Second, principles of justice provide a public standard only if they provide sufficiently determinate and accessible standards of moral permissibility, such that a “person taking part in an institution knows what the rules demand of him” (Rawls 1999a: 48). This has two components. First, principles pass the test of determinacy only if they are not so vague that they are incapable of producing clear directives.[67] Second, principles pass the test of accessibility not merely when citizens can attain knowledge of how they would be required to act if they were to have the relevant empirical information, but instead only if citizens are in fact able to attain knowledge of that empirical information (Rawls 1996: 182; Lippert-Rasmussen 2008: 41).