Medieval Philosophy

by Peter S. Adamson

One of these commentators complains that Averroes’ idea of motion as an incomplete property is itself incomplete. Each stage in the motion or change, for instance each degree of heat in the increasingly warm baseball, is a product of change just as much as the degree of heat achieved at the end of the heating process. This means we’ll need a separate motion to explain each partial change along the way. Besides, the commentator adds, some changes aren’t gradual. When a substance like an animal comes to be, it does so “all at once” and not part by part. Despite these criticisms, a theory of motion inspired by Averroes is going to be put forward by another commentator on Aristotle in the following decades, whose name is not only known but renowned: Albert the Great. He proposes that we can think of a change as being just the same form as the one that will exist at the end of the change, but with potentiality mixed in. Across time, the change “flows” towards its final result, with the form becoming progressively more actual at each moment.