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 in their being and in their acting (bodies), and unlike the measure of things that are immutable in being but mutable in acting. Therefore, the determinations of eternity, time, and aeviternity are made in relation to the process and the mode of possession of the act of being— as St. Thomas insists— and not with respect to having a beginning or an end. Only when the "presence" of being is absolute and complete, both in its constitutive principles and in its activity, do we have that eternity which the Angelic Doctor defines with Boethius: "Interminabilis vitae tota simul et perfecta possessio" (Summa Theologiae, I, q. 10, a. 1; cf. Boethius, Consolatio Philosophiae, V, prosa 6: PL 63, 858).
Of eternity as the infinite duration of 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 presentiality, in contrast to the continuous flowing and changing of physical phenomena (time) and even above the successive processes of higher spiritual substances. Therefore, while the instant in material substances bears only upon a fraction of being and is in continual forward motion, 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) in its acting: in God the instant rests in the full possession of Himself and of being. We therefore imagine eternity as the actuality of the instant extended to infinity, but in reality what we perceive as actuality in the temporal instant is only its flowing and thus the imperfection of its being. Eternity, on the other hand, is conceived as an immobile fullness, and thus the instant, passing from time to eternity, as it were, reverses— 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" (Summa Theologiae, I, q. 10, a. 2, ad 1). If Thomas intends to admit the possibility for man of some perception of eternity itself, one must think of experiences of the highest interior concentration in the higher sphere of intelligence and love, when the soul is rapt beyond its habitual contact with the visible world and, as it were, stretched out in abandonment toward God who draws II. Characteristic in this sense is the vision of Ostia, "described by St. Augustine in the Confessions (IX, 10), where eternity is spoken of as God (John 3:14) in whom properly 'there is no' was or will be, but only is, that is, the simple position of being in its metaphysical purity: in this sense, while creatures must be said to 'have existence,' of God alone must it be said that He 'is'" (Summa Theologiae, I, q. 12, a. 1, ad 3). Even Kierkegaard: "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, holding them apart from one another in succession" (Concluding Unscientific Postscript, VII, 2nd ed., Copenhagen 1925, p. 32). In his antimetafisical 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 not at all timeless (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, after, of middle, beginning and end, of movement, origin and purpose" (Die kirchliche Dogmatik, III, 1: Die Lehre von der Schöpfung, Zurich 1945, p. 72). The error here lies in conceiving eternity as perfect time and time itself as perfection; whereas time is given only in the radical otherness with respect to its moments (past, present, and future), so that affirming the 'unity' of the moments is to destroy the reality of time; consequently, in the succession that entails such otherness there is an imperfection that cannot be purified within the metaphysical sphere. Eternity, aeviternity, time are attributes of being and therefore derive directly from the being to which they relate their own nature. What is created is therefore the being by participation, which can be either in aeviternity or in time; aeviternity and time concur with being and the perfections of the being by participation: it is being, and with these perfections, that enjoy the ontological positivity as such, of which the finite truly partakes and from which the intellect ascends to conceive the infinite. Even E. Brunner, who conceives eternity as mere "fullness of time" (Erfüllung der Zeit), as "full temporality" (Vollzeitlichkeit), remains within a sphere of evident theological empiricism (Die christliche Lehre von Gott, Dogmatik, I, Zurich 1945, p. 287).
The concept of eternity in Christian theology must therefore be distinguished from that of thought which has stopped at the cosmic meaning of sempiternal duration (aeviternity, αἰών, duration without beginning). Thus Anaximander speaks of "cyclical generations and corruptions according to an indeterminate eternal duration" (ἐξ ἀπείρων αἰῶνες: H. Diels-Kranz, Die Fragmente der Vorsokratiker, 3rd ed., I, Berlin 1935, 83, 31); Anaximenes speaks of a movement of eternity (κίνησις αἰώνιος: ibid., I, 91, 31); it is attributed to the cosmos by Pseudo-Philolaus, since "the world remains αιώνιος καὶ αἰώνιος" (ibid., 8, 147, 11); Heraclitus attributes eternity to the Logos (ἀίδιος αἰών: ibid., I, 161, 13). In this first sense eternity is duration "without beginning" up to "the end" of the cosmos, according to Aristotle's statement that it "has neither beginning nor end of its entire duration (ἀίδιον μὲν καὶ ἀτέλευτόν ἐστιν οὐκ ἔχον τοῦ παντὸς αἰών), but containing and comprehending within itself unlimited time" (De caelo, II, 1, 283 b 26 ff.). For Plato, on the other hand, eternity is attributed to the immobile ideas, and time is derived from eternity as its "moving image" (εἰκὼ... κινητόν τινα αἰών: Timaeus, 37 D). Plotinus, in his treatise On Eternity and Time (Enneads, III, 7), deepens the dependence of time on eternity so as to derive it not from the measure of the physical world but from the unity of the intelligible world: eternity is shown as the absolute stability of the intelligible world and in this sense is identical with God (καὶ ταύτην τῷ Θεῷ: Enn., III, 7, 5). Proclus abandons the question and makes of eternity a hypostasis from which eternity derives for all eternal things, just as temporal things participate their temporality from time, even to admitting a distinction between what is eternal, its eternity, and eternity itself: "Not from one another, but in eternity is eternity, and not from one another in eternity" (Elem. Theol., prop. 5, ed. E. R. Dodds, Oxford 1933, p. 50, 26). Eternity is expressly elevated to a divine hypostasis in the cosmogonies of Gnostic systems, each of which has its own "pleroma" or intelligible world, and Jesus is presented in them as "the advocate of future eternity" (παράκλητος τῶν περὶ ἀνθρώπων αἰώνων: Clement of Alexandria, Stromata, ed. O. Stählin, Berlin 1936, VII, p. 114, 21).
In modern philosophy, on the other hand, the concept of eternity has lost all proper metaphysical consistency and has reverted to being an attribute of reality, of the world, of substance, of consciousness... that is, of whatever is attributed the quality of the absolute within the sphere of being: eternity, which in Spinoza remains as "sub quo infinitum Dei existentiam concipimus" (Metaphysical Thoughts, I, 4; ed. Van Vollenhoven-Land, 2nd ed., III, The Hague 1895, p. 201), disappears in the objective idealism of Hegel, for whom eternity is nothing but the "result" of the unfolding of time, just as absolute Spirit (God) is the result of its activity in the history of the world (cf.: Philosophy of World History, 3rd ed., I, ed. G. Lasson, Leipzig 1930, p. 50).
According to Catholic doctrine the eye, by its essence, is