Euthydemus, Gorgias, and the two dialogues entitled Hippias that of subversive argument. So much then for dialogue, its definition and varieties. Again, as there is great division of opinion between those who affirm and those who deny that Plato was a dogmatist, let me proceed to deal with this further question. To be a dogmatist in philosophy is to lay down positive dogmas, just as to be a legislator is to lay down laws. Further, under dogma two things are included, the thing opined and the opinion itself. Of these the former is a proposition, the latter a conception. Now where he has a firm grasp Plato expounds his own view and refutes the false one, but, if the subject is obscure, he suspends judgement. His own views are expounded by four persons, Socrates, Timaeus, the Athenian Stranger,* the Kleatic Stranger.” These strangers are not, as some hold, Plato and Parmenides, but imaginary characters without names,¢ for, even when Socrates and Timaeus are the speakers, it is Plato’s doctrines that are laid down. To illustrate the refutation of false opinions, he introduces Thrasymachus, Callicles, Polus, Gorgias, Protagoras, or again Hippias, Kuthydemus and the like. In constructing his proofs he makes most use of induction, not always in the same way, but under two forms. For induction is an argument which by means of certain true premisses properly infers a truth resembling them. And there are two kinds of induction, the one proceeding by way of contradiction, the other from agreement. In the kind which proceeds by contradiction the answer given to every question will necessarily be the contrary of the