To the delight of late-night television comedians, President George H. W. Bush used to talk incessantly about “prudence,” but in fact the term is a deadly serious watchword for the “realist” school of foreign policy. It was on realist grounds that the elder Bush refused to press on to Baghdad after defeating the Iraqi army in the Gulf War in 1991. However alluring the goal, he said, pursuing it “would have incurred incalculable human and political costs”; he was expressing the kind of unsentimental caution that is realism’s most important characteristic. In contrast, his son, George W. Bush, was arguably among the most idealistic of American presidents. The younger Bush believed that there is but a “single sustainable model for national success: freedom, democracy, and free enterprise”—the kind of universalizing ideological claim that idealists have traditionally embraced. On those grounds, he set out to sweep into Baghdad, depose Saddam Hussein, and compel Iraq to embrace that unique model—an instance of unchecked idealism whose full consequences remain to be seen. President Barack Obama must now strike his own balance between the claims of realism and idealism. But are these ways of thinking about foreign policy as incompatible as they seem?
After the Peace of Westphalia ended Europe’s religious wars in 1648, the principle of sovereignty came to dominate the theory and practice of international relations. Sovereignty was trumps. States had no right to intervene in the internal affairs of other states. Yet no “higher authority,” papal, Protestant, or otherwise, stood above them. Only the ceaseless exercise of power, especially by the weighty “great powers,” might hold contentious states in tenuous equilibrium.