[This is a slightly edited version of a piece first published two years ago.]

Does it seem as though seven years have passed since that dreadful day of the stunningly blue sky, the orange flames, the plumes of grey-black smoke?

In some ways it seems a lifetime; one looks back at before-9/11 and thinks “never such innocence again.”

But the New York skyline without its two huge exclamation points no longer seems so bereft. Yes, it happened, and somehow we have assimilated that fact, although we still haven’t comprehended all its consequences nor divined its deepest meaning.

But it no longer seems impossible that such a thing happened. Now it seems surprising that it came as such a shock at the time, because the general pattern and the shape of things to come should already have been clear. There was Khobar Towers. The twin Embassy blasts. The Cole.

But the clearest foreshadowing of the event that would henceforth be known only by those numbers, “9/11”—as though words were somehow inadequate to describe it—was its most direct predecessor, the 1993 World Trade Center bombing. That earlier attack distinguished itself in audaciousness by being the only large-scale Islamist totalitarian terrorist attack within the boundaries of the United States prior to 9/11.

And it was every bit as serious in intent. The only reason it wasn’t taken as seriously as it should have been was the seemingly Keystone Cops-like incompetence of its perpetrators. They would learn from their errors, and quickly. It would take us longer to learn what we needed to know.

Another thing that makes 9/11 feel more distant in time than seven years ago is the dissipation of the unity that seemed to unite us in the first few months afterwards. I say “seemed” because there were always many dissenting voices, even from the start—voices that blamed the US for the attack, or said that the Jews had stayed home that day. Voices that suggested America deserved what it got. Voices that were against attacking Afghanistan, saying we would kill millions of people in that country.

Yes, 9/11 seems a long time ago. But in other ways 9/11 seems fresh and recent–and especially so on the anniversary, when documentaries revisit the pain and open old wounds. Recently I rewatched much of “9/11,” the documentary film made by the Naudet brothers as they followed a downtown Manhattan fire company on a routine call that turned out to be adjacent to the World Trade Center on that fateful day at that fateful time. The brothers captured many startling images of 9/11, but the most horrifying thing in the movie was not visual. It was auditory: the harsh percussive sounds of the leapers hitting the pavement.

Viewing how events unfolded that day and knowing what we know now, the urge is to say: “Look out! Don’t go to work! Run away, fast! Don’t go up those stairs!” Or to think, “If only.” If only the people on the first planes had known what was in store, for example, they could have united to stop the hijackers the way those on Flight 93 did. If only the FBI and CIA had been allowed to speak to each other. If only. If only.

I recall one of the most poignant “if only’s” from a documentary I saw several years ago. A female air controller was monitoring flights that day, knowing what had happened at the WTC, helpless as the plane she was tracking (I believe it was the one that eventually hit the Pentagon) dropped and disappeared off the radar screen. She said that, ever since, she’s had a recurrent dream. In it, she’s watching that same radar screen. The “blip” of the plane is dropping again, and her heart sinks with it. But this time, instead of being helpless, she reaches into the screen with her hand and scoops the tiny plane out, rescuing all its passengers.

Magical thinking, of course. But very human. Many who were part of the rescue effort that day think they should somehow have done even more, despite the heroism they showed.

And of course we all somehow should have done more, both then and now. The problem, both then and now, is the same: figuring out what that “more” might be. Knowing how to interpret the past and the present in order to be able to foresee the future and act to forestall tragedy.

We can do that perfectly only in our dreams, and not even in all of those. But still we must try, to the best of our ability— because history, like life, can only be understood backwards (if at all). But it must be lived forwards.