I. F. Stone, the independent, radical pamphleteer of American journalism hailed by admirers for scholarship, wit and lucidity and denounced by critics for wrongheadedness and stubbornness, died of a heart attack yesterday in a Boston hospital. He was 81 years old and lived for many years in Washington. Mr. Stone's career in eight publications, most of them left of center, spanned more than 65 years. Its capstone was his muckraking newsletter, I. F. Stone's Weekly (1953 through 1968) and, after his pace was slowed by a heart attack, I. F. Stone's Bi-Weekly (1969 through 1971). They were essentially one-man, four-page ps and the people. Admirers of his informed skepticism praised him for courage and insights. Detractors acknowledged his integrity but accused him of obsessive opposition to the use of power, particularly military power. Everyone agreed that he annoyed some people all the time and all people one time or another. Enjoying the Maverick's Role The short, owlish maverick with dimpled cheeks and major handicaps in hearing and vision, was a tough-minded but pacifist gadfly, a tireless examiner of public records, a hectoring critic of public officials, a persistent attacker of Government distortions and evasions and a pugnacious advocate of civil liberties, peace and truth. He enjoyed being barred from background press briefings, which he denounced as ''usually brainwashings.'' He battled for many years to get a black admitted to the National Press Club. He also differed with many liberals in insisting on constitutional protections for Communists, declaring that ''once you put ifs and buts in the Bill of Rights, nobody's civil liberties will be secure.'' At the same time, he hailed the American tradition of a free press, declaring: ''There are very few countries in which you can spit in the eye of the Government and get away with it. It's not possible in Moscow.'' The primary grist for his profitable, 19-year newsletter was documents rather than people. He read at least 10 newspapers a day and ferreted out contradictions and inconsistencies in the voluminous records of official Washington, using them to oppose McCarthyism, racism, the nuclear arms race, American military involvement in Vietnam and other issues he regarded as stains on democracy. Sometimes It Was Exclusive Mr. Stone's tenacity produced some important exclusive reports. One was his disclosure in 1957 that the Atomic Energy Commission's first underground atomic test was detected not only 200 miles away, as the Government said, but 2,600 miles away. The Government's assertion suggested that a test ban would allow the Soviet Union to cheat without fear of discovery. Mr. Stone confirmed the lie by checking with a seismologist at the Coast and Geodetic Survey. In 1971, the combative journalist called himself ''a new Lefty before there was a new Left,'' but he repeatedly angered the new Left as well as the old. The controversies included his bitter denunciation of the Soviet bloc, where, he wrote, after a trip to the Soviet Union in 1956, ''the worker is more exploited than in Western welfare states.'' ''This is not a good society,'' he concluded, ''and it is not led by honest men.'' Mr. Stone enraged some readers by defending the Warren Commission report that rejected a conspiracy in the 1963 assassination of President John F. Kennedy, by deploring violence by militants and by refusing to defend pornography. The Criticism of Israel The greatest outcry among readers followed his criticism of Israel. He visited the country many times and wrote two books eloquently favorable to Zionism and Israel's fight for independence. But after the Arab-Israeli war of 1967, he urged Israelis to compensate Arab refugees for their losses and to cede the occupied territories to them to create an Arab Palestine federated with Israel, with Jerusalem the joint capital. Assessing his newsletter, he remarked, ''I tried to bring the instincts of a scholar to the service of journalism; to take nothing for granted; to turn journalism into literature; to provide radical analysis with a conscientious concern for accuracy, and in studying the current scene to do my very best to preserve human values and free institutions.'' In his 70's Mr. Stone learned classical Greek so he could read untranslated works and write ''The Trial of Socrates,'' published in 1988 after more than a decade of study. The book, his 12th, took classical scholars to task for accepting Plato's conclusion, written nearly 2,500 years ago, that Socrates was sentenced to death only for exhorting his fellow Athenians to be virtuous. Plato as a Threat Without defending the verdict, Mr. Stone sought to show that Plato had failed to report that Socrates, his mentor, was regarded as a threat to national security for assailing the Athenians' faith in participatory democracy at a time when their democratic government was threatened with overthrow by an aristocratic dictatorship. His earlier books included ''Underground to Palestine'' (1946), ''This Is Israel'' (1948), ''The Hidden History of the Korean War'' (1952) and ''The Killings at Kent State: How Murder Went Unpunished'' (1971). In the decade after World War II, critics said Mr. Stone tended to put the best face on Soviet policy and the worst on American policy. But by the mid-1950's he concluded that the Soviet hierarchy was composed of ''the same frustrating wooden Indians'' that peopled the American State Department. In a 1987 interview, he expressed grief over the ascendancy of those he termed ''right-wing kooks'' and deplored ''the ugly spirit of the subliminal message of Reaganism that you should go get yours and run.'' Mr. Stone's longtime home facing Rock Creek Park in northwest Washington was a monument to the written word, with many walls lined with books, floor to ceiling. Gazing at the volumes, in Greek, Latin, Hebrew, English, French and German, he remarked'' There's so much I haven't read. There's so much to learn.'' I. F. Stone was born Isidor Feinstein in Philadelphia on Dec. 24, 1907. (He adopted the initials and added the surname Stone at age 30). In his childhood his family moved to nearby Haddonfield, N.J., where his parents, Bernard Feinstein and the former Katherine Novack, Jewish immigrants from Russia, owned a dry goods store. The boy read widely and favored works by Walt Whitman and Jack London. He made his journalistic debut at age 14 with a neighborhood monthly called The Progress, which featured liberal editorials. This soon led to jobs as a reporter on The Haddonfield Press and The Camden (N.J.) Courier-Post. The youth studied philosophy at the University of Pennsylvania while editing and rewriting articles full time at The Philadelphia Inquirer. He dropped out of college in his junior year, but the university awarded him a B.A. degree in 1975, making him an official member of the class of 1928. Through the years, he also received many honorary doctorates. The New York Papers Mr. Stone was briefly a member of the Socialist Party, wrote editorials for The New York Post, was an associate editor and then Washington editor of The Nation and then wrote for PM, The New York Star and the New York Daily Compass. With the demise - The Star succeeded PM, and The Compass succeeded The Star, all soon toppling, one by one - of the three left-of-center New York dailies, he began publishing his newsletter, with 5,300 subscribers. Cynics were astonished to learn that it was always in the black and eventually had 70,000 subscribers when it halted publication in December 1971. Mr. Stone's wife since 1929, the former Esther Roisman, was at times his only assistant on the publication. As they closed shop, she said, ''We both feel we're at the beginning of a new life and a new career. Izzy never looks back. He has a zest for life, for every new day, that I've never seen in anyone else.'' In later years, Mr. Stone wrote for The New York Review of Books and occasionally for The Nation. Besides his wife, Mr. Stone is survived by a daughter, Celia Stone Gilbert, of Cambridge, Mass.; two sons wife, Mr. Stone is survived by a daughter, Celia Stone Gilbert, of Cambridge, Mass.; two sons, Jeremy of Chevy Chase, Md., and Christopher of Los Angeles; a brother, Louis of Glenside, Pa.; a sister, Judy of San Francisco, and four grandchildren.