Nothing corrupts intellectual power like the abuse of the language. Free speech becomes an endangered species when powerful words, misused, become shortcuts for specious argument and repetitious cliches trivialize noble ideas.

Nothing stops someone in a foot-in-the-mouth defense of himself like being told "you're in denial," meaning that he's avoiding the truth of experience. If you don't acknowledge an accurate diagnosis of a terminal disease, recognize the philandering of a mate or see the approaching death that awaits us all, "you're in denial." The truth-seeker in wolf's clothing demands that everyone look at the world through his lens, as though through a glass, lightly. Denial is based not on facts, but emotion.

All deniers aren't equal opportunity deniers, and an all-purpose stigma inhibits rational argument. We see this illustrated on Page One every morning. Skeptics of global warming are compared to Holocaust deniers. The ecologically correct become eco-heresy hunters determined to silence anyone who questions their evidence, flimsy and questionable or not. Any human destruction of nature is described as "ecocide" (like genocide.) When David Irving was sentenced to prison in Austria as a "Holocaust denier," an Australian journalist suggested making climate-change denial a similar offense. An Internet commentator wants global-warming deniers to be tried like Nazi war criminals.

"Denial" came out of the therapyspeak prevalent in the middle of the 20th century, especially as it was applied to confronting the reality of mortality. It was popularized as the first stage of grief, but was quickly expanded to include refusal to confront any bad news or disturbing ideas. Like the broken clock that's correct twice a day, denial is sometimes an accurate label for certain behavior, but as a consuming mythology in our culture it becomes the all-purpose description to deny independent thinking.

On a personal level it's used to accuse others of cowardice in refusing to face up to what is regarded as in their own best interest. It elevates a kind of psychological groupthink over independent interpretations and casts a critical eye at those who face their problems in their own way. This attitude wreaks enormous havoc when it is applied to public issues.

When denial is used against those who question the evidence of conventional wisdom it acts as a secular Inquisition creating a free-floating metaphor for post-modern blasphemy. "This targeting of denial has little to do with the specifics of the highly charged emotional issues involved in discussions of the Holocaust or AIDS or pollution," writes sociologist Frank Furedi in Spiked Online. "Rather it is driven by a wider mood of intolerance towards free thinking." It becomes an informal but dangerous form of collective censorship, limiting free speech and demanding social or civil punishment, or both. (Free speech defenders have no problem defending their own dearly held beliefs, but often when called on to defend something they consider dangerous find all manner of exceptions.)

For all of the creepiness of "Holocaust denial," making it against the law not only restricts free speech, perniciously wrong-headed as that is, but forces those who perpetuate it to go underground. When President Mahmoud Ahmadinejad of Iran held his Holocaust denial conference in Tehran, he exposed his irrational hatred to the rest of the world, making his threat to "wipe Israel off the map" and his determination to develop nuclear weapons suddenly visible as a genuine threat to everyone.

His hyperventilated rhetoric, as outrageous as it is, requires counter arguments of reason and cannot be dismissed as the ravings of a madman, a mistake many critics of Hitler made. The Tehran conference drew wide rebuke, inspiring hundreds of articles refuting speaker after speaker. Such refutations won't dissuade the anti-Semites who ply their trade in the Middle East, but will establish a contemporary historical record and heighten the alert for those in the Western democracies who understand that words can be deadly weapons of mass destruction.

No word has been so trivialized as "Holocaust." It's attached to issues that bear no relation to the crimes of the Nazis of the Third Reich. The triumph of bad taste and perversion of moral meaning is exhibited by animal rights protesters who compare the slaughter of animals to the slaughter of Jews. In one of their campaigns, called "Holocaust on Your Plate," images of animals locked in pens are superimposed on photographs of emaciated prisoners behind the barbed wire of a concentration camp.

The human talent for devising destruction is boundless, and humans of goodwill must demand the careful use of words to make reasonable distinctions.

If we don't, we are truly in denial.