We have far less evidence for Aristotle’s reception of Protagoras than we like to think, and the evidence we do have is somewhere we hardly ever look. With one exception, every reference Aristotle makes to the Measure Doctrine—Protagoras’ claim that humans are the ‘measure of all things —concerns the Doctrine as amplified in Plato’s Theaetetus, and the ‘Protagoras’ in question is Plato’s fictional character as fictional. Metaph. I 1, 1053a35–b3 provides the only exception, where Aristotle offers an anomalous reading of (...) the Doctrine incompatible with the others. The chapter interprets I 1, 1053a35–b3 and concludes that Aristotle attributes the anomalous reading to Protagoras himself. The chapter argues further that every other reference to the Doctrine derives from the Theaetetus. Aristotle formulates ‘the theory of Protagoras’ according to Plato’s self-refutation argument, and his argument that it denies the Principle of Non-contradiction includes premisses from Plato’s argument that are out of place in Aristotle’s own. He moreover attributes to ‘Protagoras’ arguments and dialectical demands that the fictional Protagoras makes in his so-called ‘apology’, so his target is specifically a Platonic invention and not the historical person. This leaves only Metaph. I 1 1053a35–b3 to join his six other references to the historical Protagoras, which makes it Aristotle’s only engagement with the Measure Doctrine as the actual view of his predecessor. (shrink)