The September 11 strikes continue to profoundly influence American foreign and national security policy choices.

This is despite the fact that the events of that day did not significantly alter the physical realities facing America. The loss of life from these criminal acts was tragic, but modest, for a society as large as America's. The economic costs, too, were modest. Nor did the attacks reveal any substantial American economic, political, or military vulnerability, or undermine America's ability to defend itself or to act on the world stage. In terms of power and interest, nothing of significance changed.

What September 11 did change however was Americans' mental landscape. The day created a new mountain that Americans needed somehow to fit into their individual and collective cognitive maps. For those who would be hard-pressed to name the seven continents, as much as for those who could correctly name the capital of Kyrgyzstan or the three largest bodies of water in Burkina Faso, September 11 created an irrefutable, inescapable Mount Everest of a mental cartographic fact.

Neither as individuals nor as societies do we deal with the world as it is. Rather, we deal with the world as we understand it. Our understanding is shaped by our own cognitive limitations and by the social—that is, collective—process by which we acquire knowledge and assign meaning. Because of the shock value, the destruction of the twin towers and the attack on the Pentagon have forced changes in how Americans construct their understanding, or mental map, of international politics, as well as what constitutes or is necessary to ensure the security of the American people and the American republic.

This impact is both individual and collective. The September 11 images change both the stories Americans tell themselves and the stories they tell each other (or at least tell with any hope of shared understanding and comprehension). Even were it possible for an American leader of the current generation to explain America's world without also explaining the meaning of September 11, such an explanation would lack political and cultural resonance with the larger American public.

This in no way suggests that the September 11 attacks set American foreign and national security policy off on some deterministic path. While the memory of September 11 constrains the way Americans can imagine and talk to each other about the world, and empowers some narratives at the expense of others, there are nonetheless a wide range of meanings Americans can give the events of that day and a wide range of ways they can, as a consequence, construct their understanding of the world and America's role in it.

Looking back over the last 10 years of American foreign policy, and looking at the pressing decisions now confronting American decision-makers, it is easy to become wrapped up in blow-by-blow accounts and "could-have, should-have, would-have" arguments about the reasons for and the wisdom of specific decisions. But for just a few minutes—for as long as it takes to read this essay—let us resist this temptation. Let us think about the larger forces shaping American foreign policy, and about how the events of September 11 may have interacted with those forces.

Let us start with the observation that ideas matter. As John Maynard Keynes once famously put it: "Ideas ... both when they are right and when they are wrong, are more powerful than is commonly understood. Indeed the world is ruled by little else .... Soon or late, it is ideas, not vested interests, which are dangerous for good or evil."

To understand American foreign policy for the last 10 years, and to guess where it will go in the foreseeable future, it is necessary to understand the ideas that are shaping it. This task requires us to recognise that ideas are contested—that they are weighed both in individual minds and in collective discussion—to see which of the proffered alternative accounts or maps is most useful in making sense of the complexities of life; which is most pleasing aesthetically; and which offers the best prospect of defending that most vulnerable of our human and societal organs, our individual and collective egos.

This task also requires that we recognise that ideas are necessarily organised into interconnected belief systems. Our ideas need to be, at least to some minimum degree, consistent with one another. Any definition of who "we" are implies who is not "we" and vice versa. Any definition of what makes us "us", or of what is the essence of "us", implies what threatens "us"—and, again, vice versa. It is not simply that any collective group is known by its enemies. It is that, in a real sense, it is defined by how it defines its enemies—and, once again, vice versa.

Any vision of America's role in the world will—because of its foundational assumptions about who "we" are and what threatens us inherent in that vision—have sweeping implications for a wide array of domestic and social policies. Conversely, any vision of domestic tranquillity will, for the same reason, have sweeping implications for the sorts of foreign policy that are conceivable. For example, it is hard to argue that September 11 demonstrated the fundamental hostility of non-Western cultures to America without also implicitly arguing that multiculturalism within American society—at least potentially—poses a threat to American identity or to the survival of a distinctly "American" polity.

What all this is to argue, of course, is that competing visions of the world and of America's place in it are deeply embedded in fundamental debates about the nature of American identity. Who is an "American" and what makes them one? What threat do "they" pose to "us"? What behaviour toward "them" is justified, and what behaviour by us would violate the essence of "us"? These are not simple questions, nor do they have simple answers.

I would suggest that what we are witnessing today is a debate in America about the nature of America—that is, about what it means to be "American"—and, by implication, a debate about America's role in the world. September 11 did not create this debate. September 11 did not even spark this particular round in what in fact has been a recurring debate in American history.

Every imagined community—and a nation is an imagined community—relies on stories we tell ourselves about who "we" are; what makes us one people; why we should be willing to make sacrifices for each other; what threatens "us" and what is right and necessary to do to the "other" who lives in our midst or outside our borders. Periodically, however, these stories cease to make sense. Economic changes (for example, the closing of the frontier, the industrial revolution, movement from an industrial economy to a post-industrial one), demographic changes, social changes, major external changes (the rise and fall of Nazi Germany and of the Soviet Union), and a variety of other systemic shocks can render the existing constructional myth nonfunctional and make it necessary to craft a new one.

Perhaps the paradigmatic example of this in American history came in the 1890s, when the realities of industrialisation, urbanisation, eastern and southern European immigration, the emergence of a proletariat, and the challenges of wrapping up post-Civil War reconstruction all combined to make unworkable what was then the dominant definition of "Americanness". This was that Americans were defined by and made distinct from the "other" by both their culture of political liberty and their status as economically self-sufficient yeoman, beholden to no one and therefore able to enter into a foundational social compact as equals. The new definition of "American" successfully pressed by the progressives defined American identity in civic, rather than cultural terms: anyone who was a loyal citizen of the American state was a member in good standing of the American nation.

What the 1890s example illustrates is that changes in how a people define themselves are of enormous consequence. In the 1890s, by creating a new civic-based notion of American identity and for the first time placing the state at the very centre of American identity, the progressives not only began the development of new, odd rituals, such as displaying and saluting the flag, saying the pledge of allegiance, singing the national anthem, and distinguishing between legal and illegal immigrants, they also created a process of identity-building in which the manifestations or embodiments of the state power took on symbolic importance even in the absence of "real" significance.

In the second half of the 20th century, the emphasis shifted to issues such as being the first state to send a dog or a man into space, or the first state to reach the moon, or the state with the greatest number or largest nuclear missiles, or the state collecting the greatest number of Olympic medals. In the 1890s, having a state worthy of totemic honour meant having a state with a world-class Navy, and a state able to compete effectively with the great imperial powers for prestige. And onto the world stage the American state went, to prove itself worthy of the American people it defined.

With the rise of a post-industrial economy, the emergence of substantial immigration pressures, and the end of the Cold War, Americans again are struggling to find a commonly shared answer to the question of what makes "us" a single community. Are Americans a single people because of a common set of values and cultural institutions? Is a multicultural "rainbow" America possible? Or are Americans a single people by dint of citizenship?

September 11 did not put these questions on the table. They were already there. Presumably the late Samuel Huntington would have written his provocative book whether al Qaeda had attacked or not. Who Are We? The Challenges to America's National Identity posited that Hispanic immigrants, because of their different values and culture, posed a threat to the preservation of American identity. But what September 11 did was to clarify and yes, to complicate, this discussion.

Whatever inner clarity he may have had regarding the larger questions of American identity, American values, and the centrality of American political culture—and this inner clarity may have been considerable—George W. Bush entered the White House without any clearly articulated vision of what this identity implied for America's relationship with the outside world. September 11, of course, changed that.

What was clear, given the Bush mental framework, was that Islamic fundamentalists attacked the United States because they hated "us". They attacked us not because they were angered by particular American actions or because they sought change in particular American foreign policy, but because they hated our values and our culture—that is, because they hated what Bush identified as the very essence of "us", the very things that define "us" as a people and community. This hatred was deep and fundamental. It existed because of the superiority of our values and culture, and because the September 11 terrorists understood that this superiority threatened the survival of their values and culture. Only by tyrannising and terrorising their people and only by destroying "us" could they hope to survive.

President Bush saw a millennial moment in climbing the new mountain that September 11 had left on the mental map. It was a moment when American values and American culture—not defined by McDonalds, Coca-Cola and American-style football, but by American visions of liberal democracy, limited government, private property, separation of church and state, and a social compact willingly entered into by free individuals—could emerge triumphant on the world stage, beginning a new era of human history.

The United States would, he announced, "use this moment of opportunity to extend the benefits of freedom across the globe". Unparalleled and unchallenged American power would be used to rid the world of tyrants and terrorism. These gone, liberty would emerge, and this liberty would fundamentally alter the character of global political life. Sovereignty and national identities might remain, but under the protecting aegis of American (military) power and with the triumph of the political values and political culture that America embodied, we would "have our best chance since the rise of the nation-state in the 17th century to build a world where the great powers compete in peace instead of prepare for war".

One can and should complain, as I have, about the fundamental flaws in this vision—that ridding the world of tyrants and terrorism is a long-term process of social change, not a matter of military strikes; that liberal democracy is a mindset and the product of organic cultural development, not a set of institutions that will spring up inevitably wherever tyrants and terrorists are removed; that, whatever their benefits, human freedom and liberal democracy may not be an absolute guarantee that great powers will compete in peace, given the still imperfect character of human nature and human institutions; and that conducting this sort of global crusade may well threaten that fragile flower that is America's liberal democratic republic. Such a vision would certainly strain relations with friends and allies, and would be likely to set back rather than to advance the organic growth around the world of the values and institutions Americans cherish.

But however wrong-headed the Bush vision and the policies that flowed from it—and, again, let me stress that I personally believe that they were deeply, profoundly, and catastrophically wrong-headed—it is necessary to acknowledge that there is a complex and internally consistent mental map here. Starting with a core belief that Americans are defined by their values and by their political culture, it follows that these values and this culture must be regarded as superior to any other, and that these values and this culture, and therefore "America" itself, is threatened by those individuals and political groups who deny the universality of these values and who see in them something profoundly threatening that demands violent resistance.

Given how little seems to have changed in the daily realities of American military involvement around the world, despite the departure of the Bush family from Pennsylvania Avenue and the arrival of the Obamas, one is sorely tempted to conclude, as David Rieff did in his essay (American Review, May 2011), that "the difference between presidents Bush and Obama on the key questions of foreign policy boil down almost exclusively to rhetorical and cosmetic exercises in pandering to their respective groups of core voters". This observation makes the very point it misses however. The rhetoric is different, and the rhetoric matters. Rhetoric is an effort to convey ideas, and the underlying ideas of the two presidents are quite different.

What the Bush policy and Obama policy share is a dangerous and wrong-headed willingness to intervene, militarily as well as economically and diplomatically, in a wide variety of nations. But the logic for these interventions is based on quite different mental maps. If one examines the rhetoric, one sees strikingly different visions of America and the world.

For Obama, September 11 did not part the curtain to reveal a great and potentially final battle between good and evil. The September 11 attacks did not reflect a fundamental hatred of American culture and American values. They were not an attack on the American essence that demanded a crusading response. Rather, the attacks were a "vicious attack to justice". They were an unforgettable reminder that violence and viciousness and the capacity for injustice are deeply rooted in human nature; that ever-evolving and ever-improving human institutions—the state being the most important—are needed to elicit the best in humanity and to limit the harm caused by the worst; and that the American state, whatever its flaws, is the embodiment of the American identity and as such must be a force for justice.

The American state's response to the September 11 act of mass murder, Obama argued, was and necessarily had to be the pursuit of justice against those responsible for the "senseless slaughter of our citizens". Justice required both that those responsible be prevented from further attacks—because innocents needed to be protected—and that the guilty be punished. The American state's war against al Qaeda was "to protect our citizens, our friends, and our allies", and the operation to kill bin Laden was necessary "to bring him to justice". By this reasoning, the war in Afghanistan was right and necessary. The war in Iraq was not.

In the same way that for the Bush administration it was the values and political culture of the American people that defined who "we" were, what threatened us, and how "we" must act, for Obama it is the American state as the embodiment of justice that is essential. Law—an attribute of a sovereign state—lies at the core of Obama's definition of who the American people are. That we are bound by a shared law is what makes us a people. For a people to willingly be bound together by a shared law however, that law must be just. Only a just state, one that maintains a rule of law and that respects the rights of its citizens can command allegiance. Only a just state can provide an essence around which a people will freely coalesce.

In his Nobel Prize acceptance speech—a speech well worth careful re-reading—Obama laid out many of these ideas. Most significantly however, he rooted justice and law, and the duty facing the American state to see that justice was done and law enforced, in two distinct traditions.

The first was that of the sovereign, Westphalian state and of the treaties, conventions, and agreements entered into by sovereign states. Military intervention in other states' affairs can be justified, but only when international "laws are flouted" or in the case of "those who violate international laws by brutalising their own people".

The post-World War II Universal Declaration of Human Rights takes on considerable importance in this mental map, establishing as it does a shared—and more importantly, a legal—foundation for holding states accountable for the treatment of their subjects. Westphalian international laws are not self-enforcing, Obama stressed, and while diplomatic and economic sanctions can be powerful tools, they may in the end be insufficient to ensure that commitments are upheld and that justice is done.

"The world must remember that it was not simply international institutions—not just treaties and declarations—that brought stability to a post-World War II world," he said. "Whatever mistakes we have made, the plain fact is this: The United States of America has helped underwrite global security for more than six decades with the blood of our citizens and the strength of our arms."

Obama, however, has also pointed to a second grounding for law and justice: the "just war" tradition. A historic and evolving body of thought with early roots in the writings of St Augustine, the "just war" tradition reasons that because of the imperfect character of human nature and human institutions, the use of violence is at times necessary for the protection of innocent life, the preservation or restoration of just possession of property, and the punishment of wrong-doers. As the president cautioned his international audience: "Make no mistake: Evil does exist in the world. A non-violent movement could not have halted Hitler's armies. Negotiations cannot convince al Qaeda's leaders to lay down their arms. To say that force may sometimes be necessary is not a call to cynicism—it is a recognition of history; the imperfections of man; and the limits of reason."

Of course, "just war" theory not only permits and at times demands the use of violence; it also seeks to limit it. In Obama's account: "Over time, as codes of law sought to control violence within groups, so did philosophers and clerics and statesmen seek to regulate the destructive power of war. The concept of "just war" emerged, suggesting that war is justified only when certain conditions were met: if it is waged as a last resort or in self-defence; if the force used is proportional; and if, whenever possible, civilians are spared from violence."

In many ways, President Obama's legalistic, state-centric interpretation of September 11 and of America's role in the world is far more attractive—and potentially far less dangerous—than Bush's cultural one. It yields a policy that is far more modest in its goals, creates at least the potential for more reasonable bounds on the scope of American military actions, and places a more plausible burden on what Joseph Nye has termed America's "soft power". Frankly, too, given the reality of America's multiculturalism and the deep division within America on the question of what American "values" are (divisions that are internal to ethnic, religious, and linguistic groups as well as to some degree cutting between them), an approach to American foreign policy that is grounded in the notion that what defines Americans is their citizenship in a shared state and adherence to a common set of just laws is more likely to unite Americans than a foreign policy based on the assumption that Americans possess a singular and unique culture, one that is superior to all others.

This said, a critic of President Obama's foreign policy (and I would count myself as one) can nonetheless be appalled by US behaviour around the world. As widely observed, Obama decisions regarding the use of force seem remarkably, and deplorably, consistent with Bush's. Within the legalistic framework for understanding America's role in the world, the Obama Administration has more often than not tilted towards intervention.

The problem arises, I would argue, because of the Obama Administration's misreading of the tradition of justice to which it appeals. Law requires interpretation and given conflicting imperatives, what constitutes justice is not always self-evident. International law, while creating some constraints, still leaves the door open to far more international interventions than it would be wise, prudent, constructive, or, by many standards of judgment, moral to undertake.

Significantly, the Obama Administration here appeals to "just war" theory for guidance. Its reading of this tradition seems to me however, distressingly shallow. The "just war" tradition focuses not simply on just cause, such as self-defence, and on last resort in evaluating the justness of a decision to intervene, and on proportionality and non-combatant immunity in the conduct of war. It also demands answers to hard questions such as the legitimacy of the intervener's presumed authority to act on behalf of the "innocent"; the intervention's prospects for success (measured in terms of protection of innocent life, restoration of property, and punishment of transgressors) and the overall evil and damage that the war is likely to cause relative to the magnitude of the injustice.

These are questions that, if honestly confronted, are likely to lead to far more restraint than has been witnessed of late in America's foreign policy. Beyond legalistic quibbling, what legitimate authority do we possess for our continued political and military intervention in Iraq and Afghanistan, for our half-hearted intervention in the struggle between various tribal, ethnic, and regional groups in Libya, and for our routine military strikes into Pakistan and Yemen? Are these interventions likely to lead to a just and stable outcome? And—without being an apologist for the horrors of the Hussein regime, or for the fundamental abridgements of human rights perpetrated by the Taliban, or the Gaddafi government repression, or the actions of tribal leaders or al Qaeda operatives in Pakistan and Yemen—how confident are we that the casualties, hardships, and long-term political, social, and economic disruption caused by our interventions are better for the people we are saving than the evil that existed before?

These are not rhetorical questions. I am not suggesting that I know the answers. These are serious questions, ones on which serious, thoughtful individuals may disagree. But to invoke "just war" theory without a serious, open discussion of them seems to me to prejudge the answers—and this in itself offends notions of justice.

My concern is not simply that the aggressive use of American military power around the globe is unwise, and likely to be counterproductive to the very goals it seeks. I fear that because it misunderstands what law and justice demand of the American state, and because it attempts to define the American nation precisely in terms of the law and justice of the American state, this policy course drives the American nation itself onto the rocks. Imagined community is more fragile than we care to admit, and more important than we often recognise.

John Quincy Adams was the American secretary of state who most clearly recognised the precious fragility of America, both as a nation and as a liberal democratic republic. For more than three generations, his advice on American foreign policy was a guiding star for decision-makers and a staple of school-house oratory. As a reflection on how to construct American identity and to understand the challenges the world poses to America, his advice warrants careful reading in today's post-September 11 setting: "Wherever the standard of freedom and independence has been or shall be unfurled, there will her heart, her benedictions and her prayers be. But she goes not abroad in search of monsters to destroy .... The fundamental maxims of her policy would insensibly change from liberty to force. The frontlet upon her brows would no longer beam with the ineffable splendour of freedom and independence; but in its stead would soon be substituted an imperial diadem, flashing in false and tarnished lustre the murky radiance of dominion and power. She might become the dictatress of the world: she would be no longer the ruler of her own spirit."