Thirty-five years later, the current U.S. president addressed a crowd in Warsaw. In his speech last week Donald Trump barely mentioned democracy. He spoke instead of the “will to defend our civilization.” Although he did not offer an explicit definition of this civilization, the basic thrust of his understanding emerged. Our civilization rests on bonds of “history, culture, and memory.” It puts “faith and family” at the center of our lives. It is best summarized in the words one million Poles chanted in response to Pope John Paul II’s Warsaw sermon in 1979: “We want God.” This is the heart of the matter, said Mr. Trump: “The people of Poland, the people of America, and the people of Europe still cry out, ‘We want God.’ ”

While this may well be true for the most devoutly Catholic nation in Europe, it would come as a surprise to most other Europeans. It is an inherently—perhaps intentionally—divisive interpretation of what we allegedly share as participants in Western civilization. Freedom of religion—the right of each to worship in his own way or not at all—would have been a more accurate way of putting it. It would also have been unifying. If this is what Mr. Trump meant, he should have said so. He is, after all, the president of a country dedicated like no other to the principle of religious liberty. But had he framed it that way, his audience might not have chanted his name. They certainly would not have done so if Mr. Trump had summoned the courage to say what many Poles and most Europeans know—that along with Hungary’s Viktor Orban, the current Polish government is Europe’s leading threat to liberal democracy.