How could he have believed these things any more if they had really existed than he did when they only seemed to exist? For it is clear that at the moment his heart was not distrusting his eyes. But all these instances are cited in order to prove that than which nothing can be more certain, namely, that between true and false perceptions there is no difference at all, as far as the assent of the mind is concerned. But you prove nothing when you merely refute those false perceptions of men who are mad or dreaming, by their own recollection. For the question is not what sort of recollection those people usually have who have awakened, or those who have recovered from madness, but what sort of perception madmen or dreamers had at the moment when they were under the influence of their madness or their dream. However, we will say no more about the senses. What is there that can be perceived by reason? You say that Dialectics have been discovered, and that that science is, as it were, an arbiter and judge of what is true and false. Of what true and false?—and of true and false on what subject? Will a dialectician be able to judge, in geometry, what is true and false, or in literature, or in music? He knows nothing about those things. In philosophy, then? What is it to him how large the sun is? or what means has he which may enable him to judge what the chief good is? What then will he judge of? Of what combination or disjunction of ideas is accurate,—of what is an ambiguous expression,—of what follows from each fact, or what is inconsistent with it? If the science of dialectics judges of these things, or things like them, it is judging of itself. But it professed more. For to judge of these matters is not sufficient for the resolving of the other numerous and important questions which arise in philosophy. But, since you place so much importance in that art, I would have you to consider whether it was not invented for the express purpose of being used against you. For, at its first opening, it gives an ingenious account of the elements of speaking, and of the manner in which one may come to an understanding of ambiguous expressions, and of the principles of reasoning: then, after a few more things, it comes to the sorites, a very slippery and hazardous topic, and a class of argument which you yourself pronounced to be a vicious one.