 In more mundane circumstances, most people exploit a ubiquitous commitment device that Adam Smith long ago made the centerpiece of his theory of social order: the value to people of their own reputations. Even if I am secretly stingy, I may wish to cause others to think me generous by tipping in restaurants, including restaurants in which I never intend to eat again. The more I do this sort of thing, the more I invest in a valuable reputation which I could badly damage through a single act of obvious, and observed, mean-ness. Thus my hard-earned reputation for generosity functions as a commitment mechanism in specific games, itself enforcing continued re-investment. In time, my benevolence may become habitual, and consequently insensitive to circumstantial variations, to the point where an analyst has no remaining empirical justification for continuing to model me as having a preference for stinginess. There is a good deal of evidence that the hyper-sociality of humans is supported by evolved biological dispositions (found in most but not all people) to suffer emotionally from negative gossip and the fear of it. People are also naturally disposed to enjoy gossiping, which means that punishing others by spreading the news when their commitment devices fail is a form of social policing they don’t find costly and happily take up. A nice feature of this form of punishment is that it can, unlike (say) hitting people with sticks, be withdrawn without leaving long-term damage to the punishee. This is a happy property of a device that has as its point the maintenance of incentives to contribute to joint social projects; collaboration is generally more fruitful with team-mates whose bones aren’t broken. Thus forgiveness conventions also play a strategic role in this elegant commitment mechanism that natural selection built for us. Finally, norms are culturally evolved mutual expectations in a group of people (or, perhaps, in a few other intelligent social animals) that have the further property that individuals who violate them may punish themselves by feeling guilt or shame. Thus they may often take cooperative actions against their narrow self-interest even when no one else is paying attention. Religious stories, or philosophical ones involving Kantian moral ‘rationality’, are especially likely to be told in explanation of norms because the underlying game-theoretic basis doesn’t occur to people; and the norms in question may function more effectively for that very reason.