  However these and like issues are to be resolved, given the primacy of form as substance, it is unsurprising to find Aristotle identifying the soul, which he introduces as a principle or source (archê) of all life, as the form of a living compound. For Aristotle, in fact, all living things, and not only human beings, have souls: ‘what is ensouled is distinguished from what is unensouled by living’ (DA 431a20–22; cf. DA 412a13, 423a20–6; De Part. An. 687a24–690a10; Met. 1075a16–25).  It is appropriate, then, to treat all ensouled bodies in hylomorphic terms: 