not seeing the same
tablecloth, the same knives and forks and spoons and glasses. But the
sense-data are private to each separate person; what is immediately
present to the sight of one is not immediately present to the sight of
another: they all see things from slightly different points of view,
and therefore see them slightly differently. Thus, if there are to be
public neutral objects, which can be in some sense known to many
different people, there must be something over and above the private
and particular sense-data which appear to various people. What
reason, then, have we for believing that there are such public neutral
objects?
The first answer that naturally occurs to one is that, although
different people may see the table slightly differently, still they
all see more or less similar things when they look at the table, and
the variations in what they see follow the laws of perspective and
reflection of light, so that it is easy to arrive at a permanent
object underlying all the different people's sense-data. I bought my
table from the former occupant of my room; I could not buy _his_
sense-data, which died when he went away, but I could and did buy the
confident expectation of more or less similar sense-data. Thus it is
the fact that different people have similar sense-data, and that one
person in a given place at different times has similar sense-data,
which makes us suppose that over and above the sense-data there is a
permanent public object which underlies or causes the sense-data of
various people at various times.
Now in so far as the above considerations depend upon supposing that
there are other people besides ourselves, they beg the very question
at issue. Other people are represented to me by certain sense-data,
such as the sight of them or the sound of their voices, and if I had
no reason to believe that there were physical objects independent of
my sense-data, I should have no reason to believe that other people
exist except as part of my dream. Thus, when we are trying to show
that there must be objects independent of our own sense-data, we
cannot appeal to the testimony of other people, since this testimony
itself consists of sense-data, and does not reveal other people's
experiences unless our own sense-data are signs of things existing
independently of us. We must therefore, if possible, find, in our own
purely private experiences, characteristics which show, or tend to
show, that there are in the world things other than ourselves and our
private experiences.
In one sense it must be admitted that we can never prove the existence
of things other than ourselves and our experiences. No logical
absurdity results from the hypothesis that the world consists of
myself and my thoughts and feelings and sensations, and that
everything else is mere fancy. In dreams a very complicated world may
seem to be present, and yet on waking we find it was a delusion; that
is to say, we find that the sense-data in the dream do not appear to
have corresponded with such physical objects as we should naturally
infer from our sense-data. (It is true that, when the physical world
is assumed, it is possible to find physical causes for the sense-data
in dreams: a door banging, for instance, may cause us to dream of a
naval engagement. But although, in this case, there is a physical
cause for the sense-data, there is not a physical object corresponding
to the sense-data in the way in which an actual naval battle would
correspond.) There is no logical impossibility in the supposition that
the whole of life is a dream, in which we ourselves create all the
objects that come before us. But although this is not logically
impossible, there is no reason whatever to suppose that it is true;
and it is, in fact, a less simple hypothesis, viewed as a means of
accounting for the facts of our own life, than the common-sense
hypothesis that there really are objects independent of us, whose
action on us causes our sensations.
The way in which simplicity comes in from supposing that there really
are physical objects is easily seen. If the cat appears at one moment
in one part of the room, and at another in another part, it is natural
to suppose that it has moved from the one to the other, passing over a
series of intermediate positions. But if it is merely a set of
sense-data, it cannot have ever been in any place where I did not see
it; thus we shall have to suppose that it did not exist at all while I
was not looking, but suddenly sprang into being in a new place. If
the cat exists whether I see it or not, we can understand from our own
experience how it gets hungry between one meal and the next; but if it
does not exist when I am not seeing it, it seems odd that appetite
should grow during non-existence as fast as during existence. And if
the cat consists only of sense-data, it cannot be hungry, since no
hunger but my own can be a sense-datum to me. Thus the behaviour of
the sense-data which represent the cat to me, though it seems quite
natural when regarded as an expression of hunger, becomes utterly
inexplicable when regarded as mere movements and changes of patches of
colour, which are as incapable of hunger as a triangle is of playing
football.
But the difficulty in the case of the cat is nothing compared to the
difficulty in the case of human beings. When human beings speak--that
is, when we hear certain noises which we associate with ideas, and
simultaneously see certain motions of lips and expressions of face--it
is very difficult to suppose that what we hear is not the expression
of a thought, as we know it would be if we emitted the same sounds.
Of course similar things happen in dreams, where we are mistaken as to
the existence of other people. But dreams are more or less suggested
by what we call waking life, and are capable of being more or less
accounted for on scientific principles if we assume that there really
is a physical world. Thus every principle of simplicity urges us to
adopt the natural view, that there really are objects other than
ourselves and our sense-data which have an existence not dependent
upon our perceiving them.
Of course it is not by argument that we originally come by our belief
in an independent external world. We find this belief ready in
ourselves as soon as we begin to reflect: it is what may be called an
_instinctive_ belief. We should never have been led to question this
belief but for the fact that, at any rate in the case of sight, it
seems as if the sense-datum itself were instinctively believed to be
the independent object, whereas argument shows that the object cannot
be identical with the sense-datum. This discovery, however--which is
not at all paradoxical in the case of taste and smell and sound, and
only slightly so in the case of touch--leaves undiminished our
instinctive belief that there _are_ objects _corresponding_ to our
sense-data. Since this belief does not lead to any difficulties, but
on the contrary tends to simplify and systematize our account of our
experiences, there seems no good reason for rejecting it. We may
therefore admit--though with a slight doubt derived from dreams--that
the external world does really exist, and is not wholly dependent for
its existence upon our continuing to perceive it.
The argument which has led us to this conclusion is doubtless less
strong than we could wish, but it is typical of many philosophical
arguments, and it is therefore worth while to consider briefly its
general character and validity. All knowledge, we find, must be built
up upon our instinctive beliefs, and if these are rejected, nothing is
left. But among our instinctive beliefs some are much stronger than
others, while many have, by habit and association, become entangled
with other beliefs, not really instinctive, but falsely supposed to be
part of what is believed instinctively.
Philosophy should show us the hierarchy of our instinctive beliefs,
beginning with those we hold most strongly, and presenting each as
much isolated and as free from irrelevant additions as possible. It
should take care to show that, in the form in which they are finally
set forth, our instinctive beliefs do not clash, but form a harmonious
system. There can never be any reason for rejecting one instinctive
belief except that it clashes with others; thus, if they are found to
harmonize, the whole system becomes worthy of acceptance.
It is of course _possible_ that all or any of our beliefs may be
mistaken, and therefore all ought to be held with at least some slight
element of doubt. But we cannot have _reason_ to reject a belief
except on the ground of some other belief. Hence, by organizing our
instinctive beliefs and their consequences, by considering which among
them is most possible, if necessary, to modify or abandon, we can
arrive, on the basis of accepting as our sole data what we
instinctively believe, at an orderly systematic organization of our
knowledge, in which, though the _possibility_ of error remains, its
likelihood is diminished by the interrelation of the parts and by the
critical scrutiny which has preceded acquiescence.
This function, at least, philosophy can perform. Most philosophers,
rightly or wrongly, believe that philosophy can do much more than
this--that it can give us knowledge, not otherwise attainable,
concerning the universe as a whole, and concerning the nature of
ultimate reality. Whether this be the case or not, the more modest
function we have spoken of can certainly be performed by philosophy,
and certainly suffices, for those who have once begun to doubt the
adequacy of common sense, to justify the arduous and difficult labours
that philosophical problems involve.
In this chapter we have to ask ourselves whether, in any sense at all,
there is such a thing as matter. Is there a table which has a certain
intrinsic nature, and continues to exist when I am not looking, or is
the table merely a product of my imagination, a dream-table in a very
prolonged dream? This question is of the greatest importance. For if
we cannot be sure of the independent existence of objects, we cannot
be sure of the independent existence of other people's bodies, and
therefore still less of other people's minds, since we have no grounds
for believing in their minds except such as are derived from observing
their bodies. Thus if we cannot be sure of the independent existence
of objects, we shall be left alone in a desert--it may be that the
whole outer world is nothing but a dream, and that we alone exist.
This is an uncomfortable possibility; but although it cannot be
strictly proved to be false, there is not the slightest reason to
suppose that it is true. In this chapter we have to see why this is
the case.
Before we embark upon doubtful matters, let us try to find some more
or less fixed point from which to start. Although we are doubting the
physical existence of the table, we are not doubting the existence of
the sense-data which made us think there was a table; we are not
doubting that, while we look, a certain colour and shape appear to us,
and while we press, a certain sensation of hardness is experienced by
us. All this, which is psychological, we are not calling in question.
In fact, whatever else may be doubtful, some at least of our immediate
experiences seem absolutely certain.
Descartes (1596-1650), the founder of modern philosophy, invented a
method which may still be used with profit--the method of systematic
doubt. He determined that he would believe nothing which he did not
see quite clearly and distinctly to be true. Whatever he could bring
himself to doubt, he would doubt, until he saw reason for not doubting
it. By applying this method he gradually became convinced that the
only existence of which he could be _quite_ certain was his own. He
imagined a deceitful demon, who presented unreal things to his senses
in a perpetual phantasmagoria; it might be very improbable that such a
demon existed, but still it was possible, and therefore doubt
concerning things perceived by the senses was possible.
But doubt concerning his own existence was not possible, for if he did
not exist, no demon could deceive him. If he doubted, he must exist;
if he had any experiences whatever, he must exist. Thus his own
existence was an absolute certainty to him. 'I think, therefore I
am,' he said (_Cogito, ergo sum_); and on the basis of this certainty
he set to work to build up again the world of knowledge which his
doubt had laid in ruins. By inventing the method of doubt, and by
showing that subjective things are the most certain, Descartes
performed a great service to philosophy, and one which makes him still
useful to all students of the subject.
But some care is needed in using Descartes' argument. 'I think,
therefore I am' says rather more than is strictly certain. It might
seem as though we were quite sure of being the same person to-day as
we were yesterday, and this is no doubt true in some sense. But the
real Self is as hard to arrive at as the real table, and does not seem
to have that absolute, convincing certainty that belongs to particular
experiences. When I look at my table and see a certain brown colour,
what is quite certain at once is not '_I_ am seeing a brown colour',
but rather, 'a brown colour is being seen'. This of course involves
something (or somebody) which (or who) sees the brown colour; but it
does not of itself involve that more or less permanent person whom we
call 'I'. So far as immediate certainty goes, it might be that the
something which sees the brown colour is quite momentary, and not the
same as the something which has some different experience the next
moment.
Thus it is our particular thoughts and feelings that have primitive
certainty. And this applies to dreams and hallucinations as well as
to normal perceptions: when we dream or see a ghost, we certainly do
have the sensations we think we have, but for various reasons it is
held that no physical object corresponds to these sensations. Thus
the certainty of our knowledge of our own experiences does not have to
be limited in any way to allow for exceptional cases. Here,
therefore, we have, for what it is worth, a solid basis from which to
begin our pursuit of knowledge.
The problem we have to consider is this: Granted that we are certain
of our own sense-data, have we any reason for regarding them as signs
of the existence of something else, which we can call the physical
object? When we have enumerated all the sense-data which we should
naturally regard as connected with the table, have we said all there
is to say about the table, or is there still something else--something
not a sense-datum, something which persists when we go out of the
room? Common sense unhesitatingly answers that there is. What can be
bought and sold and pushed about and have a cloth laid on it, and so
on, cannot be a _mere_ collection of sense-data. If the cloth
completely hides the table, we shall derive no sense-data from the
table, and therefore, if the table were merely sense-data, it would
have ceased to exist, and the cloth would be suspended in empty air,
resting, by a miracle, in the place where the table formerly was.
This seems plainly absurd; but whoever wishes to become a philosopher
must learn not to be frightened by absurdities.
One great reason why it is felt that we must secure a physical object
in addition to the sense-data, is that we want the same object for
different people. When ten people are sitting round a dinner-table,
it seems preposterous to maintain that they are not seeing the same
tablecloth, the same knives and forks and spoons and glasses. But the
sense-data are private to each separate person; what is immediately
present to the sight of one is not immediately present to the sight of
another: they all see things from slightly different points of view,
and therefore see them slightly differently. Thus, if there are to be
public neutral objects, which can be in some sense known to many
different people, there must be something over and above the private
and particular sense-data which appear to various people. What
reason, then, have we for believing that there are such public neutral
objects?
The first answer that naturally occurs to one is that, although
different people may see the table slightly differently, still they
all see more or less similar things when they look at the table, and
the variations in what they see follow the laws of perspective and
reflection of light, so that it is easy to arrive at a permanent
object underlying all the different people's sense-data. I bought my
table from the former occupant of my room; I could not buy _his_
sense-data, which died when he went away, but I could and did buy the
confident expectation of more or less similar sense-data. Thus it is
the fact that different people have similar sense-data, and that one
person in a given place at different times has similar sense-data,
which makes us suppose that over and above the sense-data there is a
permanent public object which underlies or causes the sense-data of
various people at various times.
Now in so far as the above considerations depend upon supposing that
there are other people besides ourselves, they beg the very question
at issue. Other people are represented to me by certain sense-data,
such as the sight of them or the sound of their voices, and if I had
no reason to believe that there were physical objects independent of
my sense-data, I should have no reason to believe that other people
exist except as part of my dream. Thus, when we are trying to show
that there must be objects independent of our own sense-data, we
cannot appeal to the testimony of other people, since this testimony
itself consists of sense-data, and does not reveal other people's
experiences unless our own sense-data are signs of things existing
independently of us. We must therefore, if possible, find, in our own
purely private experiences, characteristics which show, or tend to
show, that there are in the world things other than ourselves and our
private experiences.
In one sense it must be admitted that we can never prove the existence
of things other than ourselves and our experiences. No logical
absurdity results from the hypothesis that the world consists of
myself and my thoughts and feelings and sensations, and that
everything else is mere fancy. In dreams a very complicated world may
seem to be present, and yet on waking we find it was a delusion; that
is to say, we find that the sense-data in the dream do not appear to
have corresponded with such physical objects as we should naturally
infer from our sense-data. (It is true that, when the physical world
is assumed, it is possible to find physical causes for the sense-data
in dreams: a door banging, for instance, may cause us to dream of a
naval engagement. But although, in this case, there is a physical
cause for the sense-data, there is not a physical object corresponding
to the sense-data in the way in which an actual naval battle would
correspond.) There is no logical impossibility in the supposition that
the whole of life is a dream, in which we ourselves create all the
objects that come before us. But although this is not logically
impossible, there is no reason whatever to suppose that it is true;
and it is, in fact, a less simple hypothesis, viewed as a means of
accounting for the facts of our own life, than the common-sense
hypothesis that there really are objects independent of us, whose
action on us causes our sensations.
The way in which simplicity comes in from supposing that there really
are physical objects is easily seen. If the cat appears at one moment
in one part of the room, and at another in another part, it is natural
to suppose that it has moved from the one to the other, passing over a
series of intermediate positions. But if it is merely a set of
sense-data, it cannot have ever been in any place where I did not see
it; thus we shall have to suppose that it did not exist at all while I
was not looking, but suddenly sprang into being in a new place. If
the cat exists whether I see it or not, we can understand from our own
experience how it gets hungry between one meal and the next; but if it
does not exist when I am not seeing it, it seems odd that appetite
should grow during non-existence as fast as during existence. And if
the cat consists only of sense-data, it cannot be hungry, since no
hunger but my own can be a sense-datum to me. Thus the behaviour of
the sense-data which represent the cat to me, though it seems quite
natural when regarded as an expression of hunger, becomes utterly
inexplicable when regarded as mere movements and changes of patches of
colour, which are as incapable of hunger as a triangle is of playing
football.
But the difficulty in the case of the cat is nothing compared to the
difficulty in the case of human beings. When human beings speak--that
is, when we hear certain noises which we associate with ideas, and
simultaneously see certain motions of lips and expressions of face--it
is very difficult to suppose that what we hear is not the expression
of a thought, as we know it would be if we emitted the same sounds.
Of course similar things happen in dreams, where we are mistaken as to
the existence of other people. But dreams are more or less suggested
by what we call waking life, and are capable of being more or less
accounted for on scientific principles if we assume that there really
is a physical world. Thus every principle of simplicity urges us to
adopt the natural view, that there really are objects other than
ourselves and our sense-data which have an existence not dependent
upon our perceiving them.
Of course it is not by argument that we originally come by our belief
in an independent external world. We find this belief ready in
ourselves as soon as we begin to reflect: it is what may be called an
_instinctive_ belief. We should never have been led to question this
belief but for the fact that, at any rate in the case of sight, it
seems as if the sense-datum itself were instinctively believed to be
the independent object, whereas argument shows that the object cannot
be identical with the sense-datum. This discovery, however--which is
not at all paradoxical in the case of taste and smell and sound, and
only slightly so in the case of touch--leaves undiminished our
instinctive belief that there _are_ objects _corresponding_ to our
sense-data. Since this belief does not lead to any difficulties, but
on the contrary tends to simplify and systematize our account of our
experiences, there seems no good reason for rejecting it. We may
therefore admit--though with a slight doubt derived from dreams--that
the external world does really exist, and is not wholly dependent for
its existence upon our continuing to perceive it.
The argument which has led us to this conclusion is doubtless less
strong than we could wish, but it is typical of many philosophical
arguments, and it is therefore worth while to consider briefly its
general character and validity. All knowledge, we find, must be built
up upon our instinctive beliefs, and if these are rejected, nothing is
left. But among our instinctive beliefs some are much stronger than
others, while many have, by habit and association, become entangled
with other beliefs, not really instinctive, but falsely supposed to be
part of what is believed instinctively.
Philosophy should show us the hierarchy of our instinctive beliefs,
beginning with those we hold most strongly, and presenting each as
much isolated and as free from irrelevant additions as possible. It
should take care to show that, in the form in which they are finally
set forth, our instinctive beliefs do not clash, but form a harmonious
system. There can never be any reason for rejecting one instinctive
belief except that it clashes with others; thus, if they are found to
harmonize, the whole system becomes worthy of acceptance.
It is of course _possible_ that all or any of our beliefs may be
mistaken, and therefore all ought to be held with at least some slight
element of doubt. But we cannot have _reason_ to reject a belief
except on the ground of some other belief. Hence, by organizing our
instinctive beliefs and their consequences, by considering which among
them is most possible, if necessary, to modify or abandon, we can
arrive, on the basis of accepting as our sole data what we
instinctively believe, at an orderly systematic organization of our
knowledge, in which, though the _possibility_ of error remains, its
likelihood is diminished by the interrelation of the parts and by the
critical scrutiny which has preceded acquiescence.
This function, at least, philosophy can perform. Most philosophers,
rightly or wrongly, believe that philosophy can do much more than
this--that it can give us knowledge, not otherwise attainable,
concerning the universe as a whole, and concerning the nature of
ultimate reality. Whether this be the case or not, the more modest
function we have spoken of can certainly be performed by philosophy,
and certainly suffices, for those who have once begun to doubt the
adequacy of common sense, to justify the arduous and difficult labours
that philosophical problems involve.
CHAPTER III
THE NATURE OF MATTER
In the preceding chapter we agreed, though without being able to find
demonstrative reasons, that it is rational to believe that our
sense-data--for example, those which we regard as associated with my
table--are really signs of the existence of something independent of
us and our perceptions. That is to say, over and above the sensations
of colour, hardness, noise, and so on, which make up the appearance of
the table to me, I assume that there is something else, of which these
things are appearances. The colour ceases to exist if I shut my eyes,
the sensation of hardness ceases to exist if I remove my arm from
contact with the table, the sound ceases to exist if I cease to rap
the table with my knuckles. But I do not believe that when all these
things cease the table ceases. On the contrary, I believe that it is
because the table exists continuously that all these sense-data will
reappear when I open my eyes, replace my arm, and begin again to rap
with my knuckles. The question we have to consider in this chapter
is: What is the nature of this real table, which persists
independently of my perception of it?
To this question physical science gives an answer, somewhat incomplete
it is true, and in part still very hypothetical, but yet deserving of
respect so far as it goes. Physical science, more or less
unconsciously, has drifted into the view that all natural phenomena
ought to be reduced to motions. Light and heat and sound are all due
to wave-motions, which travel from the body emitting them to the
person who sees light or feels heat or hears sound. That which has
the wave-motion is either aether or 'gross matter', but in either case
is what the philosopher would call matter. The only properties which
science assigns to it are position in space, and the power of motion
according to the laws of motion. Science does not deny that it _may_
have other properties; but if so, such other properties are not useful
to the man of science, and in no way assist him in explaining the
phenomena.
It is sometimes said that 'light _is_ a form of wave-motion', but this
is misleading, for the light which we immediately see, which we know
directly by means of our senses, is _not_ a form of wave-motion, but
something quite different--something which we all know if we are not
blind, though we cannot describe it so as to convey our knowledge to a
man who is blind. A wave-motion, on the contrary, could quite well be
described to a blind man, since he can acquire a knowledge of space by
the sense of touch; and he can experience a wave-motion by a sea
voyage almost as well as we can. But this, which a blind man can
understand, is not what we mean by _light_: we mean by _light_ just
that which a blind man can never understand, and which we can never
describe to him.
Now this something, which all of us who are not blind know, is not,
according to science, really to be found in the outer world: it is
something caused by the action of certain waves upon the eyes and
nerves and brain of the person who sees the light. When it is said
that light _is_ waves, what is really meant is that waves are the
physical cause of our sensations of light. But light itself, the
thing which seeing people experience and blind people do not, is not
supposed by science to form any part of the world that is independent
of us and our senses. And very similar remarks would apply to other
kinds of sensations.
It is not only colours and sounds and so on that are absent from the
scientific world of matter, but also _space_ as we get it through
sight or touch. It is essential to science that its matter should be
in _a_ space, but the space in which it is cannot be exactly the space
we see or feel. To begin with, space as we see it is not the same as
space as we get it by the sense of touch; it is only by experience in
infancy that we learn how to touch things we see, or how to get a
sight of things which we feel touching us. But the space of science
is neutral as between touch and sight; thus it cannot be either the
space of touch or the space of sight.
Again, different people see the same object as of different shapes,
according to their point of view. A circular coin, for example,
though we should always _judge_ it to be circular, will _look_ oval
unless we are straight in front of it. When we judge that it _is_
circular, we are judging that it has a real shape which is not its
apparent shape, but belongs to it intrinsically apart from its
appearance. But this real shape, which is what concerns science, must
be in a real space, not the same as anybody's _apparent_ space. The
real space is public, the apparent space is private to the percipient.
In different people's _private_ spaces the same object seems to have
different shapes; thus the real space, in which it has its real shape,
must be different from the private spaces. The space of science,
therefore, though _connected_ with the spaces we see and feel, is not
identical with them, and the manner of its connexion requires
investigation.
We agreed provisionally that physical objects cannot be quite like our
sense-data, but may be regarded as _causing_ our sensations. These
physical objects are in the space of science, which we may call
'physical' space. It is important to notice that, if our sensations
are to be caused by physical objects, there must be a physical space
containing these objects and our sense-organs and nerves and brain.
We get a sensation of touch from an object when we are in contact with
it; that is to say, when some part of our body occupies a place in
physical space quite close to the space occupied by the object. We
see an object (roughly speaking) when no opaque body is between the
object and our eyes in physical space. Similarly, we only hear or
smell or taste an object when we are sufficiently near to it, or when
it touches the tongue, or has some suitable position in physical space
relatively to our body. We cannot begin to state what different
sensations we shall derive from a given object under different
circumstances unless we regard the object and our body as both in one
physical space, for it is mainly the relative positions of the object
and our body that determine what sensations we shall derive from the
object.
Now our sense-data are situated in our private spaces, either the
space of sight or the space of touch or such vaguer spaces as other
senses may give us. If, as science and common sense assume, there is
one public all-embracing physical space in which physical objects are,
the relative positions of physical objects in physical space must more
or less correspond to the relative positions of sense-data in our
private spaces. There is no difficulty in supposing this to be the
case. If we see on a road one house nearer to us than another, our
other senses will bear out the view that it is nearer; for example, it
will be reached sooner if we walk along the road. Other people will
agree that the house which looks nearer to us is nearer; the ordnance
map will take the same view; and thus everything points to a spatial
relation between the houses corresponding to the relation between the
sense-data which we see when we look at the houses. Thus we may
assume that there is a physical space in which physical objects have
spatial relations corresponding to those which the corresponding
sense-data have in our private spaces. It is this physical space
which is dealt with in geometry and assumed in physics and astronomy.
Assuming that there is physical space, and that it does thus
correspond to private spaces, what can we know about it? We can know
_only_ what is required in order to secure the correspondence. That
is to say, we can know nothing of what it is like in itself, but we
can know the sort of arrangement of physical objects which results
from their spatial relations. We can know, for example, that the
earth and moon and sun are in one straight line during an eclipse,
though we cannot know what a physical straight line is in itself, as
we know the look of a straight line in our visual space. Thus we come
to know much more about the _relations_ of distances in physical space
than about the distances themselves; we may know that one distance is
greater than another, or that it is along the same straight line as
the other, but we cannot have that immediate acquaintance with
physical distances that we have with distances in our private spaces,
or with colours or sounds or other sense-data. We can know all those
things about physical space which a man born blind might know through
other people about the space of sight; but the kind of things which a
man born blind could never know about the space of sight we also
cannot know about physical space. We can know the properties of the
relations required to preserve the correspondence with sense-data, but
we cannot know the nature of the terms between which the relations
hold.
With regard to time, our _feeling_ of duration or of the lapse of time
is notoriously an unsafe guide as to the time that has elapsed by the
clock. Times when we are bored or suffering pain pass slowly, times
when we are agreeably occupied pass quickly, and times when we are
sleeping pass almost as if they did not exist. Thus, in so far as
time is constituted by duration, there is the same necessity for
distinguishing a public and a private time as there was in the case of
space. But in so far as time consists in an _order_ of before and
after, there is no need to make such a distinction; the time-order
which events seem to have is, so far as we can see, the same as the
time-order which they do have. At any rate no reason can be given for
supposing that the two orders are not the same. The same is usually
true of space: if a regiment of men are marching along a road, the
shape of the regiment will look different from different points of
view, but the men will appear arranged in the same order from all
points of view. Hence we regard the order as true also in physical
space, whereas the shape is only supposed to correspond to the
physical space so far as is required for the preservation of the
order.
In saying that the time-order which events seem to have is the same as
the time-order which they really have, it is necessary to guard
against a possible misunderstanding. It must not be supposed that the
various states of different physical objects have the same time-order
as the sense-data which constitute the perceptions of those objects.
Considered as physical objects, the thunder and lightning are
simultaneous; that is to say, the lightning is simultaneous with the
disturbance of the air in the place where the disturbance begins,
namely, where the lightning is. But the sense-datum which we call
hearing the thunder does not take place until the disturbance of the
air has travelled as far as to where we are. Similarly, it takes
about eight minutes for the sun's light to reach us; thus, when we see
the sun we are seeing the sun of eight minutes ago. So far as our
sense-data afford evidence as to the physical sun they afford evidence
as to the physical sun of eight minutes ago; if the physical sun had
ceased to exist within the last eight minutes, that would make no
difference to the sense-data which we call 'seeing the sun'. This
affords a fresh illustration of the necessity of distinguishing
between sense-data and physical objects.
What we have found as regards space is much the same as what we find
in relation to the correspondence of the sense-data with their
physical counterparts. If one object looks blue and another red, we
may reasonably presume that there is some corresponding difference
between the physical objects; if two objects both look blue, we may
presume a corresponding similarity. But we cannot hope to be
acquainted directly with the quality in the physical object which
makes it look blue or red. Science tells us that this quality is a
certain sort of wave-motion, and this sounds familiar, because we
think of wave-motions in the space we see. But the wave-motions must
really be in physical space, with which we have no direct
acquaintance; thus the real wave-motions have not that familiarity
which we might have supposed them to have. And what holds for colours
is closely similar to what holds for other sense-data. Thus we find
that, although the _relations_ of physical objects have all sorts of
knowable properties, derived from their correspondence with the
relations of sense-data, the physical objects themselves remain
unknown in their intrinsic nature, so far at least as can be
discovered by means of the senses. The question remains whether there
is any other method of discovering the intrinsic nature of physical
objects.
The most natural, though not ultimately the most defensible,
hypothesis to adopt in the first instance, at any rate as regards
visual sense-data, would be that, though physical objects cannot, for
the reasons we have been considering, be _exactly_ like sense-data,
yet they may be more or less like. According to this view, physical
objects will, for example, really have colours, and we might, by good
luck, see an object as of the colour it really is. The colour which
an object seems to have at any given moment will in general be very
similar, though not quite the same, from many different points of
view; we might thus suppose the 'real' colour to be a sort of medium
colour, intermediate between the various shades which appear from the
different points of view.
Such a theory is perhaps not capable of being definitely refuted, but
it can be shown to be groundless. To begin with, it is plain that the
colour we see depends only upon the nature of the light-waves that
strike the eye, and is therefore modified by the medium intervening
between us and the object, as well as by the manner in which light is
reflected from the object in the direction of the eye. The
intervening air alters colours unless it is perfectly clear, and any
strong reflection will alter them completely. Thus the colour we see
is a result of the ray as it reaches the eye, and not simply a
property of the object from which the ray comes. Hence, also,
provided certain waves reach the eye, we shall see a certain colour,
whether the object from which the waves start has any colour or not.
Thus it is quite gratuitous to suppose that physical objects have
colours, and therefore there is no justification for making such a
supposition. Exactly similar arguments will apply to other
sense-data.
It remains to ask whether there are any general philosophical
arguments enabling us to say that, if matter is real, it must be of
such and such a nature. As explained above, very many philosophers,
perhaps most, have held that whatever is real must be in some sense
mental, or at any rate that whatever we can know anything about must
be in some sense mental. Such philosophers are called 'idealists'.
Idealists tell us that what appears as matter is really something
mental; namely, either (as Leibniz held) more or less rudimentary
minds, or (as Berkeley contended) ideas in the minds which, as we
should commonly say, 'perceive' the matter. Thus idealists deny the
existence of matter as something intrinsically different from mind,
though they do not deny that our sense-data are signs of something
which exists independently of our private sensations. In the
following chapter we shall consider briefly the reasons--in my opinion
fallacious--which idealists advance in favour of their theory.
In the preceding chapter we agreed, though without being able to find
demonstrative reasons, that it is rational to believe that our
sense-data--for example, those which we regard as associated with my
table--are really signs of the existence of something independent of
us and our perceptions. That is to say, over and above the sensations
of colour, hardness, noise, and so on, which make up the appearance of
the table to me, I assume that there is something else, of which these
things are appearances. The colour ceases to exist if I shut my eyes,
the sensation of hardness ceases to exist if I remove my arm from
contact with the table, the sound ceases to exist if I cease to rap
the table with my knuckles. But I do not believe that when all these
things cease the table ceases. On the contrary, I believe that it is
because the table exists continuously that all these sense-data will
reappear when I open my eyes, replace my arm, and begin again to rap
with my knuckles. The question we have to consider in this chapter
is: What is the nature of this real table, which persists
independently of my perception of it?
To this question physical science gives an answer, somewhat incomplete
it is true, and in part still very hypothetical, but yet deserving of
respect so far as it goes. Physical science, more or less
unconsciously, has drifted into the view that all natural phenomena
ought to be reduced to motions. Light and heat and sound are all due
to wave-motions, which travel from the body emitting them to the
person who sees light or feels heat or hears sound. That which has
the wave-motion is either aether or 'gross matter', but in either case
is what the philosopher would call matter. The only properties which
science assigns to it are position in space, and the power of motion
according to the laws of motion. Science does not deny that it _may_
have other properties; but if so, such other properties are not useful
to the man of science, and in no way assist him in explaining the
phenomena.
It is sometimes said that 'light _is_ a form of wave-motion', but this
is misleading, for the light which we immediately see, which we know
directly by means of our senses, is _not_ a form of wave-motion, but
something quite different--something which we all know if we are not
blind, though we cannot describe it so as to convey our knowledge to a
man who is blind. A wave-motion, on the contrary, could quite well be
described to a blind man, since he can acquire a knowledge of space by
the sense of touch; and he can experience a wave-motion by a sea
voyage almost as well as we can. But this, which a blind man can
understand, is not what we mean by _light_: we mean by _light_ just
that which a blind man can never understand, and which we can never
describe to him.
Now this something, which all of us who are not blind know, is not,
according to science, really to be found in the outer world: it is
something caused by the action of certain waves upon the eyes and
nerves and brain of the person who sees the light. When it is said
that light _is_ waves, what is really meant is that waves are the
physical cause of our sensations of light. But light itself, the
thing which seeing people experience and blind people do not, is not
supposed by science to form any part of the world that is independent
of us and our senses. And very similar remarks would apply to other
kinds of sensations.
It is not only colours and sounds and so on that are absent from the
scientific world of matter, but also _space_ as we get it through
sight or touch. It is essential to science that its matter should be
in _a_ space, but the space in which it is cannot be exactly the space
we see or feel. To begin with, space as we see it is not the same as
space as we get it by the sense of touch; it is only by experience in
infancy that we learn how to touch things we see, or how to get a
sight of things which we feel touching us. But the space of science
is neutral as between touch and sight; thus it cannot be either the
space of touch or the space of sight.
Again, different people see the same object as of different shapes,
according to their point of view. A circular coin, for example,
though we should always _judge_ it to be circular, will _look_ oval
unless we are straight in front of it. When we judge that it _is_
circular, we are judging that it has a real shape which is not its
apparent shape, but belongs to it intrinsically apart from its
appearance. But this real shape, which is what concerns science, must
be in a real space, not the same as anybody's _apparent_ space. The
real space is public, the apparent space is private to the percipient.
In different people's _private_ spaces the same object seems to have
different shapes; thus the real space, in which it has its real shape,
must be different from the private spaces. The space of science,
therefore, though _connected_ with the spaces we see and feel, is not
identical with them, and the manner of its connexion requires
investigation.
We agreed provisionally that physical objects cannot be quite like our
sense-data, but may be regarded as _causing_ our sensations. These
physical objects are in the space of science, which we may call
'physical' space. It is important to notice that, if our sensations
are to be caused by physical objects, there must be a physical space
containing these objects and our sense-organs and nerves and brain.
We get a sensation of touch from an object when we are in contact with
it; that is to say, when some part of our body occupies a place in
physical space quite close to the space occupied by the object. We
see an object (roughly speaking) when no opaque body is between the
object and our eyes in physical space. Similarly, we only hear or
smell or taste an object when we are sufficiently near to it, or when
it touches the tongue, or has some suitable position in physical space
relatively to our body. We cannot begin to state what different
sensations we shall derive from a given object under different
circumstances unless we regard the object and our body as both in one
physical space, for it is mainly the relative positions of the object
and our body that determine what sensations we shall derive from the
object.
Now our sense-data are situated in our private spaces, either the
space of sight or the space of touch or such vaguer spaces as other
senses may give us. If, as science and common sense assume, there is
one public all-embracing physical space in which physical objects are,
the relative positions of physical objects in physical space must more
or less correspond to the relative positions of sense-data in our
private spaces. There is no difficulty in supposing this to be the
case. If we see on a road one house nearer to us than another, our
other senses will bear out the view that it is nearer; for example, it
will be reached sooner if we walk along the road. Other people will
agree that the house which looks nearer to us is nearer; the ordnance
map will take the same view; and thus everything points to a spatial
relation between the houses corresponding to the relation between the
sense-data which we see when we look at the houses. Thus we may
assume that there is a physical space in which physical objects have
spatial relations corresponding to those which the corresponding
sense-data have in our private spaces. It is this physical space
which is dealt with in geometry and assumed in physics and astronomy.
Assuming that there is physical space, and that it does thus
correspond to private spaces, what can we know about it? We can know
_only_ what is required in order to secure the correspondence. That
is to say, we can know nothing of what it is like in itself, but we
can know the sort of arrangement of physical objects which results
from their spatial relations. We can know, for example, that the
earth and moon and sun are in one straight line during an eclipse,
though we cannot know what a physical straight line is in itself, as
we know the look of a straight line in our visual space. Thus we come
to know much more about the _relations_ of distances in physical space
than about the distances themselves; we may know that one distance is
greater than another, or that it is along the same straight line as
the other, but we cannot have that immediate acquaintance with
physical distances that we have with distances in our private spaces,
or with colours or sounds or other sense-data. We can know all those
things about physical space which a man born blind might know through
other people about the space of sight; but the kind of things which a
man born blind could never know about the space of sight we also
cannot know about physical space. We can know the properties of the
relations required to preserve the correspondence with sense-data, but
we cannot know the nature of the terms between which the relations
hold.
With regard to time, our _feeling_ of duration or of the lapse of time
is notoriously an unsafe guide as to the time that has elapsed by the
clock. Times when we are bored or suffering pain pass slowly, times
when we are agreeably occupied pass quickly, and times when we are
sleeping pass almost as if they did not exist. Thus, in so far as
time is constituted by duration, there is the same necessity for
distinguishing a public and a private time as there was in the case of
space. But in so far as time consists in an _order_ of before and
after, there is no need to make such a distinction; the time-order
which events seem to have is, so far as we can see, the same as the
time-order which they do have. At any rate no reason can be given for
supposing that the two orders are not the same. The same is usually
true of space: if a regiment of men are marching along a road, the
shape of the regiment will look different from different points of
view, but the men will appear arranged in the same order from all
points of view. Hence we regard the order as true also in physical
space, whereas the shape is only supposed to correspond to the
physical space so far as is required for the preservation of the
order.
In saying that the time-order which events seem to have is the same as
the time-order which they really have, it is necessary to guard
against a possible misunderstanding. It must not be supposed that the
various states of different physical objects have the same time-order
as the sense-data which constitute the perceptions of those objects.
Considered as physical objects, the thunder and lightning are
simultaneous; that is to say, the lightning is simultaneous with the
disturbance of the air in the place where the disturbance begins,
namely, where the lightning is. But the sense-datum which we call
hearing the thunder does not take place until the disturbance of the
air has travelled as far as to where we are. Similarly, it takes
about eight minutes for the sun's light to reach us; thus, when we see
the sun we are seeing the sun of eight minutes ago. So far as our
sense-data afford evidence as to the physical sun they afford evidence
as to the physical sun of eight minutes ago; if the physical sun had
ceased to exist within the last eight minutes, that would make no
difference to the sense-data which we call 'seeing the sun'. This
affords a fresh illustration of the necessity of distinguishing
between sense-data and physical objects.
What we have found as regards space is much the same as what we find
in relation to the correspondence of the sense-data with their
physical counterparts. If one object looks blue and another red, we
may reasonably presume that there is some corresponding difference
between the physical objects; if two objects both look blue, we may
presume a corresponding similarity. But we cannot hope to be
acquainted directly with the quality in the physical object which
makes it look blue or red. Science tells us that this quality is a
certain sort of wave-motion, and this sounds familiar, because we
think of wave-motions in the space we see. But the wave-motions must
really be in physical space, with which we have no direct
acquaintance; thus the real wave-motions have not that familiarity
which we might have supposed them to have. And what holds for colours
is closely similar to what holds for other sense-data. Thus we find
that, although the _relations_ of physical objects have all sorts of
knowable properties, derived from their correspondence with the
relations of sense-data, the physical objects themselves remain
unknown in their intrinsic nature, so far at least as can be
discovered by means of the senses. The question remains whether there
is any other method of discovering the intrinsic nature of physical
objects.
The most natural, though not ultimately the most defensible,
hypothesis to adopt in the first instance, at any rate as regards
visual sense-data, would be that, though physical objects cannot, for
the reasons we have been considering, be _exactly_ like sense-data,
yet they may be more or less like. According to this view, physical
objects will, for example, really have colours, and we might, by good
luck, see an object as of the colour it really is. The colour which
an object seems to have at any given moment will in general be very
similar, though not quite the same, from many different points of
view; we might thus suppose the 'real' colour to be a sort of medium
colour, intermediate between the various shades which appear from the
different points of view.
Such a theory is perhaps not capable of being definitely refuted, but
it can be shown to be groundless. To begin with, it is plain that the
colour we see depends only upon the nature of the light-waves that
strike the eye, and is therefore modified by the medium intervening
between us and the object, as well as by the manner in which light is
reflected from the object in the direction of the eye. The
intervening air alters colours unless it is perfectly clear, and any
strong reflection will alter them completely. Thus the colour we see
is a result of the ray as it reaches the eye, and not simply a
property of the object from which the ray comes. Hence, also,
provided certain waves reach the eye, we shall see a certain colour,
whether the object from which the waves start has any colour or not.
Thus it is quite gratuitous to suppose that physical objects have
colours, and therefore there is no justification for making such a
supposition. Exactly similar arguments will apply to other
sense-data.
It remains to ask whether there are any general philosophical
arguments enabling us to say that, if matter is real, it must be of
such and such a nature. As explained above, very many philosophers,
perhaps most, have held that whatever is real must be in some sense
mental, or at any rate that whatever we can know anything about must
be in some sense mental. Such philosophers are called 'idealists'.
Idealists tell us that what appears as matter is really something
mental; namely, either (as Leibniz held) more or less rudimentary
minds, or (as Berkeley contended) ideas in the minds which, as we
should commonly say, 'perceive' the matter. Thus idealists deny the
existence of matter as something intrinsically different from mind,
though they do not deny that our sense-data are signs of something
which exists independently of our private sensations. In the
following chapter we shall consider briefly the reasons--in my opinion
fallacious--which idealists advance in favour of their theory.
CHAPTER IV
IDEALISM
The word 'idealism' is used by different philosophers in somewhat
different senses. We shall understand by it the doctrine that
whatever exists, or at any rate whatever can be known to exist, must
be in some sense mental. This doctrine, which is very widely held
among philosophers, has several forms, and is advocated on several
different grounds. The doctrine is so widely held, and so interesting
in itself, that even the briefest survey of philosophy must give some
account of it.
Those who are unaccustomed to philosophical speculation may be
inclined to dismiss such a doctrine as obviously absurd. There is no
doubt that common sense regards tables and chairs and the sun and moon
and material objects generally as something radically different from
minds and the contents of minds, and as having an existence which
might continue if minds ceased. We think of matter as having existed
long before there were any minds, and it is hard to think of it as a
mere product of mental activity. But whether true or false, idealism
is not to be dismissed as obviously absurd.
We have seen that, even if physical objects do have an independent
existence, they must differ very widely from sense-data, and can only
have a _correspondence_ with sense-data, in the same sort of way in
which a catalogue has a correspondence with the things catalogued.
Hence common sense leaves us completely in the dark as to the true
intrinsic nature of physical objects, and if there were good reason to
regard them as mental, we could not legitimately reject this opinion
merely because it strikes us as strange. The truth about physical
objects _must_ be strange. It may be unattainable, but if any
philosopher believes that he has attained it, the fact that what he
offers as the truth is strange ought not to be made a ground of
objection to his opinion.
The grounds on which idealism is advocated are generally grounds
derived from the theory of knowledge, that is to say, from a
discussion of the conditions which things must satisfy in order that
we may be able to know them. The first serious attempt to establish
idealism on such grounds was that of Bishop Berkeley. He proved
first, by arguments which were largely valid, that our sense-data
cannot be supposed to have an existence independent of us, but must
be, in part at least, 'in' the mind, in the sense that their existence
would not continue if there were no seeing or hearing or touching or
smelling or tasting. So far, his contention was almost certainly
valid, even if some of his arguments were not so. But he went on to
argue that sense-data were the only things of whose existence our
perceptions could assure us; and that to be known is to be 'in' a
mind, and therefore to be mental. Hence he concluded that nothing can
ever be known except what is in some mind, and that whatever is known
without being in my mind must be in some other mind.
In order to understand his argument, it is necessary to understand his
use of the word 'idea'. He gives the name 'idea' to anything which is
_immediately_ known, as, for example, sense-data are known. Thus a
particular colour which we see is an idea; so is a voice which we
hear, and so on. But the term is not wholly confined to sense-data.
There will also be things remembered or imagined, for with such things
also we have immediate acquaintance at the moment of remembering or
imagining. All such immediate data he calls 'ideas'.
He then proceeds to consider common objects, such as a tree, for
instance. He shows that all we know immediately when we 'perceive'
the tree consists of ideas in his sense of the word, and he argues
that there is not the slightest ground for supposing that there is
anything real about the tree except what is perceived. Its being, he
says, consists in being perceived: in the Latin of the schoolmen its
'_esse_' is '_percipi_'. He fully admits that the tree must continue
to exist even when we shut our eyes or when no human being is near it.
But this continued existence, he says, is due to the fact that God
continues to perceive it; the 'real' tree, which corresponds to what
we called the physical object, consists of ideas in the mind of God,
ideas more or less like those we have when we see the tree, but
differing in the fact that they are permanent in God's mind so long as
the tree continues to exist. All our perceptions, according to him,
consist in a partial participation in God's perceptions, and it is
because of this participation that different people see more or less
the same tree. Thus apart from minds and their ideas there is nothing
in the world, nor is it possible that anything else should ever be
known, since whatever is known is necessarily an idea.
There are in this argument a good many fallacies which have been
important in the history of philosophy, and which it will be as well
to bring to light. In the first place, there is a confusion
engendered by the use of the word 'idea'. We think of an idea as
essentially something in somebody's mind, and thus when we are told
that a tree consists entirely of ideas, it is natural to suppose that,
if so, the tree must be entirely in minds. But the notion of being
'in' the mind is ambiguous. We speak of bearing a person in mind, not
meaning that the person is in our minds, but that a thought of him is
in our minds. When a man says that some business he had to arrange
went clean out of his mind, he does not mean to imply that the
business itself was ever in his mind, but only that a thought of the
business was formerly in his mind, but afterwards ceased to be in his
mind. And so when Berkeley says that the tree must be in our minds if
we can know it, all that he really has a right to say is that a
thought of the tree must be in our minds. To argue that the tree
itself must be in our minds is like arguing that a person whom we bear
in mind is himself in our minds. This confusion may seem too gross to
have been really committed by any competent philosopher, but various
attendant circumstances rendered it possible. In order to see how it
was possible, we must go more deeply into the question as to the
nature of ideas.
Before taking up the general question of the nature of ideas, we must
disentangle two entirely separate questions which arise concerning
sense-data and physical objects. We saw that, for various reasons of
detail, Berkeley was right in treating the sense-data which constitute
our perception of the tree as more or less subjective, in the sense
that they depend upon us as much as upon the tree, and would not exist
if the tree were not being perceived. But this is an entirely
different point from the one by which Berkeley seeks to prove that
whatever can be immediately known must be in a mind. For this purpose
arguments of detail as to the dependence of sense-data upon us are
useless. It is necessary to prove, generally, that by being known,
things are shown to be mental. This is what Berkeley believes himself
to have done. It is this question, and not our previous question as
to the difference between sense-data and the physical object, that
must now concern us.
Taking the word 'idea' in Berkeley's sense, there are two quite
distinct things to be considered whenever an idea is before the mind.
There is on the one hand the thing of which we are aware--say the
colour of my table--and on the other hand the actual awareness itself,
the mental act of apprehending the thing. The mental act is
undoubtedly mental, but is there any reason to suppose that the thing
apprehended is in any sense mental? Our previous arguments concerning
the colour did not prove it to be mental; they only proved that its
existence depends upon the relation of our sense organs to the
physical object--in our case, the table. That is to say, they proved
that a certain colour will exist, in a certain light, if a normal eye
is placed at a certain point relatively to the table. They did not
prove that the colour is in the mind of the percipient.
Berkeley's view, that obviously the colour must be in the mind, seems
to depend for its plausibility upon confusing the thing apprehended
with the act of apprehension. Either of these might be called an
'idea'; probably either would have been called an idea by Berkeley.
The act is undoubtedly in the mind; hence, when we are thinking of the
act, we readily assent to the view that ideas must be in the mind.
Then, forgetting that this was only true when ideas were taken as acts
of apprehension, we transfer the proposition that 'ideas are in the
mind' to ideas in the other sense, i.e. to the things apprehended by
our acts of apprehension. Thus, by an unconscious equivocation, we
arrive at the conclusion that whatever we can apprehend must be in our
minds. This seems to be the true analysis of Berkeley's argument, and
the ultimate fallacy upon which it rests.
This question of the distinction between act and object in our
apprehending of things is vitally important, since our whole power of
acquiring knowledge is bound up with it. The faculty of being
acquainted with things other than itself is the main characteristic of
a mind. Acquaintance with objects essentially consists in a relation
between the mind and something other than the mind; it is this that
constitutes the mind's power of knowing things. If we say that the
things known must be in the mind, we are either unduly limiting the
mind's power of knowing, or we are uttering a mere tautology. We are
uttering a mere tautology if we mean by '_in_ the mind' the same as by
'_before_ the mind', i.e. if we mean merely being apprehended by the
mind. But if we mean this, we shall have to admit that what, _in this
sense_, is in the mind, may nevertheless be not mental. Thus when we
realize the nature of knowledge, Berkeley's argument is seen to be
wrong in substance as well as in form, and his grounds for supposing
that 'ideas'--i.e. the objects apprehended--must be mental, are found
to have no validity whatever. Hence his grounds in favour of idealism
may be dismissed. It remains to see whether there are any other
grounds.
It is often said, as though it were a self-evident truism, that we
cannot know that anything exists which we do not know. It is inferred
that whatever can in any way be relevant to our experience must be at
least capable of being known by us; whence it follows that if matter
were essentially something with which we could not become acquainted,
matter would be something which we could not know to exist, and which
could have for us no importance whatever. It is generally also
implied, for reasons which remain obscure, that what can have no
importance for us cannot be real, and that therefore matter, if it is
not composed of minds or of mental ideas, is impossible and a mere
chimaera.
To go into this argument fully at our present stage would be
impossible, since it raises points requiring a considerable
preliminary discussion; but certain reasons for rejecting the argument
may be noticed at once. To begin at the end: there is no reason why
what cannot have any _practical_ importance for us should not be real.
It is true that, if _theoretical_ importance is included, everything
real is of _some_ importance to us, since, as persons desirous of
knowing the truth about the universe, we have some interest in
everything that the universe contains. But if this sort of interest
is included, it is not the case that matter has no importance for us,
provided it exists even if we cannot know that it exists. We can,
obviously, suspect that it may exist, and wonder whether it does;
hence it is connected with our desire for knowledge, and has the
importance of either satisfying or thwarting this desire.
Again, it is by no means a truism, and is in fact false, that we
cannot know that anything exists which we do not know. The word
'know' is here used in two different senses. (1) In its first use it
is applicable to the sort of knowledge which is opposed to error, the
sense in which what we know is _true_, the sense which applies to our
beliefs and convictions, i.e. to what are called _judgements_. In
this sense of the word we know _that_ something is the case. This
sort of knowledge may be described as knowledge of _truths_. (2) In
the second use of the word 'know' above, the word applies to our
knowledge of _things_, which we may call _acquaintance_. This is the
sense in which we know sense-data. (The distinction involved is
roughly that between _savoir_ and _connaître_ in French, or between
_wissen_ and _kennen_ in German.)
Thus the statement which seemed like a truism becomes, when re-stated,
the following: 'We can never truly judge that something with which we
are not acquainted exists.' This is by no means a truism, but on the
contrary a palpable falsehood. I have not the honour to be acquainted
with the Emperor of China, but I truly judge that he exists. It may
be said, of course, that I judge this because of other people's
acquaintance with him. This, however, would be an irrelevant retort,
since, if the principle were true, I could not know that any one else
is acquainted with him. But further: there is no reason why I should
not know of the existence of something with which nobody is
acquainted. This point is important, and demands elucidation.
If I am acquainted with a thing which exists, my acquaintance gives me
the knowledge that it exists. But it is not true that, conversely,
whenever I can know that a thing of a certain sort exists, I or some
one else must be acquainted with the thing. What happens, in cases
where I have true judgement without acquaintance, is that the thing is
known to me by _description_, and that, in virtue of some general
principle, the existence of a thing answering to this description can
be inferred from the existence of something with which I am
acquainted. In order to understand this point fully, it will be well
first to deal with the difference between knowledge by acquaintance
and knowledge by description, and then to consider what knowledge of
general principles, if any, has the same kind of certainty as our
knowledge of the existence of our own experiences. These subjects
will be dealt with in the following chapters.
The word 'idealism' is used by different philosophers in somewhat
different senses. We shall understand by it the doctrine that
whatever exists, or at any rate whatever can be known to exist, must
be in some sense mental. This doctrine, which is very widely held
among philosophers, has several forms, and is advocated on several
different grounds. The doctrine is so widely held, and so interesting
in itself, that even the briefest survey of philosophy must give some
account of it.
Those who are unaccustomed to philosophical speculation may be
inclined to dismiss such a doctrine as obviously absurd. There is no
doubt that common sense regards tables and chairs and the sun and moon
and material objects generally as something radically different from
minds and the contents of minds, and as having an existence which
might continue if minds ceased. We think of matter as having existed
long before there were any minds, and it is hard to think of it as a
mere product of mental activity. But whether true or false, idealism
is not to be dismissed as obviously absurd.
We have seen that, even if physical objects do have an independent
existence, they must differ very widely from sense-data, and can only
have a _correspondence_ with sense-data, in the same sort of way in
which a catalogue has a correspondence with the things catalogued.
Hence common sense leaves us completely in the dark as to the true
intrinsic nature of physical objects, and if there were good reason to
regard them as mental, we could not legitimately reject this opinion
merely because it strikes us as strange. The truth about physical
objects _must_ be strange. It may be unattainable, but if any
philosopher believes that he has attained it, the fact that what he
offers as the truth is strange ought not to be made a ground of
objection to his opinion.
The grounds on which idealism is advocated are generally grounds
derived from the theory of knowledge, that is to say, from a
discussion of the conditions which things must satisfy in order that
we may be able to know them. The first serious attempt to establish
idealism on such grounds was that of Bishop Berkeley. He proved
first, by arguments which were largely valid, that our sense-data
cannot be supposed to have an existence independent of us, but must
be, in part at least, 'in' the mind, in the sense that their existence
would not continue if there were no seeing or hearing or touching or
smelling or tasting. So far, his contention was almost certainly
valid, even if some of his arguments were not so. But he went on to
argue that sense-data were the only things of whose existence our
perceptions could assure us; and that to be known is to be 'in' a
mind, and therefore to be mental. Hence he concluded that nothing can
ever be known except what is in some mind, and that whatever is known
without being in my mind must be in some other mind.
In order to understand his argument, it is necessary to understand his
use of the word 'idea'. He gives the name 'idea' to anything which is
_immediately_ known, as, for example, sense-data are known. Thus a
particular colour which we see is an idea; so is a voice which we
hear, and so on. But the term is not wholly confined to sense-data.
There will also be things remembered or imagined, for with such things
also we have immediate acquaintance at the moment of remembering or
imagining. All such immediate data he calls 'ideas'.
He then proceeds to consider common objects, such as a tree, for
instance. He shows that all we know immediately when we 'perceive'
the tree consists of ideas in his sense of the word, and he argues
that there is not the slightest ground for supposing that there is
anything real about the tree except what is perceived. Its being, he
says, consists in being perceived: in the Latin of the schoolmen its
'_esse_' is '_percipi_'. He fully admits that the tree must continue
to exist even when we shut our eyes or when no human being is near it.
But this continued existence, he says, is due to the fact that God
continues to perceive it; the 'real' tree, which corresponds to what
we called the physical object, consists of ideas in the mind of God,
ideas more or less like those we have when we see the tree, but
differing in the fact that they are permanent in God's mind so long as
the tree continues to exist. All our perceptions, according to him,
consist in a partial participation in God's perceptions, and it is
because of this participation that different people see more or less
the same tree. Thus apart from minds and their ideas there is nothing
in the world, nor is it possible that anything else should ever be
known, since whatever is known is necessarily an idea.
There are in this argument a good many fallacies which have been
important in the history of philosophy, and which it will be as well
to bring to light. In the first place, there is a confusion
engendered by the use of the word 'idea'. We think of an idea as
essentially something in somebody's mind, and thus when we are told
that a tree consists entirely of ideas, it is natural to suppose that,
if so, the tree must be entirely in minds. But the notion of being
'in' the mind is ambiguous. We speak of bearing a person in mind, not
meaning that the person is in our minds, but that a thought of him is
in our minds. When a man says that some business he had to arrange
went clean out of his mind, he does not mean to imply that the
business itself was ever in his mind, but only that a thought of the
business was formerly in his mind, but afterwards ceased to be in his
mind. And so when Berkeley says that the tree must be in our minds if
we can know it, all that he really has a right to say is that a
thought of the tree must be in our minds. To argue that the tree
itself must be in our minds is like arguing that a person whom we bear
in mind is himself in our minds. This confusion may seem too gross to
have been really committed by any competent philosopher, but various
attendant circumstances rendered it possible. In order to see how it
was possible, we must go more deeply into the question as to the
nature of ideas.
Before taking up the general question of the nature of ideas, we must
disentangle two entirely separate questions which arise concerning
sense-data and physical objects. We saw that, for various reasons of
detail, Berkeley was right in treating the sense-data which constitute
our perception of the tree as more or less subjective, in the sense
that they depend upon us as much as upon the tree, and would not exist
if the tree were not being perceived. But this is an entirely
different point from the one by which Berkeley seeks to prove that
whatever can be immediately known must be in a mind. For this purpose
arguments of detail as to the dependence of sense-data upon us are
useless. It is necessary to prove, generally, that by being known,
things are shown to be mental. This is what Berkeley believes himself
to have done. It is this question, and not our previous question as
to the difference between sense-data and the physical object, that
must now concern us.
Taking the word 'idea' in Berkeley's sense, there are two quite
distinct things to be considered whenever an idea is before the mind.
There is on the one hand the thing of which we are aware--say the
colour of my table--and on the other hand the actual awareness itself,
the mental act of apprehending the thing. The mental act is
undoubtedly mental, but is there any reason to suppose that the thing
apprehended is in any sense mental? Our previous arguments concerning
the colour did not prove it to be mental; they only proved that its
existence depends upon the relation of our sense organs to the
physical object--in our case, the table. That is to say, they proved
that a certain colour will exist, in a certain light, if a normal eye
is placed at a certain point relatively to the table. They did not
prove that the colour is in the mind of the percipient.
Berkeley's view, that obviously the colour must be in the mind, seems
to depend for its plausibility upon confusing the thing apprehended
with the act of apprehension. Either of these might be called an
'idea'; probably either would have been called an idea by Berkeley.
The act is undoubtedly in the mind; hence, when we are thinking of the
act, we readily assent to the view that ideas must be in the mind.
Then, forgetting that this was only true when ideas were taken as acts
of apprehension, we transfer the proposition that 'ideas are in the
mind' to ideas in the other sense, i.e. to the things apprehended by
our acts of apprehension. Thus, by an unconscious equivocation, we
arrive at the conclusion that whatever we can apprehend must be in our
minds. This seems to be the true analysis of Berkeley's argument, and
the ultimate fallacy upon which it rests.
This question of the distinction between act and object in our
apprehending of things is vitally important, since our whole power of
acquiring knowledge is bound up with it. The faculty of being
acquainted with things other than itself is the main characteristic of
a mind. Acquaintance with objects essentially consists in a relation
between the mind and something other than the mind; it is this that
constitutes the mind's power of knowing things. If we say that the
things known must be in the mind, we are either unduly limiting the
mind's power of knowing, or we are uttering a mere tautology. We are
uttering a mere tautology if we mean by '_in_ the mind' the same as by
'_before_ the mind', i.e. if we mean merely being apprehended by the
mind. But if we mean this, we shall have to admit that what, _in this
sense_, is in the mind, may nevertheless be not mental. Thus when we
realize the nature of knowledge, Berkeley's argument is seen to be
wrong in substance as well as in form, and his grounds for supposing
that 'ideas'--i.e. the objects apprehended--must be mental, are found
to have no validity whatever. Hence his grounds in favour of idealism
may be dismissed. It remains to see whether there are any other
grounds.
It is often said, as though it were a self-evident truism, that we
cannot know that anything exists which we do not know. It is inferred
that whatever can in any way be relevant to our experience must be at
least capable of being known by us; whence it follows that if matter
were essentially something with which we could not become acquainted,
matter would be something which we could not know to exist, and which
could have for us no importance whatever. It is generally also
implied, for reasons which remain obscure, that what can have no
importance for us cannot be real, and that therefore matter, if it is
not composed of minds or of mental ideas, is impossible and a mere
chimaera.
To go into this argument fully at our present stage would be
impossible, since it raises points requiring a considerable
preliminary discussion; but certain reasons for rejecting the argument
may be noticed at once. To begin at the end: there is no reason why
what cannot have any _practical_ importance for us should not be real.
It is true that, if _theoretical_ importance is included, everything
real is of _some_ importance to us, since, as persons desirous of
knowing the truth about the universe, we have some interest in
everything that the universe contains. But if this sort of interest
is included, it is not the case that matter has no importance for us,
provided it exists even if we cannot know that it exists. We can,
obviously, suspect that it may exist, and wonder whether it does;
hence it is connected with our desire for knowledge, and has the
importance of either satisfying or thwarting this desire.
Again, it is by no means a truism, and is in fact false, that we
cannot know that anything exists which we do not know. The word
'know' is here used in two different senses. (1) In its first use it
is applicable to the sort of knowledge which is opposed to error, the
sense in which what we know is _true_, the sense which applies to our
beliefs and convictions, i.e. to what are called _judgements_. In
this sense of the word we know _that_ something is the case. This
sort of knowledge may be described as knowledge of _truths_. (2) In
the second use of the word 'know' above, the word applies to our
knowledge of _things_, which we may call _acquaintance_. This is the
sense in which we know sense-data. (The distinction involved is
roughly that between _savoir_ and _connaître_ in French, or between
_wissen_ and _kennen_ in German.)
Thus the statement which seemed like a truism becomes, when re-stated,
the following: 'We can never truly judge that something with which we
are not acquainted exists.' This is by no means a truism, but on the
contrary a palpable falsehood. I have not the honour to be acquainted
with the Emperor of China, but I truly judge that he exists. It may
be said, of course, that I judge this because of other people's
acquaintance with him. This, however, would be an irrelevant retort,
since, if the principle were true, I could not know that any one else
is acquainted with him. But further: there is no reason why I should
not know of the existence of something with which nobody is
acquainted. This point is important, and demands elucidation.
If I am acquainted with a thing which exists, my acquaintance gives me
the knowledge that it exists. But it is not true that, conversely,
whenever I can know that a thing of a certain sort exists, I or some
one else must be acquainted with the thing. What happens, in cases
where I have true judgement without acquaintance, is that the thing is
known to me by _description_, and that, in virtue of some general
principle, the existence of a thing answering to this description can
be inferred from the existence of something with which I am
acquainted. In order to understand this point fully, it will be well
first to deal with the difference between knowledge by acquaintance
and knowledge by description, and then to consider what knowledge of
general principles, if any, has the same kind of certainty as our
knowledge of the existence of our own experiences. These subjects
will be dealt with in the following chapters.
CHAPTER V
KNOWLEDGE BY ACQUAINTANCE AND KNOWLEDGE BY DESCRIPTION
In the preceding chapter we saw that there are two sorts of knowledge:
knowledge of things, and knowledge of truths. In this chapter we
shall be concerned exclusively with knowledge of things, of which in
turn we shall have to distinguish two kinds. Knowledge of things,
when it is of the kind we call knowledge by _acquaintance_, is
essentially simpler than any knowledge of truths, and logically
independent of knowledge of truths, though it would be rash to assume
that human beings ever, in fact, have acquaintance with things without
at the same time knowing some truth about them. Knowledge of things
by _description_, on the contrary, always involves, as we shall find
in the course of the present chapter, some knowledge of truths as its
source and ground. But first of all we must make clear what we mean
by 'acquaintance' and what we mean by 'description'.
We shall say that we have _acquaintance_ with anything of which we are
directly aware, without the intermediary of any process of inference
or any knowledge of truths. Thus in the presence of my table I am
acquainted with the sense-data that make up the appearance of my
table--its colour, shape, hardness, smoothness, etc.; all these are
things of which I am immediately conscious when I am seeing and
touching my table. The particular shade of colour that I am seeing
may have many things said about it--I may say that it is brown, that
it is rather dark, and so on. But such statements, though they make
me know truths about the colour, do not make me know the colour itself
any better than I did before so far as concerns knowledge of the
colour itself, as opposed to knowledge of truths about it, I know the
colour perfectly and completely when I see it, and no further
knowledge of it itself is even theoretically possible. Thus the
sense-data which make up the appearance of my table are things with
which I have acquaintance, things immediately known to me just as they
are.
My knowledge of the table as a physical object, on the contrary, is
not direct knowledge. Such as it is, it is obtained through
acquaintance with the sense-data that make up the appearance of the
table. We have seen that it is possible, without absurdity, to doubt
whether there is a table at all, whereas it is not possible to doubt
the sense-data. My knowledge of the table is of the kind which we
shall call 'knowledge by description'. The table is 'the physical
object which causes such-and-such sense-data'. This describes the
table by means of the sense-data. In order to know anything at all
about the table, we must know truths connecting it with things with
which we have acquaintance: we must know that 'such-and-such
sense-data are caused by a physical object'. There is no state of
mind in which we are directly aware of the table; all our knowledge of
the table is really knowledge of truths, and the actual thing which is
the table is not, strictly speaking, known to us at all. We know a
description, and we know that there is just one object to which this
description applies, though the object itself is not directly known to
us. In such a case, we say that our knowledge of the object is
knowledge by description.
All our knowledge, both knowledge of things and knowledge of truths,
rests upon acquaintance as its foundation. It is therefore important
to consider what kinds of things there are with which we have
acquaintance.
Sense-data, as we have already seen, are among the things with which
we are acquainted; in fact, they supply the most obvious and striking
example of knowledge by acquaintance. But if they were the sole
example, our knowledge would be very much more restricted than it is.
We should only know what is now present to our senses: we could not
know anything about the past--not even that there was a past--nor
could we know any truths about our sense-data, for all knowledge of
truths, as we shall show, demands acquaintance with things which are
of an essentially different character from sense-data, the things
which are sometimes called 'abstract ideas', but which we shall call
'universals'. We have therefore to consider acquaintance with other
things besides sense-data if we are to obtain any tolerably adequate
analysis of our knowledge.
The first extension beyond sense-data to be considered is acquaintance
by _memory_. It is obvious that we often remember what we have seen
or heard or had otherwise present to our senses, and that in such
cases we are still immediately aware of what we remember, in spite of
the fact that it appears as past and not as present. This immediate
knowledge by memory is the source of all our knowledge concerning the
past: without it, there could be no knowledge of the past by
inference, since we should never know that there was anything past to
be inferred.
The next extension to be considered is acquaintance by
_introspection_. We are not only aware of things, but we are often
aware of being aware of them. When I see the sun, I am often aware of
my seeing the sun; thus 'my seeing the sun' is an object with which I
have acquaintance. When I desire food, I may be aware of my desire
for food; thus 'my desiring food' is an object with which I am
acquainted. Similarly we may be aware of our feeling pleasure or
pain, and generally of the events which happen in our minds. This
kind of acquaintance, which may be called self-consciousness, is the
source of all our knowledge of mental things. It is obvious that it
is only what goes on in our own minds that can be thus known
immediately. What goes on in the minds of others is known to us
through our perception of their bodies, that is, through the
sense-data in us which are associated with their bodies. But for our
acquaintance with the contents of our own minds, we should be unable
to imagine the minds of others, and therefore we could never arrive at
the knowledge that they have minds. It seems natural to suppose that
self-consciousness is one of the things that distinguish men from
animals: animals, we may suppose, though they have acquaintance with
sense-data, never become aware of this acquaintance. I do not mean
that they _doubt_ whether they exist, but that they have never become
conscious of the fact that they have sensations and feelings, nor
therefore of the fact that they, the subjects of their sensations and
feelings, exist.
We have spoken of acquaintance with the contents of our minds as
_self_-consciousness, but it is not, of course, consciousness of our
_self_: it is consciousness of particular thoughts and feelings. The
question whether we are also acquainted with our bare selves, as
opposed to particular thoughts and feelings, is a very difficult one,
upon which it would be rash to speak positively. When we try to look
into ourselves we always seem to come upon some particular thought or
feeling, and not upon the 'I' which has the thought or feeling.
Nevertheless there are some reasons for thinking that we are
acquainted with the 'I', though the acquaintance is hard to
disentangle from other things. To make clear what sort of reason
there is, let us consider for a moment what our acquaintance with
particular thoughts really involves.
When I am acquainted with 'my seeing the sun', it seems plain that I
am acquainted with two different things in relation to each other. On
the one hand there is the sense-datum which represents the sun to me,
on the other hand there is that which sees this sense-datum. All
acquaintance, such as my acquaintance with the sense-datum which
represents the sun, seems obviously a relation between the person
acquainted and the object with which the person is acquainted. When a
case of acquaintance is one with which I can be acquainted (as I am
acquainted with my acquaintance with the sense-datum representing the
sun), it is plain that the person acquainted is myself. Thus, when I
am acquainted with my seeing the sun, the whole fact with which I am
acquainted is 'Self-acquainted-with-sense-datum'.
Further, we know the truth 'I am acquainted with this sense-datum'.
It is hard to see how we could know this truth, or even understand
what is meant by it, unless we were acquainted with something which we
call 'I'. It does not seem necessary to suppose that we are
acquainted with a more or less permanent person, the same to-day as
yesterday, but it does seem as though we must be acquainted with that
thing, whatever its nature, which sees the sun and has acquaintance
with sense-data. Thus, in some sense it would seem we must be
acquainted with our Selves as opposed to our particular experiences.
But the question is difficult, and complicated arguments can be
adduced on either side. Hence, although acquaintance with ourselves
seems _probably_ to occur, it is not wise to assert that it
undoubtedly does occur.
We may therefore sum up as follows what has been said concerning
acquaintance with things that exist. We have acquaintance in
sensation with the data of the outer senses, and in introspection with
the data of what may be called the inner sense--thoughts, feelings,
desires, etc.; we have acquaintance in memory with things which have
been data either of the outer senses or of the inner sense. Further,
it is probable, though not certain, that we have acquaintance with
Self, as that which is aware of things or has desires towards things.
In addition to our acquaintance with particular existing things, we
also have acquaintance with what we shall call _universals_, that is
to say, general ideas, such as _whiteness_, _diversity_,
_brotherhood_, and so on. Every complete sentence must contain at
least one word which stands for a universal, since all verbs have a
meaning which is universal. We shall return to universals later on,
in Chapter IX; for the present, it is only necessary to guard against
the supposition that whatever we can be acquainted with must be
something particular and existent. Awareness of universals is called
_conceiving_, and a universal of which we are aware is called a
_concept_.
It will be seen that among the objects with which we are acquainted
are not included physical objects (as opposed to sense-data), nor
other people's minds. These things are known to us by what I call
'knowledge by description', which we must now consider.
By a 'description' I mean any phrase of the form 'a so-and-so' or 'the
so-and-so'. A phrase of the form 'a so-and-so' I shall call an
'ambiguous' description; a phrase of the form 'the so-and-so' (in the
singular) I shall call a 'definite' description. Thus 'a man' is an
ambiguous description, and 'the man with the iron mask' is a definite
description. There are various problems connected with ambiguous
descriptions, but I pass them by, since they do not directly concern
the matter we are discussing, which is the nature of our knowledge
concerning objects in cases where we know that there is an object
answering to a definite description, though we are not acquainted with
any such object. This is a matter which is concerned exclusively with
definite descriptions. I shall therefore, in the sequel, speak simply
of 'descriptions' when I mean 'definite descriptions'. Thus a
description will mean any phrase of the form 'the so-and-so' in the
singular.
We shall say that an object is 'known by description' when we know
that it is 'the so-and-so', i.e. when we know that there is one
object, and no more, having a certain property; and it will generally
be implied that we do not have knowledge of the same object by
acquaintance. We know that the man with the iron mask existed, and
many propositions are known about him; but we do not know who he was.
We know that the candidate who gets the most votes will be elected,
and in this case we are very likely also acquainted (in the only sense
in which one can be acquainted with some one else) with the man who
is, in fact, the candidate who will get most votes; but we do not know
which of the candidates he is, i.e. we do not know any proposition of
the form 'A is the candidate who will get most votes' where A is one
of the candidates by name. We shall say that we have 'merely
descriptive knowledge' of the so-and-so when, although we know that
the so-and-so exists, and although we may possibly be acquainted with
the object which is, in fact, the so-and-so, yet we do not know any
proposition '_a_ is the so-and-so', where _a_ is something with which
we are acquainted.
When we say 'the so-and-so exists', we mean that there is just one
object which is the so-and-so. The proposition '_a_ is the so-and-so'
means that _a_ has the property so-and-so, and nothing else has. 'Mr.
A. is the Unionist candidate for this constituency' means 'Mr. A.
is a Unionist candidate for this constituency, and no one else is'.
'The Unionist candidate for this constituency exists' means 'some one
is a Unionist candidate for this constituency, and no one else is'.
Thus, when we are acquainted with an object which is the so-and-so, we
know that the so-and-so exists; but we may know that the so-and-so
exists when we are not acquainted with any object which we know to be
the so-and-so, and even when we are not acquainted with any object
which, in fact, is the so-and-so.
Common words, even proper names, are usually really descriptions.
That is to say, the thought in the mind of a person using a proper
name correctly can generally only be expressed explicitly if we
replace the proper name by a description. Moreover, the description
required to express the thought will vary for different people, or for
the same person at different times. The only thing constant (so long
as the name is rightly used) is the object to which the name applies.
But so long as this remains constant, the particular description
involved usually makes no difference to the truth or falsehood of the
proposition in which the name appears.
Let us take some illustrations. Suppose some statement made about
Bismarck. Assuming that there is such a thing as direct acquaintance
with oneself, Bismarck himself might have used his name directly to
designate the particular person with whom he was acquainted. In this
case, if he made a judgement about himself, he himself might be a
constituent of the judgement. Here the proper name has the direct use
which it always wishes to have, as simply standing for a certain
object, and not for a description of the object. But if a person who
knew Bismarck made a judgement about him, the case is different. What
this person was acquainted with were certain sense-data which he
connected (rightly, we will suppose) with Bismarck's body. His body,
as a physical object, and still more his mind, were only known as the
body and the mind connected with these sense-data. That is, they were
known by description. It is, of course, very much a matter af chance
which characteristics of a man's appearance will come into a friend's
mind when he thinks of him; thus the description actually in the
friend's mind is accidental. The essential point is that he knows
that the various descriptions all apply to the same entity, in spite
of not being acquainted with the entity in question.
When we, who did not know Bismarck, make a judgement about him, the
description in our minds will probably be some more or less vague mass
of historical knowledge--far more, in most cases, than is required to
identify him. But, for the sake of illustration, let us assume that
we think of him as 'the first Chancellor of the German Empire'. Here
all the words are abstract except 'German'. The word 'German' will,
again, have different meanings for different people. To some it will
recall travels in Germany, to some the look of Germany on the map, and
so on. But if we are to obtain a description which we know to be
applicable, we shall be compelled, at some point, to bring in a
reference to a particular with which we are acquainted. Such
reference is involved in any mention of past, present, and future (as
opposed to definite dates), or of here and there, or of what others
have told us. Thus it would seem that, in some way or other, a
description known to be applicable to a particular must involve some
reference to a particular with which we are acquainted, if our
knowledge about the thing described is not to be merely what follows
_logically_ from the description. For example, 'the most long-lived
of men' is a description involving only universals, which must apply
to some man, but we can make no judgements concerning this man which
involve knowledge about him beyond what the description gives. If,
however, we say, 'The first Chancellor of the German Empire was an
astute diplomatist', we can only be assured of the truth of our
judgement in virtue of something with which we are acquainted--usually
a testimony heard or read. Apart from the information we convey to
others, apart from the fact about the actual Bismarck, which gives
importance to our judgement, the thought we really have contains the
one or more particulars involved, and otherwise consists wholly of
concepts.
All names of places--London, England, Europe, the Earth, the Solar
System--similarly involve, when used, descriptions which start from
some one or more particulars with which we are acquainted. I suspect
that even the Universe, as considered by metaphysics, involves such a
connexion with particulars. In logic, on the contrary, where we are
concerned not merely with what does exist, but with whatever might or
could exist or be, no reference to actual particulars is involved.
It would seem that, when we make a statement about something only
known by description, we often _intend_ to make our statement, not in
the form involving the description, but about the actual thing
described. That is to say, when we say anything about Bismarck, we
should like, if we could, to make the judgement which Bismarck alone
can make, namely, the judgement of which he himself is a constituent.
In this we are necessarily defeated, since the actual Bismarck is
unknown to us. But we know that there is an object B, called
Bismarck, and that B was an astute diplomatist. We can thus
_describe_ the proposition we should like to affirm, namely, 'B was an
astute diplomatist', where B is the object which was Bismarck. If we
are describing Bismarck as 'the first Chancellor of the German
Empire', the proposition we should like to affirm may be described as
'the proposition asserting, concerning the actual object which was the
first Chancellor of the German Empire, that this object was an astute
diplomatist'. What enables us to communicate in spite of the varying
descriptions we employ is that we know there is a true proposition
concerning the actual Bismarck, and that however we may vary the
description (so long as the description is correct) the proposition
described is still the same. This proposition, which is described and
is known to be true, is what interests us; but we are not acquainted
with the proposition itself, and do not know it, though we know it is
true.
It will be seen that there are various stages in the removal from
acquaintance with particulars: there is Bismarck to people who knew
him; Bismarck to those who only know of him through history; the man
with the iron mask; the longest-lived of men. These are progressively
further removed from acquaintance with particulars; the first comes as
near to acquaintance as is possible in regard to another person; in
the second, we shall still be said to know 'who Bismarck was'; in the
third, we do not know who was the man with the iron mask, though we
can know many propositions about him which are not logically deducible
from the fact that he wore an iron mask; in the fourth, finally, we
know nothing beyond what is logically deducible from the definition of
the man. There is a similar hierarchy in the region of universals.
Many universals, like many particulars, are only known to us by
description. But here, as in the case of particulars, knowledge
concerning what is known by description is ultimately reducible to
knowledge concerning what is known by acquaintance.
The fundamental principle in the analysis of propositions containing
descriptions is this: _Every proposition which we can understand must
be composed wholly of constituents with which we are acquainted_.
We shall not at this stage attempt to answer all the objections which
may be urged against this fundamental principle. For the present, we
shall merely point out that, in some way or other, it must be possible
to meet these objections, for it is scarcely conceivable that we can
make a judgement or entertain a supposition without knowing what it is
that we are judging or supposing about. We must attach _some_ meaning
to the words we use, if we are to speak significantly and not utter
mere noise; and the meaning we attach to our words must be something
with which we are acquainted. Thus when, for example, we make a
statement about Julius Caesar, it is plain that Julius Caesar himself
is not before our minds, since we are not acquainted with him. We
have in mind some description of Julius Caesar: 'the man who was
assassinated on the Ides of March', 'the founder of the Roman Empire',
or, perhaps, merely 'the man whose name was _Julius Caesar_'. (In
this last description, _Julius Caesar_ is a noise or shape with which
we are acquainted.) Thus our statement does not mean quite what it
seems to mean, but means something involving, instead of Julius
Caesar, some description of him which is composed wholly of
particulars and universals with which we are acquainted.
The chief importance of knowledge by description is that it enables us
to pass beyond the limits of our private experience. In spite of the
fact that we can only know truths which are wholly composed of terms
which we have experienced in acquaintance, we can yet have knowledge
by description of things which we have never experienced. In view of
the very narrow range of our immediate experience, this result is
vital, and until it is understood, much of our knowledge must remain
mysterious and therefore doubtful.
In the preceding chapter we saw that there are two sorts of knowledge:
knowledge of things, and knowledge of truths. In this chapter we
shall be concerned exclusively with knowledge of things, of which in
turn we shall have to distinguish two kinds. Knowledge of things,
when it is of the kind we call knowledge by _acquaintance_, is
essentially simpler than any knowledge of truths, and logically
independent of knowledge of truths, though it would be rash to assume
that human beings ever, in fact, have acquaintance with things without
at the same time knowing some truth about them. Knowledge of things
by _description_, on the contrary, always involves, as we shall find
in the course of the present chapter, some knowledge of truths as its
source and ground. But first of all we must make clear what we mean
by 'acquaintance' and what we mean by 'description'.
We shall say that we have _acquaintance_ with anything of which we are
directly aware, without the intermediary of any process of inference
or any knowledge of truths. Thus in the presence of my table I am
acquainted with the sense-data that make up the appearance of my
table--its colour, shape, hardness, smoothness, etc.; all these are
things of which I am immediately conscious when I am seeing and
touching my table. The particular shade of colour that I am seeing
may have many things said about it--I may say that it is brown, that
it is rather dark, and so on. But such statements, though they make
me know truths about the colour, do not make me know the colour itself
any better than I did before so far as concerns knowledge of the
colour itself, as opposed to knowledge of truths about it, I know the
colour perfectly and completely when I see it, and no further
knowledge of it itself is even theoretically possible. Thus the
sense-data which make up the appearance of my table are things with
which I have acquaintance, things immediately known to me just as they
are.
My knowledge of the table as a physical object, on the contrary, is
not direct knowledge. Such as it is, it is obtained through
acquaintance with the sense-data that make up the appearance of the
table. We have seen that it is possible, without absurdity, to doubt
whether there is a table at all, whereas it is not possible to doubt
the sense-data. My knowledge of the table is of the kind which we
shall call 'knowledge by description'. The table is 'the physical
object which causes such-and-such sense-data'. This describes the
table by means of the sense-data. In order to know anything at all
about the table, we must know truths connecting it with things with
which we have acquaintance: we must know that 'such-and-such
sense-data are caused by a physical object'. There is no state of
mind in which we are directly aware of the table; all our knowledge of
the table is really knowledge of truths, and the actual thing which is
the table is not, strictly speaking, known to us at all. We know a
description, and we know that there is just one object to which this
description applies, though the object itself is not directly known to
us. In such a case, we say that our knowledge of the object is
knowledge by description.
All our knowledge, both knowledge of things and knowledge of truths,
rests upon acquaintance as its foundation. It is therefore important
to consider what kinds of things there are with which we have
acquaintance.
Sense-data, as we have already seen, are among the things with which
we are acquainted; in fact, they supply the most obvious and striking
example of knowledge by acquaintance. But if they were the sole
example, our knowledge would be very much more restricted than it is.
We should only know what is now present to our senses: we could not
know anything about the past--not even that there was a past--nor
could we know any truths about our sense-data, for all knowledge of
truths, as we shall show, demands acquaintance with things which are
of an essentially different character from sense-data, the things
which are sometimes called 'abstract ideas', but which we shall call
'universals'. We have therefore to consider acquaintance with other
things besides sense-data if we are to obtain any tolerably adequate
analysis of our knowledge.
The first extension beyond sense-data to be considered is acquaintance
by _memory_. It is obvious that we often remember what we have seen
or heard or had otherwise present to our senses, and that in such
cases we are still immediately aware of what we remember, in spite of
the fact that it appears as past and not as present. This immediate
knowledge by memory is the source of all our knowledge concerning the
past: without it, there could be no knowledge of the past by
inference, since we should never know that there was anything past to
be inferred.
The next extension to be considered is acquaintance by
_introspection_. We are not only aware of things, but we are often
aware of being aware of them. When I see the sun, I am often aware of
my seeing the sun; thus 'my seeing the sun' is an object with which I
have acquaintance. When I desire food, I may be aware of my desire
for food; thus 'my desiring food' is an object with which I am
acquainted. Similarly we may be aware of our feeling pleasure or
pain, and generally of the events which happen in our minds. This
kind of acquaintance, which may be called self-consciousness, is the
source of all our knowledge of mental things. It is obvious that it
is only what goes on in our own minds that can be thus known
immediately. What goes on in the minds of others is known to us
through our perception of their bodies, that is, through the
sense-data in us which are associated with their bodies. But for our
acquaintance with the contents of our own minds, we should be unable
to imagine the minds of others, and therefore we could never arrive at
the knowledge that they have minds. It seems natural to suppose that
self-consciousness is one of the things that distinguish men from
animals: animals, we may suppose, though they have acquaintance with
sense-data, never become aware of this acquaintance. I do not mean
that they _doubt_ whether they exist, but that they have never become
conscious of the fact that they have sensations and feelings, nor
therefore of the fact that they, the subjects of their sensations and
feelings, exist.
We have spoken of acquaintance with the contents of our minds as
_self_-consciousness, but it is not, of course, consciousness of our
_self_: it is consciousness of particular thoughts and feelings. The
question whether we are also acquainted with our bare selves, as
opposed to particular thoughts and feelings, is a very difficult one,
upon which it would be rash to speak positively. When we try to look
into ourselves we always seem to come upon some particular thought or
feeling, and not upon the 'I' which has the thought or feeling.
Nevertheless there are some reasons for thinking that we are
acquainted with the 'I', though the acquaintance is hard to
disentangle from other things. To make clear what sort of reason
there is, let us consider for a moment what our acquaintance with
particular thoughts really involves.
When I am acquainted with 'my seeing the sun', it seems plain that I
am acquainted with two different things in relation to each other. On
the one hand there is the sense-datum which represents the sun to me,
on the other hand there is that which sees this sense-datum. All
acquaintance, such as my acquaintance with the sense-datum which
represents the sun, seems obviously a relation between the person
acquainted and the object with which the person is acquainted. When a
case of acquaintance is one with which I can be acquainted (as I am
acquainted with my acquaintance with the sense-datum representing the
sun), it is plain that the person acquainted is myself. Thus, when I
am acquainted with my seeing the sun, the whole fact with which I am
acquainted is 'Self-acquainted-with-sense-datum'.
Further, we know the truth 'I am acquainted with this sense-datum'.
It is hard to see how we could know this truth, or even understand
what is meant by it, unless we were acquainted with something which we
call 'I'. It does not seem necessary to suppose that we are
acquainted with a more or less permanent person, the same to-day as
yesterday, but it does seem as though we must be acquainted with that
thing, whatever its nature, which sees the sun and has acquaintance
with sense-data. Thus, in some sense it would seem we must be
acquainted with our Selves as opposed to our particular experiences.
But the question is difficult, and complicated arguments can be
adduced on either side. Hence, although acquaintance with ourselves
seems _probably_ to occur, it is not wise to assert that it
undoubtedly does occur.
We may therefore sum up as follows what has been said concerning
acquaintance with things that exist. We have acquaintance in
sensation with the data of the outer senses, and in introspection with
the data of what may be called the inner sense--thoughts, feelings,
desires, etc.; we have acquaintance in memory with things which have
been data either of the outer senses or of the inner sense. Further,
it is probable, though not certain, that we have acquaintance with
Self, as that which is aware of things or has desires towards things.
In addition to our acquaintance with particular existing things, we
also have acquaintance with what we shall call _universals_, that is
to say, general ideas, such as _whiteness_, _diversity_,
_brotherhood_, and so on. Every complete sentence must contain at
least one word which stands for a universal, since all verbs have a
meaning which is universal. We shall return to universals later on,
in Chapter IX; for the present, it is only necessary to guard against
the supposition that whatever we can be acquainted with must be
something particular and existent. Awareness of universals is called
_conceiving_, and a universal of which we are aware is called a
_concept_.
It will be seen that among the objects with which we are acquainted
are not included physical objects (as opposed to sense-data), nor
other people's minds. These things are known to us by what I call
'knowledge by description', which we must now consider.
By a 'description' I mean any phrase of the form 'a so-and-so' or 'the
so-and-so'. A phrase of the form 'a so-and-so' I shall call an
'ambiguous' description; a phrase of the form 'the so-and-so' (in the
singular) I shall call a 'definite' description. Thus 'a man' is an
ambiguous description, and 'the man with the iron mask' is a definite
description. There are various problems connected with ambiguous
descriptions, but I pass them by, since they do not directly concern
the matter we are discussing, which is the nature of our knowledge
concerning objects in cases where we know that there is an object
answering to a definite description, though we are not acquainted with
any such object. This is a matter which is concerned exclusively with
definite descriptions. I shall therefore, in the sequel, speak simply
of 'descriptions' when I mean 'definite descriptions'. Thus a
description will mean any phrase of the form 'the so-and-so' in the
singular.
We shall say that an object is 'known by description' when we know
that it is 'the so-and-so', i.e. when we know that there is one
object, and no more, having a certain property; and it will generally
be implied that we do not have knowledge of the same object by
acquaintance. We know that the man with the iron mask existed, and
many propositions are known about him; but we do not know who he was.
We know that the candidate who gets the most votes will be elected,
and in this case we are very likely also acquainted (in the only sense
in which one can be acquainted with some one else) with the man who
is, in fact, the candidate who will get most votes; but we do not know
which of the candidates he is, i.e. we do not know any proposition of
the form 'A is the candidate who will get most votes' where A is one
of the candidates by name. We shall say that we have 'merely
descriptive knowledge' of the so-and-so when, although we know that
the so-and-so exists, and although we may possibly be acquainted with
the object which is, in fact, the so-and-so, yet we do not know any
proposition '_a_ is the so-and-so', where _a_ is something with which
we are acquainted.
When we say 'the so-and-so exists', we mean that there is just one
object which is the so-and-so. The proposition '_a_ is the so-and-so'
means that _a_ has the property so-and-so, and nothing else has. 'Mr.
A. is the Unionist candidate for this constituency' means 'Mr. A.
is a Unionist candidate for this constituency, and no one else is'.
'The Unionist candidate for this constituency exists' means 'some one
is a Unionist candidate for this constituency, and no one else is'.
Thus, when we are acquainted with an object which is the so-and-so, we
know that the so-and-so exists; but we may know that the so-and-so
exists when we are not acquainted with any object which we know to be
the so-and-so, and even when we are not acquainted with any object
which, in fact, is the so-and-so.
Common words, even proper names, are usually really descriptions.
That is to say, the thought in the mind of a person using a proper
name correctly can generally only be expressed explicitly if we
replace the proper name by a description. Moreover, the description
required to express the thought will vary for different people, or for
the same person at different times. The only thing constant (so long
as the name is rightly used) is the object to which the name applies.
But so long as this remains constant, the particular description
involved usually makes no difference to the truth or falsehood of the
proposition in which the name appears.
Let us take some illustrations. Suppose some statement made about
Bismarck. Assuming that there is such a thing as direct acquaintance
with oneself, Bismarck himself might have used his name directly to
designate the particular person with whom he was acquainted. In this
case, if he made a judgement about himself, he himself might be a
constituent of the judgement. Here the proper name has the direct use
which it always wishes to have, as simply standing for a certain
object, and not for a description of the object. But if a person who
knew Bismarck made a judgement about him, the case is different. What
this person was acquainted with were certain sense-data which he
connected (rightly, we will suppose) with Bismarck's body. His body,
as a physical object, and still more his mind, were only known as the
body and the mind connected with these sense-data. That is, they were
known by description. It is, of course, very much a matter af chance
which characteristics of a man's appearance will come into a friend's
mind when he thinks of him; thus the description actually in the
friend's mind is accidental. The essential point is that he knows
that the various descriptions all apply to the same entity, in spite
of not being acquainted with the entity in question.
When we, who did not know Bismarck, make a judgement about him, the
description in our minds will probably be some more or less vague mass
of historical knowledge--far more, in most cases, than is required to
identify him. But, for the sake of illustration, let us assume that
we think of him as 'the first Chancellor of the German Empire'. Here
all the words are abstract except 'German'. The word 'German' will,
again, have different meanings for different people. To some it will
recall travels in Germany, to some the look of Germany on the map, and
so on. But if we are to obtain a description which we know to be
applicable, we shall be compelled, at some point, to bring in a
reference to a particular with which we are acquainted. Such
reference is involved in any mention of past, present, and future (as
opposed to definite dates), or of here and there, or of what others
have told us. Thus it would seem that, in some way or other, a
description known to be applicable to a particular must involve some
reference to a particular with which we are acquainted, if our
knowledge about the thing described is not to be merely what follows
_logically_ from the description. For example, 'the most long-lived
of men' is a description involving only universals, which must apply
to some man, but we can make no judgements concerning this man which
involve knowledge about him beyond what the description gives. If,
however, we say, 'The first Chancellor of the German Empire was an
astute diplomatist', we can only be assured of the truth of our
judgement in virtue of something with which we are acquainted--usually
a testimony heard or read. Apart from the information we convey to
others, apart from the fact about the actual Bismarck, which gives
importance to our judgement, the thought we really have contains the
one or more particulars involved, and otherwise consists wholly of
concepts.
All names of places--London, England, Europe, the Earth, the Solar
System--similarly involve, when used, descriptions which start from
some one or more particulars with which we are acquainted. I suspect
that even the Universe, as considered by metaphysics, involves such a
connexion with particulars. In logic, on the contrary, where we are
concerned not merely with what does exist, but with whatever might or
could exist or be, no reference to actual particulars is involved.
It would seem that, when we make a statement about something only
known by description, we often _intend_ to make our statement, not in
the form involving the description, but about the actual thing
described. That is to say, when we say anything about Bismarck, we
should like, if we could, to make the judgement which Bismarck alone
can make, namely, the judgement of which he himself is a constituent.
In this we are necessarily defeated, since the actual Bismarck is
unknown to us. But we know that there is an object B, called
Bismarck, and that B was an astute diplomatist. We can thus
_describe_ the proposition we should like to affirm, namely, 'B was an
astute diplomatist', where B is the object which was Bismarck. If we
are describing Bismarck as 'the first Chancellor of the German
Empire', the proposition we should like to affirm may be described as
'the proposition asserting, concerning the actual object which was the
first Chancellor of the German Empire, that this object was an astute
diplomatist'. What enables us to communicate in spite of the varying
descriptions we employ is that we know there is a true proposition
concerning the actual Bismarck, and that however we may vary the
description (so long as the description is correct) the proposition
described is still the same. This proposition, which is described and
is known to be true, is what interests us; but we are not acquainted
with the proposition itself, and do not know it, though we know it is
true.
It will be seen that there are various stages in the removal from
acquaintance with particulars: there is Bismarck to people who knew
him; Bismarck to those who only know of him through history; the man
with the iron mask; the longest-lived of men. These are progressively
further removed from acquaintance with particulars; the first comes as
near to acquaintance as is possible in regard to another person; in
the second, we shall still be said to know 'who Bismarck was'; in the
third, we do not know who was the man with the iron mask, though we
can know many propositions about him which are not logically deducible
from the fact that he wore an iron mask; in the fourth, finally, we
know nothing beyond what is logically deducible from the definition of
the man. There is a similar hierarchy in the region of universals.
Many universals, like many particulars, are only known to us by
description. But here, as in the case of particulars, knowledge
concerning what is known by description is ultimately reducible to
knowledge concerning what is known by acquaintance.
The fundamental principle in the analysis of propositions containing
descriptions is this: _Every proposition which we can understand must
be composed wholly of constituents with which we are acquainted_.
We shall not at this stage attempt to answer all the objections which
may be urged against this fundamental principle. For the present, we
shall merely point out that, in some way or other, it must be possible
to meet these objections, for it is scarcely conceivable that we can
make a judgement or entertain a supposition without knowing what it is
that we are judging or supposing about. We must attach _some_ meaning
to the words we use, if we are to speak significantly and not utter
mere noise; and the meaning we attach to our words must be something
with which we are acquainted. Thus when, for example, we make a
statement about Julius Caesar, it is plain that Julius Caesar himself
is not before our minds, since we are not acquainted with him. We
have in mind some description of Julius Caesar: 'the man who was
assassinated on the Ides of March', 'the founder of the Roman Empire',
or, perhaps, merely 'the man whose name was _Julius Caesar_'. (In
this last description, _Julius Caesar_ is a noise or shape with which
we are acquainted.) Thus our statement does not mean quite what it
seems to mean, but means something involving, instead of Julius
Caesar, some description of him which is composed wholly of
particulars and universals with which we are acquainted.
The chief importance of knowledge by description is that it enables us
to pass beyond the limits of our private experience. In spite of the
fact that we can only know truths which are wholly composed of terms
which we have experienced in acquaintance, we can yet have knowledge
by description of things which we have never experienced. In view of
the very narrow range of our immediate experience, this result is
vital, and until it is understood, much of our knowledge must remain
mysterious and therefore doubtful.
CHAPTER VI
ON INDUCTION
In almost all our previous discussions we have been concerned in the
attempt to get clear as to our data in the way of knowledge of
existence. What things are there in the universe whose existence is
known to us owing to our being acquainted with them? So far, our
answer has been that we are acquainted with our sense-data, and,
probably, with ourselves. These we know to exist. And past
sense-data which are remembered are known to have existed in the past.
This knowledge supplies our data.
But if we are to be able to draw inferences from these data--if we are
to know of the existence of matter, of other people, of the past
before our individual memory begins, or of the future, we must know
general principles of some kind by means of which such inferences can
be drawn. It must be known to us that the existence of some one sort
of thing, A, is a sign of the existence of some other sort of thing,
B, either at the same time as A or at some earlier or later time, as,
for example, thunder is a sign of the earlier existence of lightning.
If this were not known to us, we could never extend our knowledge
beyond the sphere of our private experience; and this sphere, as we
have seen, is exceedingly limited. The question we have now to
consider is whether such an extension is possible, and if so, how it
is effected.
Let us take as an illustration a matter about which none of us, in
fact, feel the slightest doubt. We are all convinced that the sun
will rise to-morrow. Why? Is this belief a mere blind outcome of
past experience, or can it be justified as a reasonable belief? It is
not easy to find a test by which to judge whether a belief of this
kind is reasonable or not, but we can at least ascertain what sort of
general beliefs would suffice, if true, to justify the judgement that
the sun will rise to-morrow, and the many other similar judgements
upon which our actions are based.
It is obvious that if we are asked why we believe that the sun will
rise to-morrow, we shall naturally answer 'Because it always has risen
every day'. We have a firm belief that it will rise in the future,
because it has risen in the past. If we are challenged as to why we
believe that it will continue to rise as heretofore, we may appeal to
the laws of motion: the earth, we shall say, is a freely rotating
body, and such bodies do not cease to rotate unless something
interferes from outside, and there is nothing outside to interfere
with the earth between now and to-morrow. Of course it might be
doubted whether we are quite certain that there is nothing outside to
interfere, but this is not the interesting doubt. The interesting
doubt is as to whether the laws of motion will remain in operation
until to-morrow. If this doubt is raised, we find ourselves in the
same position as when the doubt about the sunrise was first raised.
The _only_ reason for believing that the laws of motion will remain in
operation is that they have operated hitherto, so far as our knowledge
of the past enables us to judge. It is true that we have a greater
body of evidence from the past in favour of the laws of motion than we
have in favour of the sunrise, because the sunrise is merely a
particular case of fulfilment of the laws of motion, and there are
countless other particular cases. But the real question is: Do _any_
number of cases of a law being fulfilled in the past afford evidence
that it will be fulfilled in the future? If not, it becomes plain
that we have no ground whatever for expecting the sun to rise
to-morrow, or for expecting the bread we shall eat at our next meal
not to poison us, or for any of the other scarcely conscious
expectations that control our daily lives. It is to be observed that
all such expectations are only _probable_; thus we have not to seek
for a proof that they _must_ be fulfilled, but only for some reason in
favour of the view that they are _likely_ to be fulfilled.
Now in dealing with this question we must, to begin with, make an
important distinction, without which we should soon become involved in
hopeless confusions. Experience has shown us that, hitherto, the
frequent repetition of some uniform succession or coexistence has been
a _cause_ of our expecting the same succession or coexistence on the
next occasion. Food that has a certain appearance generally has a
certain taste, and it is a severe shock to our expectations when the
familiar appearance is found to be associated with an unusual taste.
Things which we see become associated, by habit, with certain tactile
sensations which we expect if we touch them; one of the horrors of a
ghost (in many ghost-stories) is that it fails to give us any
sensations of touch. Uneducated people who go abroad for the first
time are so surprised as to be incredulous when they find their native
language not understood.
And this kind of association is not confined to men; in animals also
it is very strong. A horse which has been often driven along a
certain road resists the attempt to drive him in a different
direction. Domestic animals expect food when they see the person who
usually feeds them. We know that all these rather crude expectations
of uniformity are liable to be misleading. The man who has fed the
chicken every day throughout its life at last wrings its neck instead,
showing that more refined views as to the uniformity of nature would
have been useful to the chicken.
But in spite of the misleadingness of such expectations, they
nevertheless exist. The mere fact that something has happened a
certain number of times causes animals and men to expect that it will
happen again. Thus our instincts certainly cause us to believe that
the sun will rise to-morrow, but we may be in no better a position
than the chicken which unexpectedly has its neck wrung. We have
therefore to distinguish the fact that past uniformities _cause_
expectations as to the future, from the question whether there is any
reasonable ground for giving weight to such expectations after the
question of their validity has been raised.
The problem we have to discuss is whether there is any reason for
believing in what is called 'the uniformity of nature'. The belief in
the uniformity of nature is the belief that everything that has
happened or will happen is an instance of some general law to which
there are no exceptions. The crude expectations which we have been
considering are all subject to exceptions, and therefore liable to
disappoint those who entertain them. But science habitually assumes,
at least as a working hypothesis, that general rules which have
exceptions can be replaced by general rules which have no exceptions.
'Unsupported bodies in air fall' is a general rule to which balloons
and aeroplanes are exceptions. But the laws of motion and the law of
gravitation, which account for the fact that most bodies fall, also
account for the fact that balloons and aeroplanes can rise; thus the
laws of motion and the law of gravitation are not subject to these
exceptions.
The belief that the sun will rise to-morrow might be falsified if the
earth came suddenly into contact with a large body which destroyed its
rotation; but the laws of motion and the law of gravitation would not
be infringed by such an event. The business of science is to find
uniformities, such as the laws of motion and the law of gravitation,
to which, so far as our experience extends, there are no exceptions.
In this search science has been remarkably successful, and it may be
conceded that such uniformities have held hitherto. This brings us
back to the question: Have we any reason, assuming that they have
always held in the past, to suppose that they will hold in the future?
It has been argued that we have reason to know that the future will
resemble the past, because what was the future has constantly become
the past, and has always been found to resemble the past, so that we
really have experience of the future, namely of times which were
formerly future, which we may call past futures. But such an argument
really begs the very question at issue. We have experience of past
futures, but not of future futures, and the question is: Will future
futures resemble past futures? This question is not to be answered by
an argument which starts from past futures alone. We have therefore
still to seek for some principle which shall enable us to know that
the future will follow the same laws as the past.
The reference to the future in this question is not essential. The
same question arises when we apply the laws that work in our
experience to past things of which we have no experience--as, for
example, in geology, or in theories as to the origin of the Solar
System. The question we really have to ask is: 'When two things have
been found to be often associated, and no instance is known of the one
occurring without the other, does the occurrence of one of the two, in
a fresh instance, give any good ground for expecting the other?' On
our answer to this question must depend the validity of the whole of
our expectations as to the future, the whole of the results obtained
by induction, and in fact practically all the beliefs upon which our
daily life is based.
It must be conceded, to begin with, that the fact that two things have
been found often together and never apart does not, by itself, suffice
to _prove_ demonstratively that they will be found together in the
next case we examine. The most we can hope is that the oftener things
are found together, the more probable it becomes that they will be
found together another time, and that, if they have been found
together often enough, the probability will amount _almost_ to
certainty. It can never quite reach certainty, because we know that
in spite of frequent repetitions there sometimes is a failure at the
last, as in the case of the chicken whose neck is wrung. Thus
probability is all we ought to seek.
It might be urged, as against the view we are advocating, that we know
all natural phenomena to be subject to the reign of law, and that
sometimes, on the basis of observation, we can see that only one law
can possibly fit the facts of the case. Now to this view there are
two answers. The first is that, even if _some_ law which has no
exceptions applies to our case, we can never, in practice, be sure
that we have discovered that law and not one to which there are
exceptions. The second is that the reign of law would seem to be
itself only probable, and that our belief that it will hold in the
future, or in unexamined cases in the past, is itself based upon the
very principle we are examining.
The principle we are examining may be called the _principle of
induction_, and its two parts may be stated as follows:
(a) When a thing of a certain sort A has been found to be associated
with a thing of a certain other sort B, and has never been found
dissociated from a thing of the sort B, the greater the number of
cases in which A and B have been associated, the greater is the
probability that they will be associated in a fresh case in which one
of them is known to be present;
(b) Under the same circumstances, a sufficient number of cases of
association will make the probability of a fresh association nearly a
certainty, and will make it approach certainty without limit.
As just stated, the principle applies only to the verification of our
expectation in a single fresh instance. But we want also to know that
there is a probability in favour of the general law that things of the
sort A are _always_ associated with things of the sort B, provided a
sufficient number of cases of association are known, and no cases of
failure of association are known. The probability of the general law
is obviously less than the probability of the particular case, since
if the general law is true, the particular case must also be true,
whereas the particular case may be true without the general law being
true. Nevertheless the probability of the general law is increased by
repetitions, just as the probability of the particular case is. We
may therefore repeat the two parts of our principle as regards the
general law, thus:
(a) The greater the number of cases in which a thing of the sort A has
been found associated with a thing of the sort B, the more probable it
is (if no cases of failure of association are known) that A is always
associated with B;
(b) Under the same circumstances, a sufficient number of cases of the
association of A with B will make it nearly certain that A is always
associated with B, and will make this general law approach certainty
without limit.
It should be noted that probability is always relative to certain
data. In our case, the data are merely the known cases of coexistence
of A and B. There may be other data, which _might_ be taken into
account, which would gravely alter the probability. For example, a
man who had seen a great many white swans might argue, by our
principle, that on the data it was _probable_ that all swans were
white, and this might be a perfectly sound argument. The argument is
not disproved ny the fact that some swans are black, because a thing
may very well happen in spite of the fact that some data render it
improbable. In the case of the swans, a man might know that colour is
a very variable characteristic in many species of animals, and that,
therefore, an induction as to colour is peculiarly liable to error.
But this knowledge would be a fresh datum, by no means proving that
the probability relatively to our previous data had been wrongly
estimated. The fact, therefore, that things often fail to fulfil our
expectations is no evidence that our expectations will not _probably_
be fulfilled in a given case or a given class of cases. Thus our
inductive principle is at any rate not capable of being _disproved_ by
an appeal to experience.
The inductive principle, however, is equally incapable of being
_proved_ by an appeal to experience. Experience might conceivably
confirm the inductive principle as regards the cases that have been
already examined; but as regards unexamined cases, it is the inductive
principle alone that can justify any inference from what has been
examined to what has not been examined. All arguments which, on the
basis of experience, argue as to the future or the unexperienced parts
of the past or present, assume the inductive principle; hence we can
never use experience to prove the inductive principle without begging
the question. Thus we must either accept the inductive principle on
the ground of its intrinsic evidence, or forgo all justification of
our expectations about the future. If the principle is unsound, we
have no reason to expect the sun to rise to-morrow, to expect bread to
be more nourishing than a stone, or to expect that if we throw
ourselves off the roof we shall fall. When we see what looks like our
best friend approaching us, we shall have no reason to suppose that
his body is not inhabited by the mind of our worst enemy or of some
total stranger. All our conduct is based upon associations which have
worked in the past, and which we therefore regard as likely to work in
the future; and this likelihood is dependent for its validity upon the
inductive principle.
The general principles of science, such as the belief in the reign of
law, and the belief that every event must have a cause, are as
completely dependent upon the inductive principle as are the beliefs
of daily life All such general principles are believed because mankind
have found innumerable instances of their truth and no instances of
their falsehood. But this affords no evidence for their truth in the
future, unless the inductive principle is assumed.
Thus all knowledge which, on a basis of experience tells us something
about what is not experienced, is based upon a belief which experience
can neither confirm nor confute, yet which, at least in its more
concrete applications, appears to be as firmly rooted in us as many of
the facts of experience. The existence and justification of such
beliefs--for the inductive principle, as we shall see, is not the only
example--raises some of the most difficult and most debated problems
of philosophy. We will, in the next chapter, consider briefly what
may be said to account for such knowledge, and what is its scope and
its degree of certainty.
In almost all our previous discussions we have been concerned in the
attempt to get clear as to our data in the way of knowledge of
existence. What things are there in the universe whose existence is
known to us owing to our being acquainted with them? So far, our
answer has been that we are acquainted with our sense-data, and,
probably, with ourselves. These we know to exist. And past
sense-data which are remembered are known to have existed in the past.
This knowledge supplies our data.
But if we are to be able to draw inferences from these data--if we are
to know of the existence of matter, of other people, of the past
before our individual memory begins, or of the future, we must know
general principles of some kind by means of which such inferences can
be drawn. It must be known to us that the existence of some one sort
of thing, A, is a sign of the existence of some other sort of thing,
B, either at the same time as A or at some earlier or later time, as,
for example, thunder is a sign of the earlier existence of lightning.
If this were not known to us, we could never extend our knowledge
beyond the sphere of our private experience; and this sphere, as we
have seen, is exceedingly limited. The question we have now to
consider is whether such an extension is possible, and if so, how it
is effected.
Let us take as an illustration a matter about which none of us, in
fact, feel the slightest doubt. We are all convinced that the sun
will rise to-morrow. Why? Is this belief a mere blind outcome of
past experience, or can it be justified as a reasonable belief? It is
not easy to find a test by which to judge whether a belief of this
kind is reasonable or not, but we can at least ascertain what sort of
general beliefs would suffice, if true, to justify the judgement that
the sun will rise to-morrow, and the many other similar judgements
upon which our actions are based.
It is obvious that if we are asked why we believe that the sun will
rise to-morrow, we shall naturally answer 'Because it always has risen
every day'. We have a firm belief that it will rise in the future,
because it has risen in the past. If we are challenged as to why we
believe that it will continue to rise as heretofore, we may appeal to
the laws of motion: the earth, we shall say, is a freely rotating
body, and such bodies do not cease to rotate unless something
interferes from outside, and there is nothing outside to interfere
with the earth between now and to-morrow. Of course it might be
doubted whether we are quite certain that there is nothing outside to
interfere, but this is not the interesting doubt. The interesting
doubt is as to whether the laws of motion will remain in operation
until to-morrow. If this doubt is raised, we find ourselves in the
same position as when the doubt about the sunrise was first raised.
The _only_ reason for believing that the laws of motion will remain in
operation is that they have operated hitherto, so far as our knowledge
of the past enables us to judge. It is true that we have a greater
body of evidence from the past in favour of the laws of motion than we
have in favour of the sunrise, because the sunrise is merely a
particular case of fulfilment of the laws of motion, and there are
countless other particular cases. But the real question is: Do _any_
number of cases of a law being fulfilled in the past afford evidence
that it will be fulfilled in the future? If not, it becomes plain
that we have no ground whatever for expecting the sun to rise
to-morrow, or for expecting the bread we shall eat at our next meal
not to poison us, or for any of the other scarcely conscious
expectations that control our daily lives. It is to be observed that
all such expectations are only _probable_; thus we have not to seek
for a proof that they _must_ be fulfilled, but only for some reason in
favour of the view that they are _likely_ to be fulfilled.
Now in dealing with this question we must, to begin with, make an
important distinction, without which we should soon become involved in
hopeless confusions. Experience has shown us that, hitherto, the
frequent repetition of some uniform succession or coexistence has been
a _cause_ of our expecting the same succession or coexistence on the
next occasion. Food that has a certain appearance generally has a
certain taste, and it is a severe shock to our expectations when the
familiar appearance is found to be associated with an unusual taste.
Things which we see become associated, by habit, with certain tactile
sensations which we expect if we touch them; one of the horrors of a
ghost (in many ghost-stories) is that it fails to give us any
sensations of touch. Uneducated people who go abroad for the first
time are so surprised as to be incredulous when they find their native
language not understood.
And this kind of association is not confined to men; in animals also
it is very strong. A horse which has been often driven along a
certain road resists the attempt to drive him in a different
direction. Domestic animals expect food when they see the person who
usually feeds them. We know that all these rather crude expectations
of uniformity are liable to be misleading. The man who has fed the
chicken every day throughout its life at last wrings its neck instead,
showing that more refined views as to the uniformity of nature would
have been useful to the chicken.
But in spite of the misleadingness of such expectations, they
nevertheless exist. The mere fact that something has happened a
certain number of times causes animals and men to expect that it will
happen again. Thus our instincts certainly cause us to believe that
the sun will rise to-morrow, but we may be in no better a position
than the chicken which unexpectedly has its neck wrung. We have
therefore to distinguish the fact that past uniformities _cause_
expectations as to the future, from the question whether there is any
reasonable ground for giving weight to such expectations after the
question of their validity has been raised.
The problem we have to discuss is whether there is any reason for
believing in what is called 'the uniformity of nature'. The belief in
the uniformity of nature is the belief that everything that has
happened or will happen is an instance of some general law to which
there are no exceptions. The crude expectations which we have been
considering are all subject to exceptions, and therefore liable to
disappoint those who entertain them. But science habitually assumes,
at least as a working hypothesis, that general rules which have
exceptions can be replaced by general rules which have no exceptions.
'Unsupported bodies in air fall' is a general rule to which balloons
and aeroplanes are exceptions. But the laws of motion and the law of
gravitation, which account for the fact that most bodies fall, also
account for the fact that balloons and aeroplanes can rise; thus the
laws of motion and the law of gravitation are not subject to these
exceptions.
The belief that the sun will rise to-morrow might be falsified if the
earth came suddenly into contact with a large body which destroyed its
rotation; but the laws of motion and the law of gravitation would not
be infringed by such an event. The business of science is to find
uniformities, such as the laws of motion and the law of gravitation,
to which, so far as our experience extends, there are no exceptions.
In this search science has been remarkably successful, and it may be
conceded that such uniformities have held hitherto. This brings us
back to the question: Have we any reason, assuming that they have
always held in the past, to suppose that they will hold in the future?
It has been argued that we have reason to know that the future will
resemble the past, because what was the future has constantly become
the past, and has always been found to resemble the past, so that we
really have experience of the future, namely of times which were
formerly future, which we may call past futures. But such an argument
really begs the very question at issue. We have experience of past
futures, but not of future futures, and the question is: Will future
futures resemble past futures? This question is not to be answered by
an argument which starts from past futures alone. We have therefore
still to seek for some principle which shall enable us to know that
the future will follow the same laws as the past.
The reference to the future in this question is not essential. The
same question arises when we apply the laws that work in our
experience to past things of which we have no experience--as, for
example, in geology, or in theories as to the origin of the Solar
System. The question we really have to ask is: 'When two things have
been found to be often associated, and no instance is known of the one
occurring without the other, does the occurrence of one of the two, in
a fresh instance, give any good ground for expecting the other?' On
our answer to this question must depend the validity of the whole of
our expectations as to the future, the whole of the results obtained
by induction, and in fact practically all the beliefs upon which our
daily life is based.
It must be conceded, to begin with, that the fact that two things have
been found often together and never apart does not, by itself, suffice
to _prove_ demonstratively that they will be found together in the
next case we examine. The most we can hope is that the oftener things
are found together, the more probable it becomes that they will be
found together another time, and that, if they have been found
together often enough, the probability will amount _almost_ to
certainty. It can never quite reach certainty, because we know that
in spite of frequent repetitions there sometimes is a failure at the
last, as in the case of the chicken whose neck is wrung. Thus
probability is all we ought to seek.
It might be urged, as against the view we are advocating, that we know
all natural phenomena to be subject to the reign of law, and that
sometimes, on the basis of observation, we can see that only one law
can possibly fit the facts of the case. Now to this view there are
two answers. The first is that, even if _some_ law which has no
exceptions applies to our case, we can never, in practice, be sure
that we have discovered that law and not one to which there are
exceptions. The second is that the reign of law would seem to be
itself only probable, and that our belief that it will hold in the
future, or in unexamined cases in the past, is itself based upon the
very principle we are examining.
The principle we are examining may be called the _principle of
induction_, and its two parts may be stated as follows:
(a) When a thing of a certain sort A has been found to be associated
with a thing of a certain other sort B, and has never been found
dissociated from a thing of the sort B, the greater the number of
cases in which A and B have been associated, the greater is the
probability that they will be associated in a fresh case in which one
of them is known to be present;
(b) Under the same circumstances, a sufficient number of cases of
association will make the probability of a fresh association nearly a
certainty, and will make it approach certainty without limit.
As just stated, the principle applies only to the verification of our
expectation in a single fresh instance. But we want also to know that
there is a probability in favour of the general law that things of the
sort A are _always_ associated with things of the sort B, provided a
sufficient number of cases of association are known, and no cases of
failure of association are known. The probability of the general law
is obviously less than the probability of the particular case, since
if the general law is true, the particular case must also be true,
whereas the particular case may be true without the general law being
true. Nevertheless the probability of the general law is increased by
repetitions, just as the probability of the particular case is. We
may therefore repeat the two parts of our principle as regards the
general law, thus:
(a) The greater the number of cases in which a thing of the sort A has
been found associated with a thing of the sort B, the more probable it
is (if no cases of failure of association are known) that A is always
associated with B;
(b) Under the same circumstances, a sufficient number of cases of the
association of A with B will make it nearly certain that A is always
associated with B, and will make this general law approach certainty
without limit.
It should be noted that probability is always relative to certain
data. In our case, the data are merely the known cases of coexistence
of A and B. There may be other data, which _might_ be taken into
account, which would gravely alter the probability. For example, a
man who had seen a great many white swans might argue, by our
principle, that on the data it was _probable_ that all swans were
white, and this might be a perfectly sound argument. The argument is
not disproved ny the fact that some swans are black, because a thing
may very well happen in spite of the fact that some data render it
improbable. In the case of the swans, a man might know that colour is
a very variable characteristic in many species of animals, and that,
therefore, an induction as to colour is peculiarly liable to error.
But this knowledge would be a fresh datum, by no means proving that
the probability relatively to our previous data had been wrongly
estimated. The fact, therefore, that things often fail to fulfil our
expectations is no evidence that our expectations will not _probably_
be fulfilled in a given case or a given class of cases. Thus our
inductive principle is at any rate not capable of being _disproved_ by
an appeal to experience.
The inductive principle, however, is equally incapable of being
_proved_ by an appeal to experience. Experience might conceivably
confirm the inductive principle as regards the cases that have been
already examined; but as regards unexamined cases, it is the inductive
principle alone that can justify any inference from what has been
examined to what has not been examined. All arguments which, on the
basis of experience, argue as to the future or the unexperienced parts
of the past or present, assume the inductive principle; hence we can
never use experience to prove the inductive principle without begging
the question. Thus we must either accept the inductive principle on
the ground of its intrinsic evidence, or forgo all justification of
our expectations about the future. If the principle is unsound, we
have no reason to expect the sun to rise to-morrow, to expect bread to
be more nourishing than a stone, or to expect that if we throw
ourselves off the roof we shall fall. When we see what looks like our
best friend approaching us, we shall have no reason to suppose that
his body is not inhabited by the mind of our worst enemy or of some
total stranger. All our conduct is based upon associations which have
worked in the past, and which we therefore regard as likely to work in
the future; and this likelihood is dependent for its validity upon the
inductive principle.
The general principles of science, such as the belief in the reign of
law, and the belief that every event must have a cause, are as
completely dependent upon the inductive principle as are the beliefs
of daily life All such general principles are believed because mankind
have found innumerable instances of their truth and no instances of
their falsehood. But this affords no evidence for their truth in the
future, unless the inductive principle is assumed.
Thus all knowledge which, on a basis of experience tells us something
about what is not experienced, is based upon a belief which experience
can neither confirm nor confute, yet which, at least in its more
concrete applications, appears to be as firmly rooted in us as many of
the facts of experience. The existence and justification of such
beliefs--for the inductive principle, as we shall see, is not the only
example--raises some of the most difficult and most debated problems
of philosophy. We will, in the next chapter, consider briefly what
may be said to account for such knowledge, and what is its scope and
its degree of certainty.
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