Let's return to the 2009 story that Fox News correspondent James Rosen published on North Korea, kicking off a federal leak investigation and the FBI accusation that he was guilty of criminal conduct. "U.S. intelligence officials have warned President Obama and other senior American officials that North Korea intends to respond to the passage of a U.N. Security Council resolution this week... with another nuclear test," he reported that June 11. "What's more, Pyongyang's next nuclear detonation is but one of four planned actions the Central Intelligence Agency has learned, through sources inside North Korea, that the regime of Kim Jong-Il intends to take -- but not announce -- once the Security Council resolution is officially passed, likely on Friday."

Although Rosen's story asserts that it is "withholding some details about the sources and methods ... to avoid compromising sensitive overseas operations," the basic detail that the CIA has "sources inside North Korea" privy to its future plans is very compromising stuff all by itself. As Rosen continues, "U.S. spymasters regard [North Korea] as one of the world's most difficult to penetrate."

Once the North Koreans read the story, they must have asked if the source of the intel was human or if their communications had been breached. In any event, you can assume that the North Koreans commenced a leak probe that made the U.S. investigation look like the prosecution of a parking ticket. I have a hard time understanding what purpose Rosen's scoop served. He appears to have uncovered no wrongdoing by the CIA in North Korea and no dramatic or scandalous change of U.S. policy that's being concealed from the U.S. public. Boiled to its essence, the story says the U.S. has penetrated North Korean leadership. It's a story, all right, but I can't imagine any U.S. news outlet running it without more cause, and I'll bet that Fox News would take it back today if it could. I doubt that Rosen has committed any crimes against the state, but offenses against common journalistic sense?

I'm not so sure.

Kevin Drum also has harsh words for Rosen and his source.

These are strong arguments. I remain undecided about the wisdom of the story, since I know neither why Rosen's alleged source, Stephen Jin-Woo Kim, found it important to leak this information; nor why Rosen wanted to publish the story; nor what really happened in North Korea; nor what Rosen knew but excluded from his story to protect sources inside North Korea. Given what we know, it is certainly plausible that this individual story, taken in isolation, had little journalistic benefit and imposed a high cost on people working against a totalitarian regime.

But unlike BooMan, I am not ready to conclude that Rosen's story did significant harm. Most times when classified information is revealed, critics of the leak spin out a maximalist case for why it is devastating to American foreign policy or national security. Serious harm could've been done in this case, but assuming so ignores alternative possibilities that strike me as plausible. This speculation isn't meant as an argument that Rosen was right or wrong to run with his story. It is merely an argument for recognizing that we can't presently assess the cost of his actions.

Perhaps "sources inside North Korea" were caught as a result of this story.

Alternatively, perhaps the North Koreans killed a high-level official, suspecting him of being the leak, when in fact he was both loyal to the regime and important to its ability to function capably.

Or maybe Americans were slightly better informed with no particular consequences.

Perhaps the story's most damaging cost was its effect on dissidents within authoritarian regimes who are now less willing to talk to us.

Alternatively, perhaps the revelation that there are sources inside North Korea, and the North Koreans' failure to catch them, has emboldened other would be dissidents to oppose the regime.

Perhaps the story has inspired the North Koreans to respond with an even more alarming provocation that we'll only know about when it happens three days from now. Alternatively, maybe they would've gone forward with a nuclear detonation but for this story, and it would've somehow triggered the sort of military exchange that South Korea and the U.S. have long feared.

I don't pretend that all of these scenarios are equally likely. But as Malcolm Gladwell adeptly showed in his lengthy and fascinating look at a World War II spy operation, the way that spy-craft plays out is very difficult to predict, or even to discern after the fact. One passage specifically addresses what happens when a nation suspects a mole in its midst. "If you cannot know what is true and what is not, how on earth do you run a spy agency?" Gladwell asked. "In the nineteen-sixties, Angleton turned the C.I.A. upside down in search of K.G.B. moles that he was sure were there. As a result of his mole hunt, the agency was paralyzed at the height of the Cold War. American intelligence officers who were entirely innocent were subjected to unfair accusations and scrutiny. By the end, Angleton himself came under suspicion of being a Soviet mole, on the ground that the damage he inflicted on the C.I.A. in the pursuit of his imagined Soviet moles was the sort of damage that a real mole would have sought to inflict on the C.I.A."

It's easy to tell a hypothetical story about how a leak "must have" harmed national security. What the American people should demand, if they're being asked to believe that harm has been done, is the best available evidence for that conclusion. Take-my-word-for-it assertions from national security officials don't count. They've squandered their credibility on too many occasions. But neither should we assume, without evidence, that this leak did no damage. The information now available requires agnosticism.