C.A. Tripp’s work (Free Press, 384 pages, $27) reminds me of other great speculative biographies, such as Fawn Brodie’s on Thomas Jefferson or Erik Erikson’s on Martin Luther. Like his predecessors, Tripp teased out anecdotes and details that other historians have either dismissed or passed over without much comment. His book had already grabbed headlines for its case that, as Jean Baker puts it in her introduction, “Lincoln’s primary erotic response was that of a homosexual.”

It is quite easy to find lapses in Tripp’s methodological rigor, and it is to his publisher’s credit that critical views of Tripp’s book are included in the volume. Besides Ms. Baker, one of Mary Todd Lincoln’s biographers, historians Michael Burlingame and Michael Chessen both hold the work up to scrutiny. The former provides “A Respectful Dissent,” the latter “An Enthusiastic Endorsement” – although he does not ratify Tripp’s conclusions but rather hails the therapeutic nature of his effort.

In Mr. Chessen’s view, Tripp’s work has shaken up the Lincoln establishment – much as Annette Gordon’s book on Jefferson rocked historians like Joseph Ellis, who disputed her revisionist view of Jefferson’s involvement with Sally Hemings. Mr. Ellis had to recant when DNA evidence made Gordon’s case. Historians, like members of any other academic discipline, form a kind of cabal, a truth Mr. Chessen alludes to in coining the term “Orthodox Lincolnistas.” It often takes a Gordon (a law professor) or a Tripp (a psychologist) to bring a fresh perspective to hallowed ground.

Part of the strength of Tripp’s book is the author’s historiography. He spent more than a decade researching Lincoln’s life, assessing not only primary sources but also the notable biographies, in the process detecting the points at which Carl Sandberg and Ida Tarbell, for example, seemed aware of Lincoln’s homosexual tendencies but chose not to explore them.

Mr. Chessen is quite right to say it is not enough to throw obstacles in Tripp’s way – to say, for example, that just because Lincoln slept with men means nothing. Men often shared beds in the 19th century. But Lincoln slept for four years in the same bed with Joshua Speed, and in the White House he clearly developed an infatuation with a union officer, though neither Tripp nor anyone else can determine just what the nature of Lincoln’s intimacy was with this soldier. And Tripp highlights other instances of Lincoln’s intimacy with men.

Tripp died in May 2003, just two months after completing a draft of his book. So he could not have read Daniel Mark Epstein’s suggestive dual biography of Lincoln and Whitman. Like Tripp, Mr. Epstein focused on stories other historians and biographers have discounted. Mr. Epstein explored the report that Lincoln was one of Whitman’s early readers, though he could find no specific reference to Whitman in any of Lincoln’s own writings.

Supposedly, Lincoln liked to read Whitman aloud at his law office, but when he brought the book home, Mary Todd Lincoln threw a fit and banished the scandalous book from her house. Mr. Epstein notes that Lincoln would probably not have thought of mentioning Whitman in public or in print given the poet’s celebration of homoeroticism. I am surprised that Tripp makes little of this Lincoln-Whitman connection.

Instead, he focuses on one of Lincoln’s bawdy poems (the President was fond of dirty jokes, especially those of the anal variety), in which a boy marries a boy. Whereas Whitman celebrated the “love of comrades,” Tripp notes, Lincoln wrote the “most explicit literary reference to actual homosexual relations in nineteenth-century America.” Under pressure from a Chicago publisher, Lincoln’s law partner and biographer, William Herndon (a source for both Mr. Epstein and Tripp) bowdlerized the poem’s penultimate line, altering “Besides your low crotch [big penis] proclaims you a botch” to “Besides your ill shape proclaims you an ape.”

Tripp sees the stormy Lincoln-Todd marriage as more evidence of Lincoln’s uncomfortable relationship with women. Ms. Baker believes Tripp is too hard on Mary; Mr. Chessen, that Tripp is not hard enough; other historians, I am sure, would say Mary was volatile enough not to need the added tension of living with a homosexual to ignite her combustible temper. Ms. Baker, for all her reservations, believes Tripp does illuminate puzzling aspects of Lincoln’s marriage. Mary may well have been aware of her husband’s homoeroticism and the gossip it excited, which Lincoln did nothing to counteract.

But Tripp does not say that Lincoln was a homosexual. Rather, he uses the scale of measurement that his mentor Alfred Kinsey invented, to give Lincoln 5 points out of 7 – that is, Lincoln was primarily homosexual in orientation but capable of sexual relationships with women.

Historians often deplore gossip, but biographers should not so easily discard it. Why do certain people seem to stimulate certain kinds of gossip? Why did Virginia Woodbury Fox, wife of the assistant secretary of the Navy, Gustavus V. Fox, report in her diary this confidence from her friend Letitia McKean, a “player” (as Tripp puts it) in “Washington’s fashionable society”: “Tish says, ‘there is a Bucktail soldier [C. M. Derickson] here devoted to the President, drives with him, and when Mrs. L. is not home, sleeps with him.’ What stuff!”

Read the rest of Tripp’s chapter on the Lincoln/Derickson liaison, and it is difficult not to see the close bond Lincoln formed with this handsome man nearly a decade his junior. Tripp does not claim to know what happened between the sheets, but Mrs. Fox’s brief report is not a detail that Plutarch would have omitted.

Tripp did not set out on a gay pride mission. Indeed, his book makes clear that he is scornful of activists like Larry Kramer, who see Lincoln as unambiguously homosexual. The word itself did not come into currency until late in the 19th century. And as Ms. Baker points out, moralists were more concerned with self-pollution (masturbation) than with homosexuality. Both women and men slept together, kissed, and held hands in ways that began to seem inappropriate only several decades after Lincoln’s death.

What, then, is Tripp’s point? The same as any biographer’s: to explore the mystery and complexity of human identity. By any measure, his probing account deserves the deference of even his most skeptical critics.