to obtain precise causal laws in
which the causes are psychological, not material, is one of detailed
investigation. I have done what I could to make clear the nature of the
question, but I do not believe that it is possible as yet to answer it
with any confidence. It seems to be by no means an insoluble question,
and we may hope that science will be able to produce sufficient grounds
for regarding one answer as much more probable than the other. But for
the moment I do not see how we can come to a decision.

I think, however, on grounds of the theory of matter explained in
Lectures V and VII, that an ultimate scientific account of what goes on
in the world, if it were ascertainable, would resemble psychology rather
than physics in what we found to be the decisive difference between
them. I think, that is to say, that such an account would not be content
to speak, even formally, as though matter, which is a logical fiction,
were the ultimate reality. I think that, if our scientific knowledge
were adequate to the task, which it neither is nor is likely to become,
it would exhibit the laws of correlation of the particulars constituting
a momentary condition of a material unit, and would state the causal
laws* of the world in terms of these particulars, not in terms of
matter. Causal laws so stated would, I believe, be applicable to
psychology and physics equally; the science in which they were stated
would succeed in achieving what metaphysics has vainly attempted, namely
a unified account of what really happens, wholly true even if not the
whole of truth, and free from all convenient fictions or unwarrantable
assumptions of metaphysical entities. A causal law applicable to
particulars would count as a law of physics if it could be stated in
terms of those fictitious systems of regular appearances which are
matter; if this were not the case, it would count as a law of psychology
if one of the particulars were a sensation or an image, i.e. were
subject to mnemic causation. I believe that the realization of the
complexity of a material unit, and its analysis into constituents
analogous to sensations, is of the utmost importance to philosophy, and
vital for any understanding of the relations between mind and matter,
between our perceptions and the world which they perceive. It is in this
direction, I am convinced, that we must look for the solution of many
ancient perplexities.

* In a perfected science, causal laws w