De Stoicorum repugnantiis

Moreover, Zeno admits (as Plato does) several virtues with various distinctions—to wit, prudence, fortitude, temperance and justice—as being indeed inseparable, but yet divers and different from one another. But again, defining every one of them, he says that fortitude is prudence in executing, justice prudence in distributing, as being one and the same virtue, but seeming to differ in its relation to various affairs when it comes to action. Nor does Zeno alone seem to contradict himself in these matters; but Chrysippus also, who blames Ariston for saying that the other virtues are different habits of one and the same virtue, and yet defends Zeno, who in this manner defines every one of the virtues. And Cleanthes, having in his Commentaries concerning Nature said, that vigor is the striking of fire, which, if it is sufficient in the soul to perform the duties presented to it, is called force and strength; subjoins these very words: Now this force and strength, when it is in things apparent and to be persisted in, is continence; when in things to be endured, it is fortitude; when about worthiness, it is justice; and when about choosing or refusing, it is temperance.