Full Idea
Time is not change … but time is not without change, for without any change (or any noticeable change) in our minds, time does not seem to pass.
Gist of Idea
Time is not change, but requires change in our minds to be noticed
Source
Aristotle (Physics [c.337 BCE], 218b19)
Book Reference
Aristotle: 'Physics', ed/tr. Waterfield,Robin [OUP 1996], p.104
A Reaction
Aristotle has spotted what seems to be a key problem in understanding time, which is disentangling what occurs in nature from what occurs in our consciousness. The extreme views (naïve realism about time, or the view that it is imaginary) both seem wrong.