Quoting from Greek Ways: How The Greeks Created Western Civilization, by Bruce Thornton, ch. 5, p. 117-118, which is quoting Creon's son Haemon from Sophocles' Antigone:
For whoever think that they alone have sense, or have a power of speech or an intelligence that no other has, these people when they are laid open are found to be empty. It is not shameful for a man, even if he is wise, often to learn things and not to resist too much.
I recommend the Greek Ways book.