For example: (1) one of the noblest statements to be found in antiquity about the preventive nature of punishment is put into his mouth; (2) he is clearly right also in maintaining that virtue can be taught (which Socrates himself, at the end of the Dialogue, is disposed to concede); and also (3) in his explanation of the phenomenon that good fathers have bad sons; (4) he is right also in observing that the virtues are not like the arts, gifts or attainments of special individuals, but the common property of all: this, which in all ages has been the strength and weakness of ethics and politics, is deeply seated in human nature; (5) there is a sort of half-truth in the notion that all civilized men are teachers of virtue; and more than a half-truth (6) in ascribing to man, who in his outward conditions is more helpless than the other animals, the power of self-improvement; (7) the religious allegory should be noticed, in which the arts are said to be given by Prometheus (who stole them), whereas justice and reverence and the political virtues could only be imparted by Zeus; (8) in the latter part of the Dialogue, when Socrates is arguing that 'pleasure is the only good,' Protagoras deems it more in accordance with his character to maintain that 'some pleasures only are good;' and admits that 'he, above all other men, is bound to say "that wisdom and knowledge are the highest of human things."' There is no reason to suppose that in all this Plato is depicting an imaginary Protagoras; he seems to be showing us the teaching of the Sophists under the milder aspect under which he once regarded them. Nor is there any reason to doubt that Socrates is equally an historical character, paradoxical, ironical, tiresome, but seeking for the unity of virtue and knowledge as for a precious treasure; willing to rest this even on a calculation of pleasure, and irresistible here, as everywhere in Plato, in his intellectual superiority. The aim of Socrates, and of the Dialogue, is to show the unity of virtue. In the determination of this question the identity of virtue and knowledge is found to be involved. But if virtue and knowledge are one, then virtue can be taught; the end of the Dialogue returns to the beginning. Had Protagoras been allowed by Plato to make the Aristotelian distinction, and say that virtue is not knowledge, but is accompanied with knowledge; or to point out with Aristotle that the same quality may have more than one opposite; or with Plato himself in the Phaedo to deny that good is a mere exchange of a greater pleasure for a less--the unity of virtue and the identity of virtue and knowledge would have required to be proved by other arguments.