FORMER U.S. VICE PRESIDENT Al Gore urges us all to reduce our carbon footprint, yet he regularly flies in a private jet. Former drug czar William Bennett extols the importance of temperance but is reported to be a habitual gambler. Pastor Ted Haggard preached the virtues of the clean life until allegations of methamphetamine use and a taste for male prostitutes arose. Eliot Spitzer prosecuted prostitution rings as attorney general in New York State, but he was later found to be a regular client of one such ring.

These notorious accusations against public figures all involve hypocrisy, in which an individual fails to live according to the precepts he or she seeks to impose on others. Charges of hypocrisy are common in debates because they are highly effective: we feel compelled to reject the views of hypocrites. But although we see hypocrisy as a vice and a symptom of incompetence or insincerity, we should be exceedingly careful about letting our emotions color our judgments of substantive issues.

Allegations of hypocrisy are treacherous because they can function as argumentative diversions, drawing our attention away from the task of assessing the strength of a position and toward the character of the positions advocate. Such accusations trigger emotional reflexes that dominate more rational thought patterns. And it is precisely in the difficult and important cases such as climate change that our reflexes are most often inadequate.

Thus, listeners should temper such knee-jerk reactions toward the messenger and instead independently consider the validity of the message itself. It also pays to examine closely what the duplicitous deeds really mean: from some vantage points, such behavior may actually support a hypocrites point of view, significantly softening the hypocrisy charge in those cases.

Undermining Authority
One surprising truth about hypocrisy is its irrelevance: the fact that someone is a hypocrite does not mean that his or her position on an issue is false. Environmentalists who litter do not by doing so disprove the claims of environmentalism. Politicians who publicly oppose illegal immigration but privately employ illegal immigrants do not thereby prove that contesting illegal immigration is wrong. Even if every animal-rights activist is exposed as a covert meat eater, it still might be wrong to eat meat.

More generally, just because a person does not have the fortitude to live up to his or her own standards does not mean that such standards are not laudable and worth trying to meet. It therefore seems that charges of hypocrisy prove nothing about a topic. Why, then, are they so potent?

The answer is that such allegations summon emotional, and often unconscious, reactions to the argument that undermine it. Such indictments usually serve as attacks on the authority of their targets. Once the clout of an advocate is weakened, the stage is set for dismissal of the proponents position. Consider the following two examples:

Dad: You shouldnt smoke, son. Its bad for your health, and its addictive.

Son: But, Dad! You smoke a pack a day!

Amy: Have you seen Al Gores An Inconvenient Truth? We need to reduce our carbon footprint right away.

Jim: Al Gore? You know he leaves a huge footprint with all his private jet flights!

In the first example, the son feels that his father is not an appropriate source of information on smoking because Dad is a hypocrite. The accusation of hypocrisy does not so much defeat Dads position as nullify it, almost as if Dad had never spoken. The same holds in the case of Gores airplane, although the speaker, Amy, is not the alleged hypocrite but rather Gore, the authority to which she appeals. In both cases, hypocrisy is proffered as evidence of the insincerity or incompetence of a source, providing ammunition for ignoring his or her advice or instruction.

Such ammunition is particularly potent because of the power of such personal portrayals. Once people have characterized someone in a negative light, they tend to ignore evidence to the contrary. In a 2007 study psychologists David N. Rapp of Northwestern University and Panayiota Kendeou of McGill University asked student volunteers to read 24 different stories involving a character who behaves in a way that suggests he is sloppy or lazy. Later in each story, however, the individual acts in a manner that contradicts this judgment. Nevertheless, less than half of the respondents revised their view of the character.

These results suggest that a first impression of someone as lazy or hypocritical actively inhibits the consideration of other information that might be important to understanding that person or the issue at hand. In the smoking and airplane examples, the son and Jim foolishly focus on the fathers and Gores hypocrisy rather than on the perils of smoking or the human contribution to global warming.

Duplicity Understood
In fact, if the son and Jim had focused on the issues, they might have viewed the fathers and Gores behavior radically differently. Consider what Dads smoking suggests: Dad believes smoking is bad for him, yet he continues to smoke because, of course, he is addicted. So Dads behaviorhis hypocrisyactually supports his point that smoking is addictive. Gores behavior also bolsters one of his arguments for change in national energy policy: that certain ingrained aspects of the American lifestyle, such as our penchant for driving SUVs and distaste for riding city buses, lead to environmental irresponsibilityeven Gore cannot escape it. (To his credit, Gore compensates for his plane trips by buying carbon offsets, which pay for projects that reduce greenhouse gas emissions.)

Of course, hypocrisy does not always support the hypocrites view. Spitzers visits to prostitutes do nothing to reinforce his official opposition on prostitution. And in some cases, hypocrisy has precisely the significance that the son and Jim assign to it: it is reason enough to dismiss a source because the person has lost his credibility. For example, when the preacher who presents himself as a moral authority gets caught having an adulterous affair, his followers may rightly call his teachings into question.

Thus, hypocrisy is sometimes sufficient to undermine a persons authority. It can warrant the thought, Why pay attention to what he says? But hypocrisy does not always have this effect, as the Dad and Gore cases show.

Whether hypocrisy is relevant to a persons credibility usually depends on the content of the hypocrites statements. And yet hypocrisy charges, as they are popularly deployed, tend to short-circuit rational examination of that content. To skirt this danger, people should suppress their instinctual responses to accusations of duplicity so that they can focus on the real issues at hand. Such concentration is essential to our ability to rationally judge our leaders, colleagues and friends as well as to make decisions about important social issues that affect our lives.