" Thanks to our old friend non-zero-sumness, everyone’s happiness can, in principle, go up if everyone treats everyone else nicely. You refrain from cheating or mistreating me, I refrain from cheating or mistreating you; we’re both better off than we would be in a world without morality. For in such a world the mutual mistreatment would roughly cancel itself out anyway (assuming neither of us is a vastly more proficient villain than the other). And, meanwhile, we would each incur the added cost of fear and vigilance. "

― Robert Wright , The Moral Animal: Why We Are the Way We Are - The New Science of Evolutionary Psychology