Timaeus

So likewise we must conceive of that compound of soul and body which we call the living creature. Whenever the soul within it is stronger than the body and is in a very passionate state, it shakes up the whole body from within and fills it with maladies; and whenever the soul ardently pursues some study or investigation, it wastes the body; and again, when the soul engages, in public or in private, in teachings and battles of words carried on with controversy and contention, it makes the body inflamed and shakes it to pieces, and induces catarrhs; and thereby it deceives the majority of so-called physicians and makes them ascribe the malady to the wrong cause. And, on the other hand, when a large and overbearing body is united to a small and weak intellect, inasmuch as two desires naturally exist amongst men, —the desire of food for the body’s sake, and the desire of wisdom for the sake of the most divine part we have,—the motions of the stronger part prevail and augment their own power, but they make that of the soul obtuse and dull of wit and forgetful, and thereby they produce within it that greatest of diseases, ignorance. From both these evils the one means of salvation is this—neither to exercise the soul without the body nor the body without the soul, so that they may be evenly matched and sound of health. Thus the student of mathematics, or of any other subject, who works very hard with his intellect must also provide his body with exercise by practising gymnastics; while he who is diligent in molding his body must, in turn, provide his soul with motion by cultivating music and philosophy in general, if either is to deserve to be called truly both fair and good. The various parts, likewise, must be treated in the same manner, in imitation of the form of the Universe. For as the body is inflamed or chilled within by the particles that enter it, and again is dried or moistened by those without, and suffers the affections consequent on both these motions, whenever a man delivers his body, in a state of rest, to these motions, it is overpowered and utterly perishes; whereas if a man imitates that which we have called the nurturer and nurse of the Universe, and never, if possible, allows the body to be at rest but keeps it moving, and by continually producing internal vibrations defends it in nature’s way against the inward and outward motions, and by means of moderate vibrations arranges the affections and particles which stray about in the body in their due reciprocal order, according to their affinities,—as described in the previous account which we have given of the Universe—then he will not suffer foe set beside foe to breed war in the body and disease, but he will cause friend to be set beside friend so as to produce sound health.