The second century philosopher Peregrinus Proteus is best known to us because of a rather vicious satire directed at him by Lucian, The Passing of Peregrinus. The satire has achieved a wide readership because it is one of the early texts which mention the Christians.
But a far more kindly, and probably more accurate, portrait appears in Aulus Gellius, book 12, ch. 11. It is much less well-known, and I give it here from the Loeb text:
11. That those are deceived who sin in the confident hope of being undetected, since there is no permanent concealment of wrongdoing; and on that subject a discourse of the philosopher Peregrinus and a saying of the poet Sophocles.
When I was at Athens, I met a philosopher named Peregrinus, who was later surnamed Proteus, a man of dignity and fortitude, living in a hut outside the city. And visiting him frequently, I heard him say many things that were in truth helpful and noble. Among these I particularly recall the following:He used to say that a wise man would not commit a sin, even if he knew that neither gods nor men would know it; for he thought that one ought to refrain from sin, not through fear of punishment or disgrace, but from love of justice and honesty and from a sense of duty. If, however, there were any who were neither so endowed by nature nor so well disciplined that they could easily keep themselves from sinning by their own will power, he thought that such men would all be more inclined to sin whenever they thought that their guilt could be concealed and when they had hope of impunity because of such concealment. “But,” said he, “if men know that nothing at all can be hidden for very long, they will sin more reluctantly and more secretly.” Therefore he said that one should have on his lips these verses of Sophocles, the wisest of poets:
See to it lest you try aught to conceal;
Time sees and hears all, and will all reveal.
Another one of the old poets, whose name has escaped my memory at present, called Truth the daughter of Time.