This argues for a reading of PA I.1, 639b11-640a9 as a continuous argument, which I divide into 3 main sections. Aristotle’s point in the first section is that teleological explanations should precede non-teleological explanations in the order of exposition. His reasoning is that the ends cited in teleological explanations are definitions, and definitions—which are not subject to further explanation—are appropriate starting points, insofar as they prevent explanations from going on ad infinitum. Moreover, I argue that Aristotle proceeds in the following (...) two sections to criticize certain non-teleological accounts offered by his predecessors on the grounds that they are explanatorily defective: I take Aristotle’s complaints to be that those accounts—unlike teleological explanations—neither begin from appropriate starting points nor entail the phenomena that they purport to explain. Along the way, I am defending an alternative way of understanding what "hypothetical necessity" refers to, for Aristotle. Comments are welcome! (shrink)