Yet despite these unavoidable uncertainties, asking how 9/11 might be seen in 2101 is still a useful exercise because it helps place the event within a broader geopolitical context. I can think of at least two broad and radically different possibilities (plus a third wild card). Ironically, which possibility comes closest to the truth has little to do with what occurred on that sunny Tuesday morning 20 years ago and much more to do with what has happened in response to it. Moreover, what happens in the next few decades is going to determine how 9/11 is remembered a century later.

It is impossible to predict exactly how 9/11 is going to be interpreted, of course; perhaps all we can say with confidence is that the meaning attached to it will vary depending on who is doing the interpreting. Americans will view 9/11 differently than Afghans, Iraqis, Saudis, or Europeans, and for many people around the world it is likely to be little more than a historical footnote. What looms large in our consciousness today is often irrelevant to others and especially once memories fade and more recent events command our attention.

How will 9/11 be remembered on its hundredth anniversary? Will it be seen as a dramatic but ultimately minor tragedy or as a turning point that altered the United States and the trajectory of world politics in fundamental ways? Will future generations see that day as a telling reflection of underlying trends, the catalyst for a series of catastrophic foreign-policy blunders, or as an isolated one-off event whose long-term impact was relatively modest?

How will 9/11 be remembered on its hundredth anniversary? Will it be seen as a dramatic but ultimately minor tragedy or as a turning point that altered the United States and the trajectory of world politics in fundamental ways? Will future generations see that day as a telling reflection of underlying trends, the catalyst for a series of catastrophic foreign-policy blunders, or as an isolated one-off event whose long-term impact was relatively modest?

It is impossible to predict exactly how 9/11 is going to be interpreted, of course; perhaps all we can say with confidence is that the meaning attached to it will vary depending on who is doing the interpreting. Americans will view 9/11 differently than Afghans, Iraqis, Saudis, or Europeans, and for many people around the world it is likely to be little more than a historical footnote. What looms large in our consciousness today is often irrelevant to others and especially once memories fade and more recent events command our attention.

Yet despite these unavoidable uncertainties, asking how 9/11 might be seen in 2101 is still a useful exercise because it helps place the event within a broader geopolitical context. I can think of at least two broad and radically different possibilities (plus a third wild card). Ironically, which possibility comes closest to the truth has little to do with what occurred on that sunny Tuesday morning 20 years ago and much more to do with what has happened in response to it. Moreover, what happens in the next few decades is going to determine how 9/11 is remembered a century later.

Option 1: Xi Jinping gets his wish

Imagine, for a moment, that Chinese President Xi Jinping’s fondest hopes are fully realized and that the next 80 years become known as the “Chinese Century.” In this scenario, China’s economic ascendance continues apace, and it eventually casts as large a shadow as the United States did during most of the Cold War and especially the unipolar moment. China will not become a global hegemon exerting authoritative sway over every nation or dictating all world events, but it could control the commanding heights of key technologies, exercise de facto hegemony in its immediate neighborhood, and have more influence on what other states do than any other power. It would have the loudest voice in most international institutions and the greatest ability to define the rules shaping most international interactions.

Were this scenario to occur, then 9/11 will be seen as a critical event that accelerated America’s decline. Not because of the damage suffered in the attacks on the World Trade Center and Pentagon or even the short-term economic consequences (from which the United States recovered rapidly) but because of the calamitous ways that U.S. leaders chose to respond to it.

According to Brown University’s Costs of War Project, the global war on terrorism has ultimately cost the United States some $8 trillion. Even if spread over many years, this is a vast sum that could have been spent on research and development, infrastructure, education, health care, or any of the other ingredients of national power. Or it could have been left in taxpayers’ pockets and allowed them to live more bountiful lives. Much of that sum was spent on wars of choice in Iraq and Afghanistan, along with several lesser conflicts, wars that further destabilized already fragile regions and killed hundreds of thousands of lives, most of them foreign. The global war on terrorism was also a giant distraction from a host of broader strategic concerns, most notably China’s remarkable rise. It is no exaggeration to say that 9/11—and especially the U.S. response to it—was an enormous gift to Beijing.

Moreover, as Spencer Ackerman argues in his new book Reign of Terror: How the 9/11 Era Destabilized America and Produced Trump, the response to 9/11 had profoundly negative effects domestically in the United States. After a brief burst of rally-round-the-flag patriotism, the war fueled domestic division, xenophobia, and a broader fear of people of color, thereby reinforcing the white supremacists at the core of Trumpism (and increasingly, the Republican Party itself). U.S. officials embraced torture and rendition as policy tools, lied to the country about Iraqi weapons of mass destruction and the progress they were making in Afghanistan, and no one was ever held accountable. As both Thucydides and James Madison warned, perpetual warfare corrupts even the healthiest political institutions, which is precisely what happened in the United States.

Very importantly, this scenario also assumes that the United States fails to learn the right lessons from the past 20 years and is unable to reverse the partisan death spiral that now threatens the core of its democratic system. Instead of a reawakened sense of national purpose, renewed unity within an increasingly multicultural society, and a political elite recommitted to the common weal, the United States devolves into a rancorous quasi-democracy where electoral accountability vanishes in a sea of gerrymandering, voting restrictions, and mythmaking by news organizations created and run not to inform the public but to favor one side. Instead of a competitive marketplace of ideas and an empowered electorate, political power devolves even more to those with the biggest budgets, the most seductive lies, and the fewest principles.

In this unhappy future, Americans cease to work together to expand the pie for everyone and instead mostly end up squabbling over their respective shares. And if that happens, along with a few more foreign-policy blunders, it will be easy for China to blow past the United States in the fast lane and fulfill Xi’s ambitious dreams. If 9/11 is not seen as the death knell of American greatness, it will certainly be viewed as a catalytic moment that hastened its decline. Osama bin Laden’s ploy to goad the United States into a self-destructive response will have been vindicated but only because America fell into the trap he set.

Option 1 is not inevitable. There is another scenario.

Option 2: American renaissance

Suppose instead that President Joe Biden’s fondest hopes are realized and the United States gets its act together again. In this much brighter future, how will 9/11 be seen? This scenario begins by acknowledging America’s enduring strengths, strengths that its citizens tend to forget amid all their self-inflicted wounds and recriminations. Unlike most other wealthy democracies, America’s population will continue to grow for the remainder of this century. Its economy remains an engine of innovation in many key sectors, even given shrinking R&D budgets. Indeed, some economic models forecast that U.S. GDP will trail China by midcentury but regain the #1 position by 2100, largely due to more favorable demography. And although geography does not insulate the United States from all dangers, the country still exists in a far more favorable geopolitical environment than all other potential great powers (including China).

To be sure, this scenario assumes that the current feverish state of U.S. domestic politics eventually subsides and that a new era of progressivism limits the corrupting impact of money in politics. Returning to a sensible, middle-of-the-road policy on immigration would once again enable the country to attract talented, energetic, and entrepreneurial immigrants from other countries and gradually turn them into Americans, as the United States has done erratically but successfully throughout its history. White Americans adjust to their status as a plurality rather than a majority, aided by the greater racial tolerance that younger Americans already exhibit. Innovation continues to drive economic growth, fewer dollars are spent on unnecessary military capabilities or unwinnable and unnecessary wars, and political reforms reverse the current assault on voting rights and restore greater accountability in politics. Abandoning the futile quest for liberal hegemony, U.S. grand strategy returns to the realist principles that guided it so successfully for most of the nation’s history. And so forth.

Meanwhile, imagine further that China stumbles. Dragged down by unfavorable demography (i.e., an increasingly large number of unproductive, aging retirees), environmental damage, resource scarcity, and coordinated global opposition fueled by Beijing’s bare-knuckle approach to diplomacy, China never quite manages to reach a position of primacy. Perhaps Chinese leaders miscalculate as badly as U.S. leaders did after 9/11 and end up squandering resources in a fruitless war of their own. Even if China’s current and future leaders avoid errors as grave as Mao Zedong’s Great Leap Forward or the Cultural Revolution, its economic growth rate slows, and the Chinese Communist Party has to focus most of its attention on containing social discontent. Were all this to come to pass, the next 80 years will not be the Chinese Century at all.

In this scenario, by 2101, 9/11 will be a distant memory for living Americans. Not entirely, of course, but it will be seen as an isolated tragedy that led to some unfortunate responses but did not do lasting damage to America’s overall position in the world. Lest this prediction seem fanciful, consider how often Americans take a moment now to “Remember the Maine!” The explosion that sank that unfortunate warship in Havana Harbor sparked a national uproar not unlike the response to 9/11 and helped drive the United States into the Spanish-American War. We still hear a lot about the Depression, appeasement at Munich, Pearl Harbor, the Normandy landings, and Vietnam, but the destruction of the USS Maine has slipped behind the veil of national amnesia. If the United States is able to renew itself over the next few decades, 9/11 will be seen as a minor tragedy that many Americans believe is best forgotten.

The wild card

There is, however, at least one other obvious possibility. If the worst-case forecasts on climate change turn out to be correct—and it is getting harder to discount them these days—then the next 80 years will see a series of transformations in human life that will make both 9/11 and the global war on terrorism that it unleashed seem like a minor distraction. If coastal cities are inundated, island nations disappear, the Gulf Stream weakens, large areas of the world become uninhabitable due to deadly combinations of heat and humidity, and hundreds of millions of people begin to migrate in a desperate search for survival, then our descendants will have neither the time nor the inclination to reflect on a terrorist attack that occurred in the pre-dystopian era. At most, 9/11 will be seen as one of the many factors that kept the United States and many other countries from taking action when they should have.

In sum, what 9/11 means to future generations depends less on what actually occurred on that day or on how the United States and others responded and more on what the United States and others do from this day forward. I wish I were more confident that we will make the right choices.