Abstract: The folk theorem shows that cooperative behavior can be sustained as a Nash equilibrium in indefinitely repeated games — a phenomenon known as reciprocal altruism. The same theorem offers a solution to various other social mysteries. Who guards the guardians? How are authority, blame, courtesy, dignity, envy, friendship, guilt, honor, integrity, justice, loyalty, modesty, ownership, pride, reputation, status, trust, virtue, and the like to be explained as emergent phenomena? How do beliefs that many people privately know to be false survive?

Keywords: repeated games, tit-for-tat, folk theorem, reciprocal altruism, revenge, reputation, trust, authority,