Res Gestae

Now the aforesaid Barbatio was a somewhat boorish fellow, of arrogant intentions, who was hated by many for the reason that, while he commanded the household troops under Gallus Caesar, he was a perfidious traitor; and after Gallus’ death, puffed up with pride in his higher military rank, he made like plots against Julian, when he became Caesar; and to the disgust of all good men he chattered into the open ears of the Augustus many cruel accusations.

He surely was unaware of the wise saying of Aristotle of old, who, on sending his disciple and relative Callisthenes to King Alexander, charged him repeatedly to speak as seldom and as pleasantly as possible in the presence of a man who had at the tip of his tongue the power of life and death.

And it should not cause surprise that men, whose minds we regard as akin to the gods, sometimes distinguish what is advantageous from what is harmful; for even unreasoning animals are at times wont to protect their lives by deep silence, as appears from this well-known fact.