EVO. – From Greek αἰών (in the Fov: Latin aevium), it indicates time, the duration of something; thus, according to the various conceptions of being, there arise various notions of e., opposed and discordant.
Among the pre-Socratics, αἰών indicates a certain “period of time,” for example, the duration of a man’s life: thus Empedocles speaks of an “unceasing” e. (ἐμπεδος αἰών: fr. B 17, 8); Anaximenes (fr. A 6), Anaximander (fr. A 10), and Empedocles himself (fr. B 16, 2) speak of an e.
“immense” (ἀσπετὸς αἰών). In Plato, it is not known through what process of development, αἰών indicates the eternity of which the “visible world becomes the visible image” (ἐκλῶν), with time as its intermediary (Tim. 37 d–38 b). This development is instead more apparent in Aristotle: in treating of the duration of the heavenly bodies, after saying that his predecessors, with a divine sense (θεῖος), had introduced αἰών to indicate the total duration proper to each being: τὸ γὰρ τέλος τὸ περὶ ἑνὸν τὸ τέλος ἑνόντων ζωῆς γρόνων, οὐ μὴ δὲν εἶκα κατὰ γόπιν...; he goes on to affirm that “for the same reason” the duration (infinite) of time of the entire heaven and the totality of time extending to infinity may be called αἰών: “a meaning which,” Aristotle observes, “is fundamental and original, because αἰών comes from ‘always being’ (ἀπὸ τοῦ ἀσὶ εἶναι) and hence being ‘immortal and eternal’ (ἐβέλαστος καὶ θεῖος: De coelo, I, 9, 27ga 25–28). There thus remains, as in Plato, an intimate connection between time and eternity, but eternity is placed within nature itself.
This was well understood by Plotinus (Eun., III, 7; περὶ αἰώνῳ καὶ γρόνου), who, taking up the position of the Platonic Timaeus, frees αἰών from every dependence and intermediary in the physical world, placing it in direct connection with the soul and the intelligible world and making it a property (ἐβέλαστος); αἰών can only be the quality of the absolutely immutable being of that “of which it cannot be said that it was or will be, but simply that it is: stable being, which admits no modifications in the future and has not changed in the past... perennial life” (Eun., loc. cit., III, 7, 3). But in the development of Neoplatonism, Proclus criticizes Plotinus himself insofar as, faithful to his theory of hypotheses and to the technique of participation, he places αἰών above the intelligible and time above the soul: thus, before all eternal things, eternity itself exists, and before temporal things, time (Proclò elocuente Theologiae, propp. 52–53, ed. E. R. Dodds, Oxford 1935, p. 50 s.p.). According to Dodds (loc. cit., p. 228), Proclus gathers together the entire development of Greek thought, including Aristotle, up to the magical doctrines: thus the plural αἰώνες is found, and there is an Αἰών hypostatized and deified, which is its principle and almost its substance. In St. Augustine, the Plotinian conception is filtered through his experience of conversion and becomes the eternity of transcendence as the point of convergence of the history both of peoples and of individual persons (infantia, pueritia, adolescentia...). In Aristotelian scholasticism, on the other hand, e. becomes the intermediate duration between time and eternity, proper to incorruptible beings (heavenly bodies, intelligences), and St. Thomas calls it “aeternitas participata” (cf. Quod., V, 4, 7; Sum. Theol., 1ª, q. 10, p. 5), which consequently, with the abandonment of the incorruptibility of the stars, remains the exclusive property of spiritual creatures. E. is therefore the duration and the measure of the duration of finite spiritual substances whose being is distinct from their essence (In I Sent., dist. 19, q. 2, a. 2; ed. P. Mandonnet, I, Paris 1929, p. 471), or rather the fullness of being of their immutable essence as spiritual reality.