In Washington these days, people talk a lot about the collapse of the bipartisan foreign policy consensus that existed during the Cold War. But however bitter today's disputes are about Iraq or the prosecution of the so-called global war on terrorism, there is one bedrock assumption about foreign policy that remains truly bipartisan: The United States will remain the sole superpower, and the guarantor of international security and global trade, for the foreseeable future.
This assumption rests on two interrelated beliefs.
The first is that because no country or alliance of states has shown any great desire to challenge U.S. pre-eminence - or demonstrated the means of doing so - no country is going to. China's interests are regional at most, the argument goes, and the European Union is too divided, too unwilling or too weak to rebuild its once-formidable military machine. As for Russia, believers in the durability of a world order anchored in Washington insist that its declining population and excessive reliance on its energy wealth will in the long run preclude it from playing a central role in global affairs.
The second is that the world needs the United States and appreciates the role it plays. If there have been no serious challenges to American hegemony to date, it is asserted, that is because the United States provides what are referred to by foreign policy analysts as "global goods": It maintains political and economic stability around the world, it guarantees a democratic capitalist world order and, by virtue of its unparalleled military strength, it acts as a world policeman of last resort.
Whatever the merits of this case, surely it is significant that it is most often made by U.S. policy analysts and government officials, from Democrat Barack Obama to Republican Rudolph W. Giuliani, and from the conservative policy analyst Robert Kagan to the liberal academic Michael Mandelbaum. All seem convinced that the world works best with the United States at the helm, and that without American leadership, the world would soon become more dangerous and anarchic, and less prosperous.
But what if the Americans who hold these beliefs are not, in fact, clear-eyed observers of the world scene stripped of its anti-imperial mystifications? Instead, what if they are people who have fallen for the same self-delusion that the British ruling class entertained before World War I, which was that their empire was so essential to world stability and, at least when compared with the alternatives and with empires past, so just that its hegemony could and would weather all challenges?
The historical record shows that imperial moments are, in fact, fleeting, and that hegemony has a shorter and shorter shelf life. The Roman Empire lasted over 700 years (more than a millennium if you count the Byzantines). The British Empire lasted a little more than 300 years in India and less than a century in much of Africa. The economic challenges facing the United States at least suggest that America's time as sole superpower could be shorter still.
Americans, who grow up believing in their country's exceptionalism (which in foreign policy terms often seems to mean not believing that the historical constraints that apply to other nations apply to the United States), are not predisposed to believe that American predominance could possibly be coming to an end. And yet it seems more like wishful thinking than rational analysis to believe that the United States - which in the coming decades will certainly have to adapt to a multipolar world in geo-economic terms, as China and India reoccupy the central place in the global economy that they had 500 years ago - can continue indefinitely to play a hegemonic role.
The truth is that whether it is imperial Rome, imperial Spain or imperial Britain, economic strength and political strength have always gone together. Because no one denies that the United States will decline in comparative terms economically, the only way one can believe that geopolitics will not also become multipolar is to believe that America is somehow exempt from what seems one of history's few ironclad laws. And that is not analysis; that is faith.
The war in Iraq has demonstrated the limits of even America's vaunted military strength - the one arena in which the United States is likely to remain supreme for decades to come. In an era of asymmetric threats, conventional military power is rapidly becoming an anachronistic measure of a country's strength.
None of this is to say that the United States will not continue to be one of the most important powers - only that its days of first dictating and then guaranteeing the rules are numbered in an era in which it has become a debtor nation.
For the moment, the United States is the sole superpower. But instead of deluding ourselves that we will go on that way into the indeterminate future, an intelligently self-interested foreign policy would have us do everything in our power to shape, according to our most urgent priorities, the international rules that will govern relations among states after the American moment has passed - as it inevitably will.
David Rieff's books include "At the Point of a Gun: Democratic Dreams and Armed Intervention." This article originally appeared in the Los Angeles Times.