Physics

by Aristotle

Written circa 350 B.C.
Translated by R. P. Hardie and R. K. Gaye

Book VIII.1

Further, how can there be any 'before' and 'after' without the existence of time?
Or how can there be any time without the existence of motion? If, then, time is the
number of motion or itself a kind of motion, it follows that, if there is always time,
motion must also be eternal. But so far as time is concerned we see that all with one
exception are in agreement in saying that it is uncreated: in fact, it is just this that
enables Democritus to show that all things cannot have had a becoming: for time,
he says, is uncreated. Plato alone asserts the creation of time, saying that it had a
becoming together with the universe, the universe according to him having had a
becoming. Now since time cannot exist and is unthinkable apart from the moment,
and the moment a kind of middle-point, uniting as it does in itself both a beginning
and an end, a beginning of future time and an end of past time, it follows that there
must always be time: for the extremity of the last period of time that we take must
be found in some moment, since time contains no point of contact for us except the
moment. Therefore, since the moment is both a beginning and an end, there must
always be time on both sides of it. But if this is true of time, it is evident that it
must also be true of motion, time being a kind of affection of motion.)