First, the word "movement" can be used in different senses, just as
essence, when considered a genus. Further, as we have already said,
all the movements by which one thing arrives at a natural state, or
produces an action suitable to its nature, constitute so many species.
Then, the movements by which one thing arrives at a state contrary to
its nature, have to be considered as analogous to that to which they
lead.
But what common element is there in alteration, growth and generation,
and their contraries? What is there in common between these movements,
and the displacement in space, when you consider the four movements,
as such?[425] The common element is that the moved thing, after the
movement, is no longer in the former state; that it no more remains
quiet, and does not rest so long as the movement lasts. It ceaselessly
passes to another state, alters, and does not remain what it was; for
the movement would be vain if it did not make one thing other than it
was. Consequently "otherness" does not consist in one thing becoming
other than it was, and then persisting in this other state, but in
ceaseless alteration. Thus, time is always different from what it was
because it is produced by movement; for it is movement measured in its
march and not in its limit of motion, or stopping point; it follows,
carried away in its course. Further, one characteristic common to
all kinds of movement is that it is the march (or process) by which
potentiality and possibility pass into actualization; for every object
in movement, whatever be the nature of this movement, succeeds in
moving only because it formerly possessed the power of producing an
action, or of experiencing the passion of some particular nature.