ABSTRACT
This chapter considers two of Aristotle's books, the one called Physics and the one called On the Heavens. These two books are closely connected; the second takes up the argument at the point at which the first has left it. Both were extremely influential, and dominated science until the time of Galileo. Words such as 'quintessence' and 'sublunary' are derived from the theories expressed in these books. The historian of philosophy accordingly, must study them, in spite of the fact that hardly a sentence in either can be accepted in the light of modern science. In relation to physics, Aristotle's imaginative background was very different from that of a modern student. The Physics ends with the argument for an unmoved mover, which one considered in connection with the Metaphysics. To come to a more general matter: Aristotleian physics is incompatible with Newton's 'First Law of Motion', originally enunciated by Galileo.
