Are moral principles actually principles of rational choice? Starting from the view that it is rational always to choose what will give one the greatest expectation of value or utility--and the common counter-claim that this procedure, applied in many situations, will actually leave people worse off than need be--Gauthier instead proposes a principle of cooperation whereby each must choose in accordance with a principle to which all can agree. He shows that not only does such a principle ensure mutual benefit and fairness, but also that each person may expect greater utility from actually...