Abstract

Group polarization—roughly, the tendency of groups to incline towards more extreme positions than initially held by their individual members— has been rigorously studied by social psychol- ogists, though in a way that has overlooked important philosophical questions about this phenomenon which remain unexplored. Two such salient questions are metaphysical and epistemological, respectively. From a metaphysical point of view, can group polarization, understood as an epistemic feature of a group, be reduced to epistemic features of its individual members? Relatedly, from an epistemological point of view, is group polarization best understood as a kind of cognitive bias or rather in terms of intellectual vice? This book taxonomizes this possibility space by comparing four models which combine potential answers to the metaphysical and epistemological questions. The models we consider are: group polarization as a collective bias, a summation of individual epistemic vices; a summation of individual biases; and a collective epistemic vice. We defend a collective vice model of group polarization over the competing alternatives.