At the heart of Plato’s theory of erōs is the ‘ascent’ of love for an individual body, through several stages, to love of Beauty itself (Symposium 210a-212b). I argue that our understanding of the psychology of this transformation would benefit especially from bringing in Plato’s views on pain from the Republic. For erōs is presented in the Symposium as including sexual desire (207b) as well as love of wisdom (210d), but the Republic takes the former to be a painful desire, whereas the latter is apparently treated as painless. The ‘ascent’ of love, then, seems to involve the transformation of a painful desire into a painless one. I conclude that this transformation is best understood as a rechanneling of desire within the tripartite soul.