"SIR, THE BIOGRAPHICAL part of literature is what I love most," confessed Samuel Johnson. The good doctor wasn't alone in his preference; biography is reportedly the most popular of all literary genres. We Americans devour them -- from W. Jackson Bate's high-minded life of Johnson himself to the scandalous and scabrous exposes of Hollywood has beens, political hangers-on, and forgotten demi-mondaines. There are biographies for every taste yet, whoever the subject and whatever the treatment, their seductive appeal is to affirm our own uniqueness while allowing us to heights.

Until recently, though, biography was a literary form pretty much without any theory behind it. Students of the novel or of poetry could turn to innumerable works of critical interpretation, but comparable criticism of biography was relatively scarce -- a few remarks by Lytton Strachey, a couple of rather uninspired books. $1Telling Lives, a gathering of six papers written by eminent biographers for a symposium at the National Portrait Gallery, and Robert Gittings' $1The Nature of Biography help to offset this imbalance. They are introductions, prefaces to a more complete view of the biographer's art.

That art seems to have passed through three crucial phases in its development. Plutarch's $1Parallel lives of the Greeks and Romans embodies the earliest aim of biography -- to record the deeds of noble men as examples for the rest of us poor mortals. The hagiography of the Middle Ages continues this tradition by providing in the saint's life a mirror in which a sinner might find brightly reflected the Christian perfection he should strive after. Montaigne shattered this stylized ideal. Though he began his essays by copying down the sententia of the ancients, he ended by making his own quirky self -- with all his warts, bladder troubles and anxieties -- the hero of his book.

Johnson transposed Montaigne's achievement -- the portrayal of a whole man -- out of the essay and into the biography. The splendid $1Life of Savage treats no hero or saint, but a Grub Street poetaster and schemer. What Johnson began, Boswell finished by making of Johnson -- in all his bristling idiosyncracy and flashing conversation -- the most alive figure in English history.

Unfortunately, the two-volume Victorian biographies again elevated their subjects into civic saints. It took Lytton Strachey, with his debunking Eminent Victorians to establish an artistic approach to life-writing. Starchey advocated biographies that were brief, shaped according to an artistic purpose, dramatic with scenes that revealed the subject's inner life, and vealed the subject's inner life, and written with grace and wit. These qualities, modified slightly by individual taste, still characterize the modern standards recommended by the essayists in these two books.

The most theoretical-minded of the group is Leon Edel, chronicler of Henry James and author of the earlier study $1Literary Biography. Edel insists that the biographer use psychology to incover a life-myth, "the figure under the carpet," that explains the motivations of his subject's actions. He further supports a certain artistic license to create dramatic scenes, pace the action like a novel, even skip about through time -- "a biographer is a storyteller who may not invent his facts but who is allowed to imagine his form." Anathema to Edel -- and to his fellow panelist -- is the bloated academic biography that gathers between covers every picayune detail of a person's life, while failing to provide any focus or shape. [Michael Holroyd, who produced a two-volume life of that advocate of brevity, Lytton Strachey, gets a kick from nearly everyone.] Yet by a paradox never adequately explained Edel feels that is own five-volume Henry James is "one of the sorter biographies of our time."

Edel's plea for psychological and artistic structure is reinforced by Justin Kaplan, Alfred Kazin, Doris Kearns, Theodore Rosengarten and Barbara Tuchman. The words "myth" "esence" and "prism" recur regularly throughout $1Telling Lives, as these other contributors offer personal views of their field work in biography.

Justin Kaplan, for instance, examines the significance of a waiter's name. By calling himself Walt Whitman, the author of $1Leaves of Grass identified with the populist tradition of Andy Jackson and Davy Crockett, not with three-name establishment types such as James Russell Lowell and John Greenleaf Whittier. Kaplan also points up ways in which biography can -- sorry, New Critics -- illuminate poetry. Whitman's celebrated phrase "I sind the body electric" is considerably enriched when we learn of the poet's fascination with theories of "animal magnetism."

Another literary critic, Alfred Kazin, focuses on the autobiographical impulse that runs throughout American literature, all the way from Franklin's memoirs and Walden to The Crack-Up Tropic of Cancer and The Autobiography of Malcolm x. As part of this tradition himself -- his most recent book, New York Jew, is the third volume of his memoirs -- Kazin concluded that "personal history is directly an effort to find salvation, to make one's own experience come out right."

Geoffrey Wolff and Theodore Rosengarten reflect on the writing of "minor lives." Wolff's essay first recreates the composition of his biography of the lost generation's Harry Crosby [Black Sun] and then explores the personal tensionss behind the forthcoming memoir of his con-man father, $1The Duke of Deception; Rosengarten delves into the methods and pitfalls of oral history, as he recalls gathering materials for $1All God's Dangers, his biography of an illiterate black ten farmer.

If some biographers enjoy treating figures who, seemingly unimportant nonetheless embody an historical moment, others like Doris Kearns, prefer the already famous and consequential. In a case of turnabout, Kearns examines her own psychological motivations in writing the life of her employer in $1Lyndon Johnson and the American Dream. She then proceeds to explain how her Irish Catholic, political background has led to her current project -- a three-generation biography of the Kennedy family.

If Kearns reminds us that biography can be a mode off self-exploration historian Barbara Tuchman by contrast seeks in certain figures "a prism of history." In an individual like Coucy -- the power center of A Distant Mirror -- she finds a man whose life touched nearly every aspect of 14th-century society. Coucy provides the narrative peg on which she can hook both a reader's interest and a history of the late Middle Ages.

Unlike the panelist of $1Telling Lives, Robert Gittings in $1The Nature of Biography offers a brief history of the form, but little insight into his own working methods [he is a biographer of Keats and Hardy] and virtually no theory. Nonetheless, he does provide some fascinating examples of how knowledge of medicine, psychology and even geography can illuminate a figure of the past.

Because of their brevity and popular nature, these essays remain only suggestive and tentative, not to say tantalizing. Nearly all are written with charm, several offer intimate biographical glances into the biographical process, and each makes clear the variety of pleasure and instruction available from life-writing. Perhaps it is just this variety that hampers the establishment of norms for evaluating biographical products. Still, until such a critical tool chest comes into being biography is an art not a hapazard accumulation of facts and fancies. CAPTION: Illustration, Head of a Man in Profile, by Albrecht Durer