In a conversation with Dick Cavett published in The New York Times last week, David Brooks, one of the more thoughtful and effective conservative political analysts now writing, noted the American empire is in significant decline.

Brooks is hardly the first to suggest that American power, greatness and quality of life have an endpoint, as had other empires'. Brooks and Cavett's discussion was prompted by a recent essay in Foreign Affairs by Harvard financial historian Niall Ferguson, "Collapse and Complexity: Empires on the Edge of Chaos." Ferguson evokes a classic series of five paintings by the Hudson River School painter Thomas Cole (1811-1848) called "The Course of Empire," showing the birth, apotheosis and inevitable decline of imperial power. Ferguson argues that the decline of empire can be rapid and chaotic, not slow and invisible, as often portrayed.

Writing in the current issue of Newsweek, columnist Andrew Nagorski also cites Ferguson's essay. There's something in the air, writes Nagorski, and it's not talk about the promise of America.

It might seem logical that literate Americans would turn to major professional historians for meaningful analyses of an American decline. But as most historians themselves acknowledge, there are a number of reasons why readers do not. First, detailed examination of something as amorphous as decline can be difficult reading, and it's not always written well. Second, the conclusions are necessarily speculative; the writer could be quite wrong. But by far, the most pervasive reason is that decline is not a story the American public wants to hear. It cuts hard against the grain of American optimism, exceptionality and nationalism.

The Texas Board of Education made this point graphically last week with the adoption of new social studies curriculum standards. By a series of strict party-line 10-to-5 vote, the board, which includes no historians, decided to eliminate Thomas Jefferson from a list of thinkers who inspired 18th-century revolution, eliminated any Latinos as historical role models, declared that there is no basis for the constitutional separation of church and state, and replaced the word "capitalism" with "free enterprise system," among other less egregious changes. This is writing history by emotion, rather than by facts. It is like making a medical diagnosis by Ouija board rather than by the study of anatomy and physiology.

Resistance to historical realities some would rather not know about is no more new than historians writing about decline and fall. Some readers will recall the 1994 controversy over the Smithsonian Institution's exhibit on the Enola Gay, the B-29 that dropped the atomic bomb on Hiroshima. The display raised questions about the morality of using atomic weaponry. Before the resulting furor was over, the facility withdrew the exhibit and the National Air and Space Museum director resigned.

Fewer will recall that in 1992 Smithsonian curator William Truettner ran into a similar buzz saw with an exhibit reinterpreting a century of art depicting the American West. Critics did not want to know or be reminded of racism and eugenics as partial motivations for the appropriation of Hispanic and Indian land, of the raw conquest of Mexico in pursuit of the assumed American right of manifest destiny, or of the exploitation of and corporate violence used against unskilled labor in mining and logging operations in the mountain West. The exhibit led no less a power than Sen. Ted Stevens to raise on the Senate floor the question of funding for the institution.

In a perceptive new book, "Dangerous Games: The Uses and Abuses of History," Canadian historian Margaret MacMillan notes that societies use history to glorify national identity and that such use often becomes abuse when it violates the facts or the consensus toward which the facts drive. Brits and Americans, for example, don't want to acknowledge the superiority of the individual German soldier in World War II. The Japanese don't want to accept responsibility for killing as many as 50 million Chinese during that war. Hindus in India fight recognizing Muslim contributions to Indian history.

As the political manipulation of science has raised ire in informed society, so should the political manipulation of history. If America is in decline, we're better off knowing it than denying it.