however, he took life easily. He recommends idleness as
necessary to the production of good mental work. He worked and meditated
but a few hours a day: and most of those in bed. He used to think best
in bed, he said. The afternoon he devoted to society and recreation.
After supper he wrote letters to various persons, all plainly intended
for publication, and scrupulously preserved. He kept himself free from
care, and was most cautious about his health, regarding himself, no
doubt, as a subject of experiment, and wishful to see how long he could
prolong his life. At one time he writes to a friend that he shall be
seriously disappointed if he does not manage to see 100 years.

[Illustration: FIG. 53.--Descartes.]

This plan of not over-working himself, and limiting the hours devoted to
serious thought, is one that might perhaps advantageously be followed by
some over-laborious students of the present day. At any rate it conveys
a lesson; for the amount of ground covered by Descartes, in a life not
very long, is extraordinary. He must, however, have had a singular
aptitude for scientific work; and the judicious leaven of selfishness
whereby he was able to keep himself free from care and embarrassments
must have been a great help to him.

And what did his versatile genius accomplish during his fifty-four years
of life?

In philosophy, using the term as meaning mental or moral philosophy and
metaphysics, as opposed to natural philosophy or physics, he takes a
very high rank, and it is on this that perhaps his greatest fame rests.
(He is the author, you may remember, of the famous aphorism, "_Cogito,
ergo sum_.")

In biology I believe he may be considered almost equally great:
certainly he spent a great deal of time in dissecting, and he made out a
good deal of what is now known of the structure of the body, and of the
theory of vision. He eagerly accepted the doctrine of the circulation of
the blood, then being taught by Harvey, and was an excellent anatomist.

You doubtless know Professor Huxley's article on Descartes in the _Lay
Sermons_, and you perceive in what high estimation he is there held.

He originated the hypothesis that animals are automata, for which indeed
there is much to be said from some points of view; but he unfortunately
believed that they were unconscious and non-sentient automata, and this
belief led his disciples into acts of abominable cruelty. Professor
Huxley lectured on this hypothesis and