I thought about and wrote this paper over a long period of time, during which I benefited from the writings of many people and discussions with so many others that I can not possibly recognize them all. Some are mentioned in footnotes; to the others I apologize and thank each one of you. I owe special thanks to the editors of the volume for inviting me to present my preliminary thoughts at a seminar at Princeton University in November 1991. The Council on Foreign Relations, the Institute on Global Conflict and Cooperation, and the Center for German and European Studies at the University of California at Berkeley provided needed research support.