III. But there are more disorders of the mind than of the body, and
they are of a more dangerous nature; for these very disorders are the
more offensive because they belong to the mind and disturb it; and the
mind, when disordered, is, as Ennius says, in a constant error: it can
neither bear nor endure anything, and is under the perpetual influence
of desires. Now, what disorders can be worse to the body than these two
distempers of the mind (for I overlook others), weakness and desire?
But how, indeed, can it be maintained that the mind cannot prescribe
for itself, when she it is who has invented the medicines for the body,
when, with regard to bodily cures, constitution and nature have a great
share, nor do all who suffer themselves to be cured find that effect
instantly; but those minds which are disposed to be cured, and submit
to the precepts of the wise, may undoubtedly recover a healthy state?
Philosophy is certainly the medicine of the soul, whose assistance we
do not seek from abroad, as in bodily disorders, but we ourselves are
bound to exert our utmost energy and power in order to effect our cure.
But as to philosophy in general, I have, I think, in my Hortensius,
sufficiently spoken of the credit and attention which it deserves:
since that, indeed, I have been continually either disputing or writing
on its most material branches; and I have laid down in these books all
the discussions which took place between myself and my particular
friends at my Tusculan villa. But as I have spoken in the two former of
pain and death, this book shall be devoted to the account of the third
day of our disputations.

We came down into the Academy when the day was already declining
towards afternoon, and I asked one of those who were present to propose
a subject for us to discourse on; and then the business was carried on
in this manner: