What language can attain to the marvels of the Creator? What ear could understand them? And what time would be sufficient to relate them? Let us say, then, with the prophet, “O Lord, how manifold are your works! in wisdom have you made them all.” We shall not be able to say in self-justification, that we have learned useful knowledge in books, since the untaught law of nature makes us choose that which is advantageous to us. Do you know what good you ought to do your neighbor? The good that you expect from him yourself. Do you know what is evil? That which you would not wish another to do to you. Neither botanical researches nor the experience of simples have made animals discover those which are useful to them; but each knows naturally what is salutary and marvelously appropriates what suits its nature.

Virtues exist in us also by nature, and the soul has affinity with them not by education, but by nature herself. We do not need lessons to hate illness, but by ourselves we repel what afflicts us, the soul has no need of a master to teach us to avoid vice. Now all vice is a sickness of the soul as virtue is its health. Thus those have defined health well who have called it a regularity in the discharge of natural functions; a definition that can be applied without fear to the good condition of the soul. Thus, without having need of lessons, the soul can attain by herself to what is fit and conformable to nature. Hence it comes that temperance everywhere is praised, justice is in honor, courage admired, and prudence the object of all aims; virtues which concern the soul more than health concerns the body. — Homily IX.