 Numenius maintains a sharp distinction between the sensible and the intelligible world—the realms of becoming and (true or pure) being respectively (fr. 16.8–10). In his On the Good he proceeds in an ontologically ascending order, starting with sensible (physical) entities, moving to the intelligible ones (including Platonic Forms), and finally to the first principle, the Good, that is the Platonic Form of the Good in the Republic (508e) that he identifies with God (that is, the first and highest god). Arriving at this divine first principle is the final aim of the treatise. This is understandable since according to Numenius everything that exists in the world as it is, depends on the Good, the God, which is the cause of everything's goodness in the world (fr. 19.5-7). Beginning his investigation from natural elements (stoicheia), namely earth, fire, water, and air (cf. Timaeus 31b-c), Numenius argues that no such element can possibly qualify as a being (as having being), first because elements, like syllables, cannot exist by themselves but only in combination, and secondly because no bodily entity whatever can qualify as a being (as having being), because bodies are subject to change (fr.  3.1–8). This means that all bodies have, at best, being-and-not-being (cf. Republic 479c). What is more, Numenius suggests that for a body to exist, there must be something to keep it together and account for its unity (fr. 4b.11-19), and this cannot be a further body but rather must be a power (dynamis; fr. 4b18), that is an intelligible entity, for instance a soul, which is necessary to account for the unity of bodies, as we see that it does for living things (fr. 4b). In the Timaeus (33b), for instance, it is made clear that it is the world-soul that keeps the body of the world together.