When, if ever, is lying justified? I talked about this conundrum this week in a freshmen humanities class, in which we were reading Immanuel Kant on morality. Kant proposed that we judge the rightness or wrongness of an act, such as breaking a promise, by considering what happens if everyone does it. If you don't want to live in a world in which everyone routinely breaks promises, then you shouldn't do so.

That's a fine principle, in the abstract, but my students and I agreed that in certain situations lying is excusable. Shouldn't you lie if your girlfriend asks you if you like her new haircut? If your boss, who's a vindictive bastard, asks your opinion of his new business plan? What about lying in order to reveal a plot that you believe imperils all of humanity?

That brings me to the latest scandal to emerge from the debate over global warming. Two weeks ago, an anonymous source distributed internal documents from the Heartland Institute, a conservative organization, to journalists and bloggers. As reported on this site on February 15, the documents revealed, among other facts, that the Heartland Institute, as part of a larger strategy for undermining support for global warming, was supporting prominent skeptics such as physicist Fred Singer and geologist Robert Carter.

Last week, Peter Gleick, a global-warming researcher and environmental activist, admitted on Huffington Post that he had been the source of the documents. Gleick confessed that he obtained the documents by approaching the Heartland Institute under a feigned identity.

The incident has exposed a deep fissure not just between global-warming deniers and believers but within the green community. For example, the journalist Andy Revkin, author of the blog Dot Earth, deplored Gleick's actions, for the following reasons:

"One way or the other, Gleick’s use of deception in pursuit of his cause after years of calling out climate deception has destroyed his credibility and harmed others. (Some of the released documents contain information about Heartland employees that has no bearing on the climate fight.) That is his personal tragedy and shame (and I’m sure devastating for his colleagues, friends and family). The broader tragedy is that his decision to go to such extremes in his fight with Heartland has greatly set back any prospects of the country having the 'rational public debate' that he wrote—correctly--is so desperately needed."

Another blogger, Joe Romm of Climate Progress, granted that Gleick "committed a serious lapse of professional judgment and ethics. He is right to regret his actions and make a personal apology." But Romm went on to demand that Revkin apologize for quoting global-warming sources who, according to Romm, have "been repeatedly debunked, the disinformers and confusionists." Romm is referring not to deniers but to believers—such as Roger Pielke, a respected scientist--who do not accept the most extreme climate-change scenarios and solutions. To my mind, Romm is faulting Revkin—who is one of the most knowledgeable, conscientious, hard-working journalists I know--for doing his job well.

Gleick himself sounded contrite. He put it this way: "My judgment was blinded by my frustration with the ongoing efforts--often anonymous, well-funded, and coordinated--to attack climate science and scientists and prevent this debate, and by the lack of transparency of the organizations involved. Nevertheless I deeply regret my own actions in this case. I offer my personal apologies to all those affected."

Kant said that when judging the morality of an act, we must weigh the intentions of the actor. Was he acting selfishly, to benefit himself, or selflessly, to help others? By this criterion, Gleick's lie was clearly moral, because he was defending a cause that he passionately views as righteous. Gleick, you might say, is a hero comparable to Daniel Ellsberg, the military analyst who in 1971 stole and released documents that revealed that U.S. officials lied to justify the war in Vietnam.

But another philosopher my students and I are reading, the utilitarian John Stuart Mill, said that judging acts according to intentions is not enough. We also have to look at consequences. And if Gleick's deception has any consequences, they will probably be harmful. His exposure of the Heartland Institute's plans, far from convincing skeptics to reconsider their position, will probably just confirm their suspicions about environmentalists. Even if Gleick's lie was morally right, it was strategically wrong.

I'll give the last word to one of my students. The Gleick incident, he said, shows that the "debate" over global warming is not really a debate any more. It's a war, and when people are waging war, they always lie for their cause.

Image by Dave Burnham, courtesy Wikimedia Commons.