| Some of Aristotle's arguments for teleology involve a distinction between two ways of being necessary: it seems that being necessary in one of these ways precludes being for the sake of something, while being necessary in the other way entails it. This second way, which consists in being necessary for the achievement of an end, is occasionally (six times in all) referred to as a matter of "hypothetical" ( 3 'xu `poq 3&d12;s3w v ) necessity. I inquire into the meaning of this phrase, beginning with a survey of the uses to which Aristotle, throughout his writings, puts the notion of a hypothesis. One upshot is that "hypothetically necessary" ought simply to mean necessary on an assumption, where (nearly enough) q is necessary on the assumption that p iff (i) not necessarily q and (ii) necessarily, if p then q. The only passage where it is really difficult to understand the phrase this way---where one is tempted to think it needs a richer meaning, such as necessary for the achievement of an end---is the first half of Physics II.9. I offer a close reading of this passage, one of whose virtues is that it preserves the phrase's broad, straightforward meaning. Finally I consider how widely hypothetical necessity, thus broadly interpreted, reaches in the natural world according to Aristotle. I suggest that there is rather less of it than is generally supposed: this partly explains why it is called by name only in connection with end-related cases. Regarding the anti-teleological kind of necessity---which might appear to involve necessitation of later states by antecedent conditions, and so to be a species of hypothetical necessity---I argue that it is not something we would call necessity at all. I work to elucidate what it is, as well as why and how far it is incompatible with teleological relations. |
