Fudge points out that the question of immortality was a favorite of Greek philosophers. The seminal work on the subject was Plato’s Phaedo, a dialogue on the question that was well-known among First Century Hellenistic people.
The debate Plato writes is between Socrates, who argues for innate immortality of the soul, and Cebes, who argues that
when the [soul] has departed from the body, [it] nowhere any longer exists, but on whatever day a man dies, on that day it is destroyed [diaphtheiretai] and perishes [apolluetai]; the moment it departs and goes forth from the body it is dispersed like breath or smoke, and flies abroad and is gone, and no longer exists anywhere.
You’ll recognize apolluetai as a form of apollumi, the word the New Testament so frequently uses for “destroy” or “kill,” used frequently of the fate of the damned.
The New Testament writers use diaphtheiretai (root: diaphtheiro) in such verses as —
(2 Cor 4:16) Therefore we do not lose heart. Though outwardly we are wasting away, yet inwardly we are being renewed day by day.
(Rev 11:18) The nations were angry; and your wrath has come. The time has come for judging the dead, and for rewarding your servants the prophets and your saints and those who reverence your name, both small and great — and for destroying those who destroy the earth.”
Fudge writes (p. 167),
Both Plato and Paul use the terms ‘death’ (thanatos), ‘destruction’ (apoleia), ‘corruption’ (phthora), ‘perish,’ (olethros) and ‘die’ (apothnesko) — but with this difference. Plato says none of these things will ever befall a soul, for it possesses immortality; Paul says these words define the destiny of those who resist God and refuse to believe in Jesus. …
Interestingly, Plato believed that some would be punished for ever (or at least for a very long time after death). Such reprobate souls can continue in misery, he said, because they possess ‘immortality’, are ‘indestructible’ and ‘immortal’. Yet ‘not one of these terms is ever used in the New Testament to describe the future condition of the lost.’
When the New Testament speaks of immortality and such like, it is speaking to a Hellenistic audience in the Greek language regarding a subject that the Greeks had discussed in these terms for centuries. It only makes sense to read the words in this light.
Obviously, as we consider the background against which the New Testament was written, we give the heaviest weight to the Old Testament, which we’ve previously considered in two posts here and here. But we can’t ignore the Hellenistic background.