Plato's Theaetetus discusses and ultimately rejects Protagoras's famous claim that "man is the measure of all things." The most famous of Plato's arguments is the Self-Refutation Argument. But he offers a number of other arguments as well, including one that I call the 'Future Argument.' This argument, which appears at Theaetetus 178a−179b, is quite different from the earlier Self-Refutation Argument. I argue that it is directed mainly at a part of the Protagorean view not addressed before , namely, that all (...) beliefs concerning one's own future sensible qualities are true. This part of the view is found to be inconsistent with Protagoras's own conception of wisdom as expertise and with his own pretenses at expertise in teaching. (shrink)

The paper presents a subjectivist interpretation of Protagoras’ man-measure fragment, by explaining some key terms (‘all things’, ‘measure’, ‘man’) and reconstructing his ontological, epistemological and anthropological views. The argument uses other fragments and testimonies of Protagoras as well as intertextual allusions to previous authors (especially Anaxagoras) and instances of reception of Protagoras by Plato, Aristotle and Isocrates which are particularly used here for the first time in order to interpret the man-measure fragment. It is argued that Protagoras denied metaphysical speculation (...) and preferred human knowledge based on subjective perception and made plausible by intersubjective discourse. (shrink)