25. Of what do composition (blending, or mixture) and decomposition
consist? Do they constitute other kinds of movement than those already
noticed, generation and destruction, growth and decrease, movement
of displacement and alteration? Shall composition and decomposition
be reduced to some one of these kinds of motion, or shall we look
at this process inversely? If composition consist in approximating
one thing to another, and in joining them together; and if, on the
other hand, decomposition consist in separating the things which were
joined, we have here only two movements of displacement, a uniting,
and a separating one. We should be able to reduce composition and
decomposition to one of the above recognized kinds of motion, if
we were to acknowledge that this composition was mingling,[427]
combination, fusion, and union--a union which consists in two things
uniting, and not in being already united. Indeed, composition includes
first the movement of displacement, and then an alteration; just as,
in increase, there was first the movement of displacement, and then
movement in the kind of the quality.[428] Likewise, here there is first
the movement of displacement, then the composition or decomposition,
according as things approximate or separate.[429] Often also
decomposition is accompanied or followed by a movement of displacement,
but the things which separate undergo a modification different from
the movement of displacement; similarly, composition is a modification
which follows the movement of displacement, but which has a different
nature.