Collective Rationality: Equilibrium in Cooperative Games

Collective Rationality: Equilibrium in Cooperative Games

Collective Rationality: Equilibrium in Cooperative Games

Collective Rationality: Equilibrium in Cooperative Games


Groups of people perform acts that are subject to standards of rationality. A committee may sensibly award fellowships, or may irrationally award them in violation of its own policies. A theory of collective rationality defines collective acts that are evaluable for rationality and formulates principles for their evaluation. This book argues that a group's act is evaluable for rationality if it is the products of acts its members fully control. It also argues that such an act is collectively rational if the acts of the group's members are rational. Efficiency is a goal of collective rationality, but not a requirement, except in cases where conditions are ideal for joint action and agents have rationally prepared for joint action. The people engaged in a game of strategy form a group, and the combination of their acts yields a collective act. If their collective act is rational, it constitutes a solution to their game. A theory of collective rationality yields principles concerning solutions to games. One principle requires that a solution constitute an equilibrium among the incentives of the agents in the game. In a cooperative game some agents are coalitions of individuals, and it may be impossible for all agents to pursue all incentives. Because rationality is attainable, the appropriate equilibrium standard for cooperative games requires that agents pursue only incentives that provide sufficient reasons to act. The book's theory of collective rationality supports an attainable equilibrium-standard for solutions to cooperative games and shows that its realization follows from individuals' rational acts. By extending the theory of rationality to groups, this book reveals the characteristics that make an act evaluable for rationality and the way rationality's evaluation of an act responds to the type of control its agent exercises over the act. The book's theory of collective rationality contributes to philosophical projects such as contractarian ethics and to practical projects such as the design of social institutions.


Groups of agents perform acts. What are the standards of rationality for a group’s acts? Is a group’s act rational if it results from each member’s acting rationally? These are questions of perennial philosophical interest. This book presents standards of rationality for a group’s acts. They are generalizations of standards for individuals. I argue that the individual rationality of acts by the group’s members ensures the rationality of the group’s acts. I also argue that standards of collective rationality are attainable, in contrast with goals of collective rationality that circumstances may put out of reach. Collective rationality is a theoretical concept belonging to a general theory of rationality, and its explication enriches that theory.

Game theory treats complex interactions of individuals in social situations. It formulates for ideal cases standards of collective rationality such as efficiency and shows how the rational acts of individuals ensure their attainment. An account of collective rationality constructs philosophical foundations for game theory. In Equilibrium and Rationality (1998) I introduce an attainable type of equilibrium, strategic equilibrium, that generalizes Nash equilibrium in noncooperative games. This book extends strategic equilibrium to cooperative games.

The study of collective rationality has a rich history and invigorates contemporary social philosophy. It illuminates social institutions, such as social contracts and economic markets, and thereby contributes to the foundations of the social and behavioral sciences. This book addresses scholars investigating human interaction. Its arguments and results are accessible to college students and of interest to specialists.

I am grateful to the Mellon Foundation for a postdoctoral fellowship 1978–80 and an interdisciplinary faculty fellowship 1985–86, both at the University of Rochester. These fellowships introduced me to game theory and theories of collective rationality. I thank David Austen-Smith, Richard Niemi, William Riker, William Thomson, and David Weimer for guiding my studies during those fellowships. William Lucas, while visiting the University of Rochester in 1984, explained to me Robert Aumann and Michael Maschler’s ideas about . . .

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