MOTION. - Motion in general or change is the passage from one mode of being to another: πᾶσα μεταβολὴ ἔστιν ἐκ τινὸς στέρ (ibid., V, 1, 225a 8 ff.). Keeping this continuity in mind, one understands the Aristotelian definition of κίνησις: the act of being in potency insofar as such: ἡ τοῦ δυνάμει ὄντος ἐντελέχεια ἢ ἐνέργεια ἀτελής (Phys., III, 1, 201a 10-11).
MOTION. - Motion in general or change is the passage from one mode of being to another: πᾶσα μεταβολὴ ἔστιν ἐκ τινὸς στέρ (ibid., V, 1, 225a
Berlin 1888, p. 642). Philoponus’ theory was taken up by Francis of Marchia (IV Sent., princ.) and especially by J. Buridan, who, following experimental observation, maintained that impetus remains unchanged and thus motion lasts indefinitely (Phys., VIII, q. 12; ed. Paris 1509); this is a first hint at the law of inertia. This doctrine became common in later Scholasticism (cf. R. Masi, Intorno al movimento locale, in Divus Thomas Plac., 53 [1950], pp. 3-20, 178-208). Descartes states that local motion is translation: «translatio unius partis materiae sive unius corporis ex vicinia eorum corporum, quae illud immediate contingunt et tanquam quiescentia spectantur, in viciniam aliorum» (Princ. Phil., II, 25, ed. C. Adam and P. Tannery, Oeuvres, VIII, Paris 1905, p. 53). For Descartes, local motion is relative and reciprocal; it is an attribute of matter; all activities of bodies are reduced to local motion (mechanicism); even secondary qualities are produced in us by local motion. Moreover, local motion is not a becoming but a state, like the figure of a body, and thus it is conserved indefinitely: thus the law of inertia would be proven (Princ. Phil., II, 27, ed. cit., p. 55).
Characteristic is Newton’s affirmation of an absolute local motion, «translatio corporis de loco absoluto in locum absolutum» (Philosophiae naturalis principia mathematica, Amsterdam 1723, p. 6); an absolute place which is then a part of absolute space (ibid.).
E. Bergson maintains that intelligence decomposes motion in general or change into immobile states, as Zeno said. To restore the continuity of change, Aristotle admits a substratum of it (L’évolution créatrice, Paris 1912, pp. 323-53). But intuition shows what change truly is, pure change: «Il y a des changements, mais il n’y a pas, sous le changement, des choses qui changent: le changement n’a pas besoin d’un support. Il y a des mouvements, mais il n’y a pas d’objet inerte, invariable, qui se meuve: le mouvement n’implique pas un mobile» (La pensée et le mouvement, Paris 1934, p. 185). Pure change is the «Duration» (Durée), which is reality itself.
In physics, local motion is essentially relative to the frame of reference; its laws are studied by mechanics.