It is evident, now, how suitable to nature are the parts of our body, and the whole general figure, form, and stature of it; nor is there any doubt what kind of face, eyes, ears and other features are peculiar to man. But certainly it is necessary for them to be in good health and vigorous, and to have all their natural movements and uses; so that no part of them shall be absent, or disordered, or enfeebled; for nature requires soundness. For there is a certain action of the body which has all its motions and its general condition in a state of harmony with nature, in which if anything goes wrong through any distortion or depravity, either by any irregular motion or disordered condition,—as if, for instance, a person were to walk on his hands, or to walk not forwards but backwards,—then he would evidently appear to be flying from himself, and to be putting off his manhood, and to hate his own nature. On which account, also, some ways of sitting down, and some contorted and abrupt movements, such as wanton or effeminate men at times indulge in, are contrary to nature. So that even if that should happen through any fault of the mind, still the nature of the man would seem to be changed in his body. Therefore, on the contrary, moderate and equal conditions, and affections, and habits of the body, seem to be suitable to nature. But now the mind must not only exist, but must exist in a peculiar manner, so as to have all its parts sound, and to have no virtue wanting: but each sense has its own peculiar virtue, so that nothing may hinder each sense from performing its office in the quick and ready perception of those things which come under the senses.