Full Idea
It is not easy to see whether the now, which appears to be the boundary between past and future, remains always one and the same or is different from time to time.
Gist of Idea
We can't tell whether the changing present moment is one thing, or a succession of things
Source
Aristotle (Physics [c.337 BCE], 218a08)
Book Reference
Aristotle: 'Physics Books III and IV', ed/tr. Hussey,Edward [OUP 1983], p.41
A Reaction
[also 219b13] Presumably the A-series view suggests that each present moment is different, but Broad's moving spotlight analogy gives the impression of a single present instant moving through time. If the present is one, what sort of thing is it?