Someone will say: Yes, Socrates, but cannot you hold your tongue, and then you may go into a foreign city, and no one will interfere with you? Now I have great difficulty in making you understand my answer to this. For if I tell you that this would be a disobedience to a divine command, and therefore that I cannot hold my tongue, you will not believe that I am serious; and if I say that the greatest good of a man is daily to converse about virtue, and all that concerning which you hear me examining myself and others, and that the life which is unexamined is not worth living — that you are still less likely to believe.

37e–38a - Plato - Apology