Well if we're doing Greek Philosopher jokes there was the time a friend came up to Socrates with something to tell him. Socrates stopped him and explained his notion that for him to consider the matter it had to pass trough his three sieves of truth, goodness, and usefullness. "First of all", says the Great Man, "are you absolutely certain that what you are about to say to me is true", "Well, perhaps not certain, but I heard ...", whereupon Socrates stops him and moves on to the goodness sieve. "So is what you are about to say truly good", "Well not really I suppose", so Socrates explains the third sieve "Are you about to tell me something genuinely useful?". The friend thinks for a moment and concedes it is perhaps not useful. Suitably humbled the man decides not to trouble Socrates after all
And this shows the reason Socrates was such a great philosopher. It also explains why he never found out Archimedes was shagging his wife
