choices, motives, and welfare. From fact that Sarah chooses x from opportunity set {x, y}, one could not infer that she is at least as well off with x as y, nor even that she personally wanted or valued x at least as much as y, since she may have chosen x out of deference to a moral or social norm. This little gem of conceptual analysis led me to question my prior assumptions that theory of rational choice explains all behavior, and that free markets invariably improve human wellbeing. It opened up my mind, ultimately setting me on a path away from economics toward philosophy, where I found more varied and fruitful tools for criticizing and developing alternatives to my rationalist libertarian worldview. Since then, I have found in Sen's work a steady stream of insights, many of which are defended in present work. Rationality and Freedom (Cambridge: Harvard University Press, 2002) collects an important subset of Sen's vast corpus from past twenty years. Its overarching project is to expand scope and flexibility of three central tools of economics-the concept of preference, rational choice theory, and social choice theory. It enriches motivational assumptions of economics, while retaining core idea that people's motives, goals, values, and choices can be represented through a binary preference relation over states of affairs (or sets of states). It makes rational choice theory more plausible for both normative and explanatory purposes by relaxing some of its formal constraints, while retaining core idea that rationality involves the discipline of maximization. It presents and discusses implications of two central findings of social choice theory: Arrow's Impossibility Theorem and Sen's Impossibility of a Paretian Liberal. Most importantly, it extends reach of social choice theory to coverjudgments about how much freedom people enjoy in society, while retaining core idea that collective judgments should be built out of individual values. Let's consider each of these topics in turn.