The conception of eternity in the Fathers is influenced not only by the philosophical formation especially Platonic of some of them, but primarily by the biblical concept. In pre-Socratic philosophy there is no secure attestation of the term aivw,nioj, whereas eternity or perpetuality is indicated by avi dioj, employed by Heraclitus, Empedocles, Parmenides, etc.; in Democritus it refers to the absolute eternity of the atoms. In Platonism, eternity was conceived for the first time in a metaphysical manner: the aivw,n the standard term for eternity in Plato and Middle Platonism and Neoplatonism is not in time, but beyond time, in that it transcends it while time is famously defined as a moving image of eternity in Tim. 37D5: whereas eternity remains in oneness, time moves according to number; it is the eternity of the divinity, which is unbegotten. The avi?dio,thj is everlastingness throughout all times, like that of the soul, or of stars; sometimes it also refers to the Ideas.
In other philosophical schools, however, and in Greek in general, the meaning of aivw,n, aivw,nioj and avi dioj was very different. Aristotle seems never to use aivw,nioj, and aivw,n only occasionally, mostly in the traditional sense of life, whereas in his corpus there are nearly 300 occurrences of avi dioj, which is Aristotle’s preferred word to designate eternity. His conception of eternity and use of the relevant terminology is generally followed by his commentators. In the Stoics, aivw,n and aivw,nioj, rather than indicating eternity strictly, are rather related to a cyclical conception of aivwnej or cyclically recurring cosmic eras, marked by the periodic destruction and restoration of new worlds, where the events follow one another according to Necessity, always identical in each world. Eternity is rather expressed through avi dioj, which is frequent in the Stoics, occurring over thirty times in the Stoicorum veterum fragmenta in the sense of that which endures forever. It is applied to bodies and matter, the o;nta or realities that truly exist according to Stoic materialism, and above all to God. Notably, to designate eternity, Marcus Aurelius does not employ aivw,n alone, as Plato and Plotinus do, but avi dioj aivw,n, meaning eternal duration. The Epicureans, following Democritus, regularly employ avi dioj, never aivw,n, to designate the eternity of such imperishable constituents of the universe as atoms and void.
Also outside the philosophical world, in Greek eternity was not indicated by aivw,n. In Homer, early lyric, and tragedy, aivw,n principally bears the sense of life or a period of time or generation. Also in classical and Hellenistic Greek, it means long duration, perpetuity from one generation to the next, lifetime and the like; it sometimes indicates eternity only in reference to the divine, but this meaning is generally conveyed by avi dioj. In the Bible, likewise, aivw,n and aivw,nioj do not mean eternity and eternal; they only acquire this meaning, sometimes, when they refer to God. In the Hebrew Bible, the principal term for eternity is ´lam, which is almost always translated with aivw,n and aivw,nioj in the Septuagint and does not at all mean eternity or eternal, but only acquires this sense when it refers to God or what is closely related to God, and only because of God’s own eternal nature. Otherwise, it indicates a long time, a remote time in the past or in the future, the series of generations, a lifetime, or it even means worldly or mundane, or, especially in the most recent books, it refers to the other world Ramelli – Konstan, 37-49.