  One way to think of Aristotle’s strategy in Metaphysics IV is as the reverse of Plato’s. If the PNC-opponent says something significant, for example, the beginning of Protagoras’s doctrine of the measure, “human being”, then she is committed to denying the thesis that nothing is anything in itself, and to accepting a non-Protagorean view. On this interpretation of Aristotle’s strategy, at least two puzzling features in Aristotle’s discussion are resolved, why he appears to be addressing someone who claims the contrary, and not the contradictory of PNC, and how Aristotle can argue from the second version of the principle of non-contradiction to the first. Since Plato’s Protagorean is forced to reject PNC across the board, Aristotle’s Protagorean PNC-skeptic would be an opponent who claims the contrary, not merely the contradictory, of PNC. In addition, a Protagorean PNC-skeptic, who accepts that “as things appear to one, so they are” would have to be impressed by an argument that shows that things cannot appear to him in a way that would violate PNC. On his own view, showing that PNC is indubitable would also show that it is true.