(FORTUNE Magazine) – If you're worried about the fate of the world economy, here's a story that won't cheer you up. It's called the Parable of the First Global Economy.

Four score and seven years ago, our forefathers lived in what we would now call an era of globalization. It was, by some measures, even more global than our own. Free trade flourished. A "gold standard" let capital swim about the world. And people, would you believe, could pass freely across borders without even a passport or visa. (The U.S. admitted any immigrant who wasn't a criminal, a lunatic, a prostitute, or Chinese.) As a very famous British economist with three names would recall some years later:

"The inhabitant of London could order by telephone, sipping his morning tea in bed, the various products of the whole earth, in such quantity as he might see fit, and reasonably expect their early delivery upon his doorstep.... The projects and politics of militarism and imperialism, of racial and cultural rivalries ... appeared to exercise almost no influence at all on the ordinary course of social and economic life, the internationalization of which was nearly complete in practice."

There was even a book, Norman Angell's The Great Illusion, that said economic interdependence was making war obsolete.

But in the same year, 1914, it started going south. The one-two punch of the Great War and the Great Depression unleashed a spasm of de-globalization--higher tariffs, restricted immigration, walled economies--such that by the 1940s, two commentators have noted, "killing seemed to be the only global business left." Not until about 1970 would world trade as a share of world output match its 1913 level.

The moral of our parable? Today we live in a second global economy--a supersized version of the first--and it has once again been heralded as irreversible, beyond politics, and even "the end of history." "The free market has emerged triumphant," a British politician wrote recently, "accepted once again everywhere as the natural condition of mankind."

Now the terrorism of Sept. 11 has made such declarations sound as naive as those of a century ago. So it's worth asking: Could the attacks and their aftermath halt the trend toward economic openness, or even throw it into reverse?

Few would suggest we're headed down the dark hole of 1914. Stanley Fischer, formerly the second in command at the International Monetary Fund, says, "It's hard to see that this [terrorism] is going to be a permanent setback." Indeed, many have noted that the terrorists were themselves models of globalization, using its tools--satellite telecommunications, the passenger jet--to turn the system on itself.

But others think there's cause for worry. "My fear is that the world might turn inward in response to this tragedy," Morgan Stanley chief economist Stephen Roach fretted in a report after the attack. "In my opinion, the lasting impacts of this shock could well challenge many of the underpinnings of globalization--rapidly expanding trade and financial capital flows, increasingly globalized supply chains," and so on.

Already there are reminders that our borderless world has borders after all. The proposal to liberalize immigration with Mexico has been tabled indefinitely. The National Association of Manufacturers has expressed concern about new border controls impeding the flow of goods between the U.S. and Canada. And multinationals will surely become skittish about putting operations in predominantly Islamic countries. "I think this will throw some sand in the gears," says Stephen Kobrin, a Wharton professor who studies globalization.

More unknowable is whether a Fortress America mentality in security matters could spill into economic ones. Before the attacks, the Bush Administration's go-it-alone foreign policy (think: backing out of the Kyoto Agreement) had been making things awkward for American multinationals--notably GE and Honeywell--dependent on the goodwill of other countries. It has always been a short hop from nationalism to protectionism. "It means that all sorts of parochial interests in the U.S. are much more likely to get the upper hand," says Harvard economist Dani Rodrik. "If the airline industry gets help, why shouldn't the steel industry?"

Even if such concerns prove unfounded, one thing is clear: The forces aligned against globalization are far more serious than we thought. Puppet-wielding protesters in Seattle and Genoa aren't the only ones who would halt it. Huge parts of the world consider globalization synonymous with Americanization or, worse yet, recolonization. And while the terrorists weren't moved by anything so subtle as trade relations--their rage ran far, far deeper than that--the attacks should at least awaken us from our naivete.

Because there's another lesson of 1914: The biggest threats to globalization are from those who feel they don't have a stake in it. Back then it was the declining empire of Austria-Hungary that saw little to lose in igniting war. Today it's a more amorphous set of forces. Whatever America's response, it might be time to think about why so many people aren't interested in making the world safe for capitalism.

Otherwise, the second global economy runs a chance of ending up like the first.

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