Abstract

This paper offers a detailed account of arguments in De Caelo I by which Aristotle tried to demonstrate the necessity of the perpetual existence and the perpetual rotation of the cosmos. On our interpretation, Aristotle’s arguments are naturalistic. Instead of being based (as many have thought) on rules of logic and language, they depend, we argue, on natural science theories about abilities (δυνάμεις), e.g., to move and to change, which things have by nature and about the conditions under which these abilities can be exercised. Our interpretation locates the De Caelo arguments in the context of some central doctrines of the Organon, the Metaphysics, the Physics, and other texts. The De Caelo arguments fit a number of views developed in these texts. Aristotle’s treatments of local motion, of natural motion and change, of necessity and possibility, and of abilities and their exercises are examples. But, as we interpret them, the De Caelo arguments raise serious questions about the role of (and the need for) Metaphysics A’s soulful Unmoved Mover in Aristotle’s overall natural-scientific picture.