Andy believes that p because his tarot cards indicate that p. Betty believes that ∼p because her crystal ball reveals that ∼p. If Andy and Betty know that they disagree, and disagree because they engage in different practices, is Andy's belief that p rational? The answer depends in part on whether Andy has good reasons to think that reading tarot cards is reliable about the topic while reading crystal balls is not. If a person has good reasons to believe that practice P1 is reliable while a competing practice P2 is not, then it is not irrational to form beliefs by engaging in P1. What if a person does not have good reasons to think that one practice is reliable about a topic while competing practices are not, though? In such cases, would Andy's awareness of the existence of competing practices, on its own, be enough to render his belief that p irrational?
Todd Stewart is Assistant Professor in the Philosophy Department at Illinois State University. His research interests lie in epistemology (especially disagreement, epistemic circularity, internalism/externalism, and skepticism) and meta-ethics. An earlier publication is “Causation and Lehrer's Theory of Knowledge” In The Epistemology of Keith Lehrer, ed. Erik Olsson (Phil. Studies Series, V. 95: 2003).