Is game theory good for us? This may seem an odd question. In the strict sense, game theory—the axiomatic account of interaction between rational agents—is as morally neutral as arithmetic. But the popularization of game theory as a way of thinking about social interaction is far from neutral. Consider the contrast between characterizing bargaining over distribution as a “zero-sum society” and focussing on “win-win” cooperative solutions. These reflections bring us to the book under review, Prisoner's Dilemma, a popular introduction to game theory and its relation to ethics by the respected science writer William Poundstone. The book begins with a moral dilemma and ends by discussing the evolution of co-operation. Poundstone emphasizes—correctly, to my mind—the ethical potential of game theory. He concludes his first chapter with this striking claim: “Today's practitioners of game theory are attempting to forge a kind of ethical progress. Is there any way to promote the common good in a prisoner's dilemma? The attempt to answer this question is one of the great intellectual adventures of our time” (p. 9).