Though at the end of chapter 1 Aristotle announces satisfaction with the outline sketched of soul (413a9–10), this definition stands in need of shoring up at a crucial point, the assumption that only living natural beings are ensouled. He has stated, “By life I mean both nutrition through itself and growth and decline” (412a14–15); what justifies the assumption that soul links with life and with nutritive life in particular (a concern going back to 411a26–b5)? Is the account of soul adequately embracing of the various sorts of life so that it is truly the most common account of soul (κοινότατος λόγος, 412a5–6)? This chapter takes up the causes of life and argues that soul serves well as such cause. If having nutritive capacity is sufficient for life, and the other faculties of soul also sufficient for life are in succession such that they presuppose the nutritive capacity, then nutritive capacity that belongs to every ensouled being is the necessary and a sufficient condition for mortal life. And since the other sorts of life that he considers link with nutritive life, soul can account for all the kinds of life of mortal beings. Were plants denied life and animals the only ensouled beings, a quite different account of soul would perhaps be needed concentrating upon cognition, so that the hylomorphic theory would be less likely to emerge.