CONCORD, N.H. -- On May 1, 1977, more than 2,000 protesters occupied the grounds of the Seabrook power plant, chanting against nuclear power, flying kites and playing Frisbee. New Hampshire Gov. Meldrim Thomson Jr. arrived by helicopter to survey the scene. Network news crews filmed the demonstration, billed as the largest in the nation against nuclear power.

As the crowd grew, the state attorney general, David Hackett Souter, sat calmly in a vacant office at the plant, using the free time to write up the minutes of the Concord Hospital Board of Trustees, on which he served as secretary.

"I was colossally bored," Souter explained shortly after the event. "Listening to . . . a bunch of 20-year-old kids, as nice as they may be, just repeat over and over again, 'Kill the nuke. Kill the nuke' . . . that gets pretty boring after a while."

The story about President Bush's nominee to the Supreme Court suggests the otherworldliness of the man, who is often characterized by friends as a figure from another century. They describe him as a catalogue of such Puritan virtues as humility, probity, thrift and industry; a disciplined, self-reliant New Englander who is happiest collecting rare books, reading volumes of history or hiking the White Mountains.

"He really comes across as someone who has just sort of climbed out of the pages of a history book," said Melvin Levine, a close friend of Souter's since their days as Rhodes scholars. "He has these basic roots and values."

When Souter was appointed New Hampshire attorney general in 1976, his colleagues celebrated with a cake inscribed, "Forward into the 19th century." The 50-year-old jurist had so rarely used a credit card that he worried, after Bush tapped him for the court, about having enough credit to finance the frequent trips to Washington to prepare for his confirmation hearings, which begin this week. 'He's Not Like Most of Us'

The retirement of the court's foremost liberal, William J. Brennan Jr., gives the conservative justices the opportunity to cement their sometimes shaky majority -- and has focused even more attention than usual on Souter's background and ideology.

The insular nature of Souter's life in New Hampshire, and the narrowness of his life experiences, have prompted some observers to question whether the little-known judge has the range of human understanding necessary for a justice. They ask how Souter can sit on a court that deals with some of the most contested social issues of the day -- the rights of minorities and the poor; the relations between parents and children, or husbands and wives; abortion, pornography, religious freedom, the death penalty.

Even Sen. Orrin G. Hatch (R-Utah) alluded to this sense of discomfort in the days after the nomination when he said -- before quickly retracting the comment -- that he would feel more comfortable if Souter were a family man.

When his confirmation hearings start Thursday before the Senate Judiciary Committee, one of Souter's more subtle tasks, besides picking his way through a minefield of questions on legal doctrine, will be to assuage those concerns.

"I think he's charming and I think he's funny and I think he has a warmth that hasn't been captured yet, and I'd like to see the hearings fill in the blanks a little bit, to give you a chance to see the David Souter his friends have been talking about," said Souter's close friend Thomas D. Rath, who is helping him prepare for the hearings.

Others readily acknowledge that Souter is different.

"He's not like most of us," said Concord lawyer Malcolm McLane, who interviewed Souter for a Rhodes scholarship three decades ago and has remained friendly with him. "Whenever he's been at our house for dinner, he'll write a very formal, handwritten thank-you note. Most of us nowadays don't manage to do that or if we do, we spit it out on a word processor. He wouldn't think of doing that."

If Souter is something of an eccentric, he also seems a paradox.

A private, reserved man who has never married and lives alone on a dirt road in the ramshackle, dilapidated farmhouse where he grew up, he is nonetheless surrounded by a close-knit, devoted circle of friends. He is loath to have strangers to their gatherings, yet intimates describe Souter as a charming dinner companion, a gifted mimic with a wry, satirical sense of humor.

He is a well-read man whose living room is crammed with books and antiques and lined with American prints. But he has traveled little outside his native New England -- a fellow Rhodes scholar recalled Souter sniffing that Paris paled in comparison to Boston -- and is reluctant even to go on overnight hikes that will keep him away from his home in East Weare.

By all available accounts, Souter is apolitical. He has never worked in an election or made a campaign contribution, and does not even read the local newspaper. Yet his rise in New Hampshire government was orchestrated at each stage by Sen. Warren B. Rudman (R-N.H.), a blunt, outspoken and partisan politician who says he thinks of Souter as a younger brother.

Although Bush and others have billed Souter as a conservative, his close friends include liberal Democrats and abortion-rights activists. And his base of political support in New Hampshire comes primarily from moderate Republicans like Rudman rather than conservatives like White House Chief of Staff John H. Sununu and Thomson, two former governors.

Souter is a self-effacing, unassuming man who, upon his promotion to attorney general, preferred to remain in his smaller, deputy's office. According to Rudman, he had to be prodded to leave the New Hampshire Supreme Court for a more prestigious federal appeals judgeship. Now he is poised to achieve the pinnacle of his profession.

At Oxford, friends would tease Souter, who was apt to spout quotes from Oliver Wendell Holmes and rhapsodize about the high court in a New England accent so thick it seemed phony at first, about becoming a justice himself someday. Hackett, as he then liked to be called, simply smiled with quiet delight, Levine said.

"We used to call him Chief Justice Souter," Levine recalled. "There was a kind of inevitable progression there, so that when President Bush nominated him, I didn't feel very surprised. It was just destined to happen." Traits Based in Childhood

Accounts of Souter as a child and a young man precisely match those of him today: sober-minded, intellectual, independent and deeply devoted to his native New England, its rural beauty, rich history and Yankee values.

"He's essentially a person who has never changed -- in any respect, with respect to dress, habits, habits of mind," said J. Michael Beecher, his roommate at Harvard.

"All the time I knew him, he knew exactly what he wanted to do. . . . He knows exactly what he thinks and exactly where he's going," recalled James Sayle Moose, a fellow Rhodes scholar.

The only child of Helen Hackett and Joseph A. Souter, he was born in 1939 in Melrose, Mass., and spent his first years in nearby Wakefield. His mother had worked as a clerk at a gift shop there; his father was a banker.

The family moved to New Hampshire when David was 11, settling in a farmhouse that belonged to Helen Souter's family in East Weare, the same house that Souter lives in today. Souter's father died in 1976 and his mother now lives in a retirement community near Concord.

Teachers and classmates at Concord High School, where Souter graduated second out of 200 in his class in 1957, describe him as a serious, hard-working student who retreated to the library to do his homework while waiting for his ride home after school. Not Part of the 'In' Crowd

Known for his sharp wit, his ever-present leather briefcase and his bookish bent, Souter co-edited the high school yearbook and headed the National Honor Society. Souter was not involved in sports and was not part of the "in" crowd, classmates said, but they remember him as friendly and easy to talk to.

Richard O. Blanchard, a retired Concord High School teacher who often runs into Souter at rare book sales in the Concord area, recalled telling his class the story of the excavation of the ancient city of Troy.

Without any prompting, Souter went to the library, researched the expedition and surprised Blanchard with an unsolicited written report.

"He was the kind of person who did not give a hoot what other people were doing," Blanchard said. "He did what he was convinced was right."

The Souter who arrived at Harvard in the fall of 1957 was conservative in dress and demeanor, with a pronounced New England accent and "very definite views on things," according to Russell L. Munk, one of his freshman roommates.

Set in his habits, Souter would do a regular course of push-ups and sit-ups to keep in shape, and served as an acolyte in church on Sundays, enlisting his roommates to help him memorize his responses.

He was already a fervent New England partisan. Munk, now assistant general counsel at the Treasury Department, remembered Souter reciting Robert Frost to his roommates and bemoaning the decline in Harvard's standards once it opened its door to students outside New England.

A famous Souter story, repeated around the freshman dormitory, Straus Hall, involved the time the meticulous and tightfisted Souter was said to have found 6 cents missing from his accounts.

"The story was, his books then failed to balance," said Beecher, who later roomed with Souter in Lowell House. "The following April, he was doing a spring cleaning and moved his desk for the first time and allegedly found the 6 cents and balanced his books."

Souter was also somewhat formal: When the time came to choose one of Harvard's upperclass houses, Souter selected Lowell House, attracted by the "high table" tradition in which seniors were invited to dine by candlelight in formal wear.

His classmates marveled at Souter's self-discipline.

Beecher, now a municipal court judge in Orange County, Calif., remembered one Saturday night when Souter put aside a philosophy paper he had been working on to go to a party, returning close to midnight. "The last thing I felt like was doing any work," Beecher said. "But David, despite the party mood, came in the door and immediately sat down at the typewriter and resumed work on the philosophy paper and didn't stop until at least 2 o'clock."

Souter majored in philosophy, volunteered at a community service organization and helped revive the Lowell Chronicle, a yearbook about life at Lowell House. The 1960 volume recounts how the "stuff-shirted New Englander shoved and seduced Lowellians to write stories. . . . Pontificating at occasional 'writing' sessions of the staff, lubricating his oratory with Haig & Haig, Hack {Souter} put together the bulk of the year's stories."

Souter wrote his senior honors thesis on Justice Holmes and Holmes's philosophy of judicial positivism, the idea that law is not a fixed set of moral rules, waiting to be discovered. The thesis, written in a nearly impenetrable academic style, offers a self-effacing disclaimer by the young philosophy student that he was no "legal scholar."

Souter graduated magna cum laude, was elected to Phi Beta Kappa and won a Rhodes scholarship to study jurisprudence.

Beecher recalled one of his roommate's odd habits. "It wouldn't be unusual for David, in the early morning, to sit for 15 or 20 minutes with no notes, pen or anything, but just sit in an easy chair looking straight ahead," Beecher said. "He could sit and utilize that time to organize his entire day." Preferred Boston to Paris

One of Souter's closest friends at Oxford was Levine, now a professor of pediatrics at the University of North Carolina Medical School. The Jewish boy from Long Island and the New Hampshire Episcopalian were an unlikely pair; Levine distinctly remembers meeting Souter at their Rhodes interview and concluding that he was "the quintessential Harvard man."

Levine, a Brown graduate, said he "thought at the time that his accent was an affectation and was wondering whether he was a bit of a phony." Souter frequently wore tattered clothes that had been in the family for years, he said, and liked to be called Hackett, after his mother's side of the family. "He used to boast it was one of the first families in New England to lose all their money," Levine said. "He thought that was a source of tremendous pride."

But the two young men found that they shared the same "satirical view" of human nature, as Levine described it, and spent time together, both at Magdalen College and in Levine's Peugeot, touring the English countryside, France, Germany and Austria.

"The whole time he kept comparing every place to Boston and wondering why everybody traveled to these other cities. . . . He couldn't see anything in Paris that matched up to Boston, and he wasn't kidding," Levine said fondly. "He had no patience for people who couldn't speak English. He honestly believed that if he would talk louder, they would understand. The one thing that would soothe him would be to go visit a cathedral."

While at Oxford, Souter maintained a long-distance relationship with Anne Grant, the daughter of a Concord Superior Court judge whom Souter revered, Levine said.

"Hackett was very taken and fully intending to marry Miss Grant," Levine said, pronouncing the name as Souter did, GRAHNT. "He would say, 'When we leave Oxford, I will go back and take Miss Grant's hand in marriage.' {The accent} was not phony. It was 24 hours a day, and he was speaking like that. You really felt as if you were in the company of someone from the 18th century."

Back at Harvard for law school, Souter returned to Straus Hall as a freshman proctor. He did not make law review or graduate with honors, and many of his classmates say they did not know him. "He wasn't a joiner. He wasn't a social butterfly," said Louis Livingston, a law school friend. Consumed With Studies

Shortly after returning from Oxford, Souter's relationship with Grant ended -- an event that friends describe as a major disappointment in his life. Grant, now married, said they had grown apart after dating for four years. Grant was starting her career as a teacher, while Souter was consumed with his law studies.

She said the relationship ended on a cordial, uneventful note. "I don't recall talking about not seeing each other," said Grant. "We just didn't see each other."

Souter's low-key style was evident to his law school classmates.

"David is the furthest thing you can get from a showboat," said Jack Watson, a Harvard classmate and later chief of staff to President Jimmy Carter. "In law school, he was not one of those people who wanted to answer every question and lead every classroom discussion."

Souter had no doubt about his post-graduation plans. "When the New York and Washington firms came up and wooed people, Souter's reaction was he's going to go back to New Hampshire, be a country lawyer, and raise pigs," said Justin J. Stevenson III, a Harvard Law classmate.

Souter "was always very clear that he wanted to go back to Concord. He had a mystical sense about the place," Livingston said. "It really was an oasis for him."

If confirmed, David Souter will leave that oasis for the first time in his adult life. Friends describe Souter today as a proper man of regular habits, an ascetic who simply wraps himself in a long scarf against the bitter New Hampshire cold, who eats the same meager lunch every day (yogurt or cottage cheese and an apple), who does not watch television or listen to the radio, whose only indulgences seem to be rare books, antiques and classical music.

Every Sunday, before visiting his mother, Souter attends the 9 a.m. service at St. Andrew's Episcopal Church in Hopkinton. Although he chooses to sit in a pew near the back, Souter regularly takes up the brass collection plate to pass around. A workaholic, he tries to take the month of August off to read -- one year he tackled Proust, another he concentrated on English history.

His friends bristle at the notion that Souter is a weird misanthrope. They insist he is engaged in life and interested in people, a thoughtful, dependable friend they turn to in times of trouble. Although Souter may not hum Madonna songs or head out to see "Wild at Heart" on a Saturday night, they insist he is in touch with the world around him and has the ability to understand modern situations that he may not have experienced directly.

Jane Cetlin, a liberal Democrat who served as Souter's law clerk from 1984 to 1986 and worked for the Dukakis administration in Massachusetts, said the judge, the godfather of her 2-year-old daughter, scours baby catalogues to find appropriate toys. "He's a great godfather," Cetlin said. "He takes his job quite seriously."

Friends say his failure to marry has been a disappointment to Souter. He dated a woman he knew at the attorney general's office -- holding off on asking her out until after leaving the office, for reasons of propriety -- but she married someone else.

Friends say he has talked longingly of trying to cut back on his six- and seven-day weeks, and that although he has no children, their own children view him not as an imposing, remote figure but as a beloved uncle.

"The idea of David Souter as a recluse is absurd," Rudman insisted.

Scarcely known outside New Hampshire before his nomination, Souter has left little of the paper trail that proved so treacherous for Judge Robert H. Bork. But his single law review article is telling. Writing in the pages of the New Hampshire Bar Journal in 1983 about one of his predecessors on the state supreme court, Laurence I. Duncan, Souter could have been describing himself.

He was the "the most private of men," with "a gentleman's sense of the appropriate" and the "intellectual wherewithal to go it alone," Souter said of "Mr. Justice Duncan." And he found "prophetic" an essay Duncan wrote as a Concord High School senior.

Quoting from the essay, Souter wrote: "And already the boy had his vision of a life that 'in the main, we must sail alone,' though we 'must not fear to turn aside' to help our fellows as we go."

Special correspondent Christopher B. Daly in Boston contributed to this report.