EVERY GENERATION, it seems, gets the Lincoln it deserves. And so C.A. Tripp's portrait of a Lincoln for the ''Queer Eye'' generation should come as no surprise. In ''The Intimate World of Abraham Lincoln'' (Free Press), the therapist and former Kinsey sex researcher argues that Lincoln was homosexual in both thought and deed, with as many as five intimate lovers and a psychological outlook shaped by his same-sex desires. How timely to learn that the icon of the Republican Party once composed a poem about the marriage of two men. Having already provided potential talking points for Log Cabin Republicans and sketch material for ''Saturday Night Live,'' Tripp cannot fail to intrigue readers. But does he have what it takes to convince them?

Tripp was not the first to take up the question of Lincoln's sexuality, but he pursued it for the last 13 years of his life with unparalleled zeal and a breathtaking confidence in his own conclusions. By the time of his death in 2003, Tripp had amassed the world's largest database of Lincolniana, currently housed in the Lincoln Library in Springfield, Ill. As he pored over the textual fragments, he began to find what he was looking for.

In Tripp's book, Lincoln, described by one woman who rejected his marriage proposal, as ''deficient in those little links which make up the chain of woman's happiness,'' evades eligible women while panting after a dashing military officer and a handsome bodyguard. Tripp depicts a loveless nightmare of a marriage, even comparing Mary Todd Lincoln's lack of empathy to Hitler's. Lincoln sneaked sly references to same-sex desire into his bawdy humor, and penned passionate letters to Joshua Speed (signed ''yours forever,'' a phrase he never wrote to his wife), with whom he had for four years shared a single bed above Speed's store in Springfield. And Tripp puts forth this tidbit, recorded by Washington socialite Virginia Woodbury Fox in her diary in November 1862: ''Tish says, ‘there is a Bucktail soldier here devoted to the President, drives with him, and when Mrs. L. is not home, sleeps with him.' What stuff!''

What stuff indeed -- but hardly grounds for concluding, as Tripp does with a flourish of scientific certainty, that Lincoln was a 5 (''predominately homosexual, but incidentally heterosexual'') on Kinsey's famous scale of sexual desire. Throughout, Tripp employs his evidence selectively and asks readers to join him on wild leaps of historical fancy.

Take Tripp's argument about Lincoln's sex drive. He concludes, based on a childhood neighbor's hazy recollection of Lincoln as a ''long, tall, dangling'' 10-year-old, that Lincoln's puberty must have commenced at age 9. Since Kinsey found that boys who experience early puberty were more open to homosexual activity, Tripp concludes that Lincoln was too. This chain of logic is shaky enough, but when Tripp later cites Lincoln's early puberty to explain his unconventional religious views, the argument starts to wobble like a house of cards.

The flimsiness of ''The Intimate World of Abraham Lincoln'' must come as a relief to those Americans who would prefer to reject his argument out of hand. The Concerned Women of America, a conservative group, has denounced Tripp's ''vulgar accusations,'' while The Weekly Standard, in an article by Tripp's former collaborator Philip Nobile, ridiculed it as ''a hoax and a fraud.''

Established Lincoln scholars have not dismissed the book, but they have responded coolly. In his 2003 book '''We Are Lincoln Men': Abraham Lincoln and His Friends,'' distinguished Lincoln biographer David Herbert Donald refutes many of Tripp's conjectures, pointing out, for example, that two other men also shared the room above Speed's store, surely inconvenient for trysting. But when Donald quotes fellow biographer Charles Strozier's claim that a bisexual Lincoln would have been ''full of shame, confused, and hardly likely to end up in politics,'' he seems to be relying on conjecture himself.

Tripp's book will leave most readers puzzled, but that's no reason to dismiss the question of Lincoln's sexuality. If nothing else, Tripp has shown that given the evidence we have, it's intellectually reasonable to ask. But it's politically useful, too -- because just below every discussion of Lincoln is an argument over the meaning of the nation that he led. ''Getting right with Lincoln,'' as Donald once put it, not only means getting right with a man defined by his ambivalences. It also means confronting America's ongoing ambivalence about sexuality and political equality.

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Readers may hunger after proof, and Tripp's book contains much talk of ''smoking guns.'' But historians' stock in trade is ambiguity rather than certainty; they suggest hypotheses rather than indictments, crafting interpretations rather than rendering verdicts. Ambiguities abound particularly when it comes to Lincoln, described by William Herndon, his law partner of 17 years, as ''the most shut-mouthed man I knew.'' Without interpretation and speculation, we would, for example, have few insights into Lincoln's religion: His collected works don't include the word ''Jesus'' and he was frequently described as an atheist, yet the Second Inaugural Address is among history's most eloquent confrontations with the Creator.

Nor can we really ''prove'' Lincoln's sexuality at all -- beyond the fact that he and his wife produced four children. Evidence presents a thorny problem for every historian of the 19th-century boudoir, especially when it comes to same-sex desire. Here, the evidentiary standard is raised ever so slightly, almost anything can be explained away, and it gets hard to see the substance for the shadows of the doubts. The subjects themselves aren't even reliable. Lincoln's contemporary, the poet Walt Whitman -- who really, really liked men -- left nothing irrefutable in his archive. Oscar Wilde, to his grave, denied everything.

Unlike Tripp (and some of his critics), historians of sexuality have grown quite comfortable with ambiguity. In ''Love Stories: Sex between Men before Homosexuality'' (2001), Jonathan Ned Katz finds a real intimacy in the Lincoln-Speed letters, but insists this was ''a foreign land of love and lust, a universe differing substantially from today's.'' Even if you could snoop around the bunkhouses of frontier Illinois, don't be sure you'd recognize what you saw. And don't, Katz insists, slap 20th-century labels like ''gay'' or ''straight'' on anything under the sheets.

Of course, it's possible to conjure romantic notions of a gauzy innocent world where men held hands and shared beds (and sometimes even had sex in them) without fear or guilt simply because they lacked a modern terminology. But the sexual culture of rural Illinois was far more vivid and vulgar than we believe.

Surrounded by copulating animals and tolerant of prostitutes who openly plied their trade, men on the American frontier spoke frankly of sex, and many of them practiced some variety of it whenever they could. Herndon, one of the four men who roomed with Abe in Springfield, recalled Lincoln's interest in a painted lady of the town: ''desirous to have a little,'' Lincoln asked ''where I can get some.'' (Herndon insisted Lincoln was too gallant to do the deed.) Just as Lincoln once said in reference to his own off-color storytelling, a sexual history of Springfield ''would stink like a thousand privies.'' And so it's worth bearing in mind Katz's lesson -- that the past is a different country -- before anyone starts building a Lincoln float for either a Gay Pride parade or a Promise Keepers rally.

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But enough, say exasperated readers. Was he or wasn't he? At least some Americans outside the ivory tower will read the passionate letters to Speed, along with Tripp's other spicy bits about shared beds, and conclude that since Honest Abe walked and talked so much like a duck, he probably quacked like one too. Very well, then, so what? Knowing that Lincoln was different is one thing; knowing what difference is made is another.

Conservative historian Richard Brookhiser, writing last week in The New York Times Book Review, concludes that ''based on the evidence before us, Lincoln loved men, some of whom, at least, loved him back.'' But he deems that irrelevant to the real Lincoln, ''the man who saw liberty and equality as facets of the same thing.'' By contrast, Tripp (whose 1975 work ''The Homosexual Matrix'' challenged psychological notions that homosexuality was abnormal) argues here that Lincoln's sexuality shaped both his ''genius'' and his ''sense of justice.''

Neither position sits quite right. But Lincoln's sexuality must have mattered, as much as any other facet of his life. Americans have longed for every snippet about Lincoln the man, because it helps us understand Lincoln's legacy, which is among our most precious political possessions. If an eccentric and unconvincing book about Lincoln's sexuality can help America have a better conversation about same-sex marriages and Log Cabin Republicans -- if getting right with Lincoln, in short, gets us right with ourselves -- then Tripp deserves some credit.

Most historians, though, will wait for a better discussion of Lincoln's sexuality than the one found in ''The Intimate World of Abraham Lincoln.'' Reading the book, I experienced something like what Lincoln himself encountered while reading a letter from his former bedfellow Joshua Speed. On March 27, 1842, Lincoln thanked him for sending a flower. ''The sweet violet you enclosed came safely to hand,'' he wrote, ''but it was so dry, and mashed so flat, that it crumbled to dust at the first attempt to handle it.''

By every standard of scholarly inquiry, Tripp's claims for Lincoln's homosexuality crumble to dust like a dried flower. But just as Speed's violet left its mark -- ''The juice that mashed out of it stained a place in the letter, which I mean to preserve and cherish,'' Lincoln wrote -- so too with Tripp's book. Long after the dust settles, what biographer Carl Sandburg once suggestively called Lincoln's ''streak of lavender'' will remain in full view for future generations.

Christopher Capozzola teaches American history at the Massachusetts Institute of Technology.