s of that
science, and I content myself with recommending the Duke of Argyll to
devote some study to Book II. chap. v. section 4 of my friend Dr.
Foster's excellent text-book of Physiology (1st edition, 1877, p.
321), which begins thus:--

Broadly speaking, the animal body is a machine for
converting potential into actual energy. The potential
energy is supplied by the food; this the metabolism of the
body converts into the actual energy of heat and mechanical
labour.

There is no more difficult problem in the world than that of the
relation of the state of consciousness, termed volition, to the
mechanical work which frequently follows upon it. But no one can even
comprehend the nature of the problem, who has not carefully studied
the long series of modes of motion which, without a break, connect the
energy which does that work with the general store of energy. The
ultimate form of the problem is this: Have we any reason to believe
that a feeling, or state of consciousness, is capable of directly
affecting the motion of even the smallest conceivable molecule of
matter? Is such a thing even conceivable? If we answer these questions
in the negative, it follows that volition may be a sign, but cannot be
a cause, of bodily motion. If we answer them in the affirmative, then
states of consciousness become undistinguishable from material things;
for it is the essential nature of matter to be the vehicle or
substratum of mechanical energy.

There is nothing new in all this. I have merely put into modern
language the issue raised by Descartes more than two centuries ago.
The philosophies of the Occasionalists, of Spinoza, of Malebranche, of
modern idealism and modern materialism, have all grown out of the
controversies which Cartesianism evoked. Of all this the
pseudo-science of the present time appears to be unconscious;
otherwise it would hardly content itself with "making het again" the
pseudo-science of the past.

In the course of these observations I have already had occasion to
express my appreciation of the copious and perfervid eloquence which
enriches the Duke of Argyll's pages. I am almost ashamed that a
constitutional insensibility to the Sirenian charms of rhetoric has
permitted me in wandering through these flowery meads, to be
attracted, almost exclusively, to the bare places of fallacy and the
stony grounds of deficient information, which are disguised, though
not concealed, by thes