venteenth-century
philosophers. It will cause us no great surprise that Leibniz should have
quickly felt that the Formal Principle of Aristotle and of the Scholastic
philosophy must be by hook or by crook reintroduced--not as the detested
_substantial form_, but under a name by which it might hope to smell more
sweet, _entelechy_.

Nothing so tellingly revealed the difficulties of the new philosophy in[19]
dealing with living bodies as the insufficiency of the solutions Descartes
had proposed. He had boldly declared the unity of animal life to be purely
mechanical, and denied that brutes had souls at all, or any sensation. He
had to admit soul in man, but he still denied the substantial unity of the
human body. It was put together like a watch, it was many things, not one:
if Descartes had lived in our time, he would have been delighted to compare
it with a telephone system, the nerves taking the place of the wires, and
being so arranged that all currents of 'animal spirit' flowing in them
converged upon a single unit, a gland at the base of the brain. In this
unit, or in the convergence of all the motions upon it, the 'unity' of the
body virtually consisted; and the soul was incarnate, not in the plurality
of members (for how could it, being one, indwell many things?), but in the
single gland.

Even so, the relation between the soul and the gland was absolutely
unintelligible, as Descartes disarmingly confessed. Incarnation was all
very well in the old philosophy: those who had allowed the interaction of
disparate natures throughout the physical world need find no particular
difficulty about the special case of it provided by incarnation. Why should
not a form of conscious life so interact with what would otherwise be dead
matter as to 'indwell' it? But the very principle of the new philosophy
disallowed the interaction of disparate natures, because such an
interaction did not allow of exact formulation, it was a 'loose' and not a
'tight' relation.

From a purely practical point of view the much derided pineal gland theory
would serve. If we could be content to view Descartes as a man who wanted
to make the world safe for physical science, then there would be a good
deal to be said for his doctrine. In the old philosophy exact science had
been frustrated by the hypothesis of loose relations all over the field of
nature. Descartes had cleared them from as much of the field as science was
then in a position to investig