It remains to be considered in what relation the Protagoras stands to the other Dialogues of Plato. That it is one of the earlier or purely Socratic works--perhaps the last, as it is certainly the greatest of them--is indicated by the absence of any allusion to the doctrine of reminiscence; and also by the different attitude assumed towards the teaching and persons of the Sophists in some of the later Dialogues. The Charmides, Laches, Lysis, all touch on the question of the relation of knowledge to virtue, and may be regarded, if not as preliminary studies or sketches of the more important work, at any rate as closely connected with it. The Io and the lesser Hippias contain discussions of the Poets, which offer a parallel to the ironical criticism of Simonides, and are conceived in a similar spirit. The affinity of the Protagoras to the Meno is more doubtful. For there, although the same question is discussed, 'whether virtue can be taught,' and the relation of Meno to the Sophists is much the same as that of Hippocrates, the answer to the question is supplied out of the doctrine of ideas; the real Socrates is already passing into the Platonic one. At a later stage of the Platonic philosophy we shall find that both the paradox and the solution of it appear to have been retracted. The Phaedo, the Gorgias, and the Philebus offer further corrections of the teaching of the Protagoras; in all of them the doctrine that virtue is pleasure, or that pleasure is the chief or only good, is distinctly renounced. Thus after many preparations and oppositions, both of the characters of men and aspects of the truth, especially of the popular and philosophical aspect; and after many interruptions and detentions by the way, which, as Theodorus says in the Theaetetus, are quite as agreeable as the argument, we arrive at the great Socratic thesis that virtue is knowledge. This is an aspect of the truth which was lost almost as soon as it was found; and yet has to be recovered by every one for himself who would pass the limits of proverbial and popular philosophy. The moral and intellectual are always dividing, yet they must be reunited, and in the highest conception of them are inseparable. The thesis of Socrates is not merely a hasty assumption, but may be also deemed an anticipation of some 'metaphysic of the future,' in which the divided elements of human nature are reconciled. PROTAGORAS PERSONS OF THE DIALOGUE: Socrates, who is the narrator of the Dialogue to his Companion. Hippocrates, Alcibiades and Critias. Protagoras, Hippias and Prodicus (Sophists). Callias, a wealthy Athenian. SCENE: The House of Callias. COMPANION: Where do you come from, Socrates? And yet I need hardly ask the question, for I know that you have been in chase of the fair Alcibiades. I saw him the day before yesterday; and he had got a beard like a man,--and he is a man, as I may tell you in your ear. But I thought that he was still very charming.