26. Let us now examine the different kinds of movements. Shall we
classify movements of displacement in movements upwards and downwards,
rectilinear or curvilinear, or in movements of animate and inanimate
beings? There is indeed a difference between the movement of inanimate
beings, and that of animate beings; and these latter have different
kinds of motion, such as walking, flying, and swimming. Their movements
could also be analyzed in two other ways, according as it was
conformable to, or against their nature; but this would not explain
the outer differences of movements. Perhaps the movements themselves
produce these differences, and do not exist without them; nevertheless,
it is nature that seems to be the principle of the movements, and of
their exterior differences. It would further be possible to classify
movements as natural, artificial, and voluntary; of the natural, there
are alteration and destruction; of the artificial, there are the
building of houses, and construction of vessels; of the voluntary,
there are meditation, learning, devoting oneself to political
occupations, and, in general, speaking and acting. Last, we might, in
growth, alteration and generation, distinguish the natural movement,
and that contrary to nature; or even establish a classification founded
on the nature of the subjects in which these movements occur.