Imperfect epistemic duties and the justificational fecundity of evidence

Mark Nelson argues that we have no positive epistemic duties. His case rests on the evidential inexhaustibility of sensory and propositional evidence—what he calls their ‘infinite justificational fecundity’. It is argued here that Nelson’s reflections on the richness of sensory and propositional evidence do make it doubtful that we ever have an epistemic duty to add any particular beliefs to our belief set, but that they fail to establish that we have no positive epistemic duties whatsoever. A theory of epistemic obligation based on Kant’s idea of an imperfect duty is outlined. It is suggested that such a theory is consistent with the inexhaustibility of sensory and propositional evidence. Finally, one feature of our epistemic practice suggestive of the existence of imperfect epistemic duties is identified and promoted.