Do you know you are not being massively deceived by an evil demon? That is a familiar skeptical challenge. Less familiar is this question: How do you have a conception of knowledge on which the evil demon constitutes a prima facie challenge? Recently several philosophers have suggested that our responses to skeptical scenarios can be explained in terms of heuristics and biases. We offer an
alternative explanation, based in learning theory. We argue that, given the evidence available to the learner, it would be rational for the learner to infer an infallibilist
conception of knowledge.