This article advances a functionalist account of practice-dependent principles of justice. It argues that existing practice-dependent approaches fail to explain how practices can enter into the justification of principles of justice. By understanding principles of justice as social rules that respond to the structural needs of social cooperation, the article shows how those needs constrain which higher-order moral principles can appropriately justify such principles. Justice is thus understood as internal to social practice rather than an external moral ideal. This functionalist approach supports the priority of politics over morality and provides a more realistic foundation for theorizing justice.
