The inventiveness of America's popular-culture mavens has kept neologists working overtime. First they had to craft the word "factoid," followed by "infomercial," "infotainment" and "docudrama." Now along comes Edmund Morris, author of "Dutch"--a book about Ronald Reagan purporting to be "an authorized biography." When it became known a week ago that Morris had written a fictional character into the story, tongues started wagging. What would we call this latest hybrid--biofiction, imagino-realism, history lite?

The imaginary character materializing in Morris's memoir is Morris himself. He makes a staged entrance into Reagan's teenage years, when the real Morris had yet to be born, and appears sporadically throughout the pages of the book, which is set to be released on Thursday. Described innocently on the dust jacket by publisher Random House as "another character in the narrative," the Reagan-contemporary Morris responds encouragingly to the events that led the Midwestern sportscaster and former actor to the White House. From that fictional Morris, the author Morris culls wise observations and trenchant interpretations presumably lacking in the men and women who knew our 40th president's real contemporaries.

A kind of literary Forrest Gumpery, Morris's study of Reagan raises important questions for both the reading public and the historians with whom Morris--who won a Pulitzer Prize for his biography of Theodore Roosevelt--claims a family likeness. Fundamentally, "Dutch" calls into question Morris's integrity. If he would, without acknowledgment, create a fictional buddy for Reagan, what else might he do for literary effect?

Even when historians bore their readers (and few will deny that it sometimes happens), they stick to the evidence. They cleave to gleanings from archives, records and remembrances not for their dramatic potential, but because they judge them to be true. "This dull book can be believed," the reader affirms with a yawn.

The trade-off of heightened interest for documentary fidelity is the loss of trust.

Between historians (and biography is a sub-genre of history) and their readers lies an implicit contract. It sustains every exchange between them, but it often remains hidden until the contract has been breached. As a lawyer would quickly tell you, such a literary contract is only a convention, little more than a metaphor. But even if it is more concept than entitlement, the writer-reader bond packs a punch. "Why, this isn't history," the betrayed reader exclaims. "It's not even true!" The evanescent pleasure of dramatic effect morphs into indignation.

Who monitors this space where metaphorical contracts are made? For Morris's "Dutch," readers and critics will play the roles of prosecutor, jury and judge. And the verdict, no doubt, will be mixed. Unreconstructed sophisticates will tout the insurance policy of blase expectations. The naive will blame their disappointment on themselves, and the patrons of public probity will spell out the consequences of yielding a fierce attachment to reality to the allure of its virtual cousin.

For academic historians, two powerful forces focus their attention on the actual events as well as the meaning of the past: their own curiosity and the standards of their profession. Those learned journal reviews of historians' work, tedious to the outsider, throw a glaring spotlight on matters of method, representation and interpretation. To "publish or perish" could be added the wry addendum "publish that and perish."

A case can and should be made for exploiting the rich resources of history for novels and movies. The truth often is more fascinating than fiction; the two are often mixed for entertainment. In "Amistad," the 1997 movie about a historical slave ship mutiny, director Steven Spielberg also invented a character. He mingled with the real-life abolitionists, slave owners and political figures who determined the fate of the captured Africans whose ship had drifted into American waters in 1839. And in this case, the theatrical voice enhanced the record. Less conspicuously perhaps, moviemakers can play the role of historical interpreter. In Oliver Stone's 1991 film about President Kennedy's assassination, he argued his own theory about conspiracy in high places.

Historians natter about cinematic inaccuracies and distortions, motivated in part by their awareness of the power of a movie to overwrite previous impressions. Of course, moviegoers wonder too about the historical accuracy of such films, but the medium itself acts as a warning. "Oh, that's just Hollywood," is the oft-heard disclaimer against the bewitchment of Hollywood.

Even scholars are given to flights of fancy. No less a luminary than 9th Circuit Court Judge John T. Noonan Jr. displayed an artist's capacity for creation in his 1998 book "The Lustre of Our Country," a probing analysis of religious freedom in America. Challenged to refute the trenchant observations of Alexis de Tocqueville's 19th-century masterpiece "Democracy in America," Noonan offered his readers a personal translation of a hitherto undiscovered letter from an imaginary sister, Angelique. As one might expect from a wholly fictitious invention, Angelique revealed an understanding of American religiosity closer to Noonan's than her illustrious brother's was.

Historical novels abound, ranging from the altered life story to the totally made up. Skillful writers from Antonia Fraser to Gore Vidal have mined the rich vein of the past in a succession of bestsellers. The question is not the content, but rather the contract. Like information merging into the commercial, or documentaries dropping the documents for drama's sake, a biography makes certain claims to authenticity that readers rely upon.

Still, some would say that questions of truth, accuracy and representations of realities have been rendered moot by postmodernists--that amorphous collection of 20th-century philosophes, literary scholars, science skeptics and social critics who have worked hard these past three decades to expose the inherent flaws in all reconstructions. The past--according to their accumulated wisdom--can be visited only through a subjective re-creation in the mind of an author imbued with cultural biases expressed in that lamentably unstable medium we call language.

No doubt our late 20th-century cultural milieu, influenced by such postmodernism and imbued with factoids, infomercials and so on--not to mention the "virtualities" of cyberspace--encourages the Edmund Morrises of history's purlieus to reach for the imaginary when reality fails them. The court of public opinion will no doubt find a way to express its truest concerns in these matters. Maybe all we need is a new set of warnings. Right alongside "based upon real people portrayed here by actors," we'll insist on lines like "truth tampered with for dramatic effect; believe at your own risk."

Joyce Appleby is a professor of history at UCLA and a past president of the American Historical Association.