Sean Donahue

Public reason liberals claim that legitimate rules must be justifiable to diverse perspectives. This Public Justification Principle threatens that failing to justify rules to reprehensible agents makes them illegitimate. Although public reason liberals have replies to this objection, they cannot avoid the challenge of powerful deceivers. Powerful deceivers trick people who are purportedly owed public justification into considering otherwise good rules unjustified. Avoiding this challenge requires discounting some failures of justification according to what caused people’s beliefs. I offer a conception of public justification that accommodates these externalist considerations while positioning Public Reason Liberalism to provide insight into real cases of deception.

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.

Two epistemic principles are Knowledge Exclusion and Belief Exclusion. Knowledge Exclusion says that it is necessarily the case that if an agent knows that p, then she does not believe that ∼p, and Belief Exclusion says that it is necessarily the case that if an agent believes that q, then she does not believe that ∼q. Many epistemologists find it reasonable to reject the latter principle and accept the former. I argue that this is in fact not reasonable by proposing a case in which an agent can use that she has contradictory beliefs towards a proposition as decisive evidence for that proposition. A natural response is that this case conflicts with common assumptions about the relation between knowledge, contradictory beliefs and rationality. I reply by drawing ideas from Lasonen-Aarnio’s remarks on unreasonable knowledge to explain why these common assumptions do not threaten my argument.