"Evil" is at least as ancient a concept as crazy. Its hallmark is a narrow moral circle in which other people are objects of moral indifference or hatred, people deemed not to deserve to live. In this usage, the label evil is not mysterious nor derived from a belief in "the devil." Rather, it is clarifying; it denotes people inclined to be violent and to put many other people at risk.

We know evil when we see it: "mean," "violent," "full of hate," "selfish," "grandiose," "without a conscience" and "bullying" all signal evil. Whatever mental illness he may have had, Adam Lanza died and, most likely, lived at the extreme end of evil.

Unlike the classifying and unpacking of craziness, modern science has shied away from unpacking and classifying evil. The two are separable: One can be crazy, evil, neither or both.

The surprise here is that the author of this good sense is Martin Seligman, a former president of the American Psychological Association, an organization that regularly weighs in on the other side.  The APA commonly argues against holding people fully responsible for their evil deeds.  Many psychologists seem to believe that no one is just plain evil and that all serious misdeeds amount to mental illness of some kind and thus are not blameworthy.  Of course, Seligman is a former president of the APA and not speaking for the organization, but the recognition of evil as distinct from mentally ill even from a former president is refreshing nonetheless.

Unfortunately, Seligman goes off the rails when he starts talking about concrete measures, but I won't get into that.  I'm glad to see a very prominent psychologist dare to use to the word "evil" and recognize it as distinct from mentally ill.