timaeus   

For where the acid and briny phlegm and other bitter and bilious
humours wander about in the body, and find no exit or escape, but
are pent up within and mingle their own vapours with the motions of
the soul, and are blended, with them, they produce all sorts of
diseases, more or fewer, and in every degree of intensity; and being
carried to the three places of the soul, whichever they may
severally assail, they create infinite varieties of ill-temper and
melancholy, of rashness and cowardice, and also of forgetfulness and
stupidity. Further, when to this evil constitution of body evil
forms of government are added and evil discourses are uttered in
private as well as in public, and no sort of instruction is given in
youth to cure these evils, then all of us who are bad become bad
from two causes which are entirely beyond our control. In such cases
the planters are to blame rather than the plants, the educators rather
than the educated. But however that may be, we should endeavour as far
as we can by education, and studies, and learning, to avoid vice and
attain virtue; this, however, is part of another subject.
There is a corresponding enquiry concerning the mode of treatment by
which the mind and the body are to be preserved, about which it is
meet and right that I should say a word in turn; for it is more our
duty to speak of the good than of the evil. Everything that is good is
fair, and the animal fair is not without proportion, and the animal
which is to be fair must have due proportion. Now we perceive lesser
symmetries or proportions and reason about them, but of the highest
and greatest we take no heed; for there is no proportion or
disproportion more productive of health and disease, and virtue and
vice, than that between soul and body. This however we do not
perceive, nor do we reflect that when a weak or small frame is the
vehicle of a great and mighty soul, or conversely, when a little
soul is encased in a large body, then the whole animal is not fair,
for it lacks the most important of all symmetries; but the due
proportion of mind and body is the fairest and loveliest of all sights
to him who has the seeing eye. Just as a body which has a leg too
long, or which is unsymmetrical in some other respect, is an
unpleasant sight, and also, when doing its share of work, is much
distressed and makes convulsive efforts, and often stumbles through
awkwardness, and is the cause of infinite evil to its own self-in like
manner we should conceive of the double nature which we call the
living being; and when in this compound there is an impassioned soul
more powerful than the body, that soul, I say, convulses and fills
with disorders the whole inner nature of man; and when eager in the
pursuit of some sort of learning or study, causes wasting; or again,
when teaching or disputing in private or in public, and strifes and
controversies arise, inflames and dissolves the composite frame of man
and introduces rheums; and the nature of this phenomenon is not
understood by most professors of medicine, who ascribe it to the
opposite of the real cause. And once more, when body large and too
strong for the soul is united to a small and weak intelligence, then
inasmuch as there are two desires natural to man,-one of food for
the sake of the body, and one of wisdom for the sake of the diviner
part of us-then, I say, the motions of the stronger, getting the
better and increasing their own power, but making the soul dull, and
stupid, and forgetful, engender ignorance, which is the greatest of
diseases. There is one protection against both kinds of
disproportion:-that we should not move the body without the soul or
the soul without the body, and thus they will be on their guard
against each other, and be healthy and well balanced. And therefore
the mathematician or any one else whose thoughts are much absorbed
in some intellectual pursuit, must allow his body also to have due
exercise, and practise gymnastic; and he who is careful to fashion the
body, should in turn impart to the soul its proper motions, and should
cultivate music and all philosophy, if he would deserve to be called
truly fair and truly good. And the separate parts should be treated in
the same manner, in imitation of the pattern of the universe; for as