Akrasia and the Rule of Appetite in Plato's Protagoras and Republic

According to a prevalent developmentalist line of interpretation, Plato’s introduction of the three-part soul in Republic 4 was motivated in part by his desire to acknowledge and account for cases of akratic action, and thereby to repudiate the psychology and the conclusions of the earlier dialogue Protagoras. In this paper I reject this interpretation, arguing that countenancing akrasia was never a major philosophical concern for Plato, and a fortiori that it was not his motivation for introducing the tripartite soul. I argue that his moral psychological focus and concern in the Republic was rather on the notion of psychic rule, and on illuminating various ways in which reasoning is corrupted by non-rational desires (rather than overcome by them through brute psychic ‘force’). I then offer an explanation of Plato’s lack of concern for akrasia by appealing to the Protagoras itself. I conclude with a rejection of sharp developmentalism between the two dialogues.