Of course I wish it to be understood that I believe we are here dealing
with what I may call, in perhaps suitably contradictory terms,
inconceivable conceptions. But let it be remembered that I am not
responsible for this ambiguity; I am only showing what must be the
necessary outcome of analysis if we begin by endeavouring phenomenally
to unite the most antithetical of elements--mind and motion.
Materialism, at least, will not be the gainer should it ever be proved
that in the complex operations of the brain a unique exception occurs
to the otherwise universal law of the conservation of energy in space.

We may, therefore, quit the suggestion that the difficulty experienced
by Materialism of showing an equivalency between neurosis and psychosis
can ever be met by assuming that some day mental processes may admit of
being expressed in terms of physical. But before leaving this difficulty
with regard to equivalency, I may mention one other point that seems to
me of importance in connexion with it. I have already said that if we
suppose causation to proceed from brain to mind, we must suppose this
essential requirement of equivalency between the cerebral causes and the
mental effects to be satisfied somewhere.

But where are we to say that it is satisfied? Even if we suppose that
thought has a mechanical equivalent, and that causation proceeds in the
direction from energy to thought, still, when we have regard to the
supposed effects, we find that even yet they bear no kind of equivalency
to their supposed causes. The brain of a Shakespeare probably did not,
as a system, exhibit so much energy as does the brain of an elephant;
and the cerebral operations of a Darwin may not have had a very
perceptibly larger mechanical equivalent than those of a banker's clerk.
Yet in the world of thought the difference between our estimate of the
results, or 'work done,' in these cases is such as to drive all ideas of
equivalency to the winds. Doubtless, a materialist will answer that it
is not fair to take our estimate of 'work done' in the world of mind as
the real equivalent of the energy supposed to have passed over from the
world of motion, seeing that our estimate is based, not on the
quantitative amount of thought produced, but rather on its qualitative
character with reference to the social requirements of the race. But to
this it is enough to answer that we have no means of gauging the
quantity of thought produced other than by