 In Book III Aristotle defines motion once as “the perfection of that which is in potentiality under the aspect that it is in potentiality” (201a10–11) and another as “the perfection of that which is movable under the aspect that it is movable” (202a7–8). Before reaching the first passage, Averroes distinguishes four premises in Aristotle’s approach to defining motion (LC 86H TC3; Phys. III.1, 200b25–32):