Full Idea
Some suspicion arises that time does not exist, since some of it has happened and does not exist, and some of it is in the future and does not yet exist. It appears impossible for anything that consists of things that do not exist to exist itself.
Gist of Idea
If all of time has either ceased to exist, or has not yet happened, maybe time does not exist
Source
Aristotle (Physics [c.337 BCE], 217b34)
Book Reference
Aristotle: 'Physics', ed/tr. Waterfield,Robin [OUP 1996], p.102
A Reaction
This generates the popular paradox that Socrates cannot die, because no moment exists when his death could occur. It may be (as David Marshall has pointed out) that we do not experience the present, but only a vivid memory of the immediate past.