  This also seems to be the purport of Aristotle’s rejection of the simple mechanistic accounts of growth which he considers when discussing the nutritive soul (De Anima ii 4, 415b27–416a20; cf. De Generatione et Corruptione i 5). Aristotle objects to those who want to account for growth merely in terms of the natural tendencies of material elements. For growth is a constrained pattern of development, the source of which Aristotle ascribes to the soul. He takes it as evident that growth in organisms proceeds along structured paths, in end-directed ways. These structures in turn manifest capacities whose explication cannot be given in crude materialistic terms; for materialistic terms, as Aristotle understands them, fail to account for the fact that mature members of species cease growing, having realized the structures characteristic of their kind. Fire, for example, by contrast “grows” haphazardly, without directionality, flowing towards the combustible without end, until hindered by external impediments or lack of fuel.