ABSTRACT
According to one usage, rationality is a capacity for cognitive activity, and according to another related usage, it is a standard of evaluation for acts, beliefs, and desires that issue from the capacity. Rationality demands more of an adult than of a child, and demands more of an adult with time for reflection than of an adult harried by adverse circumstances. Rationality lacks practical, action-guiding value if it is impossible to follow all its directives. The foregoing accounts of collective rationality and cooperation yield an analysis of a famous game, the Prisoner's Dilemma. Some theorists, such as A. Sen, state that individual and collective rationality conflict in the Dilemma. Opportunities for cooperation arise in many situations besides the Dilemma. The argument from rationality to cooperation, which P. Weirich elaborates, shows that rational agents head off realization of a non-optimal outcome because some agent proposes a contract binding all to joint action that realizes an optimal outcome instead.
