I’m currently reading Jonathan Haidt’s book The Happiness Hypothesis. It sounds like a “self-help” book, but really its an outline of modern scientific understanding of factors influencing happiness, relationships, motivations and so on. On the other hand the book does make it easy to apply some of the scientific findings to one’s own situation.
I liked his comment on the relationship between ideology and evil. I think it is far more applicable than the often quoted comment of Steven Weinberg (“With or without [religion] you’d have good people doing good things and evil people doing evil things. But for good people to do evil things, it takes religion.”) I have commented on this before (see Sources of evil?).
Haidt lays the blame of idealism, rather than just religion:
“but to really get a mass atrocity going you need idealism— the belief that your violence is a means to a moral end. The major atrocities of the twentieth century were carried out largely either by men who thought they were creating a Utopia or else by men who believed they were defending their homeland or tribe from attack. Idealism easily becomes dangerous because it brings with it, almost inevitably, the belief that the ends justify the means. If you are fighting for good or for God, what matters is the outcome, not the path. People have little respect for rules; we respect the moral principles that underlie most rules. But when a moral mission and legal rules are incompatible, we usually care more about the mission.”
I think this makes sense of the state sponsored atrocities the world has seen. It also makes sense of the atrocities and harm caused by idealism at the personal level.