MOTION. — Motion in general or change is the passage from one mode of being to another: in this sense everything moves, except God, pure act.
The Eleatic school (v. ELEATICISM) denied all motion. Zeno, supposing local motion to be composed of infinites, demonstrated its absurdity with the four famous paradoxes: the dichotomy, Achilles, the arrow, and the stadium (cf. ARISTOTLE, Phys., VI, 9). Leucippus and Democritus affirmed local motion of atoms in the void; this is the only possible motion (ibid., De gen. et corr., I, 8, 325a). ARISTOTLE admitted motion in general or change (μεταβολή, elsewhere κίνησις; Phys., III, 1, 200b 33 ff. etc.), which is the passage from one mode of being to another: πᾶσα μεταβολή ἔστιν ἐκ τινὸς εἰς τι (ibid., V, 1, 225a 1). He explains it by a substratum that assumes different modifications (Metaph., VIII, 1, 1042a 32 ff.; Phys., I, 7, 190a 13). There are three kinds of μεταβολή: from subject (ὑποκείμενον) to non-subject (μὴ ὑποκείμενον) and vice versa; or from subject to subject, i.e., corruption (φθορὰ), generation (γένεσις); and motion in the proper sense, κίνησις, which is continuous change between two contraries through intermediate states (ibid., V, 225a 8 ff.). Keeping this continuity in mind, one understands the Aristotelian definition of κίνησις: the act of a being in potency insofar as it is such: ἡ τοῦ δυνάμει ὄντος ἐντελέχεια ἢ ἐνέργεια ἀτελής (Phys., III, 1, 201a 10-11).