Contractualists seek to publicly justify moral principles, but it seems doubtful that a set of specific principles or policies can be definitively justified. In this sense, the contractualist project has an indeterminate result: the precise content of liberal morality is open to reasonable dispute. Liberal citizens thus find themselves disagreeing about the demands of liberal morality. They require, as Locke argued, an umpire to resolve their disputes. This paper analyzes what is required of such an umpire, and then employs a four-stage argument to show that constitutional representative democracy is the uniquely justified umpiring procedure for resolving these disputes. Democratic politics, on this view, is the continuation of ethical dispute by other means.