Eventually, as the casualties are counted, the immediate human costs of yesterday's apocalyptic events will become horribly clear. Though the broader political, economic and social consequences will emerge much more slowly, at least one thing seems clear. They will be huge, ubiquitous and long-lasting. The US will be changed for a generation, and that change will profoundly alter our world.
Some ripples will reach this side of the Atlantic quickly. The economy will be severely affected as a sense of crisis exacerbates the already deep difficulties on Wall Street and that most essential element of economic recovery, confidence, evaporates. The peace process will be affected, as waves of revulsion against terrorism wash over the US. Gerry Adams will not be feted in the White House again.
Tourism from America will dry up as its people become wary and suspicious. The direction of the EU will be altered as Europe, caught between a savage act of terrorism and the perhaps equally savage response from the US, is forced to rethink its place in the world.
To grasp the impact of yesterday on the US itself, it is necessary to remember that for well over a century America's wars have all happened elsewhere. For Americans, the horror of war has been summed up by the image of the body bags being unloaded from the plane, coming home from another continent.
In the 18th and 19th centuries, military violence drenched the American homeland in blood: the Anglo-French War, the War of Independence, the Civil War, the extermination of the native peoples. Since the 1880s, however, the notion of America itself as an inviolate sanctuary has remained intact.
Warlike violence has been so rare in the US that the two significant exceptions still have a huge psychological impact. The Japanese attack on Pearl Harbour, which is not even part of the continental US, was the subject of this summer's biggest movie blockbuster. The shock of the Oklahoma City bombing was so great that the area where it happened is still frozen in time, encased in a magnificent monument that suggests that this event can never be forgotten.
The scale of yesterday's events dwarfs Oklahoma City and, as an attack on peaceful cities, far outdoes the outrage of Pearl Harbour. Yesterday's wounds will cut right to the bone of America and no one knows whether the society has the cultural and psychic resources to heal the wound.
The terrorists slashed their way right into the heart of the American Dream: the belief that the US is not just another country but a special place, a safe haven, a great power that is ultimately invulnerable.
For many Americans, and especially for those who are now in office, that notion has a religious dimension. America is also the Promised Land, favoured and protected by God. When you hit so devastatingly at such a deeply held belief, you stir up a response that is likely to be as blindly passionate as the emotions that led yesterday's killers to sacrifice themselves and so many others.
The terrible probability is that America will react viscerally to such a visceral hurt. There will, of course, be a positive response at one level. New Yorkers will see the scale of the devastation as a challenge to their famous spirit and energy.
The scale of the loss will evoke a Blitz spirit, a determination to rebuild, not just Lower Manhattan, but the fragile sense of community and solidarity that may emerge far stronger than it was before. Some of the hurt will be assuaged by that outpouring of energy.
But there will almost certainly be a dark side. For there is in American culture a fundamentalism no less strong than that of those who may have plotted yesterday's carnage. The tendency to divide the world between the forces of God and the forces of Satan, the elect and the damned, is, ironically one of the things that America shares with its most ferocious enemies.
Just as there are deluded people who believe that murdering thousands is a blow against the Great Satan, there will be a strong tendency in America to demonise whatever enemy is responsible and to visit a godly punishment, not just on the perpetrators but on a whole category of humanity.
Americans have always been wedded to a sense of power. The power to shape the world, to invent new things, to solve problems, to land on the Moon, to crush your enemies, has been one of the underlying assumptions of the entire culture. It is what has made America so inventive and attractive and also so arrogant and merciless.
Yesterday America seemed suddenly powerless. The urge to reassert the national potency will be immense. The cry to demonstrate its power by some mighty act of violence will be deafening. Reasonable, careful calculation of where the nation's self-interest lies is not what assuages the kind of anger that will begin to replace the shock. Reason, for example, would say that yesterday's events prove the absolute futility of George W. Bush's revival of the Star Wars project. Critics of that project have long pointed out that the real threat was likely to come, not from intercontinental ballistic missiles, but from clever terrorists using conventional technologies to strike against civilian targets.
That the critics have been proved right in the most awful way imaginable will be beside the point, however. The illusion of safety provided by Bush's supposed nuclear umbrella will be all the more frantically desired by middle America. The military-industrial complex, which has been troubled by the lack of a credible threat since the end of the Cold War, will reap a massive harvest.
The deep paranoia fostered in American culture by the Cold War and that was beginning to lose its grip in the 1990s will return with a vengeance. The temptation to withdraw into an isolationist fortress, sallying forth only to smite the enemy with ferocious force whenever required may be irresistible.
AND the worst thing of all is that the paranoia will not be entirely delusional. It is, for example, by no means unthinkable that the hijacked planes yesterday could have been used to carry small nuclear devices. And whatever happens in the coming weeks will take place in an altered world, whose rules have suddenly become unpredictable. Basic notions of the international order like the distinction between war and terrorism have been destroyed.
Before yesterday there was war and there was terrorism. For the victims, the difference was meaningless. But in every other respect it was immense. In scale, in political context, in the nature of the consequences, the distinction between the state violence of war and the conspiratorial violence of terrorism made sense. Yesterday it was literally blown apart.
We will have to come to terms with the fact that we are now in a world where small groups, not sovereign states, can make war. What is probably a tiny, shadowy group has declared war on the most powerful nation on Earth and inflicted the kind of human and physical damage that previously came from massive bombing raids.
This is a new world, and not at all a brave one. In the short term, we will have to decide whether an America deranged with grief and anger will be capable of leading the democratic world. In the longer term, we may have to look to a different kind of Europe for sanity in a maddened world.