The proper foundation of welfare economics is a characterization of the fundamental principles embodied in our moral and legal framework, which constitutes a conception of the public interest. We may use a conception of the public interest as a predictive or expiratory device. We may also use a conception of the public interest as a guide to making policy. Welfare economics should formulate and analyze different conceptions of the public interest. There will always be tension over which one is right, but that does not initiate an academic inquiry.