roduced and modified? And what
living man, if he had unlimited control over all the nerves supplying
the mouth and larynx of another person, could make him pronounce a
sentence? Yet, if one has anything to say, what is easier than to say
it? We desire the utterance of certain words: we touch the spring of the
word-machine, and they are spoken. Just as Descartes' engineer, when he
wanted a particular hydraulic machine to play, had only to turn a tap,
and what he wished was done. It is because the body is a machine that
education is possible. Education is the formation of habits, a
superinducing of an artificial organization upon the natural
organization of the body; so that acts, which at first required a
conscious effort, eventually became unconscious and mechanical. If the
act which primarily requires a distinct consciousness and volition of
its details, always needed the same effort, education would be an
impossibility.

According to Descartes, then, all the functions which are common to man
and animals are performed by the body as a mere mechanism, and he looks
upon consciousness as the peculiar distinction of the "_chose
pensante_," of the "rational soul," which in man (and in man only, in
Descartes' opinion) is superadded to the body. This rational soul he
conceived to be lodged in the pineal gland, as in a sort of central
office; and, here, by the intermediation of the animal spirits, it
became aware of what was going on in the body, or influenced the
operations of the body. Modern physiologists do not ascribe so exalted
a function to the little pineal gland, but, in a vague sort of way, they
adopt Descartes' principle, and suppose that the soul is lodged in the
cortical part of the brain--at least this is commonly regarded as the
seat and instrument of consciousness.

Descartes has clearly stated what he conceived to be the difference
between spirit and matter. Matter is substance which has extension, but
does not think; spirit is substance which thinks, but has no extension.
It is very hard to form a definite notion of what this phraseology
means, when it is taken in connexion with the location of the soul in
the pineal gland; and I can only represent it to myself as signifying
that the soul is a mathematical point, having place but not extension,
within the limits of the pineal gland. Not only has it place, but it
must exert force; for, according to the hypothesis, it is competent,
when it wills, to change th