By Paul Krugman — The New York Times.

The official Financial Crisis Inquiry Commission — the group that aims to hold a modern version of the Pecora hearings of the 1930s, whose investigations set the stage for New Deal bank regulation — began taking testimony on Wednesday. In its first panel, the commission grilled four major financial-industry honchos. What did we learn?

Well, if you were hoping for a Perry Mason moment — a scene in which the witness blurts out: “Yes! I admit it! I did it! And I’m glad!” — the hearing was disappointing. What you got, instead, was witnesses blurting out: “Yes! I admit it! I’m clueless!”

O.K., not in so many words. But the bankers’ testimony showed a stunning failure, even now, to grasp the nature and extent of the current crisis. And that’s important: It tells us that as Congress and the administration try to reform the financial system, they should ignore advice coming from the supposed wise men of Wall Street, who have no wisdom to offer.

Consider what has happened so far: The U.S. economy is still grappling with the consequences of the worst financial crisis since the Great Depression; trillions of dollars of potential income have been lost; the lives of millions have been damaged, in some cases irreparably, by mass unemployment; millions more have seen their savings wiped out; hundreds of thousands, perhaps millions, will lose essential health care because of the combination of job losses and draconian cutbacks by cash-strapped state governments.

And this disaster was entirely self-inflicted. This isn’t like the stagflation of the 1970s, which had a lot to do with soaring oil prices, which were, in turn, the result of political instability in the Middle East. This time we’re in trouble entirely thanks to the dysfunctional nature of our own financial system. Everyone understands this — everyone, it seems, except the financiers themselves.

There were two moments in Wednesday’s hearing that stood out. One was when Jamie Dimon of JPMorgan Chase declared that a financial crisis is something that “happens every five to seven years. We shouldn’t be surprised.” In short, stuff happens, and that’s just part of life.

But the truth is that the United States managed to avoid major financial crises for half a century after the Pecora hearings were held and Congress enacted major banking reforms. It was only after we forgot those lessons, and dismantled effective regulation, that our financial system went back to being dangerously unstable.

As an aside, it was also startling to hear Mr. Dimon admit that his bank never even considered the possibility of a large decline in home prices, despite widespread warnings that we were in the midst of a monstrous housing bubble.

Still, Mr. Dimon’s cluelessness paled beside that of Goldman Sachs’s Lloyd Blankfein, who compared the financial crisis to a hurricane nobody could have predicted. Phil Angelides, the commission’s chairman, was not amused: The financial crisis, he declared, wasn’t an act of God; it resulted from “acts of men and women.”

Was Mr. Blankfein just inarticulate? No. He used the same metaphor in his prepared testimony in which he urged Congress not to push too hard for financial reform: “We should resist a response … that is solely designed around protecting us from the 100-year storm.” So this giant financial crisis was just a rare accident, a freak of nature, and we shouldn’t overreact.

But there was nothing accidental about the crisis. From the late 1970s on, the American financial system, freed by deregulation and a political climate in which greed was presumed to be good, spun ever further out of control. There were ever-greater rewards — bonuses beyond the dreams of avarice — for bankers who could generate big short-term profits. And the way to raise those profits was to pile up ever more debt, both by pushing loans on the public and by taking on ever-higher leverage within the financial industry.

Sooner or later, this runaway system was bound to crash. And if we don’t make fundamental changes, it will happen all over again.

Do the bankers really not understand what happened, or are they just talking their self-interest? No matter. As I said, the important thing looking forward is to stop listening to financiers about financial reform.

Wall Street executives will tell you that the financial-reform bill the House passed last month would cripple the economy with overregulation (it’s actually quite mild). They’ll insist that the tax on bank debt just proposed by the Obama administration is a crude concession to foolish populism. They’ll warn that action to tax or otherwise rein in financial-industry compensation is destructive and unjustified.

But what do they know? The answer, as far as I can tell, is: not much.