  One way to think of Anaxagoras’ point in B17 is that animals, plants, human beings, the heavenly bodies, and so on, are natural constructs. They are constructs because they depend for their existence and character on the ingredients of which they are constructed (and the pattern or structure that they acquire in the process). Yet they are natural because their construction occurs as one of the processes of nature. Unlike human-made artifacts (which are similarly constructs of ingredients), they are not teleologically determined to fulfill some purpose. This gives Anaxagoras a two-level metaphysics. Things such as earth, water, fire, hot, bitter, dark, bone, flesh, stone, or wood are metaphysically basic and genuinely real (in the required Eleatic sense): they are things-that-are. The objects constituted by these ingredients are not genuinely real, they are temporary mixtures with no autonomous metaphysical status: they are not things-that-are. (The natures of the ingredients, and the question of what is included as an ingredient, are addressed below; see 3.2 “Ingredients and Seeds”). This view, that the ingredients are more real than the objects that they make up, is common in Presocratic philosophy, especially in the theories of those thinkers who were influenced by Parmenides’ arguments against the possibility of what-is-not and so against genuine coming-to-be and passing-away. It can be found in Empedocles, and in the pre-Platonic atomists, as well as, perhaps, in Plato’s middle period Theory of Forms (Denyer, 1983, Frede 1985, W.-R. Mann 2000, Silverman 2002).