  Against Aristotle’s critique in De Caelo I 10, Proclus defends the view that the cosmos is “both eternal and generated (genêtos).” As a corporeal being, the universe cannot produce itself and maintain itself in being. It depends for its existence upon a superior cause, and it is for that reason “generated.” This does not prevent it, however, from existing for ever, in an infinite time. As we just saw, Proclus distinguishes between what is eternal in an absolute sense (the intelligible realm) and what is eternal because it continues to exist for the whole of time, what Boethius later called “aevum” in distinction from “aeternum.” As Proclus notices, at the end of the Physics (8.10, 266a27–28), Aristotle himself establishes that no body can possess from itself an unlimited power to exist. If the world exists eternally, it must have this power from an incorporeal principle. Therefore, Aristotle too is forced to admit that the world is somehow generated, though it continues to exist for eternity. For it always receives from its cause its infinite power and never possesses it at once as a whole, because it is limited. The world is eternal, because it has an infinite power of coming to be, not because it exists of infinite power (In Tim. I 252.11–254.18).