 Animals are complex structures organized so as to be able to perform an integrated set of functions and activities; yet the Posterior Analytics provides one with very little guidance as to how to apply its norms to such things. Again PA I, and especially chapters 1 and 5, appears designed to provide that guidance. It seeks to establish [a] the priority of goal-causation to motive-causation, [b] the priority of the study of an animal’s form (which, he argues, should be identified with its soul) to the study of its material constituents (i.e. its body), and [c] the presence of a special kind of necessity operative where goals and form take priority, namely hypothetical or conditional necessity (cf. PA I 1, 640a10–641a32, 642a1–31).