It's ironic that one of the examples New York Times Public Editor Arthur Brisbane used in asking whether reporters should be “truth vigilantes” has already been fact-checked.

In March 2010 PolitiFact ruled that it's not true that President Barack Obama has apologized for American misdeeds, as Mitt Romney has claimed.

Brisbane's other example – whether Supreme Court Justice Clarence Thomas really misunderstood a financial disclosure form – is not the sort of thing that can be fact-checked, no matter how implausible it may seem. (Brisbane said as much in a response to Jim Romenesko and in a followup post.)

“I wonder if Art hasn't confused matters a bit by his choice of examples,” said Bill Keller, former executive editor and current op-ed columnist, via email.

The question of whether Obama “apologized for America” is a matter that lends itself to testing. … The question of whether Clarence Thomas “misunderstood” a financial reporting requirement, on the other hand, is not a checkable fact, unless you hook Justice Thomas to a polygraph or pump him full of sodium pentathol. You can't “check” what was in his head. But readers can decide for themselves whether they find his explanation credible. My point is, there's a continuum of types of information that cannot all be handled in the same way.

Keller said the Times and other news orgs have already formalized its fact-checking. For example, it's common to assign Times reporters to fact-check during debates. And PolitiFact Editor Bill Adair noted that Times reporters already cite PolitiFact in news stories – the sort of situations in which Brisbane asked if reporters should knock down untruths.

"I think calling out mistakes or misrepresentations is very much part of the journalistic obligation," Keller said. (Executive Editor Jill Abramson lists some examples in a response to Brisbane.)

Fact-checking has become so popular that two conferences were held recently on the subject in about a month. “I hope Mr. Brisbane understands that there is in fact a tremendous movement in journalism toward more fact-checking,” Adair said.

Almost no punchline has gone unuttered in the reaction to Brisbane's post. Many people said that it should go without saying that journalists should try to report the truth and verify facts.

“A lot of people responded to a question I was not asking,” Brisbane told Romenesko.

“What I was trying to ask was whether reporters should always rebut dubious facts in the body of the stories they are writing. … I was also hoping to stimulate a discussion about the difficulty of selecting which 'facts' to rebut, facts being troublesome things that seem to shift depending on the beholder’s perspective.”

Adair took issue with that idea. “It's wrong to equate fact-checking with opinions. Fact-checking is simply good accountability journalism.”