ABSTRACT
People cooperate to form societies that benefit their members. The value of cooperation is evident in everyday life, as when drivers regulate their behavior to keep traffic flowing smoothly. When some cut corners, exploiting the cooperativeness of others, cooperation may break down, hurting all. Are the prospects of gains from cooperation enough to win the participation of rational people? An answer needs an account of rationality and an account of cooperation. After formulating these accounts, I advance a position about the rationality of cooperation.
