For the past two decades, the American political imagination has been possessed by a hazardous geopolitical vision; the United States is defined as the dominant power in a closely integrated and 'unipolar' international system. A century of history has done much to encourage this view. Americans have trouble realising how revolutionary and threatening their unipolar vision can appear to others. A world system dominated by one superpower is a bold and radical programme. If successful, it would mean, for the first time in modern history, a world without a general balance of power. Pursuing such a goal implies numerous confrontations with other nations. It antagonises both states that fear decline and those that anticipate improvement. Nevertheless, Americans now find it difficult to entertain any other view of the world. They have been slow to see, let alone accept, what to many others seems a more probable and desirable future - a plural world with several centres of power.