Dionysadros's Contradiction

Dionysadros said there was no such thing as contradiction. Katisipo replied that he had often heard this thesis of yours, which to me appears to be quite wonderful and suicidal, as well as destructive. The dictum is that a man must either say what is true, or say nothing; but if he cannot speak falsely, may he not think falsely? No, he said. Then, there is noSuch thing as ignorance, or men who are ignorant,. And that is impossible? Impossible, he replied.