Hugo Mercier and Dan Sperber have proposed an “argumentative theory of rea-soning” in which the function of reasoning is to devise and evaluate arguments intended to persuade. Mercier and Sperber note that the theory does not work when we reason alone or with people who share our beliefs. However, the theory also fails in deliberations involving “framework beliefs”—beliefs that are only indirectly related to empirical evidence but that have a particular importance for the believer because of their centrality to a dense web of other beliefs and their connections to social practices. Framework beliefs not only include many ethical, religious, and political beliefs, but also paradigmatic scientific beliefs. An alterna-tive theory of reasoning, derived from philosophical pragmatism, is presented that explains the rigidity of framework beliefs and is more optimistic about individual reasoning. A consequence of the pragmatist theory is that certain types of bias and polarization are functional.