  Aristotle's treatment of time (Physics iv.10-14) includes some observations about numbers which come closest to being an account of number. Aristotle defines time as the number or count of change and then proceeds to distinguish two senses of number, what is counted (e.g., ten cows as measured by the cow-unit, or ten feet as measured by the foot-unit) and that by which we count. Time is number in the first sense, not as so-many changes, but as so-much change as measured by a unit of change. Aristotle clarifies the distinction between what is counted (or is countable) and that by which we count. These five black cats (number as what is counted) are different from these five brown cats, but their number (that by which we count) is the same. 