If you want a big swig of despair, listen to the people who know something about the global economy.

Roger Altman, a former deputy Treasury secretary, is arguing that America and Europe are on the verge of a disastrous double-dip recession. Various economists say it will be at least another three years before we see serious job growth. Others say European banks are teetering.

Walter Russell Mead, who teaches foreign policy at Bard College, recently laid out some worst-case scenarios on his blog:

"It is about whether the international financial system will survive the next six months in the form we now know it. It is about whether the foundations of the postwar order are cracking in Europe. It is about whether a global financial crash will further destabilize the Middle East. ...

"It is about whether the incipient signs of a bubble burst in China signal the start of an extended economic and perhaps even political crisis there. It is about whether the American middle class is about to be knocked off its feet once again."

The prognosis for the next few years is bad, with a chance of worse. And the economic conditions are not even the scary part. The scary part is the inability of the political class to think about the economy in a realistic way.

This crisis has many currents, which merge and feed off one another.

There is the lack of consumer demand, the credit crunch, the continuing slide in housing prices, the freeze in business investment, the still hefty consumer debt levels and the skills mismatch -- not to mention regulatory burdens, the utter lack of confidence in the White House by the business class, the looming explosion of entitlement costs and the public's lack of confidence in institutions across the board.

No single one of these currents prolongs the crisis. It is the product of the complex interplay between them.

Yet the ideologues who dominate the political conversation are unable to think in holistic ways. They pick out the one factor that best conforms to their preformed prejudices and, like blind men grabbing a piece of the elephant, they persuade themselves they understand the whole thing.

Many Democrats are predisposed to want more government spending. So they pick up on the one current they think can be cured with more government spending: low consumer demand. Increase government spending and that will pump up consumer spending.

Many Republicans, meanwhile, are predisposed to want lower taxes and less regulation. So they pick up on the one current they think can be solved with tax and regulatory cuts: low business investment. Cut taxes. Reduce regulation. All will be well.

Both orthodoxies take a constricted view of the situation. If we're stuck with these two mentalities, we will be forever presented with proposals that are incommensurate with the problem at hand. Look at the recent Obama stimulus proposal.

You may like it or not, but it's trivial. It's simply not significant enough to make a difference, given the size of the global mess.

We need an approach that is both grander and more modest. When you are confronted by a complex problem, don't try to pick out the one lever that is the key to the whole thing. There is no one lever. You wouldn't be smart enough to find it even if there was.

Instead, try to reform whole institutions and hope that by getting the long-term fundamentals right you'll set off a positive cascade to reverse the negative ones.

Simplify the tax code. End corporate taxes and create a consumption tax. Reshape the European Union to make it either more unified or less, but not halfway as it is now.

Reduce the barriers to business formation. Reform Medicare so it is fiscally sustainable. Break up the banks and increase capital requirements. Lighten debt burdens even if it means hitting the institutional creditors.

The Simpson-Bowles report on the deficit was an opportunity to begin a wave of institutional reform. But that proposal died because our political leaders are too ideologically rigid to take on big subjects like tax reform, which involve combining Republican and Democratic ideas.

The failure to seize that moment was one of Obama's gravest errors.

The world economy has many rigidities. The worst ones are in people's heads.

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David Brooks' column is distributed by the New York Times News Service.