Disagreement and Belief Dependence: Why Numbers Matter

At the center of work in the epistemology of disagreement is a debate regarding what is rationally required when one is faced with an epistemic peer with whom one disagrees about a given question. A and B are epistemic peers relative to the question whether p when A and B are roughly evidential and cognitive equals with respect to this question. While there is considerable dissent regarding the appropriate response to peer disagreement, there is nonetheless universal acceptance of the following Belief Independence thesis: When A disagrees with peers B, C, and so on, with respect to a given question and A has already rationally taken into account the disagreement with B, A's disagreement with C, and so on, requires doxastic revision for A only if the beliefs of C, and so on, are independent of B's belief. Despite both the widespread acceptance and intuitive plausibility of Belief Independence, Jennifer Lackey argues in this paper that there is no interpretation of this thesis that turns out to be true.