Abstract
Belief polarization occurs when individuals with opposing initial beliefs strengthen their beliefs in response to the same evidence. In previous work (“Disagreement, Dogmatism, and Belief Polarization,” Journal of Philosophy 2008), I explored the hypothesis that the psychological mechanisms that give rise to belief polarization are rational ones, given what was then the best available account of those mechanisms provided by psychologists who had documented the phenomenon. In this talk I will further explore questions about the rationality of belief polarization in the light of the latest work in psychology, philosophy, and other disciplines. Particular attention will be devoted to questions about whether the reasoning that gives rise to belief polarization is biased reasoning, in an objectionable sense of “biased.” Such questions seem especially pressing given that, as is sometimes noted, even exemplary reasoning and paradigmatic episodes of knowledge acquisition are naturally described as involving certain epistemically innocuous or even beneficial biases. (Consider, for example, the ways in which vision scientists refer to the “biases” of our perceptual systems, without which perceptual knowledge would be impossible; or the ways in which cognitive scientists and philosophers seeking to understand exemplary inductive reasoning routinely speak of our “inductive biases.”) Finally, I consider the role that the mechanisms that give rise to belief polarization play in contexts of group polarization. In cases of group polarization, groups of like-minded individuals become increasingly extreme in their point of view as they share their opinions with one another, and thus, ever more polarized from other like-minded groups who begin with different opinions. I argue that although sharing evidence across different groups would often be socially desirable and epistemically beneficial, given plausible empirical assumptions it will often be practically rational for individuals within the groups to pass up opportunities to do so. \end{abstract}
