Friedrich Hayek, whose thoughts used to count for something among well-educated conservatives, made short work of nationalism as a guiding principle in politics. “It is this nationalistic bias which frequently provides the bridge from conservatism to collectivism,” he wrote in “The Constitution of Liberty.”

That point alone ought to have been enough to dim the right’s new enthusiasm for old-style nationalism. It hasn’t.

A three-day public conference this month on “national conservatism” featured some bold-faced right-wing names, including John Bolton, Tucker Carlson and Peter Thiel. The Wall Street Journal’s editorial page published a piece from Christopher DeMuth, a former president of the American Enterprise Institute, on the “nationalist awakening.” Yoram Hazony, an Israeli political theorist, has gained wide attention among U.S. conservatives with his book, “The Virtue of Nationalism.”

And, of course, Donald Trump: “You know, they have a word, it sort of became old-fashioned, it’s called a nationalist,” the president said last October. “And I say, really, we’re not supposed to use that word. You know what I am, I’m a nationalist.”

It says something about the soundness of an idea that its currency owes less to its intrinsic merits than it does to the power of a man who has no ideas. It also says something about the intellectual plasticity of some newly minted national conservatives that they now champion a concept they would have disdained just three years ago.

But let’s give nationalism its due. Much of the world, including the free world, is organized around the concept of the nation-state. Nations — that is, people whose ties involve not merely citizenship but also ancestry, culture, history, language, territory and sometimes religion — can have deeper political cohesion, and inspire greater solidarity and mutual self-sacrifice, than mere states. Nationalism offers protection to “somewhere people” against the political and moral preferences of “anywhere people.” And transnational bodies like the European Union have largely failed the test of democratic representation and accountability.

The problem is, the United States is not “much of the world.” We are a sovereign state, not a nation-state. Unlike, say, Denmark, we have no official language and no state religion.

Our identity is oriented toward the future, not the past. We do have birthright citizenship — though that, curiously, is something many of today’s national conservatives want to abolish.

Our national borders have changed repeatedly and may change again.

America is the country under whose banner the descendants of slaves give military orders to the descendants of slave owners and stand guard alongside the children of immigrants from Greece and Mexico in places like Panmunjom. It’s where the biological son of a Syrian immigrant created our first trillion-dollar company. It’s where Jews celebrate Christmas by going out for Chinese food.

All this is the essence of America’s exceptionalism. It does not require open borders, rule by U.N. mandarins, obeisance to progressive pieties or any of the other ostensible predations of “globalism” that conservative nationalism claims to oppose.

On the other hand, conservative nationalism does require the mainstream conservative movement to jettison its best principles. Three in particular stand out.

First, faith in free markets. As Hayek noted, “to think in terms of ‘our’ industry or resource is only a short step away from demanding that these national assets be directed in the national interest.” The path from nationalism to nationalization, or from the “national interest” to the political interests of the people in power, can be brutally short. Conservatives have already forsaken the cause of free trade. What does Chris DeMuth think will happen when President Elizabeth Warren invokes nationalism on behalf of her economic agenda?

Second, faith in free people. Conservatives used to believe in the overwhelming benefits of immigration. Most nationalists want to restrict even legal immigration. Conservatives used to believe that America should always speak and sometimes act in defense of freedom-seekers everywhere. Nationalists strike the bargain that America will mind its own business if others mind theirs.

Conservatives used to oppose identity politics for being hostile to individual freedom. Nationalism is the superimposition of one form of identity politics over various others.

Finally, faith in the American example. Novus ordo seclorum: We are a new order of the ages, not just a copy of the old states of Europe writ large. Unlike most other nations, we have opened our doors to human capital wherever it comes from (and hence attracted a greater share of it); and adopted good ideas irrespective of who first had them (and hence developed or commercialized them more successfully); and found ways to smooth, adapt and enjoy cultural differences (and hence rendered them generally benign). Nationalists only want to sharpen or weaponize those differences. To what end?

I’m not one to conflate nationalism with “white nationalism,” much less with fascism. Nor would I deny that a nationalism moderated by liberalism can serve other countries well.

When it comes to the United States, however, we should recognize nationalism for what it really is: un-American.

— Bret L. Stephens has been an Opinion columnist with The New York Times since April 2017.