Change, motion, and explanation › Time as countable change

Aristotle describes time as the number of motion in respect of before and after. He distinguishes time from motion itself: movements can be faster or slower, whereas time provides the measure by which such differences are judged. We recognize an interval by distinguishing an earlier and a later phase of change (Physics IV.10–11).

Here, number concerns what is counted or countable. A clock offers a contemporary illustration: a regular process supplies distinguishable intervals with which other processes can be compared. The example does not show that time is identical with this clock's particular movement. Aristotle likewise distinguishes the measurement relationship from identifying time with one motion (Physics IV.11–12).

His account includes a difficulty about the soul. If counting requires a soul capable of counting, would time exist without soul? In IV.14 he distinguishes motion and its before-and-after structure from that structure as countable. The passage raises a question about time's dependence on a counter; it should not be flattened into either "time is only in the mind" or an unqualified claim that counting is irrelevant.

This distinction also limits easy appeals to subjective experience. A meeting may feel long, but its measured duration and that feeling are different questions. Aristotle's account here concerns ordered, countable change. Treating it as a direct explanation of boredom or attention would add a psychological theory the passage does not supply.