Third, principles of justice provide a public standard only if compliance with their demands is sufficiently verifiable to others. For Rawls, what matters is not only that “the institutions of the basic structure are just” but also that “everyone recognizes this” (1996: 66). This test of verifiable compliance therefore requires the possibility of widespread knowledge of the extent to which citizens discharge their duties. This test is most plausibly understood as an aggregative one. For example, the duty not to litter is verifiable to others in virtue of the fact that we can attain knowledge of the extent to which others on aggregate refrain from littering, even though we may not be able to attain knowledge of the extent to which any given citizen refrains from littering.[68]