Vitae philosophorum

This is why Zeno was the first (in his treatise On the Nature of Man) to designate as the end life in agreement with nature (or living agreeably to nature), which is the same as a virtuous life, virtue being the goal towards which nature guides us. So too Cleanthes in his treatise On Pleasure, as also Posidonius, and Hecato in his work On Ends. Again, living virtuously is equivalent to living in accordance with experience of the actual course of nature, as Chrysippus says in the first book of his De finibus; for our individual natures are parts of the nature of the whole universe.

And this is why the end may be defined as life in accordance with nature, or, in other words, in accordance with our own human nature as well as that of the universe, a life in which we refrain from every action forbidden

By the nature with which our life ought to be in accord, Chrysippus understands both universal nature and more particularly the nature of man, whereas Cleanthes takes the nature of the universe alone as that which should be followed, without adding the nature of the individual.

And virtue, he holds, is a harmonious disposition, choice-worthy for its own sake and not from hope or fear or any external motive. Moreover, it is in virtue that happiness consists; for virtue is the state of mind which tends to make the whole of life harmonious. When a rational being is perverted, this is due to the deceptiveness of external pursuits or sometimes to the influence of associates. For the starting-points of nature are never perverse.

Virtue, in the first place, is in one sense the perfection of anything in general, say of a statue; again, it may be non-intellectual, like health, or intellectual, like prudence. For Hecato says in his first book On the Virtues that some are scientific and based upon theory, namely, those which have a structure of theoretical principles, such as prudence

These are called non-intellectual, because they do not require the mind’s assent; they supervene and they occur even in bad men: for instance, health, courage. The proof, says Posidonius in the first book of his treatise on Ethics, that virtue really exists is the fact that Socrates, Diogenes, and Antisthenes and their followers made moral progress. And for the existence of vice as a fundamental fact the proof is that it is the opposite of virtue. That it, virtue, can be taught is laid down by Chrysippus in the first book of his work On the End, by Cleanthes, by Posidonius in his Protreptica, and by Hecato; that it can be taught is clear from the case of bad men becoming good.