ARISTOTELIAN NECESSITIES

In his Parts of Animals, Aristotle distinguishes three modes of the ne cessary. However, it is not clear just what these three modes are. Nor is it clear how this passage fits with other texts where Aristotle di stinguishes modalities in different ways. Here I present and explain A ristotle's three modes of necessity, and claim that they are the only three recognized by Aristotle. I then explain how this passage agrees with other passages where Aristotle mentions formal and structural fea tures of the modalities. I end by showing how having three modes of ne cessity does not make 'necessary' ambiguous. Rather, I claim, Aristotl e has a single, central notion of necessity and hence a unified theory of modality.