When is it justifiable to exclude a person who wishes to enter a country? What are the acceptable moral bases for immigration policy? These questions lie at the heart of this book, the first interdisciplinary study of the fundamental normative issues underpinning immigration policy. A distinguished group of economists, political scientists, and philosophers offer a provocative discussion of this complex topic. Among the issues addressed are the proper role of the state in supporting a particular culture, the possible destabilization of the political and social life of a country through immigration, the size and distribution of economic losses and gains, and the legitimacy of discriminating against potential immigrants in favor of members of the resident population. The need for serious consideration of this subject is beyond question. This volume should advance discussion in an area of great practical as well as philosophical importance.