THROUGHOUT its history of controversy, one thing the Confederate battle flag has consistently stood for is the tendency of human beings to muddle their best instincts and their worst. As the banner of Southern nationalism, the star-spangled cross is an emblem of heroic self-determination, of the Confederacy's rebellion against federal ''oppression.'' But the ideal that urged the secessionists on to their blood-drenched sacrifice was the freedom to subject a race of people to enslavement.

Nearly a century and a half after the Civil War ended, the battle flag remains a standard in the eternal struggle between tradition and change, a conflict that is looking increasingly like a culture war. The most protracted ''flag flaps'' have been sparked by the campaigns of African-Americans, along with sympathetic whites, to compel Southern states to purge from their official insignia an icon widely seen as the badge of white supremacy. The subject is so inflammatory that Howard Dean's overture to voters with Confederate flags on their pickup trucks during his presidential campaign set off a cross-fire of recrimination and bad faith. John M. Coski's history, ''The Confederate Battle Flag,'' brings some needed rationality to a debate driven by the raw emotion of soul injury.

But reason, it turns out, is unequal to ''the duality of the Southern thing'' -- as the dialectics of Southern identity is called by Drive-By Truckers, contemporary rock's interpreters of Dixie. It takes more magic than is attempted by this academic study to conjure a region that balances so many polar extremes -- generous hospitality and casual violence, rebellious individualism and docile conformity, scrappy sectionalism and hyperpatriotism, military discipline and warrior impulsivity, redneck pride and genteel modesty -- all under a flag claimed equally by the Ku Klux Klan and the liberators of Soviet-bloc Europe.

The battle flag exemplified this duality from the beginning. It was embraced as a belligerent alternative to the original official flag of the Confederacy, the Stars and Bars, which blood-lusty rebels condemned as a ''servile imitation'' of the North's Stars and Stripes. Yet its signature cross was positioned diagonally in order not to alienate the South's Jewish citizens through overt Christian symbolism. In the post-bellum decades of segregation, when black voices were excluded from civic discourse, the two competing camps of flag protocol were the ''correct use'' purists, dedicated to the sacred honor of the Confederate dead, and the admen, frat boys and politicians who believed the image belonged to the popular culture. It was not until 1948 that the flag resurfaced in connection with a white-supremacist political movement, the Dixiecrats, those Southern Democrats who bolted their party in protest against its civil rights program.

As useful as it is to have the record set straight on, say, the fact that the Klan did not take up the Confederate colors until the 1940's, too much of this book is a catalog of flag moments, with an elusive organizing principle and scant sociopolitical context. When Coski, the historian at the Museum of the Confederacy in Richmond, Va., does sally forth from the thicket of Southern-crossed Klan rallies, segregation fests, football games, Old South balls, stock car races and military operations (he informs us that some marines signaled the American victory on Okinawa during World War II by raising the Confederate flag), the analysis is refreshingly direct and nonpolemical, especially on the merits of the various controversies. Coski points out that the ''Heritage, Not Hate'' flag advocates are engaged in a futile exercise when they try ''to divorce the defense of Confederate symbols and the honor of Confederate soldiers from the cause for which the soldiers fought.'' But he likewise tweaks the opponents for their excesses of historical revisionism: ''Elected officials, community leaders and intellectuals must cease encouraging the untenable belief that there is an inherent American right not to be offended.''

Coski's unsentimental approach is admirable, but by slighting the emotional essence of the ''Southern thing'' he sidesteps the basic, tragic question: Why are so many white people so irrationally invested in their regional mythology? However inept the flag's defenders are at articulating it, the reason does in fact transcend race. The South's ferocious sectional pride is the flip side of an inferiority complex, a chip-on-the-shoulder legacy of its savage defeat by a civilization it rejected long before the Civil War. Consider the South's antebellum obsession with the ''lost cause'' of Scotland's struggle for independence against cold, mercantile England. In his fascinating study of vanquished nations, ''The Culture of Defeat,'' Wolfgang Schivelbusch describes how this romance of the underdog reflected the agrarian Southern cavaliers' doomed sense of obsolescence when confronted with the inexorable moneymaking machines of the North. (The Confederacy's Southern cross was actually the cross of St. Andrew, Scotland's patron saint.) The North's scorched-earth war strategy was indeed designed to annihilate not just the South's army but its entire civilization. As the Union general Philip Henry Sheridan declared, ''The people must be left nothing but their eyes to weep with over the war.''

The South has long expressed its grief through unconstructive displays of resentment. According to Drive-By Truckers: ''We ain't never gonna change. / We ain't doin' nothin' wrong.'' In 2001 white Mississippians voted overwhelmingly to preserve the Southern cross on their state flag (just as, in a grosser act of nobody-can-tell-us-what-to-do defiance nearly 50 years earlier, local jurors acquitted the coldblooded murderers of the black teenager Emmett Till).

The perversely empowering allure of victimhood calls out even to the South's most critical daughters. Some years ago, I was looking into a potential elementary school for my younger child. It was a highly recommended prospect, located on the politically correct Upper West Side of Manhattan and named after one of General Sheridan's colleagues. Halfway through the school's guided tour, I decided ''no way,'' explaining to a fellow Southern mom who was there, ''Do you really think you could tell the folks back home that you're sending your child to the William Tecumseh Sherman School?''

Such are the dwindling stakes of the continuing North-South conflict, a clash of values nowadays defined in terms of blue states and red states. As with most of the issues in the culture wars, the battle over the Confederate flag may bring moral satisfaction to the victors, but little in the way of improvement to their daily lives. Fighting over the spoils of a tattered cloth is another example of ordinary people taking passionate political stands that distract them from the likelier source of their distress, the widening division not between whites and blacks but between have-mores and have-lesses.

Diane McWhorter is the author of ''Carry Me Home. Birmingham, Alabama: The Climactic Battle of the Civil Rights Revolution,'' and a young adult history of the civil rights movement, ''A Dream of Freedom.''