  The science of physics, Aristotle stresses, contains almost all there is to know about the world. Were there no separate forms—entities such as the unmoved mover at the pinnacle of the cosmos—which are without matter and are not part of the physical world, physics would be what Aristotle calls first philosophy (Metaphysics 6.1, 1026a27–31).  As there are such separate entities, physics is dependent on these, and is only a second philosophy (Metaphysics 7.11, 1037a14f).  Nevertheless, the interaction between these two “philosophies” is not completely exhausted by the causal influence exerted on the world by the supra-physical entities—the prime movers  as it turns out. Aristotle’s metaphysics  and physics use a common conceptual framework, and they often address  similar issues. The prime and distinctive task of first philosophy is  an inquiry into first entities; these, however, are not perceptible  entities, and as a result they have to be investigated through a  metaphysical investigation of physical entities.  Hence the overlap  between the two disciplines, which often verges on inseparability.