Here Ctesippus was silent; and I in my astonishment said: What do you mean, Dionysodorus? I have often heard, and have been amazed to hear, this thesis of yours, which is maintained and employed by the disciples of Protagoras, and others before them, and which to me appears to be quite wonderful, and suicidal as well as destructive, and I think that I am most likely to hear the truth about it from you. The dictum is that there is no such thing as falsehood; a man must either say what is true or say nothing. Is not that your position? He assented. But if he cannot speak falsely, may he not think falsely? No, he cannot, he said. Then there is no such thing as false opinion? No, he said. Then there is no such thing as ignorance, or men who are ignorant; for is not ignorance, if there be such a thing, a mistake of fact? Certainly, he said. And that is impossible? Impossible, he replied. Are you saying this as a paradox, Dionysodorus; or do you seriously maintain no man to be ignorant? Refute me, he said. But how can I refute you, if, as you say, to tell a falsehood is impossible? Very true, said Euthydemus. Neither did I tell you just now to refute me, said Dionysodorus; for how can I tell you to do that which is not? O Euthydemus, I said, I have but a dull conception of these subtleties and excellent devices of wisdom; I am afraid that I hardly understand them, and you must forgive me therefore if I ask a very stupid question: if there be no falsehood or false opinion or ignorance, there can be no such thing as erroneous action, for a man cannot fail of acting as he is acting--that is what you mean? Yes, he replied. And now, I said, I will ask my stupid question: If there is no such thing as error in deed, word, or thought, then what, in the name of goodness, do you come hither to teach? And were you not just now saying that you could teach virtue best of all men, to any one who was willing to learn? And are you such an old fool, Socrates, rejoined Dionysodorus, that you bring up now what I said at first--and if I had said anything last year, I suppose that you would bring that up too--but are non-plussed at the words which I have just uttered? Why, I said, they are not easy to answer; for they are the words of wise men: and indeed I know not what to make of this word 'nonplussed,' which you used last: what do you mean by it, Dionysodorus? You must mean that I cannot refute your argument. Tell me if the words have any other sense. No, he replied, they mean what you say. And now answer. What, before you, Dionysodorus? I said. Answer, said he. And is that fair? Yes, quite fair, he said. Upon what principle? I said. I can only suppose that you are a very wise man who comes to us in the character of a great logician, and who knows when to answer and when not to answer--and now you will not open your mouth at all, because you know that you ought not.