December 7, 1951, came and went with scant ceremony. Harry Truman spent the day vacationing in Key West. Alben Barkley gave a speech in Honolulu in which he defended the war in Korea. Time magazine skipped the Pearl Harbor anniversary altogether: Its cover story that week was a lengthy profile of DeWitt and Lila Wallace. The Daily Double goes to the reader who can identify Barkley or the Wallaces without first turning to Google.

Compare that to the wall-to-wall attention being given to the 10th anniversary of 9/11. Leon Panetta will speak at the Washington National Cathedral on Friday. President Obama will speak there Sunday, after visits to the three memorial sites in Virginia, Pennsylvania and New York. The World Trade Center memorial plaza will open to the families of the victims. Smaller commemorations and remembrances will take place everywhere from Boston to Bagram.

And in the press, we will reprise the now-ritual debates over where-we-are-now, whither-are-we-going and what-it-all-means. Most everybody will have some sort of answer, and only the lowest common denominator of those answers will satisfy everybody.

All this is unavoidable and largely appropriate. But there is some irony in the fact that our frenzy to memorialize is inversely proportionate to our collective capacity to extract meaning from memory.

Consider the Trade Center’s new memorial: two dark, enormous, sunken reflecting pools placed within the footprints of the old towers, faced on all sides by towering waterfalls that in turn lead to a deeper void within, surrounded by a parapet of brass plates bearing the names of the nearly 3,000 victims. Aptly—maybe too aptly—the memorial was called “Reflecting Absence” by its designer, architect Michael Arad.

I live near the memorial and I’ve tried my best to like it, though mainly because it’s a relief no longer to have to stare into that pit in the ground. I certainly hope the families of the victims like it. But despite the impressive scale and the affecting nod to the individual dead, there’s no getting around the sense that the central element of the memorial is emptiness, a giant vacancy. The pools are too deep even to offer an actual reflection, the way Washington’s reflecting pool does. Instead there is a void into which we can weep or scream or just hold still. But it gives nothing back.

I suppose there’s an argument that that’s as it should be. September 11 was nothing if not a day of loss, and this memorial cannot avoid expressing something of that loss. The problem is that it’s exclusively about loss, while 9/11 was also a day of extraordinary giving: of the first responders, the passengers on Flight 93, the people in the towers who helped each other out, the emergency crews, the volunteers. A better 9/11 tribute would reflect those deeds, not sound an echo to the nihilism that was at the core of al Qaeda’s designs.

There is, however, a deeper problem, this one not the fault of the memorial’s designers. In 1951, Americans could look back to Pearl Harbor and see its bookends in VE Day and the Japanese surrender on the USS Missouri. In that light, Pearl Harbor may have been a day of infamy but it was also, for the intelligence failures and military defeat it represented, a day to live down.

The war that was begun on September 11 has no bookend. We don’t even know whether we are in the early, middle or late chapters—or whether we’re still in the same book. Perhaps that’s why dates like November 13, 2001 (the day Kabul fell to the Northern Alliance) or April 9, 2003 (when Baghdad fell to the U.S. Army) go down the memory hole. I doubt many people can recall the exact date Osama bin Laden was killed.

So 9/11 remains a date and an event unto itself, somehow disconnected from everything that still flows from it. No doubt that helps draw a line between our feelings about it and the controversies over Iraq, Guantanamo, waterboarding, drone strikes, the freedom agenda and all the rest of it. But it also strips the day of any context, intelligibility or a sense of the greater purposes that might flow from it. This is how an act of evil and of war has been reduced, in our debased correct parlance, to a “tragedy.”

There is something dangerous about this. Dangerous because we risk losing sight of what brought 9/11 about. Dangerous because nations should not send men to war in far-flung places to avenge an outrage and then decide, mid-course, that the outrage and the war are two separate things. Dangerous above all because nations define themselves through the meanings they attach to memories, and 9/11 remains, 10 years on, a memory without a settled meaning.

None of that was true in 1951. We had gone to war to avenge Pearl Harbor. We had won the war. We had been magnanimous in victory. The principal memorial that generation built was formed of the enemies they defeated, the people they saved, the world they built and the men and women they became. Our task on this 9/11 is to strive to do likewise.

Write to bstephens@wsj.com