 In the Theaetetus, Plato explores the kind of cultural relativism that is associated with some sophists. In his examination relativism is extended to a general theory, not restricted to the domain of values. Socrates (as main speaker of the dialogue) ascribes relativism to Protagoras, who is famous for saying that “man is the measure.” Socrates reformulates this claim as follows: what appears to A is true for A, and what appears to B is true for B. On this premise, Socrates argues, there is no rational way to prefer our perceptions while awake to our perceptions while asleep, or similarly, to prefer sober to intoxicated or deranged perceptions. In each state, our perceptions are true for us. Socrates analyzes relativism in several steps, pointing to ever more radical implications. Along the way, he envisages a moderate metaphysics of flux, where objects do not have stable properties. But eventually he points out that relativism is committed to an even starker revisionist metaphysics, radical flux. For it to be possible that what seems to A is true for A, and what seems to B is true for B, there cannot be a stable world that A and B both refer to. Rather, “everything is motion” (Tht. 179c-184b). The skeptics employ versions of some of the arguments in the Theaetetus, without, however, arriving at relativist conclusions. Schematically speaking, the relativist says that, if X is F for A and F* for B, then X is F-for-A and F*-for-B. Pyrrhonian skepticism of the variant found in Sextus reacts by continued investigation into whether X is F or F* (or both or neither).