If you and I were in a bar together, and you suffered a nasty bump on your head when I accidentally whacked you with a pool cue, there probably would be no disputing that my action caused your harm. But for my careless swing of the stick, the injury wouldn’t have happened.

Not all examples of causation are so simple. Often there is more than one cause when a person is hurt, just as there are usually multiple causes for any major historical event. This brings us to the long-running kerfuffle over the role that Fannie Mae and Freddie Mac played in causing the financial crisis of 2008, which hasn’t really ended.

The way the discussion gets framed tends to go like this: Did Fannie and Freddie cause the crisis? Although this is the wrong question, I’ll try to answer it anyway by highlighting the difference between the meaning of the words “a” and “the.”

Here goes. Fannie Mae was a cause of the financial crisis. So was Freddie Mac. U.S. government housing policies, which often encouraged people to take out loans they couldn’t repay to buy homes they couldn’t afford, were also a cause. None of these was “the” cause of the crisis, because there was no single cause. What we can say is this: But for the actions of a vast number of actors, including Fannie and Freddie, the crisis wouldn’t have happened the way that it did.

That seems straightforward enough. Yet this silly debate -- over whether the government-backed housing financiers and their enablers were a cause or the cause -- keeps raging anyway.

Causality Proponents

Two people often cited as proponents of the notion that Fannie and Freddie caused the crisis are Peter Wallison and Edward Pinto. Both are fellows at the American Enterprise Institute, a Washington think tank. Wallison was a Republican member of the Financial Crisis Inquiry Commission who wrote a 98-page dissent to the panel’s final report in 2011.

Last month, in an article responding to a column by Joe Nocera of the New York Times, Wallison and Pinto framed their thesis this way: “Our argument is and has been that the financial crisis would not have occurred but for government housing policy implemented principally through Fannie and Freddie and the Department of Housing and Urban Development.”

It’s a debatable, if not a particularly useful, observation. One reason Wallison and Pinto have drawn so much criticism for their work is that they consistently dismiss every other possible cause of the crisis, so that only Fannie, Freddie and U.S. housing policies survive the scholars’ own “but for” test. Never mind interest rates held too low for too long, worthless regulators or banks with excessive leverage, for instance.

At most these may have been contributing factors, not causes, Wallison said in his dissent to the crisis commission’s final report last year. It’s an extreme position, for sure.

Last week in an article for the Real Clear Markets website called “How Fannie, Freddie and Politicians Caused the Crisis,” Pinto concluded by saying that “government housing policies and the toxic mortgages they spawned were the sine qua non of the financial crisis.” (Plain English translation: Each was something absolutely essential or indispensable to the crisis.)

The same could be said of so many other things, though. There were the credit raters that dispensed AAA ratings for garbage mortgage bonds that otherwise never would have been issued. There was the recklessness of top executives at American International Group Inc. and Lehman Brothers Holdings Inc.

These were also essential elements of the crisis, to name just a couple of examples. Plenty of other countries had housing and credit bubbles at the same time the U.S. did, even though they lacked institutions similar to Fannie or Freddie.

Three-Year Outrage

No doubt, it’s an outrage that Fannie and Freddie still exist, more than three years after they collapsed into government conservatorship. Last February, President Barack Obama’s administration released a report to Congress in which it proposed winding down the two companies. Yet there’s been little action on this front since then.

The Treasury Department’s gross investments in Fannie and Freddie totaled $176 billion as of Sept. 30, according to the department’s fiscal 2011 annual report, released in November. More important, if the Treasury suddenly stopped supporting the companies, the housing markets in many parts of the country probably would crash. Although Fannie and Freddie weren’t the only causes of the 2008 crisis, letting them fail now could cause a new one, as might the collapse of any systemically important financial institution. For now, we’re stuck with them.

Let’s just stipulate that Fannie and Freddie were a cause of the crisis, even a big one, and leave it at that. The crucial discussion our leaders need to be having now is how to end them. If they can’t come up with an answer, it’s probably by choice. Nobody is willing to take the hit today any more than they were in 2008. Some things seem to never change.

(Jonathan Weil is a Bloomberg View columnist. The opinions expressed are his own.)

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To contact the writer of this column: Jonathan Weil in New York at jweil6@bloomberg.net.

To contact the editor responsible for this column: James Greiff at jgreiff@bloomberg.net.