Introduction
This chapter introduces the book’s central themes. Arguments are offered to support the assumption that there is a single concept of ‘rationality’, which applies univocally to mental states (like beliefs and intentions) and processes of reasoning (like choices and belief revisions), and plays a central role in epistemology, ethics, and the study of practical reason. It will be widely believed that ‘rationality’ is a normative concept: to think rationally is in a sense to think properly, or as one should think. The goal of the book is to defend this belief, and to explain how ‘rationality’ differs from other normative concepts. Although normative language is not the main topic, reflections on language will be methodologically important, to ensure that we are not misled by our linguistic intuitions.