The start of the Trump administration has been a vindication of the American nation-state.

Anyone who thought it was a "borderless world," a category that includes some significant portion of the country’s corporate and intellectual elite, has been disabused of the notion within about the first five days of the Trump years.

The theme running throughout President Donald Trump’s inaugural address was the legitimacy of the nation-state as a community, a source of unity and the best means of advancing the interests of its citizens. The address was widely panned, but early polling indicates the public didn’t share the revulsion of the commentariat. The speech’s broadly nationalistic sentiments were bound to strike people as common sense.

"At the center of this movement is a crucial conviction: that a nation exists to serve its citizens." Who else would it serve?

"From this moment on, it’s going to be America first." Why would anything else come first?

Trump’s speech was less poetic, but in one sense more grounded than George W. Bush’s call for universal liberty in 2005 or Barack Obama’s vision of international cooperation leading to a new era of peace in 2009. Trump spoke of "the right of all nations to put their own interests first."

If Bush was a vindicator of universal freedom, and Obama, in his more soaring moments, a citizen of the world, Trump is a dogged citizen of the United States, concerned overwhelmingly with vindicating its interests.

His executive order authorizing the building of the wall is an emphatic affirmation of one of the constituent parts of a nation, namely borders.

In general, immigration is an important focus for Trump’s nationalism because it involves the question of whether the American people have the sovereign authority to decide who gets to live here or not; of whether the interests of American or foreign workers should be paramount; of whether we assimilate the immigrants we already have into a common culture before welcoming even more. A proper American nationalism should express not just an affinity for this country’s people, as Trump did in his inaugural address, but for its creed, its institutions and its history. These are absent from Trump’s rhetoric and presumably his worldview, impoverishing both.

Trump’s nationalism has the potential to appeal across racial and ethnic lines, so long as he demonstrates that it isn’t just cover for his loyalty to his preferred subnational group. Finally, Trump’s trade agenda also is an expression of his nationalism. Trade deals should have to pass the national-interest test. But protectionism is, historically, a special-interest bonanza that delivers benefits to specific industries only at a disproportionate cost to the rest of the economy.

All that said, the nation-state is back, despite all the forecasts of its demise. It is no more in eclipse than religion, which we also were told would fade away as humanity embraced a more secular, cosmopolitan future.

The lesson is that it’s a mistake to predict the inevitable decline of things that give meaning to people’s lives and involve fundamental human attachments. The nation is one of them, something that Trump, if he gets nothing else, instinctively understands.