When Socrates refers to ‘Hades’ in Plato’s dialogue Phaedo, he describes it as the afterlife reserved for the good; and he describes the good man as the ‘philosopher.’
Bust of Socrates, Vatican Collection
Throughout Antiquity, there were many variations on the theme of life after death, all of which predate Christianity and Islam. The insistance on a “final judgement” in both Christianity and Islam comes directly from the early civilizations of Mesopotamia, the Mediterranean, and the Levant.
Religion and the Honest Student 