World politics both creates opportunities for modern governments and imposes constraints on the range of actions that it is feasible for them to pursue. One way to think about these opportunities and constraints is to analyze the operation of the contemporary international political-military system, or the world political economy, and to consider how these systems aﬀect state action. Much of the modern study of international relations is devoted to this task. Yet another perspective on the impact of world politics on states can be gained by asking how perceptive observers of politics have reﬂected on these issues in the past. This approach, which looks to the history of political thought for insights into contemporary international aﬀairs, will be pursued here.2 Although the form and intensity of the constraints and opportunities created by the contemporary world system are diﬀerent from those in earlier centuries, the impact of international politics and economics on state action has been evident for a long time, and has occasioned a great deal of sophisticated commentary.