 The
Problems of Philosophy
Bertrand Russell
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 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 m 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 hypothsis 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
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.
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