Book 1
2
When, therefore, such and such a body undergoes no change from its existing state, we say that it is at rest; but, notwithstanding, if it departs from this in any respect we then say that in this respect it undergoes motion.Motion (kinesis) is Aristotle's general term for what we would rather call change. It includes various kinds of change, as well as movement proper. cf. Introduction, p. xxix. Accordingly, when it departs in various ways from its preexisting state, it will be said to undergo various kinds of motion. Thus, if that which is white becomes black, or what is black becomes white, it undergoes motion in respect to colour; or if what was previously sweet now becomes bitter, or, conversely, from being bitter now becomes sweet, it will be said to undergo motion in respect to flavour; to both of these instances, as well as to those previously mentioned, we shall apply the term qualitative motion. And further, it is not only things which are altered in regard to colour and flavour which, we say, undergo motion; when a warm thing becomes cold, and a cold warm, here too we speak of its undergoing motion; similarly also when anything moist becomes dry, or dry moist. Now, the common term which we apply to all these cases is alteration.
2
This is one kind of motion. But there is another kind which occurs in bodies which change their position, or as we say, pass from one place to another; the name of this is transference. Conveyance, transport, transit; purely mechanical or passive motion, as distinguished from ateration (qualitative change).
