Time present and time past
Are both, perhaps, present in time future
And time future contained in time past.
If all time is eternally present,
All time is unredeemable.
What might have been is an abstraction
Remaining a perpetual possibility
Only in a world of speculation.
What might have been and what has been
Point to one end, which is always present.

T. S. Eliot, Burnt Norton

http://www.davidgorman.com/4quartets/1-norton.htm