Euthydemus

Then after all the wise are the learners and not the unlearned; and your last answer to Euthydemus was wrong. Then once more the admirers of the two heroes, in an ecstasy at their wisdom, gave vent to another peal of laughter, while the rest of us were silent and amazed. Euthydemus, observing this, determined to persevere with the youth; and in order to heighten the effect went on asking another similar question, which might be compared to the double turn of an expert dancer. Do those, said he, who learn, learn what they know, or what they do not know? Again Dionysodorus whispered to me: That, Socrates, is just another of the same sort. Good heavens, I said; and your last question was so good! - Taken from "Euthydemus" written by Plato