A year later, we’ve found no better way to refer to the attacks on New York City and Washington, D.C., than “9/11.” The simultaneous assault on two cities rules out a geographical name, like Pearl Harbor or Gettysburg. Probably the only other date burned so indelibly into the American consciousness is the Fourth of July, though it, unlike September 11, has a proper name: Independence Day. The massacres of a year ago are referred to almost exclusively by numbers (Arabic numerals, at that), by the date, which caught on partly because of the coincidence with 9-1-1, the well-known emergency telephone number. 9/11 was an emergency call answered by thousands of firemen and policemen, hundreds of whom lost their lives in the World Trade Center.

July 4 is significant for something Americans did; September 11 for something that was done to us. The identification of the vicious attacks with a date impresses us with the arbitrariness of the attacks on that day, emphasizes almost the fatedness of them, as though an existential stroke of doom had befallen us. We saw the images, over and over and over again, of those shimmering airplanes crashing into the Twin Towers, but it was still hard to fathom that the planes caused the buildings’ collapse. Our minds associated the events together, the impact preceding the downfall, but that the one caused the other remained a thought somehow so appalling that it was hard to believe. We had to see the images again.

Still more unfathomable was the cause behind the cause—the terrorists’ motive in attacking our people and buildings. How to describe it, to conceive it? It was (still is) hard for us, and so the day’s events remained for a while an effect without a cause, a mystery; indeed, a kind of evil miracle. Our enemies saw in it Allah’s hand. The word most used to describe it in the early going was “tragedy,” which suggested inexplicable suffering, as though an earthquake had toppled the towers. Of course, “tragedy” also implied a tragic flaw: the Twin Towers’ fall recalled, dimly, memories of the story of the Tower of Babel. The daring of the Towers’ architecture, their very altitude, seemed to have invited the stroke of fate. And was man really meant to fly?

And so the political meaning of 9/11 has been less clear than one might have expected. To be sure, the political reaction has been impressive—a formidable military and diplomatic effort culminating in the war in Afghanistan, which crushed the Taliban, disrupted al-Qaeda, and sent Osama bin Laden…somewhere he did not want to be. To the extent these operations had a slogan, it was “Let’s Roll,” the last recorded words of Todd Beamer, one of the passengers on United Flight 93, which crashed in the Pennsylvania countryside. His words were uttered at a very American moment, after the passengers had said a prayer and taken a vote to resist their murderous captors.

But “Let’s Roll” became a kind of slogan precisely because it signaled heroic resistance in a moment of otherwise disheartening national paralysis. President Bush adopted the phrase when he led the nation to war in Afghanistan. But a year after 9/11, is America still rolling forward?

President Bush pointed out repeatedly that 9/11 had reminded Americans of the difference between good and evil, vanquishing the moral confusion of our times. There’s little doubt that most Americans exhibit such moral confidence: they know who the bad guys are and why they are bad. Yet already there are signs that this patriotic resolve may erode—certainly there are many on the extreme Left who would like to erode it, and many more in the liberal center who may be unable to resist the extremists’ arguments.

One of the great themes of liberal postmodernism is that the past has nothing to teach us: that history is all interpretation, and morals and politics are entirely relative. Is it to some extent a reflection of this view that the atrocities of 9/11 have not, like previous insults against America, been made into a watchword meant to engage our memory and our conscience? Think how past generations of Americans did this: Remember Pearl Harbor. Remember the Lusitania. Remember the Maine. Remember the Alamo.

Yet no one says, “Remember 9/11.” We may wish it, but it’s not on our lips, our billboards, or our televisions. We have not vowed it, at least not as we should. Without such a political watchword, we are prone to forget why and where we are “rolling.” Victory loses its luster, and its urgency, when prescinded from the reasons we fight. Our enemies struck at us not so much because of anything we had done but because of the kind of nation we are; a nation that prays and votes freely. Let us defy them, and at the same time save ourselves, by recalling who we are and what we stand for. 9-1-1 is a call for help. 9/11 must be a call to arms. Remember 9/11.