n of the brain; and it has to obey the same laws in
regard to exertion and repose as any other organic function. The brain
can be ruined by overstrain, just like the eyes. As the function of
the stomach is to digest, so it is that of the brain to think. The
notion of a _soul_,--as something elementary and immaterial, merely
lodging in the brain and needing nothing at all for the performance
of its essential function, which consists in always and unweariedly
_thinking_--has undoubtedly driven many people to foolish practices,
leading to a deadening of the intellectual powers; Frederick the
Great, even, once tried to form the habit of doing without sleep
altogether. It would be well if professors of philosophy refrained
from giving currency to a notion which is attended by practical
results of a pernicious character; but then this is just what
professorial philosophy does, in its old-womanish endeavor to keep on
good terms with the catechism. A man should accustom himself to
view his intellectual capacities in no other light than that of
physiological functions, and to manage them accordingly--nursing or
exercising them as the case may be; remembering that every kind of
physical suffering, malady or disorder, in whatever part of the body
it occurs, has its effect upon the mind. The best advice that I know
on this subject is given by Cabanis in his _Rapports du physique et du
moral de l'homme_.[1]

[Footnote 1: _Translator's Note_. The work to which Schopenhauer
here refers is a series of essays by Cabanis, a French philosopher
(1757-1808), treating of mental and moral phenomena on a physiological
basis. In his later days, Cabanis completely abandoned his
materialistic standpoint.]

Through neglect of this rule, many men of genius and great scholars
have become weak-minded and childish, or even gone quite mad, as they
grew old. To take no other instances, there can be no doubt that the
celebrated English poets of the early part of this century, Scott,
Wordsworth, Southey, became intellectually dull and incapable towards
the end of their days, nay, soon after passing their sixtieth year;
and that their imbecility can be traced to the fact that, at that
period of life, they were all led on? by the promise of high pay, to
treat literature as a trade and to write for money. This seduced them
into an unnatural abuse of their intellectual powers; and a man who
puts his Pegasus into harness, and urges on his Muse with the whip,