Abstract

A concept that can be expressed by the term ‘rationality’ plays a central role in both epistemology and ethics -- and especially in formal epistemology and decision theory. It is argued here that when the term is used in this way, the concept of “rationality” is the concept of a kind of virtue, with all the central features that are ascribed to the virtues by Plato and Aristotle, among others. Interpreting rationality as a kind of virtue helps to solve several problems, such as the relations between “rationality” and “rational requirements” and between “propositional” and “doxastic justification”, and to answer objections to the thesis that “rationality” is a normative concept that are based on the principle that ‘ought’ implies ‘can’.