Although the contractarian tradition is relatively new compared to other traditions of ethical and political thought such as natural law, the idea of the social contract has frequently dominated modern political philosophy. In the seventeenth and eighteenth centuries, the tradition was developed and criticized by such influential thinkers as Hobbes, Locke, Rousseau, and Kant. In the nineteenth and early twentieth centuries, its influence declined in contrast with more recent traditions such as utilitarianism and Marxism. Yet contractarianism has shown great staying power, and today it is again one of the most influential traditions in political theory, largely due to the work of contemporary American philosopher John Rawls.

All contractarian arguments have a common structure, and it is this common structure that unifies the tradition. At the same time, the tradition is broad enough to permit a wide range of disagreements. The first section of this chapter presents a logical analysis that maps the common structure of contractarian arguments. With this map in hand, we will be better able to understand why the contractarian tradition has often yielded radically different conclusions across a variety of issues in international ethics.

The second and third sections of this chapter illustrate the historical range and diversity of the tradition by discussing some of the most influential classical and contemporary contractarian theorists who have written on international ethics. As we shall see, classical contractarians have been pessimistic about the possibility of international justice, whereas contemporary contractarians emphasize the possibility of international reciprocity and social cooperation.

There are many discussions of ethics and international affairs written from within a particular tradition like political realism or natural law. There are also many books and articles that deal with particular international issues, like military intervention or global justice. But there is no general work that teachers, students, and others interested in international affairs can consult to orient themselves to the full diversity of the major traditions of inquiry and debate concerning the ethics of international relations. The contributors to this book have worked together with the hope that a comprehensive and systematic study of how these ethical traditions approach the basic questions of international relations would help to clarify the disagreements and misunderstandings that characterize current discussions of international ethics.

While no volume short of an encyclopedia could cover the entire range of ethical thinking about international affairs, most of the important voices in the continuing debate on this subject are represented here. The most obvious omissions are the traditions of Islamic, Chinese, and other non-Western civilizations. We did not attempt to examine these partly because the debate about international ethics for many years has been so decisively shaped by Western ideas, partly because we were afraid to take on a task so obviously beyond our abilities. The result is a gap which we hope others will be able to fill in coming years.

Our aim was to produce a basic reference work on international ethics, rather than a collection of individual essays.

Now that we have considered some ethical traditions of major importance for international relations, what fundamental points of convergence and divergence in international ethics can be identified? The present chapter presents a taxonomy of these traditions, using it to gain a synoptic view of the conversation among them and of the implications of this conversation for international affairs. Any method of classification is bound to ignore much of the internal diversity within each tradition as well as many similarities and differences among the traditions. A taxonomy is like a caricature, which may reveal a face more clearly than a portrait but only by selecting and exaggerating a few prominent features. As we proceed we will explain why these traditions do not always fit neatly into the categories to which they have been assigned, but we also invite the reader to refer back to the fuller discussions of each tradition in earlier chapters, as well as to the larger literature on which those chapters are based.

Arguably, the most fundamental distinction between these traditions is whether they link judgments of right and wrong to consequences or to rules. Political realism, utilitarianism, and Marxism belong to the first class of traditions, which assign primary importance to consequences; international law, natural law, Kantianism, and contractarianism belong to the second class of traditions, which emphasize the interpretation of rules. The traditions of biblical argument and of rights also belong here because of the importance they assign to rules.