From the standpoint of world history, the collapse of the Soviet Union is unremarkable. That this event took the world by surprise suggests that political analysts, their attention focused on current affairs, can overlook underlying trends and countertrends that eventually make even dramatic events seem secondary. When trends and countertrends are in equilibrium, they generate an illusion of stability. But in the long run, the possibility of disequilibrium approaches certainty and the result is discontinuity.

Terry Nardin’s chapter grows out of an experiment in cross-cultural teaching that has flourished at the Yale-NUS College in Singapore. The program crosses the civilizational boundaries that often define the way political theory is taught and refuses the usual distinction between “Western” and “non-Western” thought. This distinction privileges European thought, throwing the rest of the world into a residual category, obscuring the fact that the rise of “the West” brought much of the world under the dominating rule of Europeans. Drawing on ancient and modern texts from India, China, and the Islamic world as well as from Europe, the course combines the close reading of both political and philosophical texts. By drawing on a wider range of texts than is usual in political theory courses, it invites students and teachers to explore a diversity of genres and their associated contexts, presuppositions, and reverberations. It addresses disputes about canons, relevance, translations, and expertise, inviting students to engage with a broad intellectual inheritance. It illustrates how faculty can educate one another as they teach all the students in a liberal arts college how to transcend parochialism by sharpening their capacities for philosophical and political reasoning.

Despite repeated claims during the past century that the international legal order has been radically transformed, the contours of that order are in many ways the same in 2019 as they were in 1919. New laws govern international institutions, human rights, trade, and the environment and new institutions have emerged that affect how international law is interpreted and applied. War has lost legitimacy as a tool of foreign policy and individual responsibility for aggression and crimes against humanity has been affirmed. Yet these changes build on ideas and practices that may have been rudimentary but were not absent a century ago. Underlying them are persistent differences involving a shifting cast of old and new states as well as differences between local and universal ideals and between instrumental and noninstrumental conceptions of law. The traditional understanding of state sovereignty on which the international legal order rests has been qualified but not discarded, and its persistence confirms that the system it orders remains a system of states.

What should be done when a massacre or similar atrocity occurs in a country other than one's own? The suggestion that other countries should halt the atrocity, using force if necessary, yields the idea of humanitarian intervention. The moral principle underlying that doctrine is not hard to grasp. When human lives are threatened by violence, those who are able to resist the violence and rescue the victims should intervene, if they can do so by morally permissible means and without imposing disproportionate costs. The rationale for intervening is strongest when violence rises to the level of so‐called “crimes against humanity,” an expression adopted for the trial of German leaders at Nuremberg in 1945 to cover large‐scale violence by a government against its own people. Because it is in tension with the idea of state sovereignty, humanitarian intervention has an insecure place in international law and is problematic on practical grounds as well, but that tension has only fueled debate on the circumstances in which forcible interference by one state in the territory of another, or by the international community acting collectively, is justified.

The tradition of political realism denies the relevance of morality to politics and asserts the value of prudence. The new realists in political theory repeat these claims in the context of criticising a style of political theorising they identify with Rawls and Kant. Some affirm the importance of experience and judgment, echoing an earlier generation of political theorists, including Oakeshott and Arendt. Others locate the distinctive character of politics in the problem of establishing order and legitimising it, and because they are moral sceptics they treat legitimacy as contextual and plural. But arguments about legitimacy must address the difference between governing people and dominating them. The new realists therefore find themselves encountering the question of justice, from which their tradition has tried without success to distance itself. To show that questions of order and justice are related, I briefly consider Kant's political thought. Like the new realists, Kant treats politics as distinct from ethics and looks for principles of legitimacy that are internal to political order. Instead of making Kant a target for criticism, the new realists could draw on his insights to strengthen their own account of the autonomy of politics. Doing so would also strengthen their case against the simplistic moralising of academic political philosophy and further illuminate the contribution of realism to political thought.

The history of international thought has traditionally focused on a limited number of canonical texts. Such an approach now seems both naive and parochial. International Relations scholars often read their own ideas into these texts instead of getting ideas from them – ideas that if properly understood have the potential to undermine theirs. By ignoring non-canonical texts, we overlook resources that are not only necessary to establish the historical contexts of canonical writings but that can also help theorists of International Relations to understand their subject better. Judgements of what is and is not canonical are in any case themselves context-bound and contestable. Intellectual history can help us understand how the International Relations canon was constructed and for what purposes. It can also counter the abstractions of theory by reminding us not only that theories are abstractions from the activities of people living in particular times and places but also that our own theories are embedded in historicity. In these and other ways, paying attention to intellectual history expands the repertoire of ideas on which International Relations theorists can draw and against which they can measure their conclusions. The articles in this issue illustrate these points in relation to a wide range of texts and contexts. They suggest that whether one approaches international relations from the angle of description, explanation, policy or ethics, knowing how past thinkers have understood the subject can lead to better informed and more robust scholarship.

Kant's primary concern in writing on international relations is how to achieve 'justice' (Recht) between states. This means that instead of reading Kant as a theorist of peace or world government, as IR theorists have usually done, he is better read as a theorist international justice. His view of justice, which identifies it with a legal order that respects freedom as independence or nondomination, is broadly republican. But he equivocates on the possibility of justice at the international level, and this narrows what is usually seen as a wide gap between Kant's thought and political realism. The paradox his uncertainty reveals is that it is wrong for states to remain in a lawless condition yet impossible for them to escape it so long as they remain independent. An international order cannot generate genuine law because there are no institutions to make, interpret, or enforce it. This means that states are entitled to determine their own foreign affairs. The gap between sovereignty and justice cannot be closed so long as these ideas are defined as they are within the state. The problem is not that a full, secure, and nonvoluntary system of justice that preserves the sovereignty of states is contingently unlikely. It is conceptually impossible. This conclusion poses a challenge to current theories of global justice.

Michael Walzer’s Just and Unjust Wars remains the standard account of just war theory despite the criticism it has received. Much of that criticism denies the political character of just war discourse by substituting general moral principles for principles generated in reflecting on the use of military force. It challenges Walzer’s view of the relationship between morality and politics and his conclusions about the moral standing of states, the moral equality of soldiers, the moral basis of humanitarian intervention, and the limits of morality in emergencies. Instead of providing a foundational argument, the book reconstructs a tradition of discourse that transcends particular contexts because of the range of historical experience on which it draws. The critics raise genuine issues but their objections do not undermine the book’s argument. That argument stands in a complex relationship with political realism, which it rejects in some ways and embraces in others.

Summary The transmission of ideas about sovereignty and its related practices from one time, place, or intellectual context to another is sometimes characterised as a process of ‘diffusion’ or even ‘contagion’. Intellectual historians may use such metaphors but the explanations they provide are historical, not scientific. Sovereignty was transmitted when European states brought their forms of government to other peoples and when those peoples embraced such forms in declaring their independence from imperial rule. It was also transmitted when the idea of sovereignty was itself transformed in the course of these and other historical passages. In Foundations of Modern International Thought, David Armitage explores some of these historical passages, the outcome of which he sees as the world of sovereign states that defines the modern period and the disappearance of which would signal its end. In doing so, he illuminates the larger enterprise of writing the history of international thought or, as he prefers to call it, international intellectual history, inviting reflection on its relationship to other kinds of historical inquiry and the opportunities and dangers it poses.

The word ‘rationality’ and its cognates, like ‘reason’, have multiple contexts and connotations. The rationality of calculation (as in ‘rational man’) can be contrasted with the rationality of inte...

The expression ‘theory and practice’ implies a separation between the two, even when that separation is denied. Political theorists are divided on the question of their relationship, some regretting the abstraction of theory and its consequent irrelevance to practical discourse and action, others insisting that no theory is without practical biases or implications. Oakeshott's contribution has been to suggest that theory and practice – or, more exactly, the activities those words identify, theorizing, and doing – are conceptually distinct. Much can be learned about the vocation of political theorist, in contrast to that of the citizen or politician, by distinguishing theory and theorizing from practice and doing. Whether political theorizing emerges as an autonomous activity only when it is distinguished from political activity and whether this autonomy should be cultivated or rejected are questions that invite continued debate.

The 5th edition of this best-selling textbook provides a systematic and comprehensive introduction to the main theoretical approaches in the study of international relations. While maintaining focus o