Political Epistemology, Rationality, and Externalism About Bias

ABSTRACT This article develops and defends the idea that some of our biases have an externalist character, with particular attention to cases in which the phenomenon arises in political contexts. A person who consistently defers to biased sources can count as biased even while responding impeccably to their total evidence. On the basis of such cases, I argue for three connected theses: Externalism about Bias (a person's biases do not supervene on their internal states and the causal relations among those states); Rationality is Compatible with Bias ; and Rationality Requires Bias (in certain environments, full rationality can require being biased, in a pejorative sense of “biased”). These theses are supported by compelling judgments about cases, independently of commitment to any specific theory of bias. They are also naturally accommodated by the norm‐theoretic account of bias, on which biases involve systematic departures from genuine norms. I argue that many central attributions of bias to human believers are grounded in departures from the externalist norm of truth. Finally, I draw a further consequence: Because many biases are environmentally constituted, the empirically documented unreliability of introspection as a method for detecting bias is not a contingent fact but holds of necessity.