What makes John run?

John Forbes Kerry is an alumnus of West Newton's Fessenden School, whose motto is ''Work conquers all." He seems to have taken the sentiment to heart. Throughout his life, Kerry has evinced an outsize capacity for hard work and a pronounced taste for disputation, much of it internal. At St. Paul's, a prep school in Concord, N.H., he founded the John Winant Society, a debate and discussion club that continues today, and he was the star of the Yale University debate team.

Kerry was ''probably the most natural trial lawyer on his feet I ever saw," said J. William Codinha, as relayed in ''John F. Kerry," by Boston Globe writers Michael Kranish, Brian C. Mooney, and Nina J. Easton (PublicAffairs, paperback, $14.95). Codinha served with Kerry in the 1970s as an assistant district attorney for Middlesex County.

Trained to argue either side of any question, Kerry doesn't just tolerate ambiguity, he relishes it. His cast of mind can madden his staff, who sometimes don't know his position on a particular bill until he votes, and makes him easy to caricature (''flip-flopper," anyone?). But the early biographies of Kerry reveal a figure far too complex to stay within the bounds of caricature. The inquiring reader-voter will want to know if Kerry's deliberative style is thorough and open-minded or merely indecisive. That's a question that the first chroniclers of his life understandably have difficulty answering.

When we read a biography, we're looking for something we recognize as human: achievements and failures, certainly, but also motivation. What tangle of wounds and dreams, loves and hates, drives a person to write a great symphony, start a miserable war, run for president? To answer that question, a biographer might wish for the interiority that novelists use. But interiority is verboten to journalists. Their code of objectivity and balance demands that they refrain from overt speculation about motive, lest they betray a point of view of their subject and leave themselves open to charges of bias.

To their credit, the Globe team scrupulously avoids bias. But a journalistic approach has its limits when it comes to psychological understanding. Lacking the knowledge of the sources of Kerry's ferocious energy and evident lifelong ambition (wise guys at Yale would pipe up with ''Hail to the Chief" when he entered a room), we can never bring him completely into focus. He turns against a war in which he performed heroically; becomes a celebrity, then a has-been; is elected to the US Senate; skirts scandal; helps restore relations with his former enemy; marries a wealthy widow; and runs for president. Yet he remains stubbornly opaque.

Unconstrained by objectivity, we can speculate about the most significant people in Kerry's life, beginning with his mother, Rosemary Forbes Kerry. As a young woman, she found herself alone in Paris as the Nazis were closing in on the city. She escaped by bicycle, eventually making her way to Portugal, and from there back to the United States. She reunited with her fianc, Richard Kerry, married him, and bore him four children, including John. The son saw little of his parents, passing through a succession of boarding schools while Rosemary accompanied Richard from one Foreign Service posting to the next. But the Kerrys were prodigious letter writers, and John's letters and journal entries are quoted liberally by the Globe team and lavishly by historian Douglas Brinkley in ''Tour of Duty" ( Morrow, $25.95).

Neither book says much about Rosemary's letters to her elder son, and so we can only guess how she might have addressed him. One guess is that Kerry has his mother to thank both for his deep reserves of self-confidence and his astonishing physical daring -- danger, except in the form of snakes, seems hardly to register on him. From his father he inherited a darker legacy. When Richard Kerry was 6 years old, his own father shot himself in the men's washroom of the Copley Plaza Hotel. The trauma seems to have left Richard with a lifelong distrust of the wider world. That distrust, we might permit ourselves to think, reappears as the hooded, indrawn quality remarked upon by many who encounter John Kerry. Is it, as his detractors contend, the snobbishness of a wealthy elitist out of touch with ordinary people? Or is it rather the wariness of a perpetual outsider, endlessly adaptable but never truly at home?

Few men who served under Kerry in Vietnam complained of aloofness on his part. Most of Kerry's blue-collar crewmen took to the young Navy lieutenant, and he risked his life for them. Both the Globe and Brinkley books recount the incident in which a wounded Kerry fishes sailor James Rassmann out of a Vietnamese river while exposing himself to hostile fire. It is spine-tingling, heart-stirring stuff, and it ought to shame into silence those who, at three decades' remove, have latterly sought to cast doubt on Kerry's valor in combat.

His political opponents use words like ''treason" and, perhaps worse, ''opportunism" to impugn Kerry's opposition to the Vietnam War. But Brinkley's book reveals a deliberative process that isn't recognizable in his critics' terms. The historian seems determined to include every shred of his research, but beneath the layers of not-always-relevant detail is the story of a reflective, articulate young man torn between his love of service and his hatred of the war he was called to fight. Those who condemn Kerry's use of the term ''war crimes" in his congressional testimony in 1971 might want to look again at the context of his remarks. It is clear from his testimony and his later comments that he accuses himself first and foremost: His words are hottest when he speaks with disgust at his own complicity in what he came to regard as evil. Remarkably, his war experience left him bitter but not cynical, and determined to prevent a repetition of Vietnam -- an attitude that might fairly be described as patriotism, not its lack.

Kerry's patriotism is likely to be a fall campaign issue, and two new books offer hints of the Democrats' likely response to such attacks. Paul Alexander's ''The Candidate" (Riverhead, $23.95) is a retelling of the foreshortened Democratic primary campaign. The book is no more or less than a serviceable clip job, but it contains one rather juicy memo that assures it a wide readership, at least among Republican opposition researchers. Described, with the author's customary vagueness about sourcing, as perhaps coming from ''an adviser to the campaign, based in New York, though not a staffer," the memo urges a rapid, ruthless response to every opposition assault. And it does so in bitterly personal terms, directed not so much at President George W. Bush as at Karl Rove, who directs Bush's political operation. Whatever the merits of its advice, the memo is vivid evidence of Democrats' near-desperate fury at the GOP's muscular version of power politics.

The tone of Kerry's own ''A Call to Service" (Viking, $24.95) is far more statesmanlike. Like its title, the book is stuffed with high-minded phrases that don't offer up much meaning. It is best read not as a detailed list of proposed policies but as a statement of the principles that will guide those policies if Kerry becomes president. This is tactically shrewd -- Kerry gains nothing by limiting his options months before Inauguration Day -- and it affords him an opportunity to test-market themes. Look for the Democrats, led by Kerry, to contest the Republicans for ownership of the rhetoric of patriotism and values.

If Kerry wins in November, we'll likely hear less about ''moral clarity" and more about ''difficult decisions." Kerry's world holds few obvious choices between good and evil. Most choices are imperfect versions of the good, and his practice is to suspend judgment as he sifts each alternative's pros and cons. If president, Kerry likely will declare his commitment to principles -- fiscal prudence, equal opportunity, international cooperation -- long before he states a preference for a given policy. Once he commits, though, expect him to stick to his position. The various Kerry books, as different as they are, agree on this point: Once the battle is joined, Kerry doesn't flip-flop.