What has social science learned about the common good? Would humanists even want to alter their definitions of the common good based on what social scientists say? In this volume, six social scientists—from economics, political science, sociology, and policy analysis—speak about what their disciplines have to contribute to discussions within Catholic social thought about the common good. None of those disciplines talks directly about “the common good”; but nearly all social scientists believe that their scientific work can help make the world a better place, and each social science does operate with some notion of human flourishing. Two theologians examine the insights of social science, including such challenging assertions that theology is overly irenic, that it does not appreciate unplanned order, and that it does not grasp how in some situations contention among self-interested nations and persons can be an effective path to the common good. In response, one theologian explicitly includes contention along with cooperation in his (altered) definition of the common good.