 One of the questions Kilwardby addresses in his treatise On time (De tempore)—written most probably after DOS—is whether time, as the measure of motion, is defined in relation to the diurnal motion (DT 35), a view identified with Averroes. The aim of his treatise is to understand time in such a way that it reveals compatibility between Aristotle’s (Physics IV, 10–14) definition of time—which Kilwardby calls ‘physical’—as relative to motion (and motion relative to continuous quantity) and the Augustinian (Confessions XI) definition of time—which he calls ‘metaphysical’—as an extension (distensio) of the mind, thus existing only in the mind (DT 10–11). Kilwardby’s solution is to argue for a distinction between indeterminate and determinate time: on the one hand, indeterminate time exists outside of and independent from the numbering mind (it is neither numbered nor measured) as, prior to any measuring, that which is measured is already in motion (DT 77). Determinate time, on the other hand, has existence in the mind only, as it can only exist in the measuring mind. In Kilwardby’s own words, “time comes into existence when we perceive the direction of that which is earlier and later in motion” (DT 77). Time is, therefore, the measure not of any specific motion but the measure of motion (DT 42) defined by an instant before and an instant after. The quantity of motion between these two instants, before and after, has a numerical expression (DT 34), and this number is then used to measure all other motions (DT 49): time “measures the whole motion by determining the motion which will measure the whole” (DT 27). Time is the number of motion because number is the appropriate name for that  measure.[31]  We determine time by measuring motion according to fixed measures (days, hours, and so on) (DT 77). As the measure for any kind of motion, time has unity.