  Perhaps Plato replaces Socrates with the visitor from Elea because Elea was the hometown of Parmenides, and in the Sophist Plato plans to criticize Parmenides’ dictum that we cannot speak or think of what-is-not (Sophist 237a). Perhaps, too, readers are meant to recall the Parmenides, a dialogue staged some fifty years earlier, in which Parmenides himself led the conversation. After criticizing Plato’s middle period treatment of forms (inadequately defended by a youthful Socrates), Parmenides announced that before positing forms Socrates should undertake rigorous philosophical training. In the second part of the dialogue, Parmenides then demonstrated with a youthful respondent the sort of exercise he had in mind, focusing on another thesis for which he was famous, that there is only one thing (Parmenides 128a–b, 137b). By using a visitor from Elea, Plato invites his audience to recall Parmenides’ own positions and performance in that earlier dialogue. (For discussion of the dialogue form in these late works, cf. Frede 1996, Rowe 1996, and C. Gill 1996).