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This paper shows that Plato’s Protagoras does not conflict with his Republic on a point scholars standardly suppose marks a profound contradiction in moral psychology between his earlier and middle periods. According to scholarly consensus, Socrates in Republic contradicts the Socrates of Protagoras, by allowing that, in human motivation and action, nonrational factors have power to overrule reason. Scholars generally suppose that in the earlier Protagoras Socrates denies the possibility that reason can lose control over emotion and appetite, while in Republic he bases the soul’s tripartition on precisely this possibility. But scrutiny of the two relevant Protagoras passages shows that Socrates denies the possibility of akrasia in a sense qualified and hedged so very precisely as not to conflict, as commonly supposed, with the later moral psychology of Republic.

Inexactitude abounds among scholars about what exactly, in Protagoras, Socrates denies. He is not adumbrating in Protagoras, as he is in Republic, an account of the soul’s structure and function, but challenging a popular view about weakness of the will as internally inconsistent. This popular view is that sometimes persons choose to do something, while “knowing” that something else, equally possible, is better, because they are overcome by nonrational factors like fear or desire (Prt. 352b-e). Socrates denies this, and very many scholars report him as denying that “reason” can prove weaker than nonrational factors. Further, scholars cite this passage as evidence that Socrates “overlook[s] a nonrational aspect of human motivation” and thinks virtue is “a purely intellectual matter” (Kraut 1992, 5-6). But the sense of akrasia Socrates denies in Protagoras does not fit this standard picture. In Protagoras, Socrates does not deny that nonrational factors can overcome a person’s reason, or their better judgment. He denies only that such factors can overcome knowledge. It is a hedge for Socrates to specify knowledge, rather than one’s better judgment, as unconquerable by emotions, because in this way he refrains from denying what so many scholars believe he denies can be overcome by nonrational factors, namely,“reason.” This hedge crops up so naturally, as to escape notice as a significant move. Although Socrates introduces it, he does so in the voice of Most People. It is their claim that sometimes they “know” the difference between good and bad, which Socrates disputes. They do make a claim about the relative strength of knowledge and nonrational factors, but Socrates disputes their understanding of knowledge for being internally inconsistent, not for underestimating knowledge’s strength. In his account of the Measuring Art, Socrates makes clear that he assumes knowledge is precisely the tool the soul uses, when deliberating morally, to manage nonrational factors (Prt. 356b-d). The Measuring Art treats nonrational factors as distortions in perception, and corrects for these distortions (356d). In this way, knowledge rationalizes the influence of nonrational factors on decision-making. It is not knowledge if these influences are not rationalized, and, Socrates argues, it is self-contradictory to say that knowledge is present when these influences determine one’s choice (355d).

In this way, Socrates treats the popular view of akrasia as a knowledge claim, and denies only that people, who are thought to commit errors while knowing better, actually know better. He does not dispute whether such people are overcome by fear or desire, only that they possess knowledge when thus overcome. Even if in Protagoras Socrates intends the statement of his denial to cover akrasia more broadly, he limits his discussion and arguments to only this epistemological sense. This sense of akrasia is much more narrowly restricted than scholars generally appreciate, and does not run afoul of the soul’s tripartition in Republic, where Socrates assumes that nonrational factors frequently do disrupt the leadership of the soul by its rational faculty.