Evil is a moral problem for everyone, difficult to acknowledge in ourselves, hard to understand in others, and difficult to defeat without committing lesser evils. Liberals—I count myself as one—have a special problem with evil, connected to our particular form of self-regard. Liberals like to believe we are tolerant, but evil, by definition, cannot be tolerated. We believe that politics ought to be deliberative, but we can't deliberate with evil. We think compromise can be honorable, but there are no honorable compromises with evil. We think politics ought to be governed by reason, but evildoers, while they may reason, are not reasonable.
Alan Wolfe, a distinguished and prolific professor of political science at Boston College, and author of more than 20 books, including The Future of Liberalism, has written a dispassionate guide to these quandaries in Political Evil. He distinguishes between evil in general and political evil in particular, and argues that we should think politically about evil because the evil that we can actually do something about is a form of politics and can be defeated only if understood as such.