Evil can be undone, but it cannot ‘develop into good.’ Time does not heal it. The spell must be unwound, bit by bit, ‘with backward mutters of dissevering power’–or else not. It still ‘either-or’. If we insist on keeping Hell (or even Earth) we shall not see Heaven: if we accept Heaven we shall not be able to retain even the smallest and most intimate souvenirs of Hell.
– CS Lewis–
from The Great Divorce