A theory of rationality is a theory that evaluates instances of reasoning as rational, irrational, or (ir)rational to some degree. Theories can be categorized as rule‐based or consequentialist. Rule‐based theories say that rational reasoning accords with certain rules (e.g., of logic or probability). Consequentialist theories say that rational reasoning tends to produce good consequences. For instance, the reliabilist takes rationality to be reasoning that tends to produce mostly true beliefs. The pragmatist takes it to be reasoning that tends to produce mostly useful beliefs. This article reviews some of the features and the challenges of rule‐based, reliabilist, and pragmatist theories of rationality. WIREs Cogn Sci 2014, 5:27–37. doi: 10.1002/wcs.1263This article is categorized under: Philosophy > Foundations of Cognitive Science