THE RISE of China presents the most complex international challenge any American president has ever faced. China is at one and the same time the fiercest rival the United States has ever seen, and also a nation with which the United States will have to find ways to co-exist—since the only alternative is to co-destruct. If Xi Jinping’s Party-led autocracy realizes its dream, Beijing will displace Washington from many of the positions of leadership it has become accustomed to during the American Century. Unless China can be persuaded to constrain itself and indeed cooperate with the United States, it will be impossible to avoid catastrophic war or preserve a climate in which both can breathe.

To meet this challenge, President-elect Joe Biden and his team will have to craft a strategy that passes what F. Scott Fitzgerald defined as the test of a first-class mind. In Fitzgerald’s words, it is “to hold two contradictory ideas in one’s head at the same time and still function.” Fortunately, in sharp contrast with his predecessor, Biden comes to this test well prepared. Seasoned by decades of experience as vice president, chairman of the Senate Foreign Relations Committee, and a legislator during the Cold War, he has wrestled with the hardest choices and developed considered views about how the world works.

On the one hand, unless it crashes or cracks up, Xi’s China will be “the biggest player in the history of the world,” as Lee Kuan Yew once put it. With four times as many people as the United States, if the Chinese were only one-half as productive as Americans, China would have a GDP twice our size. That would allow it to invest twice as much in defense as we do. Since the beginning of this century, China has risen to become the largest economy in the world (according to the metric the CIA judges the best yardstick for comparing national economies). Today, it is also the manufacturing workshop of the world, the No. 1 trading partner of most major economies, and since the financial crisis of 2008, the primary engine of global economic growth. At the end of 2020, only one major economy will be larger than it was at the beginning of the year. And that is not the United States of America.

To create a correlation of forces that can shape China’s behavior, the United States will have to attract other nations with heft to sit on our side of the seesaw of power. Despite President Donald Trump’s disdain for allies, his vice president and secretary of state-recognized this imperative. But their hope to take a page from America’s successful strategy in the Cold War by persuading other nations to “decouple” from China behind a new economic iron curtain misunderstood the underlying realities. As a politician, Biden knows that the mandate of other countries’ leaders to govern depends on their ability to deliver increasing standards of living for their people. Any attempts to force them to choose between their military relationship with the United States that makes them secure, and their economic relationship with China that is essential for their prosperity, are thus a fool’s errand. Enlisting allied and aligned powers in a much more complex web will be vastly more difficult than it was when confronting the Soviet Union.

On the other hand, Biden knows full well that the United States and China share a small globe on which each faces existential challenges it cannot defeat by itself. Technology and nature have condemned these two great powers to find ways to live together in order to avoid dying together. As a veteran Cold Warrior, Biden understands in a way most of today’s generation do not that we continue to live in a MAD world. He recalls how difficult it was for American policymakers to get their minds around the concept of nuclear MAD—mutually assured destruction—and to accept its strategic implications for sane statecraft. After the Cuban Missile Crisis, John F. Kennedy and his successors learned the lesson Ronald Reagan summarized succinctly in his favorite bumper sticker: a nuclear war cannot be won and must therefore never be fought. Realizing what that meant in practice for the U.S. rivalry with the Evil Empire was a huge struggle—one in which Biden spent countless hours helping Senate colleagues appreciate.

Today, in addition to nuclear MAD, President-elect Biden knows that we also face Climate MAD. Sharing a small globe on which we breathe the same air, either one of the top two emitters of greenhouse gases can disrupt the climate so severely that neither can live in it. Recognizing that reality, Biden worked with President Barack Obama and Secretary of State John Kerry to hammer out a climate accord with China that made possible the international Paris Agreement that began to bend these curves. While Trump withdrew from this agreement, Biden will rejoin it on Day 1 and seek to work with China to stretch to more ambitious targets.

In sum, the challenge posed by China is daunting. But brute facts are impossible to ignore. Having overcome seemingly insurmountable obstacles to become the forty-sixth president of the United States, Biden will be ruthlessly realistic about the magnitude of this challenge, and unflinching in his determination to do what has to be done.

Graham T. Allison is the Douglas Dillon Professor of Government at the Harvard Kennedy School. He is the former director of Harvard’s Belfer Center and the author of Destined for War: Can America and China Escape Thucydides’s Trap?

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