Two intellectuals who debated this question both favor a policy of global intervention for the United States but disagreed about what it means and how to characterize that role.
A recent overflow crowd at the American Enterprise Institute heard them address the motion: "The United States is, and should be, an empire." The debate was sponsored by the New Atlantic Initiative.
Niall Ferguson of New York University's Stern School of Business embraced the "e" word, but reframed the proposition. "The motion should be that the United States is an empire, acknowledge the fact, and do the job properly," he said.
Ferguson is a senior research fellow at Jesus College, Oxford. In his most recent book, "Empire: The Rise and Demise of the British World Order and the Lessons for Global Power" (2003), he argues that the United States -like Britain before it - should sustain a world order based on trade, economic assistance, investment, and military power.
Robert Kagan, a senior associate of the Carnegie Endowment for International Peace, argued against the motion. He said that to equate empire with "great power," as Ferguson does, is to define the word out of existence.
Although Kagan said he sought to avoid "a definitional argument," much of the disagreement between the two scholars was over semantics, with Ferguson defining "empire" broadly and Kagan restricting the word to its more traditional interpretation.
Kagan is author of "Of Paradise and Power: America and Europe in the New World Order" (2003).
Ferguson presented his argument first.
"Not all Europeans come from Venus," he began, adding that he offers his criticisms of the United States "from the vantage point of a passionate pro-American." In fact, the Oxford historian sees the U.S. federal structure as worthy of emulation around the globe.
Ferguson resigned himself to losing the debate before it began, "so profound is the antipathy of the typical American to the word empire."
Americans' creation myth is one of shaking off of empire. But having once been a colony does not preclude becoming an empire. "It's easy to forget that England had once been a colony of the Roman Empire," he said.
Ferguson warned against what he considers too narrow a definition of empire that would exclude the United States - i.e., as having colonies or subject populations without direct legislative representation under direct American rule. An empire doesn't necessarily preclude the existence of representative institutions in its overseas dominions, he said.
In the broader definition he favors, the United States ranks as one of the most powerful empires in all history.
"Militarily, economically and culturally, the United States has all the attributes of past empires," he said. U.S. bases exist in almost two-thirds of the world's countries. The United States accounts for roughly 40 percent of the world's military spending. No empire has ever been as powerful as the United States in its ability to project its power around the world and into space.
The U.S. share of the world's economic output is more than 30 percent, Ferguson said -- three times larger in its share of global output than Great Britain at the height of the Industrial Revolution.
And the United States has the ability to make its cultural values attractive to other peoples.
But Americans refuse to believe in the existence of their empire. Ferguson said it is good for public officials to maintain this position. However, academics and intellectuals can afford to tell the truth.
"This is an empire in denial," he said. "One that refuses to acknowledge its own existence." For Ferguson, this state of denial constitutes the problem. He said that despite its power the United States has been one of the least successful empires in history. In its foreign interventions, it has failed far more often than it has succeeded in leaving behind its democratic institutions.
Ferguson listed three fundamental problems with a hyperpower that refuses to recognize its own imperial role in the world.
First, he said, all American military interventions since the 1960s have been conducted on the false premise that U.S. involvement could be concluded in a matter of months or at most a few years. We are seeing the results of this error in Iraq and Afghanistan, he said. All empires are based less on force than on the willingness of indigenous elites to collaborate in the creation of stable institutions. "Why would you collaborate with an occupying power that says it's about to leave?"
Ferguson said that since the administration of Woodrow Wilson, U.S. policy has been based on the belief that "you shoot people, and then you hold elections, and then you go home. And it doesn't work."
Second, an empire in denial doesn't spend enough money on its imperial undertakings. In Iraq, for example, much money is being spent to support the military operations, but very little on reconstructing the Iraqi economy. In Afghanistan, only a pittance has been spent trying to support the government the United States created there. "You cannot run an empire on a shoestring." He urged more funding for the occupation of Iraq and discouraged tax cuts.
Third, an empire in denial thinks it can operate unilaterally. But an empire requires cooperation with other powers. It cannot be based on isolation. The United States needs the European Union nations, which spend roughly three times as much on foreign aid as does Washington.
"The United States has long been an empire," Ferguson said. "It should be an empire. But it's a colossus with an attention deficit disorder practicing cut-price colonization."
Kagan took the podium and said it is important to make the distinction between "actual empire" and "mere colossal power."
He rejected Ferguson's assertion that the United States has been unsuccessful in its use of hegemonic power. "It has been the most successful global power in history," Kagan said.
He cited the U.S. role in maintaining world peace through a frightening Cold War and successful "nation building" in the most important countries of Europe and Asia.
Kagan argued that the Cold War ended peacefully because the United States was decidedly not imperial. "More specifically, the leaders of the Soviet Union knew that the leaders of the United States were not imperial and that the Soviet Union would in fact benefit from surrender rather than be taken over in classic imperial fashion."
Kagan said he and Ferguson share "enormous common ground" regarding America's key role in maintaining world order, both in its own interests and the interests of humanity.
He added that he is acutely aware of the problems America has had in playing that role caused by the inconstancy of its foreign policy, its short attention span and inefficiency.
Kagan said both he and Ferguson dispute the isolationist "myth of Edenic innocence" that existed at the founding of the United States.
"Americans were very enthusiastic imperialists before they became Americans," Kagan said. Benjamin Franklin and others hoped that the seat of the British Empire would eventually move from London to the American continent. The United States was at its most imperial in the early years of the republic, Kagan said, with enormous acquisition of territory by purchase, persuasion, blackmail or force.
When the United States was dominated by slave interests, it very much acted as an imperial power.
Kagan said the Civil War turned America away from the imperialist idea. As the United States moved through the late 19th century and into the 20th century, it became less imperialist, not more. The essence of American foreign policy is that the expansion of U.S. power is good for America and the world. "The irony is that as American imperialism diminished, American power grew. This is the great source of confusion that I believe Niall (Ferguson) has also succumbed to."
It is not true that America is an imperial power because it has garrisons overseas, or because it has influence abroad, or because it exports its culture Kagan said.
"I don't think we have to accept this kind of definition. I think we can tell the difference between a great power, and even the world's greatest power, and a country that seeks to exercise dominion over others - which is the true definition of empire."
"America is not an empire, even though it has exercised more influence in some respects than any empire has."
Kagan acknowledged that the U.S. proclivity to leave foreign lands has led to great difficulties and failures. "But ultimately if you look at the great success of American foreign policy, it is precisely because everyone has always known that the United States did not intend to exercise imperial control that America's rising hegemony in the world was so widely accepted and so little feared.
"What would the world think of a power America's size that had an imperial design, that was expanding to take control of others for its own purposes?" Kagan asked.
He said those who use the term empire are hopeful that they can get Americans to accept their responsibilities as citizens of the world's leading power. "But in any real sense, does that seem to be plausible? Does anyone think the American people would rally behind the banner of empire?
"The American people and the vast majority of the world's people do not accept empire as the purpose of foreign policy. The effort to find an easy answer to this problem needs to be avoided. The truth is we must continue to engage in the difficult task of constantly arguing the case for why the United States must remain engaged in the world - why it must have more constancy."
In his rejoinder, Ferguson said his debate with Kagan was not so much a question of definition as one of euphemism.
As if playfully conjugating a verb, he said: "I am a hegemon. You are a power. He is an empire. We are nation-building. You are occupying. They are colonizing."
A hegemon that exercises great power in a unipolar world is in fact an empire, Ferguson insisted.
The droll historian got a big laugh from the packed house by saying: "There is no surer sign that you are an empire than to invade Afghanistan."
Ferguson said a global power cannot invade Iraq and occupy Baghdad and pretend it's not an empire, the altruism of its intentions notwithstanding. British empire-builders made altruistic arguments throughout the 19th century. They saw themselves, in the words of David Livingston, as the bearers of Christianity, commerce and civilization.
"It is a distinguishing feature of both the great Anglophone empires that they insist that they are acting in the best interests of the people they subjugate," Ferguson concluded.
Kagan acknowledged that Ferguson's remark about Afghanistan was a good joke, but he implicitly reminded those present that America invaded that country to prevent it from being used as a base from which attacks against the United States, its embassies, and its Navy were planned and launched.
"We really haven't forgotten why the United States invaded Afghanistan, have we?" he asked. "I think the reasons for the American invasion of Afghanistan are somewhat different from the reasons for the British and the Russian invasions of Afghanistan. In fact, in some respects, they may be all the difference. ... These difference are important and not to be laughed away."
The United States couldn't bring around continental Europe, Turkey, or Saudi Arabia in supporting the war against Saddam Hussein. "What kind of empire is that?" Kagan asked.