China’s obvious project is building a state. Its less obvious project is building a world. And while Beijing needs its tanks and guns and factories to build up and fortify the state, it needs ideas to build a world — and it needs the world to embrace those ideas, or at least to accept institutions and arrangements derived from them. Tingyang Zhao presents his Tianxia as the “acceptable empire,” and the idea has some real resonance in China. “In the early 20th century,” Callahan writes, “imperial China’s hierarchical world order was seen as the problem, but now many Chinese people see it as the solution to the world’s ills.”

Turn up your noses at the professors all you like — ideas matter, and, in the long run, all important political conflicts are ideological and philosophical conflicts. The Chinese people are giving some thought to what a Chinese view of the world — a Chinese world — should look like. Americans are not. And if the world no longer believes that the American-led international order provides such benefits as to command allegiance to the system and its institutions, it is only following the example set by the United States itself, with its increasing bipartisan hostility to trade and trade accords, its nickel-and-dime approach to NATO and other trans-Atlantic institutions, its heavy-handedness in relations with the European Union, its peevishly short-tempered diplomacy. Joe Biden’s economic nationalism is in all but rhetoric indistinguishable from Donald Trump’s.

We are unprepared to defend the U.S.-led world order on intellectual grounds — and, worse, a great many Americans, both on the left and on the right, would not be inclined to mount such a defense even if they were able to do so. Right-wing populists and left-wing populists both reject the liberal order developed and cultivated by the United States from World War II through the early 21st century, and both sides hold its institutions and organizing principles in low regard. The fashionable young men of the right are as hostile to capitalism as any batty socialist wandering the streets of Brooklyn. Some Americans thrill to Karl Marx, and others to Viktor Orbán, Marine Le Pen, or the memory of Francisco Franco.