οὐδείς ἑκὼν πονηρὸς οὐδ' ἄταν ἔχων → no one is willingly wretched or unlucky (Epicharmus fr. 7, early 5th cent. BCE)
The phrase was much mutilated and misinterpreted in later eras when πονηρὸς had lost its original sense of "burdened by toil" and had come to mean "worthless, evil." Aristotle misquotes it in Nichomachean Ethics 1113b.15 as οὐδεὶς ἑκὼν πονηρὸς οὐδ' ἄκων μακάριος to mean "No one is willingly evil or unwillingly happy" (which, BTW, Aristotle declares to be untrue). It's an easy jump, then, from πονηρός to κακός ("bad") to produce the modern concoction, attributed of course (especially on the Internet) to "Socrates": οὐδεὶς ἑκὼν κακός ("No one is willingly bad"). That phrase and its attribution may be a faint echo of Plato's Republic 360c6, where Glaucon, discoursing with Socrates, asserts, using the words οὐδεὶς ἑκὼν δίκαιος, "And this we may truly affirm to be a great proof that a man is just, not willingly or because he thinks that justice is any good to him individually, but of necessity, for wherever any one thinks that he can safely be unjust, there he is unjust" (Jowett trans.).
