It is precisely because one act can balance ten thousand kind ones that we call it "evil".
-Steven Pinker, The Blank Slate
All these years I chased after a definition of evil, struggled to determine what true evil is, and here comes Steven Pinker with a simple and true definition, justlikethat. That's as good a working definition of evil as I've ever found.
He's also a fascinating writer who can make language utterly entrancing. I had no idea he existed before I bought a mis-shelved copy of The Language Instinct on a lark. It turned out to be one of the best books I've ever read, and helped me appreciate Tolkien much more deeply.