Broad agreement exists among politicians and policymakers that the family is a critical institution of American life. Yet the role that the state should play with respect to family ties among citizens remains deeply contested. This controversy over the state's role undergirds a broad range of public policy debates: Does the state have a responsibility to help resolve conflicts between work and family? Should same-sex marriage be permitted? Should parents who receive welfare benefits be required to work? Yet while these individual policy issues are endlessly debated, the underlying theoretical...