Knowledge and Truth in the Greatest Difficulty Argument: Parmenides 133b4–134b5

One of Plato’s central tenets is that we can know forms. In Parmenides 133b4–134b5, Plato presents an argument whose sceptical conclusion is that we can’t know forms. Although he indicates that the argument doesn’t succeed, he also says it’s difficult to explain how it fails. Commentators have suggested a variety of flaws. I argue that the argument can be defended against some, though not all, of the alleged flaws. But I also argue that Plato hints at a crucial distinction that hasn’t been brought to bear in this context, and that indeed he is sometimes thought not to draw: that between the content and object of knowledge. Once we are clear about this distinction, we can see that the sceptical argument doesn’t imply that we can’t know forms.