John Broome has made major contributions to, and radical innovations in, contemporary moral philosophy. His research combines the formal method of economics with philosophical analysis. Broome’s works stretch over formal axiology, decision theory, philosophy of economics, population axiology, the value of life, the ethics of climate change, the nature of rationality, and practical and theoretical reasoning. Weighing and Reasoning brings together fifteen original essays from leading philosophers who have been influenced by the work and thought of John Broome. It aims to offer a comprehensive evaluation of Broome’s wide-ranging and far-reaching philosophical works over the past thirty years. The volume comprises two parts. The first part is focused on Broome’s work on the theory of value, as exemplified in his books Weighing Goods, Weighing Lives, Economics out of Economics, and Climate Matters. The second part is focused on his work on practical and theoretical reasoning, which culminated in his Rationality through Reasoning. This volume also includes a piece by Broome on his intellectual history to date.