Why did Plato need Hell?
In the opening pages of the Republic, Cephalus relates that old age lends new terror to the “stories we’re told about Hades, about how people who’ve been unjust here must pay the penalty there.” Many people prefer to act unjustly if they can get away with it, but the prospect of punishment in the afterlife ensures that the guilty pay for their misdeeds. Thus the conventional wisdom of the social utility of Hell: it scares people into being good.
However, in the Republic, Socrates accepts the challenge of showing that a just life is its own reward and an unjust one its own punishment. He argues that the practice of injustice mutilates the soul and prevents happiness, and that it is therefore better to be a just man, even if that means suffering injustice—perhaps being mistreated and killed—than to be an unjust man who enjoys all the pleasures and praise this world can offer. Plato even provides some (dubious) calculations to demonstrate precisely how miserable the tyrant’s life must be compared to that of other men. He concludes that a tyrant is 729 times more wretched than a (philosopher) king.
This would seem to eliminate the need to stoke fear of posthumous retribution awaiting the wicked. Yet Plato nonetheless revisits Hades following his calculation of tyrannical misery. After demonstrating the immortality of the soul, he concludes with the Myth of Er, which tells of a man who bore witness to the afterlife, with its rewards for the just and its tenfold punishments for the wicked. For most evildoers, the punishment eventually ends and they are reincarnated, but the worst are dragged away for further torment. Plato told similar tales elsewhere. In both the Gorgias and the Phaedo, Socrates states that those who have become incurably wicked are punished forever.
If virtue is its own reward, why did Plato repeatedly invoke the prospect of eternal punishment in Hades?
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