President Trump delivered one of the most important speeches of his young presidency on Thursday. Billed as "Remarks to the people of Poland," the address was as clear a statement we've heard of Trump's nation-state populism. This philosophy, which differs in emphasis and approach from that of other post-Cold War Republican presidents, is both enduring and undefined. Reaching as far back as Andrew Jackson, and carrying through, in different ways, William Jennings Bryan, Franklin Delano Roosevelt, Spiro Agnew, Ronald Reagan, Ross Perot, Patrick Buchanan, James Webb, and Sarah Palin, the nation-state populist tradition has suffered from its lack of intellectuals, professors, and wordsmiths. But that is beginning to change.

The most important concept in nation-state populism is the people. These are citizens of the folk community, membership in which crosses ethnic, racial, and sectarian lines. Note, for example, Trump's reference to the Nazis' systematic murder of "millions of Poland's Jewish citizens, along with countless others, during that brutal occupation." Or as Trump put it, in a different context, in his Inaugural Address: "Whether we are black or brown or white, we all bleed the same red blood of patriots, we all enjoy the same glorious freedoms, and we all salute the same great American flag."

Together, the people constitute the nation. Borders define the nation's physical extent, but not its nature. Indeed, the nation may exist independent of statehood or political sovereignty. "While Poland could be invaded and occupied," Trump said, "and its borders even erased from the map, it could never be erased from history or from your hearts. In those dark days, you had lost your land but you never lost your pride." Nor is the nation always represented in the corridors of power. "Today, we are not merely transferring power from one administration to another," Trump said at the inaugural, "or from one party to another—but we are transferring power from Washington, D.C, and giving it back to you, the American people."

Poland and the United States are among the "free nations" that make up the "civilization" of "the West." And the West is unified, not only by "bonds of culture, faith, and tradition" and "history, culture, and memory," but also by shared values. These include "individual freedom and sovereignty," innovation, creativity, and exploration, meritocracy, "the rule of law," the "right to free speech and free expression," female empowerment, and "faith and family." And, "above all, we value the dignity of every human life, protect the rights of every person, and share the hope of every soul to live in freedom."

Western civilization faces threats. Foremost among them is the heir to Nazism and communism. The "oppressive ideology" of radical Islam, Trump said, "seeks to export terrorism and extremism all around the globe." There are also "powers that seek to test our will, undermine our confidence, and challenge our interests"—namely Russia but also, farther away, China and North Korea. Finally, there is "the steady creep of government bureaucracy that drains the vitality and wealth of the people" and overrides their sovereignty.

How to respond? Material wealth, martial glory, and technological achievement are all necessary to sustain a nation. But they are not sufficient. What matters more, Trump said, is national spirit. In fact, the word "spirit" occurs no fewer than seven times in the address. There are also several mentions of related ideas such as "confidence" and "will."

Trump cited Bishop Michael Kozal, who died in Dachau: "More horrifying than a defeat of arms is a collapse of the human spirit." A nation can endure economic recession, and even military occupation. What it cannot recover from is loss of pride. "As the Polish experience reminds us," Trump said, "the defense of the West ultimately rests not only on means but also on the will of its people to prevail and be successful and get what you have to have."

This lesson raises "the fundamental question of our time":

Do we have the confidence in our values to defend them at any cost? Do we have enough respect for our citizens to protect our borders? Do we have the desire and the courage to preserve our civilization in the face of those who would subvert and destroy it?

What Trump is saying is that the future of the liberal democratic West depends on the non-liberal-democratic institutions from which we derive our values: family and faith. "We can have the largest economies and the most lethal weapons anywhere on Earth, but if we do not have strong families and strong values, then we will be weak and we will not survive." Nor will we survive if we neglect the non-liberal-democratic institutions that enforce liberal-democratic values: the military and police.

Trump doesn't just want victory over ISIS. What he is calling for is nothing less than a reinvigoration of national spirit, of confidence, of pride in America and her allies. "Our own fight for the West does not begin on the battlefield—it begins with our minds, our wills, and our souls."

These are more than remarks to the Poles. They describe a world of sovereign nation-states, governed by peoples proud of their histories and confident in their futures, united in common cause against the enemies of civilization, of freedom and human dignity. And Trump presents a challenge in the form of a question: Are we still made of that stuff that populated a continent, became an industrial powerhouse, went to the moon, and defeated the Kaiser and the Führer and the Emperor and the Politburo? I hope the answer is yes.