Political philosophers tend to think that Rousseau is significant because his contractarianism anticipates Kant. However, reading Rousseau in this way requires us to ignore his frequent and emphatic appeals to the role of happiness as collective flourishing (eudaimonia) in establishing the rational authority of justice. I offer a reading of Rousseau’s political theory which accounts for this eudaimonistic aspect of his thought. I argue that for Rousseau, as for Kant, obligations are structured by the autonomous willing of agents who bind themselves by the norms of reason alone. But unlike Kant, Rousseau thinks that such formal considerations of rational autonomy provide necessary but not sufficient reasons for fulfilling our duties to one a...