Abstract

The supposed fact of reasonable disagreement plays a crucial role in standard accounts of political liberalism. The standard account posits reasonable disagreement as arising primarily from the supposed fact that, in at least some circumstances, people can permissibly respond in different ways to the same evidence. That is to say, the standard account presupposes permissivism: It is possible that more than one doxastic attitude towards a proposition is rationally permissible, given a body of evidence. In this thesis, I shall show that the standard account is mistaken in presupposing permissivism by arguing for Uniqueness: Given a total body of evidence at most one doxastic attitude is rationally permissible. I shall argue for this by first rehearsing White’s two objections to permissivism and showing that, at the very least, they show that an intrapersonal version of Uniqueness is true. That is to say, at most one doxastic attitude is justified for a given agent given a total body of evidence. I shall then present different accounts of permissivism consistent with intrapersonal uniqueness and show that none of these accounts are successful. If my argument is successful, the standard account of political liberalism may have to be revised.