Bernard Werber. The secret of the gods (№ 92569)

Hell is a concept invented by people to punish themselves. Everyone you have seen, voluntarily crossed the Styx and chose suffering. When they get tired, they can leave and return to life as and where they want.
- We don't believe you! - cuts Oedipus.
- Sadly, it's true. The only thing that keeps them here is their own will to be punished. You underestimate the power of guilt.