The purpose of evil is to complement the good. If there is no hatred in this world, there can’t be any love too. While love is a positive emotion, hatred is a negative emotion. Yet the feeling of love can’t exist in a person without invoking hatred. The more you are capable of loving, the more you are capable of hating, since the source of love and hatred is the same – passion. A man without passion can experience neither love nor hatred.
Awdhesh Singh, Good and Evil: Two Sides of the Same Coin
evil, good, good-and-evil, hatred, love