 One answer is that we do not need to know everything about ourselves, including our primary purposes, to make rational decisions about the background social conditions needed to pursue those primary purposes. For example, whatever our ends, we know that personal security and an absence of social chaos are conditions of most anyone’s living a good life (as Hobbes contends). Similarly, though Rawls’s parties do not know their particular values and commitments, they do know that they require an adequate share of primary social goods (rights and liberties, powers and opportunities, income and wealth, and the social bases of self-respect) to effectively pursue their purposes, whatever they may be. They also know they have a “higher-order interest” in adequately developing and exercising their “moral powers” – the capacities to be rational and reasonable – which are conditions of responsible agency and social cooperation. Rawls contends that knowledge of these basic social needs (he also calls them “essential goods”) is sufficient for a rational choice on principles of justice by the parties in the original position. To resolve this controversy, critics need to examine the details of Rawls’s argument and be more specific about where it is claimed to fail. 