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.