He looks like a cross between Santa Claus and a New Age guru, and he calls himself an alternative healer. But Radovan Karadzic, who was arrested in Serbia last Monday, stands accused of war crimes, genocide and crimes against humanity.

To those who know his history, Karadzic, former president of the "Republika Srpska" and one of the chief architects of the brutal Bosnian war, is the man who brought the concentration camp back to Europe and ordered Europe's worst massacre since World War II (in 1995, Bosnian-Serb forces slaughtered more than 7,000 unarmed Bosnian Muslim men and boys near Srebrenica). With Karadzic's approval, torture and starvation became routine methods of prisoner control, organized mass rape became a spectator sport and snipers were authorized to fire on children during the siege of Sarajevo.

Karadzic's arrest was long overdue. He was indicted by the U.N.'s International Criminal Tribunal for the Former Yugoslavia at The Hague 13 years ago, and since then, he had hidden in plain sight, protected by tolerant Serbian officials. At some point, Karadzic even stopped bothering with his once-heavy security detail: He simply replaced his trademark bouffant hairdo with a jolly white beard, took up acupuncture and holistic medicine and opened a practice as a New Age healer.

The irony has been lost on no one. Here's a man accused of the worst crimes devised by human ingenuity — and he calls himself a "healer"?

But this shouldn't surprise us. The perpetrators of atrocities have always favored metaphors of healing. Just as a physician might use purges to rid a patient's body of internal toxins, Stalin imagined that his purges would rid the Soviet body politic of dangerous internal corruption. Hitler saw the Jews as "a cancer on the breast of Germany" and was convinced that the extermination of the Jews was essential to restoring the health of the Aryan nation.

Pol Pot wanted to "purify" Cambodian society, eliminating those infected with a Western taint as ruthlessly as a physician wipes out infections. In Rwanda, Hutu "genocidaires" derided the Tutsi as "cockroaches," spreaders of dirt and disease who needed to be destroyed for the well-being of society. For Karadzic as well, there was probably no sense of discontinuity between healing and destroying; one was essential to the other.

It's easy to dismiss all this with a cynical snort. Karadzic and other perpetrators of atrocities may use metaphors of healing, but they can't really believe that killing and healing can be reconciled, right?

I'm not so sure. All the evidence we have suggests that human beings are adept at self-deceit. Alone among animals, humans are tellers of stories — and we tell stories to ourselves as well as to others. We trick ourselves constantly, in countless tiny ways, into believing that the bad deeds of others are very bad indeed, while our own are necessary, minor, forgivable — or maybe not even bad at all.

In one recent study, for instance, Northeastern University psychologists Piercarlo Valdesolo and David DeSteno found that when subjects were asked to assign tasks to themselves and to strangers, nearly all gave themselves easy tasks while assigning unpleasant tasks to people they didn't know. When asked if their actions were fair, subjects were quick to find appealing rationales to justify saddling strangers with all the lousy jobs. But these same subjects were quick to condemn the same selfish behavior when they saw others engage in it.

At least on a microscopic level, then, most of us aren't all that different from Karadzic or any of the other killers who cloaked their atrocities in the soothing rhetoric of healing. We're all moral hypocrites, willing to believe our own justifications for the rotten things we want to do.

There's a depressing lesson here. Uplifting rhetoric — even the language of healing, generosity and compassion — can genuinely mask the true nature of bad deeds (even from those who carry them out). As a nation at war, it's a lesson we should remember.

But there's some intriguing and potentially good news as well from the world of social psychology: Valdesolo and DeSteno also found that when experimental subjects were asked to assess the fairness of their own selfish behavior while simultaneously engaging in some other difficult mental task (memorizing a long string of numbers), they judged their behavior far more harshly. It seems, Valdesolo and DeSteno concluded, that if you tie up some cognitive capacity with a difficult task, there's just not enough brain power left over to successfully lie to yourself any more.

And maybe that's reason for optimism, in the end. If hypocrisy is created and sustained by mental effort, maybe it's something that we — and even the worst moral hypocrites — can eventually learn to unlearn.

Rosa Brooks is a professor at the Georgetown University Law Center. She wrote this commentary for the Los Angeles Times.