Aristotle correspond to privileged or
salient moments in the history of things--those, in general, that have
been fixed by language. They are supposed, like the childhood or the old
age of a living being, to characterize a period of which they express
the quintessence, all the rest of this period being filled by the
passage, of no interest in itself, from one form to another form. Take,
for instance, a falling body. It was thought that we got near enough to
the fact when we characterized it as a whole: it was a movement
_downward_; it was the tendency toward a _centre_; it was the _natural_
movement of a body which, separated from the earth to which it belonged,
was now going to find its place again. They noted, then, the final term
or culminating point ([Greek: telos, akme]) and set it up as the
essential moment: this moment, that language has retained in order to
express the whole of the fact, sufficed also for science to characterize
it. In the physics of Aristotle, it is by the concepts "high" and "low,"
spontaneous displacement and forced displacement, own place and strange
place, that the movement of a body shot into space or falling freely is
defined. But Galileo thought there was no essential moment, no
privileged instant. To study the falling body is to consider it at it
matters not what moment in its course. The true science of gravity is
that which will determine, for any moment of time whatever, the position
of the body in space. For this, indeed, signs far more precise than
those of language are required.

We may say, then, that our physics differs from that of the ancients
chiefly in the indefinite breaking up of time. For the ancients, time
comprises as many undivided periods as our natural perception and our
language cut out in it successive facts, each presenting a kind of
individuality. For that reason, each of these facts admits, in their
view, of only a _total_ definition or description. If, in describing it,
we are led to distinguish phases in it, we have several facts instead of
a single one, several undivided periods instead of a single period; but
time is always supposed to be divided into determinate periods, and the
mode of division to be forced on the mind by apparent crises of the
real, comparable to that of puberty, by the apparent release of a new
form.--For a Kepler or a Galileo, on the contrary, time is not divided
objectively in one way or another by the matter that fills it. It has no