Socrates meets, in the house of Callias, the eminent sophist Protagoras, who is very attractively drawn and represented as a great admirer of the younger man's ability. Protagoras explains that his profession is the "teaching of goodness," and that by "goodness" he means the art of making a success of one's own life, that of one's household and that of one's "city." (Thus he teaches "the conduct of life, private and public," and has done so for years with success.) Socrates urges that there are two considerations which make it look doubtful whether this art can be taught. The Athenians have a high reputation for in telligence, but it is notorious that the Ecclesia requires no evidence of expert knowledge in a speaker who discusses the morality of a proposed course of action.
Also the eminent democratic statesmen have never taught their own "goodness" to their sons. Public opinion and the practice of the eminent few alike suggest that the "conduct of life" is not teachable. Protagoras, to be sure, thinks that the absence of special teachers only proves that every citizen of a civilized city can, in his degree, act as teacher, exactly as he can teach his children his native language or his trade. Goodness depends on 8fi1tri and al&bs; the sense of right and conscience, and the whole of life in a civilised society, is a process of education in these. His exposition at once raises the problem of the unity of virtue. Are the various commonly recognized "virtues" really different, so that a man may be strong in one but weak in an other? Protagoras is at first inclined to say that they are, but on reconsideration is ready to identify all of them but one with wisdom or sound judgment.
An exception must be made for courage, a virtue which is popularly regarded as having something conspicuously non rational about it. The dialogue culminates in an argument by which Socrates attempts to show that there is no need to make this exception. The general public, the party which insists so
much on the non-rational character of courage, would be ready to accept the identification of the good and the pleasant, and to grant that the goodness of courage means that by facing pain and danger one escapes worse pain or danger. On their own theory, then, courage, and the rest of virtue, can be reduced to prudent computation of pleasures and pains. The humour of the situation is that Socrates and Protagoras have thus changed places. Socrates, who had raised a difficulty about the teach ability of virtue, is left satisfied that virtue must be knowledge; Protagoras, who claimed to be able to teach it, ends by declaring that, whatever virtue may be, it cannot be knowledge. It is important to observe that the dialogue does not teach Hedonism. The equation good.,--pleasant is advanced only as one which would be accepted by "the mass of men," and should forbid them to find a paradox in the identification of virtue with knowledge; it is expressly repudiated by Protagoras as unworthy of a man of high character.
All that Socrates asserts is that virtue is knowledge and wrong doing consequently involuntary. There is no disagreement in moral principle between the Protagoras and the Phaedo or Gorgias. If the "mass of men" are ready to accept the Hedonist formula, that is because they are votaries of the body-loving life (131..os (InXoo-c'op,aros); this is why we are told in the Phaedo that "popular" virtue is illusory. The true explanation of Socrates' doubts is that though he holds that true virtue, being knowledge, is teachable, he does not believe that what Protagoras is trying to teach is true virtue. "Success" depends on personal "tact" and "tact" cannot be learned from an instructor.