Sokrates then attempts to show that intelligence and moderation are identical with each other (σοφία and σωφροσύνη). The proof which he produces, elicited by several questions, is — that both the one and the other are contrary to folly (ἀφροσύνη), and, that as a general rule, nothing can have more than one single contrary.[65]
[65] Plat. Protag. p. 332.
Insufficient reasons given by Sokrates. He seldom cares to distinguish different meanings of the same term.
Sokrates thus seems to himself to have made much progress in proving all the names of different virtues to be names of one and the same thing. Moderation and intelligence are shown to be the same: justice and holiness had before been shown to be nearly the same:[66] though we must recollect that this last point had not been admitted by Protagoras. It must be confessed however that neither the one nor the other is proved by any conclusive reasons. In laying down the maxim — that nothing can have more than one single contrary — Plato seems to have forgotten that the same term may be used in two different senses. Because the term folly (ἀφροσύνη), is used sometimes to denote the opposite of moderation (σωφροσύνη), sometimes the opposite of intelligence (σοφία), it does not follow that moderation and intelligence are the same thing.[67] Nor does he furnish more satisfactory proof of the other point, viz.: That holiness and justice are the same, or as much alike as possible. The intermediate position which is assumed to form the proof, viz.: That holiness is holy, and that justice is just — is either tautological, or unmeaning; and cannot serve as a real proof of any thing. It is indeed so futile, that if it were found in the mouth of Protagoras and not in that of Sokrates, commentators would probably have cited it as an illustration of the futilities of the Sophists. As yet therefore little has been done to elucidate the important question to which Sokrates addresses himself — What is the extent of analogy between the different virtues? Are they at bottom one and the same thing under different names? In what does the analogy or the sameness consist?
[66] Plato, Protag. p. 338 B. σχέδον τι ταὐτὸν ὄν.
[67] Aristotle would probably have avoided such a mistake as this. One important point (as I have already remarked, [vol. ii. p. 170]) in which he is superior to Plato is, in being far more careful to distinguish the different meanings of the same word — τὰ πολλαχῶς λεγόμενα. Plato rarely troubles himself to notice such distinction, and seems indeed generally unaware of it. He constantly ridicules Prodikus, who tried to distinguish words apparently synonymous.
Protagoras is puzzled, and becomes irritated.
But though little progress has been made in determining the question mooted by Sokrates, enough has been done to discompose and mortify Protagoras. The general tenor of the dialogue is, to depict this man, so eloquent in popular and continuous exposition, as destitute of the analytical acumen requisite to meet cross-examination, and of promptitude for dealing with new aspects of the case, on the very subjects which form the theme of his eloquence. He finds himself brought round, by a series of short questions, to a conclusion which — whether conclusively proved or not — is proved in a manner binding upon him, since he has admitted all the antecedent premisses. He becomes dissatisfied with himself, answers with increasing reluctance,[68] and is at last so provoked as to break out of the limits imposed upon a respondent.
[68] Plato, Protag. pp. 333 B, 335 A.