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.
The victory of Socrates over Protagoras is in every way complete when their minds are fairly brought together. Protagoras falls before him after two or three blows. Socrates partially gains his object in the first part of the Dialogue, and completely in the second. Nor does he appear at any disadvantage when subjected to 'the question' by Protagoras. He succeeds in making his two 'friends,' Prodicus and Hippias, ludicrous by the way; he also makes a long speech in defence of the poem of Simonides, after the manner of the Sophists, showing, as Alcibiades says, that he is only pretending to have a bad memory, and that he and not Protagoras is really a master in the two styles of speaking; and that he can undertake, not one side of the argument only, but both, when Protagoras begins to break down. Against the authority of the poets with whom Protagoras has ingeniously identified himself at the commencement of the Dialogue, Socrates sets up the proverbial philosophers and those masters of brevity the Lacedaemonians. The poets, the Laconizers, and Protagoras are satirized at the same time.
Not having the whole of this poem before us, it is impossible for us to answer certainly the question of Protagoras, how the two passages of Simonides are to be reconciled. We can only follow the indications given by Plato himself. But it seems likely that the reconcilement offered by Socrates is a caricature of the methods of interpretation which were practised by the Sophists – for the following reasons: (1) The transparent irony of the previous interpretations given by Socrates. (2) The ludicrous opening of the speech in which the Lacedaemonians are described as the true philosophers, and Laconic brevity as the true form of philosophy, evidently with an allusion to Protagoras' long speeches. (3) The manifest futility and absurdity of the explanation of (Greek), which is hardly consistent with the rational interpretation of the rest of the poem. The opposition of (Greek) and (Greek) seems also intended to express the rival doctrines of Socrates and Protagoras, and is a facetious commentary on their differences. (4) The general treatment in Plato both of the Poets and the Sophists, who are their interpreters, and whom he delights to identify with them. (5) The depreciating spirit in which Socrates speaks of the introduction of the poets as a substitute for original conversation, which is intended to contrast with Protagoras' exaltation of the study of them – this again is hardly consistent with the serious defence of Simonides. (6) the marked approval of Hippias, who is supposed at once to catch the familiar sound, just as in the previous conversation Prodicus is represented as ready to accept any distinctions of language however absurd. At the same time Hippias is desirous of substituting a new interpretation of his own; as if the words might really be made to mean anything, and were only to be regarded as affording a field for the ingenuity of the interpreter.
This curious passage is, therefore, to be regarded as Plato's satire on the tedious and hypercritical arts of interpretation which prevailed in his own day, and may be compared with his condemnation of the same arts when applied to mythology in the Phaedrus, and with his other parodies, e.g. with the two first speeches in the Phaedrus and with the Menexenus. Several lesser touches of satire may be observed, such as the claim of philosophy advanced for the Lacedaemonians, which is a parody of the claims advanced for the Poets by Protagoras; the mistake of the Laconizing set in supposing that the Lacedaemonians are a great nation because they bruise their ears; the far-fetched notion, which is 'really too bad,' that Simonides uses the Lesbian (?) word, (Greek), because he is addressing a Lesbian. The whole may also be considered as a satire on those who spin pompous theories out of nothing. As in the arguments of the Euthydemus and of the Cratylus, the veil of irony is never withdrawn; and we are left in doubt at last how far in this interpretation of Simonides Socrates is 'fooling,' how far he is in earnest.
All the interests and contrasts of character in a great dramatic work like the Protagoras are not easily exhausted. The impressiveness of the scene should not be lost upon us, or the gradual substitution of Socrates in the second part for Protagoras in the first. The characters to whom we are introduced at the beginning of the Dialogue all play a part more or less conspicuous towards the end. There is Alcibiades, who is compelled by the necessity of his nature to be a partisan, lending effectual aid to Socrates; there is Critias assuming the tone of impartiality; Callias, here as always inclining to the Sophists, but eager for any intellectual repast; Prodicus, who finds an opportunity for displaying his distinctions of language, which are valueless and pedantic, because they are not based on dialectic; Hippias, who has previously exhibited his superficial knowledge of natural philosophy, to which, as in both the Dialogues called by his name, he now adds the profession of an interpreter of the Poets. The two latter personages have been already damaged by the mock heroic description of them in the introduction. It may be remarked that Protagoras is consistently presented to us throughout as the teacher of moral and political virtue; there is no allusion to the theories of sensation which are attributed to him in the Theaetetus and elsewhere, or to his denial of the existence of the gods in a well-known fragment ascribed to him; he is the religious rather than the irreligious teacher in this Dialogue. Also it may be observed that Socrates shows him as much respect as is consistent with his own ironical character; he admits that the dialectic which has overthrown Protagoras has carried himself round to a conclusion opposed to his first thesis. The force of argument, therefore, and not Socrates or Protagoras, has won the day.
But is Socrates serious in maintaining (1) that virtue cannot be taught; (2) that the virtues are one; (3) that virtue is the knowledge of pleasures and pains present and future? These propositions to us have an appearance of paradox – they are really moments or aspects of the truth by the help of which we pass from the old conventional morality to a higher conception of virtue and knowledge. That virtue cannot be taught is a paradox of the same sort as the profession of Socrates that he knew nothing. Plato means to say that virtue is not brought to a man, but must be drawn out of him; and cannot be taught by rhetorical discourses or citations from the poets. The second question, whether the virtues are one or many, though at first sight distinct, is really a part of the same subject; for if the virtues are to be taught, they must be reducible to a common principle; and this common principle is found to be knowledge. Here, as Aristotle remarks, Socrates and Plato outstep the truth – they make a part of virtue into the whole. Further, the nature of this knowledge, which is assumed to be a knowledge of pleasures and pains, appears to us too superficial and at variance with the spirit of Plato himself. Yet, in this, Plato is only following the historical Socrates as he is depicted to us in Xenophon's Memorabilia. Like Socrates, he finds on the surface of human life one common bond by which the virtues are united, – their tendency to produce happiness, – though such a principle is afterwards repudiated by him.
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