Galileo replaced concern with the nature of movement with concern with the measurable characteristics of movement (first of all, velocity). But when we say something moved so many miles/Km an hour, we are talking, in a sense about a kind of disposition. Not the sort of disposition to act that exists when something is inactive. But the disposition to continue to act a certain way. It seems to me that Galileo, in focusing on the measurement, took this disposition as a given, whereas Aristotle, in defining motion as the act of a potency as such, is much more interested in the nature of this disposition.
Commentary and discussion regarding science, faith and culture by Leo White