Rush Rhees, one of Wittgenstein’s three trustees, lectured on Plato and the Presocratics for two decades. In his lecture notes on the Sophists, Rhees briefly mentions Wittgenstein’s views on set theory and claims that mathematicians have responded to them like Sophists. This essay discusses and contextualises Rhees’s claim, including a brief discussion of how Rhees’s understanding of Plato might have influenced him as an editor of Wittgenstein’s Remarks on the Foundations of Mathematics.