 When it is just a matter of a priori justification, not knowledge, Philip Kitcher thinks that if there is such a thing as all things considered a priori justification, then “a person is entitled to ignore empirical information about the type of world she inhabits” (Kitcher 1983: 30; see, also, 24, 80–87). This view seems to rest on Kant’s idea but applied to justification, not just knowledge. If a priori justification is independent of all empirical experience, then no such experience can count either for or against a proposition that is justified a priori. Hilary Putnam thinks that if there is a priori justification, then there are “truths which it is always rational to believe” (Putnam 1983: 90). On Kitcher’s understanding of a priori justification, it is not defeasible by empirical information; on Putnam’s, it is not defeasible at all.