The tension between our need to cooperate on a large scale and our individual, primate-driven selfishness appears clearly in the sort of dilemmas inherent to social cooperation. Any time tension arises between the public good and individual interests there is the danger of what economists call “defection,” a situation in which a selfish individual benefits from the public good while not contributing to it. This tension goes by many names, including the “tragedy of the commons” or the “free-rider problem.”
