Of the Impossibility of Biography : DECEITS OF TIME <i> by Isabel Colegate (Viking: $17.95; 216 pp; 0-670-82400-3)</i>

The reading and writing of biography is an English habit. Biography in its many forms--from the memoir to the definitive life; from the obituary essay to the entry in the Dictionary of National Biography--has long been, James Atlas says, “a national obsession.” The ingredients of biography--time and memory, documentation and judgment--are the subjects of this novel.

Isabel Colegate is not afraid of ideas nor of using fiction to express them. In her memorable novel “The Shooting Party,” she demonstrates that the summer of 1914 marked the end of feudalism, the beginning of the modern world.

In this novel, the title is the thesis. The heroine of “Deceits of Time,” biographer Catherine Hillery, concludes that “Lives were stories. . . . Time and the innate human need to give shape to things, to select so as to find order, meant that life was just a story, one’s own or anyone else’s. . . .”

What is Catherine’s own story? Nearly beautiful, Irish-born, she is “the straight-speaking, free-thinking widow of a professional man. She had two grown-up sons and three biographies to her credit; she had a pleasant little house . . . and a calm demeanor which spoke of her victory over doubt.” It will not be a permanent victory.

Like other Colegate heroines, Catherine is capable of tact and perspicacity, of the making of fine distinctions. She’s funny, shrewd, a touch skeptical, tougher than she looks, bent on seeing life as a pleasant place.

Yet she has more than one “forbidden subject,” thoughts she doesn’t wish to think, a dangerous habit of seeing things with “icy clarity.” She cannot forgive her husband, Bernard, for having been disappointed in life and glad to die. She cannot forgive her son Nicholas his greed, nor her son Tom his middle-aged caution. There are things for which she cannot forgive herself.

Why, and why now, Catherine wonders, has she been asked to write the “official” biography of Neil Campion? A survivor of the Great War’s Royal Flying Corps, pilot-for-hire in East Africa, Campion returned to England and to politics, was elected a Conservative Party member of Parliament, married a rich and beautiful woman in 1933, farmed at the Durdans (his country home), worked to revive the vanishing skills and fading values of rural life, promoted pan-European unity, served as junior minister of aviation and as a minister in Churchill’s 1940 government, and happened to die on the same day in 1941 that Rudolf Hess landed in Scotland, when, headed north to an unknown destination, he drove his car into a stone wall.

The “recognizable” Campion Catherine wants to describe proves elusive. “I’m beginning to worry that it’s going to be a boring book,” she says. “Has it occurred to you that they might want a boring book?” asks Tom. “I mean if it’s been commissioned by the family. . . .”

Perhaps the moment she must admit “I’ve not the faintest idea who’s paying me,” is the moment Catherine’s curiosity sharpens. Campion begins to seem to her to be two different men: one the member of Parliament, a land-owner, Conservative Party member; the other a lonelier brooding figure, always an individualist, more ambitious, arrogant and romantic, caught up in an ideal of international brotherhood.

Exactly what were Campion’s German connections? Was he a coward or the “perfection” his wife claims? Was he a patriot or a traitor? Does anyone know? The family’s solicitor would prefer that Catherine stop trying to find out.

At first, Catherine does not give much thought to Sam Campion, Neil’s wild grandson; he “did not come into her story.” Like a changeling prince, Sam is taller, paler, longer-haired, more graceful, more secretive and more seeking of privacy than his contemporaries.

In all but the coldest weather, Sam lives and sleeps on the roof of the Durdans, once his grandparents’ home and now his dreadful school. “Each angle, apex, gulley, gutter, of the complex roofing system was familiar to him; this was his kingdom.” Orphaned by a plane crash and grandson of a noted flyer, Sam gets as close as he can to the sky and dreams and daydreams of himself with wings, and of flying.

His romanticism is unchecked and unchanneled, his ignorance profound. “If there’s one thing Sam does know it’s how to make a dry martini,” says his grandmother. It may indeed be the one thing Sam does know.

Sam is in need of affection, instruction, discipline, time, tact, and doses of common sense. He is in need of rescue; in need, in fact, of Catherine. So the life of the subject entangles the life of his biographer.

To Sam’s great credit, when he must decide what to do about publishing his grandfather’s biography, his response is practical, kind and shrewd. There is hope for him.

There is hope for Catherine too. All stories, she finds, can be retold. Even her own. The coil of narrative is endless. All that is needed is the “right light” by which to see.

In this rich and fascinating book, someone is hiding something--possibly everyone is. Time itself obscures the truth. Can the past be known? Or is what we call history the best of recollection, not absolute but consensual, and always subject to interpretation?