ETERNITY. - It is the proper measure of the divine nature, absolutely immutable in its simple fullness and in the totality of the presence of its own being: unlike time, which measures mutable things both as to their being and as to their action (bodies), and unlike the aevum, which is the measure of things immutable in being but mutable in action. It is therefore in function of the process and the mode of possession of being and of life that the determinations of eternity, time and aevum are made - as St. Thomas insistently observes - and not with respect to having a beginning and an end; only if the "presence" of being is absolute and complete, both as to its constitutive principles and as to its activity, is there that eternity which the Angelic Doctor defines with Boethius: "Interminabile vitae tota simul et perfecta possessio" (Sum. Theol., 1a, q. 10, a. 1; cf. Boethius, Cont. philos., V, prose 6: PL 63, 858).
Of eternity, as the infinite duration of the divine life, man cannot have a proper and adequate concept: just as he grasps the divine nature and its attributes only by analogy with bodies, so too he thinks of its immobile duration according to an absolute presentness, in contrast to the continuous flowing and changing of physical phenomena (time) and also above the successions of the higher processes of spiritual substances. Therefore, while the instant in material substances bears only upon a fraction of being and is in continuous forward movement; and while in spiritual substances, although it is fixed with respect to being, it is subject to succession (discontinuous, because it depends especially on the free will of the spirit itself) as to action: in God the instant rests in the full possession of itself and of being. We therefore imagine eternity as the actuality of the instant dilated to infinity, but the reality of what we perceive of actuality in the temporal instant is only its flowing and therefore the imperfection of its being. Eternity, on the other hand, is conceived as immobile fullness, and thus the instant, passing from time to eternity, overturns - so to speak - its ontological quality: "Dicendum quod nunc stans dicitur facere aeternitatem, secundum nostram apprehensionem. Sicut enim causatur in nobis apprehensio temporis eo quod apprehendimus fluxum ipsius nunc, ita causatur in nobis apprehensio aeternitatis, in quantum apprehendimus nunc stans" (Sum. Theol., 1a, q. 10, a. 2, ad 1). If St. Thomas intends to admit the possibility for man of some perception of eternity itself, one must think of the experiences of maximum interior concentration in the higher sphere of intelligence and love, when the soul is rapt outside its habitual contact with the visible world and as it were stretched out in abandonment toward God who draws it. Characteristic in this sense is the "vision at Ostia" described by St. Augustine in the Confessions (IX, 10), where of eternity it is said as of God (Ex. 3, 14) that in it properly there "is no" was or will be, but only is, that is, the simple positing of being in its metaphysical purity: in this sense, while of creatures one must say that they "exist," of God alone one must say that He "is" (Sum. Theol., 1a, q. 12, a. 1, ad 3). Kierkegaard too: "God does not think (in the abstract), he creates; God does not exist, he is eternal. Man thinks and exists, and existence separates thought and being, holds them outside one another in succession" (Concluding Unscientific Postscript, S. V., VII, 2nd ed., Copenhagen 1925, p. 32). In his anti-metaphysical position the Protestant K. Barth seems instead to conceive eternity as a kind of absolute time and as the synthesis of the moments of time: "Eternity is by no means without time (zeitlos). It is rather the place of origin of time, properly the eminent, absolute time, that is, the immediate unity of present, past and future, of now, before and after, of middle, beginning and end, of movement, origin and goal" (Die kirchliche Dogmatik, III, 1: Die Lehre von der Schöpfung, Zurich 1945, p. 72). The error here is to conceive eternity as perfect time and to conceive time itself as perfection; whereas time is given only in the radical otherness with respect to its moments (past, present and future), so that to affirm the "unity" of its moments is to destroy the reality of time: consequently, in the succession that such otherness entails there is inherent an imperfection that cannot be purified within the metaphysical sphere. Eternity, the aevum and time are attributes of being and therefore derive directly from the being to which they relate their own nature. What is created, therefore, is the entity by participation, which can be either in the aevum or in time; aevum and time concern the being and the perfections of the entity by participation: it is being, and it is these perfections, that therefore enjoy the ontological positivity as such, of which the finite truly participates and from which the intellect rises to conceive the infinite. Even E. Brunner, who conceives eternity as a mere "fullness of time" (Erfüllung der Zeit), as "full temporality" (Vollzeitlichkeit), remains in a sphere of evident theological empiricism (Die christliche Lehre von Gott, Dogmatik, I, Zurich 1946, p. 287).
The concept of eternity in Christian theology must therefore be distinguished from that of thought which stopped at the cosmic meaning of sempiternal duration (the aevum, αἰών, duration without beginning and end). Thus Anaximander speaks of "cyclical generations and corruptions according to an indeterminate eternal duration" (ἐξ ἀπείρου αἰώνης: H. Diels-Kranz, Die Fragmente der Vorsokratiker, 3rd ed., I, Berlin 1935, 83, 31); Anaximenes speaks of a "movement of eternity" (Κίνησις ἐξ αἰώνης: ibid., I, 91, 31); it is an attribute of the cosmos for the Pseudo-Philolaus, since the world remains ἐξ αἰώνης καὶ εἰς αἰών (ibid., 8, 117, 11); Heraclitus attributes eternity to the Logos (λόγον αἰώνα: ibid., I, 161, 13). In this first sense eternity is a duration "without beginning and end" of the cosmos according to Aristotle's declaration that it "has neither beginning nor end of its whole duration (ἀρχὴν μὲν καὶ τελευτὴν οὐκ ἔχων τοῦ παντὸς αἰῶνος), but having and comprehending in itself unlimited time" (De caelo, II, 1, 283 b. 26). For Plato, on the other hand, eternity is an attribute of the immobile ideas, and time is derived from eternity as its "moving image" (εἰκώ... παντὸν τινὰ αἰώνος: Tim., 37 D). Plotinus in his Treatise on Eternity and Time (Enn., III, 7) deepens the dependence of time on eternity so as to make it spring not from the measure of the physical world but from the soul of the world: eternity shows itself as the absolute stability of the intelligible world and in this sense is identical with God (καὶ ταὐτὸν τῷ θεῷ: Enn., III, 7, 5). Proclus abandons this conception and makes of eternity a hypothesis in itself, from which eternity derives for all eternal things, just as temporal things participate their temporality from time, to the point of admitting a distinction between what is eternal, its eternity, and eternity per se: θῆλον ὅτι ἄλλο μὲν αἰώνιον, ἄλλο δὲ ὁ ἐν τῷ αἰωνίῳ αἰών, ἄλλο δὲ ὁ καθ'αυτὸν αἰών: Elem. Theol., prop. 54, ed. E. R. Dodds, Oxford 1933, p. 50, 26). Eternity is expressly elevated to a divine hypostasis in the cosmogonies of the genetic systems, each of which has its own "pleroma" or intelligible world, and Jesus is presented in them as "the advocate of the future eternity" (παρὰ λῆτος τῷ παρελθόντι αἰώνι: Clement of Alexandria, Stromata, ed. O. Stählin, Berlin 1936, VII, p. 114, 21).
In modern philosophy, by contrast, the concept of eternity has lost all its own metaphysical consistency and has returned to being the attribute of reality, of the world, of substance, of consciousness... that is, of whatever is ascribed the quality of the absolute within the sphere of being: eternity, which in Spinoza remains as « sub quo infinitam Dei existentiam concipimus » (Cog. metaph., I, 4; ed. Van Vloten-Land, 2nd ed., III, The Hague 1895, p. 201), disappears in Hegel's objective idealism, for which eternity is nothing but the "result" of the unfolding of time, just as the absolute Spirit (God) is the result of its activity in the history of the world (cf.: Philosophie der Weltgeschichte, 3rd ed., I, ed. G. Lasson, Leipzig 1930, p. 50).
Secondo la dottrina cattolica l'e. per essenza è proper to God, creatures can be said to be "participants" in eternity "insofar as they enjoy some perpetuity of existence." This holds for the physical world itself taken as a whole in its aftermath; although individual corporeal beings are corruptible, the end of the world will not be its annihilation but a transformation with "new heavens and a new earth" (2 Pt 3:13). In a more proper sense, spiritual creatures that are individually immortal participate in eternity; but the highest participation in eternity is what St. Thomas calls "secundum operationem sicut Angeli et beati qui Verbo fruuntur" (Sum. Theol., I, q. 10, a. 3), who are in full possession of "eternal life." But the punishments of the demons and of the wicked in hell must also be called eternal, against Origen's theory of a final "restoration" or reintegration (ἀνακτήστασις) of the same to happiness, and of the cessation of hell (Denz-U, 211). For modern immanentism this doctrine is not at all a dogma, but a "puerile question" (eine Kinderfrage: J. Kant, Die Religion innerhalb der Grenzen der blossen Vernunft, ed. K. Vorländer, Leipzig 1937, p. 76), since consciousness is reality and law unto itself.
In medieval Scholasticism there was lengthy dispute over the abstract possibility (that is, "de potentia Dei absoluta") of a creation of the world "ab aeterno": denied by the schools of Platonist-Augustinian inspiration, it was instead energetically affirmed by St. Thomas, for whom "mundum non semper fuisse sola fide tenetur et demonstrative probari non potest sicut et supra de mysterio Trinitatis dictum est" (Sum. Theol., I, q. 46, a. 2). In confirmation of the metaphysical compatibility between creation and the existence ab aeterno of the world, the Angelic Doctor cites the text of St. Augustine: "Sicut si pes ex aeternitate semper fuisse in pulvere, semper subesse vestigium quori a calcarte factum nemo dubitaret" (Sum. Theol., loc. cit., ad 1; Augustine, De Civ. Dei, XI, 4; PL 41, 319). A world that were "ab aeterno" would always have, in its unfolding, the character of temporality, and eternity would not be so much in it as on the part of the divine will in creating it "ab aeterno," just as it now manifests itself in conserving it "in aeterno."