His companion replied that it seemed quite clear to him that it would be absurd if it were impossible to tell whether one speaker was speaking truly or falsely and yet possible to tell whether two speakers were; or if it were impossible to learn from someone who spoke the truth and yet possible to be instructed in the same matters by the same man together with someone else who spoke falsely; or if one man who spoke correctly and truly could not make clear what he was saying and yet two men, one of whom spoke falsely and not correctly, could make clear what the man who spoke correctly could not make clear. '