1 Cf. (for example) Projective Geometry by Veblen and Young, vol. i. 1910, vol. ii. 1917, Ginn and Company, Boston, U.S.A.
Ii] Theories of Bifurcation of Nature 37
to that extent my thoughts are in space. But it seems
nonsense to ask how much volume of the room they
occupied, whether it was a cubic foot or a cubic inch;
whereas the same thoughts occupy a determinate dura-
tion of time, say, from eleven to twelve on a certain date.
Thus whereas the relations of a relative theory of time are required to relate thoughts, it does not seem so obvious that the relations of a relative theory of space are required to relate them. The connexion of thought with space seems to have a certain character of indirect- ness which appears to be lacking in the connexion of thought with time.
Again the irrevocableness of time does not seem to have any parallel for space. Space, on the relative theory, is the outcome of certain relations between objects commonly said to be in space ; and whenever there are the objects, so related, there is the space. No difficulty seems to arise like that of the inconvenient instants of time which might conceivably turn up again when we thought that we had done with them.
The absolute theory of space is not now generally popular. The knowledge of bare space, as a system of entities known to us in itself and for itself independently of our knowledge of the events in nature, does not seem to correspond to anything in our experience. Space, like time, would appear to be an abstraction from events. According to my own theory it only differentiates itself from time at a somewhat developed stage of the abstractive process. The more usual way of expressing the relational theory of space would be to consider space as an abstraction from the relations between material objects.
Suppose now we assume absolute time and absolute
38 THE CONCEPT OF NATURE [ch.
space. What bearing has this assumption on the con-
cept of nature as bifurcated into causal nature and
apparent nature ? Undoubtedly the separation between
the two natures is now greatly mitigated. We can pro-
vide them with two systems of relations in common ; for
both natures can be presumed to occupy the same space
and the same time. The theory now is this : Causal events
occupy certain periods of the absolute time and occupy
certain positions of the absolute space. These events
influence a mind which thereupon perceives certain
apparent events which occupy certain periods in the
absolute time and occupy certain positions of the
absolute space ; and the periods and positions occupied
by the apparent events bear a determinate relation to
the periods and positions occupied by the causal events.
Furthermore definite causal events produce for the
mind definite apparent events. Delusions are apparent
events which appear in temporal periods and spatial
positions without the intervention of these causal
events which are proper for influencing of the mind to
their perception.
The whole theory is perfectly logical. In these dis-
cussions we cannot hope to drive an unsound theory to
a logical contradiction. A reasoner, apart from mere
slips, only involves himself in a contradiction when he
is shying at a reductio ad absurdum. The substantial
reason for rejecting a philosophical theory is the 'ab-
surdum' to which it reduces us. In the case of the
philosophy of natural science the * absurdum ' can only
be that our perceptual knowledge has not the character
assigned to it by the theory. If our opponent affirms
that his knowledge has that character, we can only
after making doubly sure that we understand each
Ii] Theories of Bifurcation of Nature 39
other — agree to differ. Accordingly the first duty of
an expositor in stating a theory in which he disbeheves
is to exhibit it as logical. It is not there where his
trouble lies. .
Let me summarise the previously stated objections
to this theory of nature. In the first place it seeks for
the cause of the knowledge of the thing known instead
of seeking for the character of the thing known:
secondly it assumes a knowledge of time in itself apart
from events related in time : thirdly it assumes a know-
ledge of space in itself apart from events related in
space. There are in addition to these objections other
flaws in the theory.
Some light is thrown on the artificial status of causal
nature in this theory by asking, why causal nature is
presumed to occupy time and space. This really raises
the fundamental question as to what characteristics
causal nature should have in common with apparent
nature. Why — on this theory — should the cause which
influences the mind to perception have any character-
istics in common with the effluent apparent nature?
In particular, why should it be in space ? Why should
it be in time? And more generally, What do we
know about mind which would aliow us to infer any
particular characteristics of a cause which should in-
fluence mind to particular effects?
The transcendence of time beyond nature gives some
slight reason for presuming that causal nature should
occupy time. For if the mind occupies periods of time,
there would seem to be some vague reason for assuming
that influencing causes occupy the same periods of
time, or at least, occupy periods which are strictly
related to the mental periods. But if the mind does not
40 THE CONCEPT OF NATURE [ch.
occupy volumes of space, there seems to be no reason
why causal nature should occupy any volumes of space.
Thus space would seem to be merely apparent in the
same sense as apparent nature is merely apparent.
Accordingly if science is really investigating causes
which operate on the mind, it would seem to be entirely
on the wrong tack in presuming that the causes which
it is seeking for have spatial relations. Furthermore
there is nothing else in our knowledge analogous to
these causes which influence the mind to perception.
Accordingly, beyond the rashly presumed fact that they
occupy time, there is really no ground by which we can
determine any point of their character. They must
remain for ever unknown.
Now I assume as an axiom that science is not a
fairy tale. It is not engaged in decking out unknowable
entities with arbitrary and fantastic properties. What
then is it that science is doing, granting that it is
eifecting something of importance } My answer is that
it is determining the character of things known, namely
the character of apparent nature. But we may drop the
term 'apparent'; for there is but one nature, namely
the nature which is before us in perceptual knowledge.
The characters which science discerns in nature are
subtle characters, not obvious at first sight. They are
relations of relations and characters of characters. But
for all their subtlety they are stamped with a certain
simplicity which makes their consideration essential in
unravelling the complex relations between characters
of more perceptive insistence.
The fact that the bifurcation of nature into causal and
apparent components does not express what we mean
by our knowledge is brought before us when we realise
Ii] Theories of Bifurcation of Nature 41
our thoughts in any discussion of the causes of our perceptions. For example, the fire is burning and we see a red coal. This is explained in science by radiant energy from the coal entering our eyes. But in seeking for such an explanation we are not asking what are the sort of occurrences which are fitted to cause a mind to see red. The chain of causation is entirely different. The mind is cut out altogether. The real question is, When red is found in nature, what else is found there also? Namely we are asking for an analysis of the accom- paniments in nature of the discovery of red in nature. In a subsequent lecture I shall expand this line of thought. I simply draw attention to it here in order to point out that the wave-theory of light has not been adopted because waves are just the sort of things which ought to make a mind perceive colours. This is no part of the evidence which has ever been adduced for the wave-theory, yet on the causal theory of perception, it is really the only relevant part. In other words, science is not discussing the causes of knowledge, but the coherence of knowledge. The understanding which is sought by science is an understanding of relations within nature.
So far I have discussed the bifurcation of nature in
connexion with the theories of absolute time and of
absolute space. My reason has been that the intro-
duction of the relational theories only weakens the case
for bifurcation, and I wished to discuss this case on
its strongest grounds.
For instance, suppose we adopt the relational theory
of space. Then the space in which apparent nature is set
is the expression of certain relations between the appa-
rent objects. It is a set of apparent relations between
42 THE CONCEPT OF NATURE [ce
apparent relata. Apparent nature is the dream, and th apparent relations of space are dream relations, and th space is the dream space. Similarly the space in whic] causal nature is set is the expression of certain rela tions between the causal objects. It is the expressioi of certain facts about the causal activity which is goinj on behind the scenes. Accordingly causal space belong to a different order of reality to apparent space. Henc there is no pointwise connexion between the two an( it is meaningless to say that the molecules of the gras are in any place which has a determinate spatial relatioi to the place occupied by the grass which we see. Thi conclusion is very paradoxical and makes nonsense o all scientific phraseology. The case is even worse if w admit the relativity of time. For the same argument apply, and break up time into the dream time and causa time which belong to different orders of reality.
I have however been discussing an extreme form o
the bifurcation theory. It is, as I think, the mos
defensible form. But its very definiteness makes it th
more evidently obnoxious to criticism. The intermediat
form allows that the nature we are discussing is alway
the nature directly known, and so far it rejects th
bifurcation theory. But it holds that there are psychi
additions to nature as thus known, and that thes
additions are in no proper sense part of nature. Fo
example, we perceive the red biUiard ball at its prope
time, in its proper place, with its proper motion, wit
its proper hardness, and with its proper inertia. Bi]
its redness and its warmth, and the sound of the clic
as a cannon is made off it are psychic additions, namely
secondary qualities which are only the mind's wa
of perceiving nature. This is not only the vaguel
Ii] Theories of Bifurcation of Nature 43
prevalent theory, but is, I believe, the historical form of the bifurcation theory in so far as it is derived from philosophy. I shall call it the theory of psychic additions.
This theory of psychic additions is a sound common- sense theory which lays immense stress on the obvious reality of time, space, solidity and inertia, but distrusts the minor artistic additions of colour, warmth and sound.
The theory is the outcome of common-sense in
retreat. It arose in an epoch when the transmission
theories of science were being elaborated. For example,
colour is the result of a transmission from the material
object to the perceiver's eye; and what is thus trans-
mitted is not colour. Thus colour is not part of the
reality of the material object. Similarly for the same
reason sounds evaporate from nature. Also warmth is
due to the transfer of something which is not tempera-
ture. Thus we are left with spatio-temporal positions,
and what I may term the ' pushiness ' of the body. This
lands us to eighteenth and nineteenth century material-
ism, namely, the belief that what is real in nature is
matter, in time and in space and with inertia.
Evidently a distinction in quality has been presup-
posed separating off some perceptions due to touch from
other perceptions. These touch-perceptions are per-
ceptions of the real inertia, whereas the other perceptions
are psychic additions which must be explained on the
causal theory. This distinction is the product of an
epoch in which physical science has got ahead of medical
pathology and of physiology. Perceptions of push are
just as much the outcome of transmission as are per-
ceptions of colour. When colour is perceived the nerves
of the body are excited in one way and transmit their
message towards the brain, and when push is perceived
44 THE CONCEPT OF NATURE [cH.
other nerves of the body are excited in another way and
transmit their message towards the brain. The message
of the one set is not the conveyance of colour, and the
message of the other set is not the conveyance of push.
But in one case colour is perceived and in the other
case the push due to the object. If you snip certain
nerves, there is an end to the perception of colour; and
if you snip certain other nerves, there is an end to the
perception of push. It would appear therefore that any
reasons which should remove colour from the reality of
nature should also operate to remove inertia.
Thus the attempted bifurcation of apparent nature
into two parts of which one part is both causal for its
own appearance and for the appearance of the other
part, which is purely apparent, fails owing to the failure
to establish any fundamental distinction between our
ways of knowing about the two parts of nature as thus
partitioned. I am not denying that the feeling of
muscular effort historically led to the formulation of
the concept of force. But this historical fact does not
warrant us in assigning a superior reality in nature to
material inertia over colour or sound. So far as reality
is concerned all our sense-perceptions are in the same
boat, and must be treated on the same principle. The
evenness of treatment is exactly what this compromise
theory fails to achieve.