" A sound theory of value demands something different. It demands that good should be original and evil a mere perversion; that good should be the tree and evil the ivy; that good should be able to see all round evil (as when sane men understand lunacy) while evil cannot retaliate in kind; that good should be able to exist on its own while evil requires the good on which it is parasitic in order to continue its parasitic existence. "

― C.S. Lewis , God in the Dock: Essays on Theology and Ethics