"Credibility" is one of the most popular ideas in the Washington foreign policy community. Basically, the theory goes, the United States keeps the peace in the world through reputation — because foreign states know that when the US threatens the use of force to protect the status quo order, we mean it. Foreign countries know not to test us, so everyone stays in line.

In this theory, if the US fails to act, especially when it's said it will, America's enemies abroad will be, in the common parlance, "emboldened," believing they can now get away with more aggression and other forms of bad behavior.

"Credibility" has been central, to name one example, in the debate over US policy on Syria; some argue that the US, having drawn its "red line" over Bashar al-Assad's use of chemical weapons, must intervene to win back its credibility in the eyes of a wary and suspicious world.

But there's at least one person who thinks the concept of credibility is total bullshit: President Barack Obama.

"This theory is so easily disposed of that I’m always puzzled by how people make the argument," Obama tells the Atlantic's Jeffrey Goldberg in a just-out profile in the magazine.

"Dropping bombs on someone to prove that you’re willing to drop bombs on someone is just about the worst reason to use force."

To demonstrate his point, Obama cites Russia's 2008 invasion of Georgia — which came when George W. Bush was in the White House:

"I don’t think anybody thought that George W. Bush was overly rational or cautious in his use of military force. And as I recall, because apparently nobody in this town does, Putin went into Georgia on Bush’s watch, right smack dab in the middle of us having over 100,000 troops deployed in Iraq."

Obama went back to the Reagan administration, pointing out that Reagan was perfectly willing to withdraw from countries militarily (as he did from Lebanon in 1983) if it wasn't in America's interests.

Moreover, Obama cites Reagan's military adventure in tiny Grenada, saying it's "hard to argue" that the 1983 war "helped our ability to shape world events." Reagan also presided over "the Iran-Contra affair, in which we supported right-wing paramilitaries and did nothing to enhance our image in Central America, and it wasn’t successful at all."

"Apparently all these things really helped us gain credibility with the Russians and the Chinese," Obama added sarcastically. "That’s the narrative that is told."

He continued:

Now, I actually think that Ronald Reagan had a great success in foreign policy, which was to recognize the opportunity that Gorbachev presented and to engage in extensive diplomacy—which was roundly criticized by some of the same people who now use Ronald Reagan to promote the notion that we should go around bombing people.

Clearly, Obama thinks the theory — so popular in Washington — is bunk.

And he has a point.

Obama is right, and it really matters

Political science research into this question suggests that Obama may be correct that if America backs away from one crisis in one part of the world, it does not tempt countries elsewhere in the world to test American "credibility."

"Do leaders assume that other leaders who have been irresolute in the past will be irresolute in the future and that, therefore, their threats are not credible? No," the University of Washington's Jonathan Mercer concludes flatly in a Foreign Affairs piece. "Broad and deep evidence dispels that notion."

Credibility, for example, was a key argument for the Vietnam War: Kennedy and Johnson advisers warned that the Soviets would see American inaction there as evidence of American weakness, which they would seek to exploit.

The National University of Singapore's Ted Hopf, after looking at Russian archives, concluded that this ended up being false.

"No Soviet ever inferred from Vietnam that dominoes would fall in strategic areas of the world," Hopf writes. "While Soviets were in agreement that revolutionary movements around the globe would be greatly encouraged by the gains in Southeast Asia, they simultaneously expected continued US resistance to these challenges in the Third World."

The Vietnam example is supported by studies of other periods, including World War I and II. The latter is especially important: Credibility proponents often cite the concessions made to Hitler at the 1938 Munich conference as evidence that "appeasement" emboldens dictators.

But it turns out that Hitler's continued expansions were rooted in ideology and cold calculations of his military superiority to his neighbors, not a nebulous sense that British and French leaders were afraid to use force.

"Every time analysts and leaders call for war, they warn that inaction will jeopardize America’s credibility," Dartmouth professors Jennifer Lind and Daryl Press write in Foreign Policy. "What is more surprising, however, is how little evidence there is for this view."

The bottom line, then, is that the best evidence we have suggests Obama is correct about the Washington-chic notion of credibility.

This, perhaps in part, also speaks to Obama's 2014 quote that a major principle of his foreign is, "Don't do stupid shit."

Going to war for "credibility" could be considered an example of how Obama might define "stupid shit." The theory is unsupported by the historical record or available research, yet it remains mystifyingly popular — to the point where people are willing to put American lives on the line on its behalf.