 Averroes disagrees with Avempace concerning the movements of the four elements. He maintains that mover and movable among them are not really different (distincta per se) because “the movable thing is in potentiality, and the mover in actuality” (LC 161K; MC Wolfson  673–674).[7]  The four elements are composed each of prime matter and a simple form, for instance, the elementary form of earth is coldness and dryness. Averroes affirms that the form is their mover, and matter, their movable thing (see below c. 12). Under this conception the movable cannot oppose resistance to the mover, and motion without medium would be impossible, because it would be in no time. The medium makes motion possible because it introduces time (LC 161H; MC Wolfson 403–408). Averroes wanted to defend Aristotle and found this explanation. Its weakness is obvious but the denial of motion in a void prevailed in medieval science (Maier 1952: 221–223, 1958: 244–274).