Full Idea
Two successive lengths of duration, however measured, can never be demonstrated to be equal.
Gist of Idea
We can never show that two successive periods of time were equal
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.14.21)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.190
A Reaction
Nice thought. You can't lay the durations next to one another, the way you can lengths. You can only count the clock ticks, but not be sure whether their speed remained constant.