(FORTUNE Magazine) – The phrase "enemies of capitalism" is one the post-war generations grew up with, but even during the bitterest of the Cold War years it never seemed to be much more than an ideological handle, a convenient shorthand for complex political and economic forces. Once the Berlin Wall fell, and capitalism swept across vast new stretches of the world, the words acquired a comforting patina of age, sounding like a bit of cant from a bygone era. The matter was put behind us. Capitalism had won.

Who could foresee, then, that the enemies of capitalism would manifest themselves in the bright September sky as murderous kidnappers flying incendiary bombs? When the terrorists boarded those four airplanes on that awful morning, they aimed to strike a blow at America's economic and military might. They chose the World Trade Center as their symbol of American capitalism. Now it's our symbol too.

It's been said that we haven't seen anything like this in America since Pearl Harbor, 60 years ago. Some 2,300 people died in the attack on Pearl Harbor; as FORTUNE goes to press, the death toll from the World Trade Center is likely to be at least twice as high. Not since the Galveston flood of 1900, in which more than 6,000 lives were lost, has there been an American tragedy in which more people died.

Still, the Pearl Harbor analogy is apt. A surprise attack has, in an instant, changed the way we think about the world around us. It has scared us, angered us, galvanized us--and it has the potential to mobilize us as nothing has since World War II. "The biggest mistake they make is waking sleeping giants," says Leo Melamed, the 68-year-old chairman emeritus of the Chicago Mercantile Exchange.

Here's something else Melamed told FORTUNE: "The financial markets are not based on a building, but something in our mind." That's mostly true--though not to the degree that we had thought before Sept. 11. The market still has a huge physical dimension, and the World Trade Center attacks did incalculable damage to its machinery. Billions of dollars of infrastructure were vaporized; firms were decimated; grand Wall Street buildings like 1 Liberty Plaza--given that patriotic name, by the way, by an ex-Marine named Donald Regan, back when he ran Merrill Lynch--became uninhabitable. And of course thousands of Wall Street traders and brokers and market makers--people who kept our financial markets vibrant--perished in the flames.

By the time you read this, the exchanges will likely be back up. Even Cantor Fitzgerald, the hardest-hit firm in the World Trade Center, is already doing some business. Surely that says something about capitalism's resiliency. But the market was down for four days--the longest it's been shut in 68 years. And there will inevitably be bankruptcies and other business setbacks as a result of the attack. Surely that suggests something about capitalism's fragility as well.

Over the coming weeks and months--and perhaps years--this is the tension that will play out in our economy: the tension between its resiliency and its fragility. How long will it take for the market to truly return to normal? Will consumers be too shaken to spend money? Will the country bounce back economically, or will we spiral into a recession--or worse?

Usually, when an American tragedy takes place, it feels wrong--unclean, even--to discuss the economic consequences. Not this time. This time, terrorists were trying to put a bullet through the heart of our system. How well we recover from that grievous wound is the story we are covering, sadly but unblinkingly, in this issue of FORTUNE--and, no doubt, in many issues to come.

--Joseph Nocera