Despite the overuse of the word in movies, political speeches, and news reports, "evil" is generally seen as either flagrant rhetoric or else an outdated concept: a medieval holdover with no bearing on our complex everyday reality. In "A Philosophy of Evil," however, acclaimed philosopher Lars Svendsen argues that evil remains a concrete moral problem: that we're all its victims, and all guilty of committing evil acts. "It's normal to be evil," he writes--the problem is, we have lost the vocabulary to talk about it.

Taking up this problem--how do we speak about evil?--"A Philosophy of...