An important distinction, I think, is that good and evil are tangible and unambiguous as forces in the world, but there is still plenty of room for complexity in the struggle of good and evil within an individual. Is Smeagol truly evil? Is Denethor? Especially true if you move beyond beyond LotR proper -- Feanor, Turin, etc. Plenty of complex individual struggles even within a relatively simple and immutable binary of good and evil in the world's epistemology.