In all that we have said hitherto concerning philosophy, we have
scarcely touched on many matters that occupy a great space in the
writings of most philosophers. Most philosophers--or, at any rate, very
many--profess to be able to prove, by _a priori_ metaphysical reasoning,
such things as the fundamental dogmas of religion, the essential
rationality of the universe, the illusoriness of matter, the unreality
of all evil, and so on. There can be no doubt that the hope of finding
reason to believe such theses as these has been the chief inspiration of
many life-long students of philosophy. This hope, I believe, is vain. It
would seem that knowledge concerning the universe as a whole is not to
be obtained by metaphysics, and that the proposed proofs that, in virtue
of the laws of logic such and such things _must_ exist and such and such
others cannot, are not capable of surviving a critical scrutiny. In
this chapter we shall briefly consider the kind of way in which such
reasoning is attempted, with a view to discovering whether we can hope
that it may be valid.
The great representative, in modern times, of the kind of view which
we wish to examine, was Hegel (1770-1831). Hegel's philosophy is very
difficult, and commentators differ as to the true interpretation of it.
According to the interpretation I shall adopt, which is that of many, if
not most, of the commentators and has the merit of giving an interesting
and important type of philosophy, his main thesis is that everything
short of the Whole is obviously fragmentary, and obviously incapable of
existing without the complement supplied by the rest of the world. Just
as a comparative anatomist, from a single bone, sees what kind of animal
the whole must have been, so the metaphysician, according to Hegel,
sees, from any one piece of reality, what the whole of reality must
be--at least in its large outlines. Every apparently separate piece of
reality has, as it were, hooks which grapple it to the next piece;
the next piece, in turn, has fresh hooks, and so on, until the whole
universe is reconstructed. This essential incompleteness appears,
according to Hegel, equally in the world of thought and in the world of
things. In the world of thought, if we take any idea which is
abstract or incomplete, we find, on examination, that if we forget
its incompleteness, we become involved in contradictions; these
contradictions turn the idea in question into its opposite, or
antithesis; and in order to escape, we have to find a new, less
incomplete idea, which is the synthesis of our original idea and its
antithesis. This new idea, though less incomplete than the idea we
started with, will be found, nevertheless, to be still not wholly
complete, but to pass into its antithesis, with which it must be
combined in a new synthesis. In this way Hegel advances until he reaches
the 'Absolute Idea', which, according to him, has no incompleteness,
no opposite, and no need of further development. The Absolute Idea,
therefore, is adequate to describe Absolute Reality; but all lower ideas
only describe reality as it appears to a partial view, not as it is
to one who simultaneously surveys the Whole. Thus Hegel reaches the
conclusion that Absolute Reality forms one single harmonious system, not
in space or time, not in any degree evil, wholly rational, and wholly
spiritual. Any appearance to the contrary, in the world we know, can be
proved logically--so he believes--to be entirely due to our fragmentary
piecemeal view of the universe. If we saw the universe whole, as we may
suppose God sees it, space and time and matter and evil and all striving
and struggling would disappear, and we should see instead an eternal
perfect unchanging spiritual unity.
In this conception, there is undeniably something sublime, something to
which we could wish to yield assent. Nevertheless, when the arguments
in support of it are carefully examined, they appear to involve much
confusion and many unwarrantable assumptions. The fundamental tenet
upon which the system is built up is that what is incomplete must be not
self-subsistent, but must need the support of other things before it can
exist. It is held that whatever has relations to things outside itself
must contain some reference to those outside things in its own nature,
and could not, therefore, be what it is if those outside things did not
exist. A man's nature, for example, is constituted by his memories and
the rest of his knowledge, by his loves and hatreds, and so on; thus,
but for the objects which he knows or loves or hates, he could not be
what he is. He is essentially and obviously a fragment: taken as the
sum-total of reality he would be self-contradictory.
This whole point of view, however, turns upon the notion of the 'nature'
of a thing, which seems to mean 'all the truths about the thing'. It is
of course the case that a truth which connects one thing with another
thing could not subsist if the other thing did not subsist. But a
truth about a thing is not part of the thing itself, although it must,
according to the above usage, be part of the 'nature' of the thing.
If we mean by a thing's 'nature' all the truths about the thing, then
plainly we cannot know a thing's 'nature' unless we know all the thing's
relations to all the other things in the universe. But if the word
'nature' is used in this sense, we shall have to hold that the thing
may be known when its 'nature' is not known, or at any rate is not known
completely. There is a confusion, when this use of the word 'nature' is
employed, between knowledge of things and knowledge of truths. We may
have knowledge of a thing by acquaintance even if we know very few
propositions about it--theoretically we need not know any propositions
about it. Thus, acquaintance with a thing does not involve knowledge of
its 'nature' in the above sense. And although acquaintance with a thing
is involved in our knowing any one proposition about a thing, knowledge
of its 'nature', in the above sense, is not involved. Hence, (1)
acquaintance with a thing does not logically involve a knowledge of its
relations, and (2) a knowledge of some of its relations does not involve
a knowledge of all of its relations nor a knowledge of its 'nature' in
the above sense. I may be acquainted, for example, with my toothache,
and this knowledge may be as complete as knowledge by acquaintance ever
can be, without knowing all that the dentist (who is not acquainted
with it) can tell me about its cause, and without therefore knowing its
'nature' in the above sense. Thus the fact that a thing has relations
does not prove that its relations are logically necessary. That is to
say, from the mere fact that it is the thing it is we cannot deduce
that it must have the various relations which in fact it has. This only
_seems_ to follow because we know it already.
It follows that we cannot prove that the universe as a whole forms a
single harmonious system such as Hegel believes that it forms. And if we
cannot prove this, we also cannot prove the unreality of space and time
and matter and evil, for this is deduced by Hegel from the fragmentary
and relational character of these things. Thus we are left to the
piecemeal investigation of the world, and are unable to know the
characters of those parts of the universe that are remote from our
experience. This result, disappointing as it is to those whose hopes
have been raised by the systems of philosophers, is in harmony with
the inductive and scientific temper of our age, and is borne out by the
whole examination of human knowledge which has occupied our previous
chapters.
Most of the great ambitious attempts of metaphysicians have proceeded by
the attempt to prove that such and such apparent features of the actual
world were self-contradictory, and therefore could not be real. The
whole tendency of modern thought, however, is more and more in the
direction of showing that the supposed contradictions were illusory, and
that very little can be proved _a priori_ from considerations of what
_must_ be. A good illustration of this is afforded by space and
time. Space and time appear to be infinite in extent, and infinitely
divisible. If we travel along a straight line in either direction, it
is difficult to believe that we shall finally reach a last point,
beyond which there is nothing, not even empty space. Similarly, if in
imagination we travel backwards or forwards in time, it is difficult to
believe that we shall reach a first or last time, with not even empty
time beyond it. Thus space and time appear to be infinite in extent.
Again, if we take any two points on a line, it seems evident that there
must be other points between them however small the distance between
them may be: every distance can be halved, and the halves can be halved
again, and so on _ad infinitum_. In time, similarly, however little
time may elapse between two moments, it seems evident that there will be
other moments between them. Thus space and time appear to be infinitely
divisible. But as against these apparent facts--infinite extent and
infinite divisibility--philosophers have advanced arguments tending to
show that there could be no infinite collections of things, and that
therefore the number of points in space, or of instants in time, must
be finite. Thus a contradiction emerged between the apparent nature of
space and time and the supposed impossibility of infinite collections.
Kant, who first emphasized this contradiction, deduced the impossibility
of space and time, which he declared to be merely subjective; and since
his time very many philosophers have believed that space and time are
mere appearance, not characteristic of the world as it really is. Now,
however, owing to the labours of the mathematicians, notably Georg
Cantor, it has appeared that the impossibility of infinite collections
was a mistake. They are not in fact self-contradictory, but only
contradictory of certain rather obstinate mental prejudices. Hence the
reasons for regarding space and time as unreal have become inoperative,
and one of the great sources of metaphysical constructions is dried up.
The mathematicians, however, have not been content with showing that
space as it is commonly supposed to be is possible; they have shown also
that many other forms of space are equally possible, so far as logic
can show. Some of Euclid's axioms, which appear to common sense to be
necessary, and were formerly supposed to be necessary by philosophers,
are now known to derive their appearance of necessity from our mere
familiarity with actual space, and not from any _a priori_ logical
foundation. By imagining worlds in which these axioms are false, the
mathematicians have used logic to loosen the prejudices of common
sense, and to show the possibility of spaces differing--some more, some
less--from that in which we live. And some of these spaces differ so
little from Euclidean space, where distances such as we can measure are
concerned, that it is impossible to discover by observation whether our
actual space is strictly Euclidean or of one of these other kinds.
Thus the position is completely reversed. Formerly it appeared that
experience left only one kind of space to logic, and logic showed this
one kind to be impossible. Now, logic presents many kinds of space as
possible apart from experience, and experience only partially decides
between them. Thus, while our knowledge of what is has become less
than it was formerly supposed to be, our knowledge of what may be is
enormously increased. Instead of being shut in within narrow walls, of
which every nook and cranny could be explored, we find ourselves in an
open world of free possibilities, where much remains unknown because
there is so much to know.
What has happened in the case of space and time has happened, to some
extent, in other directions as well. The attempt to prescribe to the
universe by means of _a priori_ principles has broken down; logic,
instead of being, as formerly, the bar to possibilities, has become the
great liberator of the imagination, presenting innumerable alternatives
which are closed to unreflective common sense, and leaving to experience
the task of deciding, where decision is possible, between the many
worlds which logic offers for our choice. Thus knowledge as to what
exists becomes limited to what we can learn from experience--not to
what we can actually experience, for, as we have seen, there is much
knowledge by description concerning things of which we have no direct
experience. But in all cases of knowledge by description, we need some
connexion of universals, enabling us, from such and such a datum, to
infer an object of a certain sort as implied by our datum. Thus in
regard to physical objects, for example, the principle that sense-data
are signs of physical objects is itself a connexion of universals; and
it is only in virtue of this principle that experience enables us to
acquire knowledge concerning physical objects. The same applies to
the law of causality, or, to descend to what is less general, to such
principles as the law of gravitation.
Principles such as the law of gravitation are proved, or rather are
rendered highly probable, by a combination of experience with some
wholly _a priori_ principle, such as the principle of induction. Thus
our intuitive knowledge, which is the source of all our other knowledge
of truths, is of two sorts: pure empirical knowledge, which tells us of
the existence and some of the properties of particular things with
which we are acquainted, and pure _a priori_ knowledge, which gives us
connexions between universals, and enables us to draw inferences from
the particular facts given in empirical knowledge. Our derivative
knowledge always depends upon some pure _a priori_ knowledge and usually
also depends upon some pure empirical knowledge.
Philosophical knowledge, if what has been said above is true, does not
differ essentially from scientific knowledge; there is no special
source of wisdom which is open to philosophy but not to science, and the
results obtained by philosophy are not radically different from those
obtained from science. The essential characteristic of philosophy,
which makes it a study distinct from science, is criticism. It examines
critically the principles employed in science and in daily life; it
searches out any inconsistencies there may be in these principles,
and it only accepts them when, as the result of a critical inquiry, no
reason for rejecting them has appeared. If, as many philosophers have
believed, the principles underlying the sciences were capable, when
disengaged from irrelevant detail, of giving us knowledge concerning
the universe as a whole, such knowledge would have the same claim on our
belief as scientific knowledge has; but our inquiry has not revealed any
such knowledge, and therefore, as regards the special doctrines of the
bolder metaphysicians, has had a mainly negative result. But as regards
what would be commonly accepted as knowledge, our result is in the main
positive: we have seldom found reason to reject such knowledge as the
result of our criticism, and we have seen no reason to suppose man
incapable of the kind of knowledge which he is generally believed to
possess.
When, however, we speak of philosophy as a _criticism_ of knowledge, it
is necessary to impose a certain limitation. If we adopt the attitude
of the complete sceptic, placing ourselves wholly outside all knowledge,
and asking, from this outside position, to be compelled to return within
the circle of knowledge, we are demanding what is impossible, and our
scepticism can never be refuted. For all refutation must begin with
some piece of knowledge which the disputants share; from blank doubt,
no argument can begin. Hence the criticism of knowledge which philosophy
employs must not be of this destructive kind, if any result is to be
achieved. Against this absolute scepticism, no _logical_ argument can be
advanced. But it is not difficult to see that scepticism of this kind
is unreasonable. Descartes' 'methodical doubt', with which modern
philosophy began, is not of this kind, but is rather the kind of
criticism which we are asserting to be the essence of philosophy. His
'methodical doubt' consisted in doubting whatever seemed doubtful; in
pausing, with each apparent piece of knowledge, to ask himself whether,
on reflection, he could feel certain that he really knew it. This is the
kind of criticism which constitutes philosophy. Some knowledge, such as
knowledge of the existence of our sense-data, appears quite indubitable,
however calmly and thoroughly we reflect upon it. In regard to such
knowledge, philosophical criticism does not require that we should
abstain from belief. But there are beliefs--such, for example, as the
belief that physical objects exactly resemble our sense-data--which are
entertained until we begin to reflect, but are found to melt away
when subjected to a close inquiry. Such beliefs philosophy will bid us
reject, unless some new line of argument is found to support them.
But to reject the beliefs which do not appear open to any objections,
however closely we examine them, is not reasonable, and is not what
philosophy advocates.
The criticism aimed at, in a word, is not that which, without reason,
determines to reject, but that which considers each piece of apparent
knowledge on its merits, and retains whatever still appears to be
knowledge when this consideration is completed. That some risk of error
remains must be admitted, since human beings are fallible. Philosophy
may claim justly that it diminishes the risk of error, and that in some
cases it renders the risk so small as to be practically negligible. To
do more than this is not possible in a world where mistakes must occur;
and more than this no prudent advocate of philosophy would claim to have
performed.