When we say people are evil, call them psychopaths, we separate them into another species. We have the idea we are so different we cannot do anything with each other. In conversation with each other we cannot bring out new ideas, we cannot understand each other. But that is not the case.
With a little theory we can describe psychopathic behavior: acting without sympathy for other people.
The little theory tells us that acting without sympathy is an essential component of our lives. All creative work, art, thought occurs without sympathy because what is being made is in movement. Sympathy is a relation of one thing to another thing, person to person. While we are making things we do not see ourselves at all: our attention is on what we are doing, and what we see, what we are making, is undefined because in progress.
Creative work has a goal outside itself: happiness, rest in sight of something beautiful, love, getting home. In psychopathic behavior work becomes an end in itself. It is a recourse, an evasion, which has becomes a habit. It is an evasion from failed attempts to establish a fixed relation, in one's mind, between one's idea of oneself and one's idea of the world. This attempt, which also becomes a habit, goes by the name of narcissism.
So the person we were tempted to call evil, and consider to be outside the reach of our reasoning and reflections is the opposite of that, is the product of habits locking him into entirely describable, repetitive, and mechanical actions.
People said to be evil often see this themselves. They deliberately choose to lower themselves into mechanical practice to avoid life's insecurity. Their work takes the quantitative form of money, fame, or scale of destruction, all expressive of power to make a change in the group as a whole, as it must be with caring for individuals not involved. They tell themselves they deserve to feel pride in their efficiency, submission to the austerity of working with thoughts only of the group. These are the people we like to call evil. They have made a principle, a positive social good, of their psychopathology.
A man sits at a restaurant with his wife. She is looking at him with her familiar stillness, watching him eat. He doesn't understand what is happening. He feels like everything is over with her because she has told him so, yet what he sees, actually sees, says otherwise. He's had years of this and it is wearing him down. He doesn't have any idea what to do. He is too attached to his habits, to being his wife's satellite. Solving this problem would require original action, and he doesn't even consider the possibility. His only strategy is to stick around and hope her love grows. He can see her love is growing, but her resolution to leave is not lessened.
The man is determined to hold onto his wife's love but is unable to love her. He is working at it, and while he works he cannot feel. And his wife, though she loves him, is determined not to. He is determined at all costs to hold onto his wife, she is determined she deserves better. Working to achieve their goals neither is capable of feeling deeply for the other. Both man and wife are, at least with each other, psychopaths. They create circumstances for each other in which they cannot feel the love they in fact have for each other.