"A certain traditional conception of the afterlife is binary. After death one proceeds either to heaven or hell. Heaven is very, very good; hell is very, very bad. There are no possibilities for the afterlife other than heaven and hell, and membership in heaven or hell is never indeterminate or a matter of degree. The problem with the binary conception is that it contradicts God's justice. God must employ some criterion to decide who goes to heaven and who goes to hell. No reasonable criterion would be sharp; any reasonable criterion will have borderline cases. But the binary conception of the afterlife allows for no corresponding fuzziness in how the dead are to be treated. Hell must therefore contain people who are nearly indiscernible in relevant respects from people in Heaven. No just Cod would allow such a monstrously unfair thing."
- Sider, "Hell and vagueness"