<blockquote>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.

Source: Lives of the Eminent Philosophers (1925) by Diogenes Laërtius, translated by Robert Drew Hicks. A Loeb Classical Library edition; volume 1 published 1925; volume 2 published 1925. WikiSource.
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