From things consider’d, while we think on some
As present, some as past, or yet to come.
No thought can think on Time,
But thinks on things in motion or at rest.
Ovid has some illustrations, which Dryden has thus translated:
Nature knows
No steadfast motion, but or ebbs or flows.
Ever in motion, she destroys her old,
And casts new figures in another mould.
Even times are in perpetual flux, and run,