In this volume a diverse group of economists, philosophers, political scientists, and psychologists address the problems, principles, and practices involved in comparing the well-being of different individuals. A series of questions lie at the heart of this investigation: What is the relevant concept of well-being for the purposes of comparison? How could the comparisons be carried out for policy purposes? How are such comparisons made now? How do the difficulties involved in these comparisons affect the status of utilitarian theories? This collection constitutes the most advanced and comprehensive treatment of one of the cardinal issues in social theory.