AROUND 1974, the Firesign Theater, a once celebrated satirical troupe of the '60s, released a splendid album purporting to be a radio broadcast by a California seer. This adept was the possessor of much secret knowledge. "Did you know," he asked his listeners, "that everything you know is wrong?" His revelations were startling. Dogs fly spaceships. The Aztecs invented the vacation. Men and women are the same sex. And so on.

The more I think about it, the more I'm convinced that the Firesign Theater was on to something. Two experiences in particular have lately caused me to reexamine the thesis. Not long ago, I was wandering around the Iwo Jima memorial and found myself next to a pair of young men about my age. One turned to the other and said, "You know this was faked. One guy really put the flag up there. Then, like a week later, the general got a cameraman and he made these guys go up there with a much bigger, flashier flag. They practiced putting the flag up for hours."

He looked deeply serious and, although he had the story quite wrong, a shade self-congratulatory.

A couple of months later I was walking around Canterbury, Kent. Not a hundred yards from the cathedral where Thomas a` Becket met his unhappy fate at the hands of Henry II's courtiers, I glanced in the window of a bookseller and saw a piece of curled parchment, copies of which were presumably for sale.

Taking issue with the view of Becket as a "holy blissful martyr," it called him and Henry "two arrogant and single-minded men . . . who fought out their personal quarrels on the field of history and made a thorough nuisance of themselves doing it.

"The story is far from heroic," it went on. "Everything that happened could have been avoided with a bit of common sense . . . ."

I recalled what the Firesign Theater's seer had said, after imparting his litany of esoterica: "If you were never a special person, you are a special person now."

So many of us boomers are special persons now, prepared to shrug off at a moment's notice the frumpy frock of common knowledge for the hip Nehru jacket of revisionism. It's the quickest way to be thought independent of mind, impervious to hogwash, above the herd. For the enlightened baby boomers -- and who among us is not enlightened? -- revisionism is a habit of mind.

The habit informs everything. In journalism, the hippest editor craves a piece proving that what you thought to be history is actually bunk. A recent issue of a national art magazine, for example, alerted us to the "Gauguin myth." Initiates now know that the French painter, who we thought created charming works in a South Seas idyll, in truth led a shabby life wracked with disease on a Tahiti which, having long before his arrival abandoned native ways, lacked only a Pizza Hut to complete its descent into Western decadence. Those lovely native robes? Of European design. And the lubricious maidens? Hookers. A splendid piece: Everything you know about Gauguin is wrong.

The smart boomer has wised up to the con in its infinite forms. In his hands, any book, any movie, any scholarly treatise, any conversation might at any moment transmogrify into a game of one-upsmanship: How big a truth can you topple? By embracing revisionism, the baby boomers make themselves heirs to an honored tradition. Debunking goes back beyond Tacitus, who portrayed Tiberius as a bloodthirsty hypocrite. In America, debunking has more often been the business of misanthropes: Mark Twain pooh-poohing the charge up San Juan Hill, Ambrose Bierce recasting the Civil War as simple man-to-man barbarism, H.L. Mencken setting the record straight on the Gettysburg Address. From this distance the practice seems refreshing, in a democratic sort of way. Moreover, complicated truths are more satisfying than simple ones.

The origins of compulsive debunking lie in the triumph of scientism over religion, perceived as a victory for sophistication and good character. The discrediting of biblical revelation filled the smart guys with a giddy confidence from which the culture has never quite recovered. It is this strain of revisionism to which the boomers are heir.

By now, there is a whole genre dedicated explicitly to the proposition that everything you know is wrong, with titles like "The Prevalence of Nonsense," "Legends, Lies & Cherished Myths of American History," "They Never Said It," "Fabulous Fallacies," "Popular Fallacies" and so forth. The best-selling "Legends, Lies" is the most recent of these. Its jacket copy could have been written by the Firesign Theater: Pilgrims never lived in log cabins; no one ever died in a frontier shootout at high noon; independence wasn't declared on July 4.

Not surprisingly, these collections can stale with time. Bergen Evans's pathbreaking collection of the '40s, "The Natural History of Nonsense," devotes several pages to refuting beliefs in mermaids, wolves that raise children, conception without coition and other "vulgar errors." In attempting to free us from the "barbarism and slavery" of common wisdom, however, Evans casts rather a wide net, hauling up some items that would strike a less astringent mind as harmless: It's not true, he insists, that "there are no atheists in foxholes."

In 1967, Ashley Montagu and Edward Darling pressed ahead with the business of dismantling the edifice of bushwa in "The Prevalence of Nonsense." They ticked off the lies with clinical dispatch: The apple never fell on Newton's head. Fulton's boat wasn't called the Clermont. Mussolini did not make the trains run on time. Spectators at the Coliseum never called for the death of a vanquished combatant by turning thumbs down.

But though Montagu and Darling affirm their dedication to the exposure of untruth, "{W}e do so without entertaining the alluring whimsy that to expose it will end it." To no whimsy -- not even the notion that he might be doing some good -- does the debunker succumb. Just as Montagu and Darling published their book, that unprecedented carnival of debunking, the baby boom, was unpacking its tent. The main attractions were gaudy and numberless: books, magazine articles, movies, plays and TV shows. But very few of them were tempered by Montagu and Darling's sense of futility. The new zeal was the zeal of the reformer; revisionism now aimed not simply at correcting factual errors but at moral improvements too.

One of the most popular movies of the day, "Litle Big Man," from the Thomas Berger novel, starred Dustin Hoffman as a dwarfish picaro who dragged us through an Old West unknown to devotees of the Duke and John Ford. The truth could at last be told: a moral truth. Here the white man was avarice and hypocrisy made flesh.

Little Big Man's Indians, by contrast, were gentle and close to the earth. As the cameras panned the inside of a teepee you half expected to see well-thumbed copies of Khalil Gibran lying about. And this idyll was destroyed in a river of blood by an icon of prerevisionist America: George Armstrong Custer, psychopath.

Soon afterward, Gore Vidal began his series of historical novels. Vidal's America is irredeemably debased by the slithery forces of commerce and the bumbling of buffoonish pols. It is revealing of his method that he chose Aaron Burr as the subject of his most entertaining (and ridiculous) romance. In "Burr," the founding of America is told through one of America's most cynical men.

Here, for example, is our first glimpse of George Washington: "I looked up into his face: the yellow pockmarked skin was slightly covered with powder, the gray eyes sunk in cavernous sockets were lustreless; the expression was grave but somewhat vacant." Moreover, "he had the hips, buttocks, and bosom of a woman." George's innards were worse: Washington is vain, willful, an oaf on the battlefield and infinitely susceptible to flattery. One by one the heroes fall: Jefferson, Hamilton, Clay. "History, as usual," Burr writes, "has got it all backward."

The Founding Fathers routinely take it on the chin from debunkers. The first roundhouse was delivered 75 years ago by Charles A. Beard, who argued that the Consitution was merely "an economic document" written by a "consolidated economic group . . . whose property interests were immediately at stake"; and by God (whom they didn't believe in), the fat cats meant to keep what they had and expand it too.

Fawn Brodie's life of Thomas Jefferson, published in the early '70s is surely one of the most notorious debunkings in generations. Most of her claims have faded with time, but her tale about Jefferson and his love slave Sally Hemings is now indelibly part of his public portrait.

But if you want to prove everything you know about America is wrong, why stop with the Founders? As the 500th anniversary of Christopher Columbus's voyage approaches (it was 1492, wasn't it?), the truth-telling will likely reach a deafening crescendo. Columbus, if you didn't know, was "a murderer, he was a slave-trader, he was a rapist, he was the architect of a policy of genocide that continues today in this hemisphere." I quote the remarks of Glenn Morris, professor of the University of Colorado's department of political science, delivered in honor of Columbus Day 1989. Academics face unremitting pressure to reject accepted wisdom. Prof. B. J. Whiting of Harvard once formulated a principle of academic careerism: The easiest way for a scholar to advance is to seize a proposition that everyone knows to be true and pronounce it false. Whole departments of our great universities have been constructed according to Whiting's Law. Sometimes the method is a simple shift of emphasis. Just as often, though, the rejection comes wholesale.

But revisionism can get to be a strain, as Robert William Fogel will tell you. By the mid '70s, Prof. Fogel was already something of a superstar in the ever-widening revisionist circles, having announced -- pace everybody -- that railroads weren't a crucial factor in the development of the American West. It was a tough act to follow, but Fogel followed it. With the aid of census data and plantation ledgers and computer processing, he formulated perhaps the most daring thesis in the history of history: Slavery wasn't as bad as all that.

Fogel and his colleague Stanley Engerman took pains to argue, convincingly, that they weren't racists. They insisted that their book, "Time on the Cross," represented "the honest efforts of scholars whose central aim has been the discovery of what really happened." They were merely hosing off our sticky sentimentality.

The truth, then: The antebellum South was not an economic basket case but a boom region; slave agriculture was 35 percent more efficient (note the exactitude) than family farming; the typical slave, far from being exploited, received a 90 percent (precisely!) return on his labor, much more than industrial workers in the North; black slave families were only rarely broken up and were in truth encouraged by slave owners; and so on.

Their findings launched the authors on a tortuous path of argument, though they never lost sight of their revisionist destination. The only reason, as it turns out, the rest of us have a negative view of slavery is that we inherited our view from the abolitionists, and abolitionists despised slavery because they were . . . racists -- more odious, indeed, than slave owners, who at least thought highly enough of blacks to prize them as laborers. Not at all incidentally, the effect of this conclusion is to shift blame for the sorry lot of some present-day blacks away from the legacy of slavery and the perniciousness of slave-owners -- those distant men we hold in contempt -- onto the deceit of abolitionists, with whom most people today like to feel some identification. And if we praise these our heroes for their racism, then it follows that we too are racist.

Extraordinary! In the annals of revisionism there is really nothing else quite like it. Utterly counterintuitive, subversive not only of common knowledge but of common morality, wholly irrational yet possessing an ineluctable interior logic, the Fogel-Engerman book achieved a kind of perfection in the art of revisionist one-upmanship. Reading "Time on the Cross," you wonder: How could Fogel -- how could anyone -- top this?

He couldn't. Indeed, it all went kaput. In 1989, Fogel published another book on slavery whose purpose was to retract many of the conclusions of "Time on the Cross." Slavery, the post-Reagan Fogel decided, was a "profound injustice." As James McPherson pointed out in a review of the book in The New Republic, Fogel's new findings sound almost banal -- surely the lowest blow a critic can land on a professional debunker. There is thus little comfort to be had in Prof. Fogel's retreat. If debunking were truly inspired by a desire to find out "what really happened," it might slowly dissipate as individual assertions were meticulously disproved. But not only is much revisionism beyond disproof, its inspiration is often different: an attempt to trim the past according to a fashionably crabbed view of the present.

There remains this consolation: The particularities of our present revisionism will pass from fashion by and by, and on that day the baby boomers who pride themselves on a world-weary wisdom will find the tables turned. A new generation of smart guys is being educated even now, soon to discover its own list of items for debunking, many of them notions dear to the boomer heart. Watch for a biography asserting that Ringo was the genius behind the Beatles, for example. How daring it will all be. How new. How fresh!

Andrew Ferguson writes for Scripps-Howard newspapers. This article is adapted from "Beyond the Boom," edited by Terry Teachout and published by Poseidon Press.