You are devoted to interests from which it is impossible to gain intelligence or prudence or a proper disposition of reverence toward the gods, but o… - Dio Chrysostom

[Diogenes] was surprised by the fact that had he claimed to be a physician for the teeth, everybody would flock to him who needed to have a tooth pulled; yes, and by heavens, had he professed to treat the eyes, all who were suffering from sore eyes would present themselves, and similarly, if he had claimed to know of a medicine for diseases of the spleen or for gout or for running of the nose; but when he declared that all who should follow his treatment would be relieved of folly, wickedness, and intemperance, not a man would listen to him or seek to be cured by him, ... as though it were worse for a man to suffer from an enlarged spleen or a decayed tooth than from a soul that is foolish, ignorant, cowardly, rash, pleasure-loving, illiberal, irascible, unkind, and wicked, in fact utterly corrupt.

Should you be willing to read [Xenophon's Anabasis] very carefully you shall discover how ... to deceive one’s enemies to their harm and one’s friends to their advantage, and to speak the truth in a way that will not pain those who are needlessly disturbed by it.

When [Diogenes] observed how other men were harassed throughout their whole lives, ever plotting against one another, ever encompassed by a thousand ills and never able to enjoy a moment’s rest, nay, not even during the great festivals nor when they proclaimed a truce; and when he beheld that they did or suffered all this simply in order to keep themselves alive, and that their greatest fear was lest their so-called necessities should fail them, and how, furthermore, they planned and strove to leave great riches to their children, he marvelled that he too did not do the like, but was the only independent man in the world.