The Prisoner’s Dilemma (PD) plays a central, but shifting, role in David Gauthier’s moral theorizing. In “Morality and Advantage,” it provides a model, demonstrating how morality can have seemingly contradictory properties. In Morals by Agreement, it poses a special problem for the view that moral behaviour is individually rational. Authorities on game theory have subsequently disputed the idea that the PD is an appropriate tool for thinking about moral theory. In the first part of this paper, I examine the roles of the PD in Gauthier’s writings. In the second part, I outline a project, with both descriptive and normative components, that develops the insights of “Morality and Advantage” while preserving it from the game theorists’ attack.