timaeus   

called sacred. An acid and salt phlegm, again, is the source of all
those diseases which take the form of catarrh, but they have many
names because the places into which they flow are manifold.
Inflammations of the body come from burnings and inflamings, and all
of them originate in bile. When bile finds a means of discharge, it
boils up and sends forth all sorts of tumours; but when imprisoned
within, it generates many inflammatory diseases, above all when
mingled with pure blood; since it then displaces the fibres which
are scattered about in the blood and are designed to maintain the
balance of rare and dense, in order that the blood may not be so
liquefied by heat as to exude from the pores of the body, nor again
become too dense and thus find a difficulty in circulating through the
veins. The fibres are so constituted as to maintain this balance;
and if any one brings them all together when the blood is dead and
in process of cooling, then the blood which remains becomes fluid, but
if they are left alone, they soon congeal by reason of the surrounding
cold. The fibres having this power over the blood, bile, which is only
stale blood, and which from being flesh is dissolved again into blood,
at the first influx coming in little by little, hot and liquid, is
congealed by the power of the fibres; and so congealing and made to
cool, it produces internal cold and shuddering. When it enters with
more of a flood and overcomes the fibres by its heat, and boiling up
throws them into disorder, if it have power enough to maintain its
supremacy, it penetrates the marrow and burns up what may be termed
the cables of the soul, and sets her free; but when there is not so
much of it, and the body though wasted still holds out, the bile is
itself mastered, and is either utterly banished, or is thrust
through the veins into the lower or upper-belly, and is driven out
of the body like an exile from a state in which there has been civil
war; whence arise diarrhoeas and dysenteries, and all such
disorders. When the constitution is disordered by excess of fire,
continuous heat and fever are the result; when excess of air is the
cause, then the fever is quotidian; when of water, which is a more
sluggish element than either fire or air, then the fever is a tertian;
when of earth, which is the most sluggish of the four, and is only
purged away in a four-fold period, the result is a quartan fever,
which can with difficulty be shaken off.
Such is the manner in which diseases of the body arise; the
disorders of the soul, which depend upon the body, originate as
follows. We must acknowledge disease of the mind to be a want of
intelligence; and of this there are two kinds; to wit, madness and
ignorance. In whatever state a man experiences either of them, that
state may be called disease; and excessive pains and pleasures are
justly to be regarded as the greatest diseases to which the soul is
liable. For a man who is in great joy or in great pain, in his
unseasonable eagerness to attain the one and to avoid the other, is
not able to see or to hear anything rightly; but he is mad, and is
at the time utterly incapable of any participation in reason. He who
has the seed about the spinal marrow too plentiful and overflowing,
like a tree overladen with fruit, has many throes, and also obtains
many pleasures in his desires and their offspring, and is for the most
part of his life deranged, because his pleasures and pains are so very
great; his soul is rendered foolish and disordered by his body; yet he
is regarded not as one diseased, but as one who is voluntarily bad,
which is a mistake. The truth is that the intemperance of love is a
disease of the soul due chiefly to the moisture and fluidity which
is produced in one of the elements by the loose consistency of the
bones. And in general, all that which is termed the incontinence of
pleasure and is deemed a reproach under the idea that the wicked
voluntarily do wrong is not justly a matter for reproach. For no man
is voluntarily bad; but the bad become bad by reason of an ill
disposition of the body and bad education, things which are hateful to
every man and happen to him against his will. And in the case of
pain too in like manner the soul suffers much evil from the body.