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.
