Without hyperbole, no postwar intellectual of the first rank has done more good for more people-above all, many of the world's poorest-than Amartya Sen. -- Boyd Tonkin The Independent What is Arrow's impossibility theorem? Why is it true? What are its implications for democratic decision making? Is its nihilism justified? These are the kinds of questions addressed in Maskin and Sen's masterful Arrow lectures. These lectures and the accompanying essays provide an accessible introduction to Kenneth J. Arrow's theorem for the neophyte and much food for thought for the cognoscente. -- John A. Weymark, Vanderbilt University How vital it is to understand the ideas behind Kenneth J. Arrow's impossibility theorem if we want to design reasonably fair ways of coming to consensus decisions that take equitable account of individual preferences. This book is a marvelous introduction to the theorem, a keystone in the theory of social choice. We are treated to a discussion of that theory-its origin, background, and the challenges it points to-by some of its great architects. -- Barry Mazur, Harvard University, author of Imagining Numbers The pioneers of social choice theory give us lively, enjoyable, and stimulating lectures and exchanges of ideas. Their views, more than sixty years after the publication of Kenneth J. Arrow's theorem, are of paramount interest to anyone aware of the difficulties of collective decisions. -- Marc Fleurbaey, Princeton University