 For example, the constraints on choice in Rawls's contract situation, such as the veil of ignorance that keeps us from knowing facts about ourselves and our specific preferences, require justification. Rawls needs to show that these constraints are “fair” to all contractors (thus “justice as fairness” is his label for this procedural account of how we find out what is just.) To provide such justification, Rawls appeals to beliefs about the fundamental “moral powers” of “free and equal” agents (they can form and revise their conceptions of what is good and they have a sense of justice). He also appeals to the ideal of a well-ordered society in which principles of justice play a particular role as public principles for reconciling disputes. Rawls must even provide us with an account of “primary social goods,” necessary if agents who do not know their own actual preferences are to decide what principles would be better for them to choose.