The Public Justification Principle requires that coercive institutions be justified to all who live under them. I argue that this principle often cannot be satisfied without persons depending on the pure informative testimony of others, even under realistically idealized situations. Two main results follow. First, the sense of justification relevant to this principle has a strongly externalist component. Second, normative expectations of trust are essential to public justification. On the view I propose, whether the Public Justification Principle is satisfied depends (...) on the features of the network of testifiers in which persons are embedded. I consider several such networks to show which features are plausibly relevant. The importance of testimony for public justification ultimately suggests that we should moderate our expectations about the kind of conciliation we can achieve with the social order in which we live. (shrink)