Horribly pretentious title, I know, and barely deserved as I will add almost nothing to these words from Aleksandr Solzhenitsyn.
the line dividing good and evil cuts through the heart of every human being.
I must have seen them before, because I have read The Gulag Archipelago, but they were fresh when I saw them in a review in The Economist of a new book from Greg Lukianoff and Jonathan Haidt. Better add it to my reading list.
I praised an earlier article by Haidt in a somewhat prescient blog post in July 2016. There's been an awful lot of chatter on the topic since, but I think this point, that very few people are good or evil through and through, continues to escape many of the chatterers. The Solzhenitsyn quote is worth giving in full.
If only there were evil people somewhere insidiously committing evil deeds, and it were necessary only to separate them from the rest of us and destroy them. But the line dividing good and evil cuts through the heart of every human being. And who is willing to destroy a piece of his own heart?