MOVEMENTS DIVIDED IN NATURAL, ARTIFICIAL, AND VOLUNTARY.
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.