First, principles of justice provide a public standard only if they are not self-effacing—that is, only if the success of the principles from which the rules derive does not depend upon some citizens being ignorant of these principles, or upon some citizens being ignorant of others’ knowledge of these principles (see §1.3.1). In other words, the idea of publicity requires mutual knowledge, and not mere general knowledge (see §1.1). In clarifying what he means by a public system of rules, Rawls writes,