Socrates first persuades Agathon to agree that eros is directed towards things it lacks, and that these things must be kala. Then, at 201C2, he asks whether it does not seem to Agathon that good things are beautiful, and Agathon concurs.
This passage argues that Plato’s dialectic in the Symposium depends on the coextensiveness of agathon and kalon, so that Socrates can demonstrate Eros necessarily lacks good things as well as beautiful ones.
, Plato and the Hero: Courage, Manliness and the Impersonal Good, 2000thesis