These days, we are having a national debate over the direction of foreign policy. Beyond the obvious difficulties in Iraq and Afghanistan, there is a broader sense that our nation has gone astray. We have become too militaristic, too idealistic, too arrogant; we have become an "empire." Much of the world views us as dangerous. In response, many call for the United States to return to its foreign policy traditions, as if that would provide the answer.

What exactly are those traditions? One tradition is this kind of debate, which we've been having ever since the birth of the nation, when Patrick Henry accused supporters of the Constitution of conspiring to turn the young republic into a "great and mighty empire." Today, we are mightier than Henry could have ever imagined. Yet we prefer to see ourselves in modest terms--as a reluctant hegemon, a status quo power that seeks only ordered stability in the international arena. James Schlesinger captured this perspective several years ago, when he said that Americans have "been thrust into a position of lonely preeminence." The United States, he added, is "a most unusual, not to say odd, country to serve as international leader." If, at times, we venture forth and embroil ourselves in the affairs of others, it is either because we have been attacked or because of the emergence of some dangerous revolutionary force--German Nazism, Japanese imperialism, Soviet communism, radical Islamism. Americans do not choose war; war is thrust upon us. As a recent presidential candidate put it, "The United States of America never goes to war because we want to; we only go to war because we have to. That is the standard of our nation."

But that self-image, with its yearning for some imagined lost innocence, is based on myth. Far from the modest republic that history books often portray, the early United States was an expansionist power from the moment the first pilgrim set foot on the continent; and it did not stop expanding--territorially, commercially, culturally, and geopolitically--over the next four centuries. The United States has never been a status quo power; it has always been a revolutionary one, consistently expanding its participation and influence in the world in ever-widening arcs. The impulse to involve ourselves in the affairs of others is neither a modern phenomenon nor a deviation from the American spirit. It is embedded in the American DNA.

Long before the country's founding, British colonists were busy driving the Native American population off millions of acres of land and almost out of existence. From the 1740s through the 1820s, and then in another burst in the 1840s, Americans expanded relentlessly westward from the Alleghenies to the Ohio Valley and on past the Rocky Mountains to the Pacific, southward into Mexico and Florida, and northward toward Canada--eventually pushing off the continent not only Indians, but the great empires of France, Spain, and Russia as well. (The United Kingdom alone barely managed to defend its foothold in North America.) This often violent territorial expansion was directed not by redneck "Jacksonians" but by eastern gentlemen expansionists like George Washington, Thomas Jefferson, and John Quincy Adams.

It would have been extraordinary had early Americans amassed all this territory and power without really wishing for it. But they did wish for it. With 20 years of peace, Washington predicted in his valedictory, the United States would acquire the power to "bid defiance, in a just cause, to any earthly power whatsoever." Jefferson foresaw a vast "empire of liberty" spreading west, north, and south across the continent. Hamilton believed the United States would, "erelong, assume an attitude correspondent with its great destinies--majestic, efficient, and operative of great things. A noble career lies before it." John Quincy Adams considered the United States "destined by God and nature to be the most populous and powerful people ever combined under one social compact." And Americans' aspirations only grew in intensity over the decades, as national power and influence increased. In the 1850s, William Seward predicted that the United States would become the world's dominant power, "the greatest of existing states, greater than any that has ever existed." A century later, Dean Acheson, present at the creation of a U.S.-dominated world order, would describe the United States as "the locomotive at the head of mankind" and the rest of the world as "the caboose." More recently, Bill Clinton labeled the United States "the world's indispensable nation."

From the beginning, others have seen Americans not as a people who sought ordered stability but as persistent disturbers of the status quo. As the ancient Corinthians said of the Athenians, they were "incapable of either living a quiet life themselves or of allowing anyone else to do so." Nineteenth-century Americans were, in the words of French diplomats, "numerous," "warlike," and an "enemy to be feared." In 1817, John Quincy Adams reported from London, "The universal feeling of Europe in witnessing the gigantic growth of our population and power is that we shall, if united, become a very dangerous member of the society of nations." The United States was dangerous not only because it was expansionist, but also because its liberal republicanism threatened the established conservative order of that era. Austria's Prince Metternich rightly feared what would happen to the "moral force" of Europe's conservative monarchies when "this flood of evil doctrines" was married to the military, economic, and political power Americans seemed destined to acquire.

What Metternich understood, and what others would learn, was that the United States was a nation with almost boundless ambition and a potent sense of national honor, for which it was willing to go to war. It exhibited the kind of spiritedness, and even fierceness, in defense of home, hearth, and belief that the ancient Greeks called thumos. It was an uncommonly impatient nation, often dissatisfied with the way things were, almost always convinced of the possibility of beneficial change and of its own role as a catalyst. It was also a nation with a strong martial tradition. Eighteenth- and nineteenth-century Americans loved peace, but they also believed in the potentially salutary effects of war. "No man in the nation desires peace more than I," Henry Clay declared before the war with Great Britain in 1812. "But I prefer the troubled ocean of war, demanded by the honor and independence of the country, with all its calamities, and desolations, to the tranquil, putrescent pool of ignominious peace." Decades later, Oliver Wendell Holmes Jr., the famed jurist who had fought--and been wounded three times--in the Civil War, observed, "War, when you are at it, is horrible and dull. It is only when time has passed that you see that its message was divine."

Modern Americans don't talk this way anymore, but it is not obvious that we are very different in our attitudes toward war. Our martial tradition has remained remarkably durable, especially when compared with most other democracies in the post-World War II era. From 1989 to 2003, a 14-year period spanning three very different presidencies, the United States deployed large numbers of combat troops or engaged in extended campaigns of aerial bombing and missile attacks on nine different occasions: in Panama (1989), Somalia (1992), Haiti (1994), Bosnia (1995-1996), Kosovo (1999), Afghanistan (2001), and Iraq (1991, 1998, 2003). That is an average of one significant military intervention every 19 months--a greater frequency than at any time in our history. Americans stand almost alone in believing in the utility and even necessity of war as a means of obtaining justice. Surveys commissioned by the German Marshall Fund consistently show that 80 percent of Americans agree with the proposition that "[u]nder some conditions, war is necessary to obtain justice." In France, Germany, Italy, and Spain, less than one-third of the population agrees.

How do we reconcile the gap between our preferred self-image and this historical reality? With difficulty. We are, and have always been, uncomfortable with our power, our ambition, and our willingness to use force to achieve our objectives. What the historian Gordon Wood has called our deeply rooted "republicanism" has always made us suspicious of power, even our own. Our enlightenment liberalism, with its belief in universal rights and self-determination, makes us uncomfortable using our influence, even in what we regard as a good cause, to deprive others of their freedom of action. Our religious conscience makes us look disapprovingly on ambition--both personal and national. Our modern democratic worldview conceives of "honor" as something antiquated and undemocratic. These misgivings rarely stop us from pursuing our goals, any more than our suspicion of wealth stops us from trying to accumulate it. But they do make us reluctant to see ourselves as others see us. Instead, we construct more comforting narratives of our past. Or we create some idealized foreign policy against which to measure our present behavior. We hope that we can either return to the policies of that imagined past or approximate some imagined ideal to recapture our innocence. It is easier than facing the hard truth: America's expansiveness, intrusiveness, and tendency toward political, economic, and strategic dominance are not some aberration from our true nature. That is our nature.

Why are we this way? In many respects, we share characteristics common to all peoples through history. Like others, Americans have sought power to achieve prosperity, independence, and security as well as less tangible goals. As American power increased, so, too, did American ambitions, both noble and venal. Growing power changes nations, just as it changes people. It changes their perceptions of the world and their place in it. It increases their sense of entitlement and reduces their tolerance for obstacles that stand in their way. Power also increases ambition. When Americans acquired the unimaginably vast territory of Louisiana at the dawn of the nineteenth century, doubling the size of their young nation with lands that would take decades to settle, they did not rest content but immediately looked for still more territory beyond their new borders. As one foreign diplomat observed, "Since the Americans have acquired Louisiana, they appear unable to bear any barriers round them."

But, in addition to the common human tendency to seek greater power and influence over one's surroundings, Americans have been driven outward into the world by something else: the potent, revolutionary ideology of liberalism that they adopted at the nation's birth. Indeed, it is probably liberalism, more than any other factor, that has made the United States so energetic, expansive, and intrusive over the course of its history.

Liberalism fueled the prodigious territorial and commercial expansion in the eighteenth and nineteenth centuries that made the United States, first, the dominant power in North America and, then, a world power. It did so by elevating the rights of the individual over the state--by declaring that all people had a right to life, liberty, property, and the pursuit of happiness and by insisting it was the government's primary job to safeguard those rights. American political leaders had little choice but to permit, and sometimes support, territorial and commercial claims made by their citizens, even when those claims encroached on the lands or waters of foreigners. Other eighteenth- and nineteenth-century governments, ruled by absolute monarchs, permitted national expansion when it served personal or dynastic interests--and, like Napoleon in the New World, blocked it when it did not. When the king of England tried to curtail the territorial and commercial expansionism of his Anglo-American subjects, they rebelled and established a government that would not hold them back. In this respect, the most important foreign policy statement in U.S. history was not George Washington's farewell address or the Monroe Doctrine but the Declaration of Independence and the enlightenment ideals it placed at the heart of American nationhood. Putting those ideals into practice was a radical new departure in government, and it inevitably produced a new kind of foreign policy.

Liberalism not only drove territorial and commercial expansion; it also provided an overarching ideological justification for such expansion. By expanding territorially, commercially, politically, and culturally, Americans believed that they were bringing both modern civilization and the "blessings of liberty" to whichever nations they touched in their search for opportunity. As Jefferson told one Indian leader: "We desire above all things, brother, to instruct you in whatever we know ourselves. We wish to learn you all our arts and to make you wise and wealthy." In one form or another, Americans have been making that offer of instruction to peoples around the world ever since.

Americans, from the beginning, measured the world exclusively according to the assumptions of liberalism. These included, above all, a belief in what the Declaration of Independence called the "self-evident" universality of certain basic truths--not only that all men were created equal and endowed by God with inalienable rights, but also that the only legitimate and just governments were those that derived their powers "from the consent of the governed." According to the Declaration, "whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it." Such a worldview does not admit the possibility of alternative truths. Americans, over the centuries, accepted the existence of cultural distinctions that influenced other peoples to rule themselves differently. But they never really accepted the legitimacy of despotic governments, no matter how deeply rooted in culture. As a result, they viewed them as transitory. And so, wherever Americans looked in the world, they saw the possibility and the desirability of change.

The notion of progress is a central tenet of liberalism. More than any other people, Americans have taken a progressive view of history, evaluating other nations according to where they stood on the continuum of progress. The Russians, Theodore Roosevelt believed, were "below the Germans just as the Germans are below us ... [but] we are all treading the same path, some faster, some slower." If Roosevelt's language sounds antiquated, our modern perspective is scarcely different. Although we may disagree among ourselves about the pace of progress, almost all Americans believe that it is both inevitable and desirable. We generally agree on the need to assist other nations in their political and economic development. But development toward what, if not toward the liberal democratic ideal that defines our nationalism? The "great struggle of the epoch," Madison declared in the 1820s, is "between liberty and despotism." Because the rights of man were written "by the hand of the divinity itself," as Hamilton put it, that struggle could ultimately have only one outcome.

It was a short step from that conviction to the belief that the interests of the United States were practically indistinguishable from the interests of the world. "The cause of America is in a great measure the cause of all mankind," Thomas Paine argued at the time of the revolution. Herman Melville would later write that, for Americans, "national selfishness is unbounded philanthropy; for we cannot do a good to America but we give alms to the world." It was another short step to the belief that the United States had a special, even unique, role to play in serving as a catalyst for the evolution of mankind. "The rights asserted by our forefathers were not peculiar to themselves," Seward declared, "they were the common rights of mankind." Therefore, he said, the United States had a duty "to renovate the condition of mankind" and lead the way to "the universal restoration of power to the governed" everywhere in the world. Decades earlier, John Quincy Adams had noted with pride that the United States was the source of ideas that made "the throne of every European monarch rock under him as with the throes of an earthquake." Praising the American Revolution, he exhorted "every individual among the sceptered lords of mankind: 'Go thou and do likewise!'"

A Russian minister, appalled at this "appeal to the nations of Europe to rise against their Governments," noted the hypocrisy of Adams's message, asking, "How about your two million black slaves?" Indeed. The same United States that called for global revolution on behalf of freedom was, throughout its first eight decades, also the world's great defender of racial despotism. The slaveholding South was itself a brutal tyranny, almost totalitarian in its efforts to control the speech and personal behavior of whites as well as blacks. Much of the U.S. territorial expansion in the nineteenth century--including the Mexican War, which garnered today's American Southwest and California--was driven by slaveholders, insisting on new lands to which they could spread their despotic system.

In the end, the violent abolition of slavery in the United States was a defining moment in the country's foreign policy: It strengthened the American tendency toward liberal moralism in foreign affairs. The Northern struggle against slavery, culminating in the Civil War, was America's first moral crusade. The military defeat of the Southern slaveholders was America's first war of ideological conquest. And what followed was America's first attempt at occupation and democratic nation-building (with the same mixed results as later efforts). The effect of the whole struggle was to intensify the American dedication to the universality of rights and to reaffirm the Declaration of Independence, rather than the Constitution with its tacit acceptance of slavery, as the central document of American nationhood. The Civil War fixed in the American mind, or at least in the Northern mind, the idea of the just war--a battle, fought for moral reasons, whose objectives can be achieved only through military action.

Such thinking led to the Spanish-American War of 1898. One of the most popular wars in U.S. history, it enjoyed the support of both political parties, of William Jennings Bryan and Andrew Carnegie, of eastern Brahmin Republicans like Henry Cabot Lodge, radical prairie populists, and labor leaders. Although one would not know it from reading most histories today, the war was motivated primarily by humanitarian concerns. Civil strife in Cuba and the brutal policies of the Spanish government--in particular the herding of the civilian population into "reconcentration" camps--had caused some 300,000 deaths, one-fifth of Cuba's population. Most of the victims were women, children, and the elderly. Lodge and many others argued that the United States had a responsibility to defend the Cuban people against Spanish oppression precisely because it had the power to do so. "Here we stand motionless, a great and powerful country not six hours away from these scenes of useless bloodshed and destruction," he said, imploring that, if the United States "stands for humanity and civilization, we should exercise every influence of our great country to put a stop to that war which is now raging in Cuba and give to that island once more peace, liberty, and independence." The overwhelming majority of the nation agreed. The U.S. intervention put an end to that suffering and saved untold thousands of lives. When John Hay called it a "splendid little war," it was not because of the smashing military victory--Hay was no militarist. It was the lofty purposes and accomplishments of the war that were splendid.

It was also true that the United States had self-interested reasons for going to war: commercial interests in Cuba, as well as the desire to remove Spain from the hemisphere and establish our preeminence in the region. Most of Europe condemned the United States as selfish and aggressive, failing to credit it with humanitarian impulses. Moreover, the war produced some unintended and, for many who idealistically supported it, disillusioning consequences. It led to the acquisition of the Philippines and a most unsplendid war against independence-minded Filipinos. It also produced a well-intentioned, but ultimately disappointing, multiyear occupation of Cuba that would haunt Americans for another century. And it reignited an old debate over the course of U.S. foreign policy--similar to the one that consumes us today.

Now, as then, the projection of U.S. power for liberal purposes faces its share of domestic criticism--warnings against arrogance, hubris, excessive idealism, and "imperialism." Throughout the eighteenth and nineteenth centuries, conservatives in the republican tradition of Patrick Henry worried about the effect at home of expansive policies abroad. They predicted, correctly, that a big foreign policy generally meant a big federal government, which--in their eyes--meant impingements on the rights and freedoms of the individual. The conservatives of the slaveholding South were the great realists of the nineteenth century. They opposed moralism, rightly fearing it would be turned against the institution of slavery. As Jefferson Davis put it, "We are not engaged in a Quixotic fight for the rights of man. Our struggle is for inherited rights. ... We are conservative." At the end of the century, when Americans were enthusiastically pushing across the Pacific, critics like Grover Cleveland's long-forgotten secretary of state, Walter Q. Gresham, warned that "[e]very nation, and especially every strong nation, must sometimes be conscious of an impulse to rush into difficulties that do not concern it, except in a highly imaginary way. To restrain the indulgence of such a propensity is not only the part of wisdom, but a duty we owe to the world as an example of the strength, the moderation, and the beneficence of popular government."

But, just as progressivism and big government have generally triumphed in domestic affairs, so, too, has the liberal approach to the world beyond our shores. Henry failed to defeat the Constitution. Southern realism lost to Northern idealism. The critics of liberal foreign policy--whether conservative, realist, or leftist--have rarely managed to steer the United States on a different course.

The result has been some accomplishments of great historical importance--the defeat of German Nazism, Japanese imperialism, and Soviet communism--as well as some notable failures and disappointments. But it was not as if the successes were the product of a good America and the failures the product of a bad America. They were all the product of the same America. The achievements, as well as the disappointments, derived from the very qualities that often make us queasy: our willingness to accumulate and use power; our ambition and sense of honor; our spiritedness in defense of both our interests and our principles; our dissatisfaction with the status quo; our belief in the possibility of change. And, throughout, whether succeeding or failing, we have remained a "dangerous" nation in many senses--dangerous to tyrannies, dangerous to those who do not want our particular brand of liberalism, dangerous to those who fear our martial spirit and our thumos, dangerous to those, including Americans, who would prefer an international order not built around a dominant and often domineering United States.

Whether a different kind of international system or a different kind of America would be preferable is a debate worth having. But let us have this debate about our future without illusions about our past.

Robert Kagan is a contributing editor at The New Republic and the author of Dangerous Nation: America's Place in the World from its Earliest Days to the Dawn of the Twentieth Century.