Eric Hoffer, 80, the self-educated scholar who worked as a longshoreman while he wrote philosophy that was praised by professors and pondered by presidents, died yesterday at his home in San Francisco.

Death was attributed to natural causes.

An original, provocative and sometimes controversial thinker who expressed himself in a pungent, aphoristic style, Mr. Hoffer spent his early years as a migratory laborer, and through reading and observation gradually amassed the insights and ideas for which he eventually became known.

A man without any formal education, who had been blind as a child, Mr. Hoffer came dramatically to public attention with the appearance in 1951 of his first book, "The True Believer."

A keen and penetrating study of the fanaticism behind extremist mass movements, the book won widespread acclaim. It impressed literary critics, lay readers and President Dwight D. Eisenhower, and it focused considerable interest on the author, a man of simple habits who lived alone, haunted public libraries and worked out philosophical problems during long walks through Golden Gate Park.

More books and articles followed, as did television appearances. On the air, Mr. Hoffer, a burly, six-footer with the seamed face and callused hands of a veteran stevedore, attracted hordes of new admirers and beguiled audiences with a warmth and enthusiasm that appeared to belie his shy and retiring nature.

A man of words, who warned against their dangers, a man of ideas, who was skeptical of those he called intellectuals, Mr. Hoffer circulated his often coldly common-sensical views on man and society in a syndicated column once carried in almost 200 newspapers. He was also appointed to the philosophy department of the University of California at Berkeley, where he held the specially created post of "conversationalist at large."

In February, President Reagan awarded him and 11 other Americans the nation's highest civilian honor, the Presidential Medal of Freedom. The president recalled that when he was governor of California, Mr. Hoffer came to see him.

"I got some pretty good, sound--and salty--advice," Mr. Reagan said.

In 1967 Mr. Hoffer, who has been described as nonideological, was quoted by President Lyndon B. Johnson ("America is the only new thing in history") and then was invited to visit Johnson at the White House.

After a half-hour chat during a stroll on the lawn, Mr. Hoffer, a former lumberjack, railroad worker and skid-row resident, called the occasion "the finest day of my life." He was appointed the next year to the President's Commission on violence.

The son of a cabinetmaker who had immigrated to the United States from Germany, Mr. Hoffer was born on July 25, 1902 in the Bronx in New York City. Although he was often called the common man's philosopher, Mr. Hoffer's hereditary endowments and early life appear to have been anything but common.

By the age of five he had learned to read both English and German. At the age of seven he was blinded by a fall. After his mother died, he was cared for by a housekeeper, who led him to believe he did not have long to live.

"My childhood was a nightmare, and its shadow still hovers in the back of my mind," he once said.

Regaining his sight at the age of 15, he was gripped by a sudden hunger for the printed word. He began reading voraciously.

"Reading was my only occupation and pastime," he recalled. "I was not a normal American youth--no friends, no games, no interest in machines, no plans and ambitions, no sense of money, no grasp of the practical."

Left to make his own way after his father died in 1920, Mr. Hoffer was described as determined not to be a factory worker, under the control of a boss. Instead, armed with a bundle of books, he headed west, on the physical and intellectual odyssey that was the making of a philosopher.

After exhausting his funds and starving for three days on Los Angeles' skid row, he began washing restaurant dishes in return for dinner, then moved to a box factory for three years of work that enabled him to save enough for two months of uninterrupted reading.

Next, he went on the road, working on farms, in fields, forests and kitchens, always reading. In time, he began to write as well, and in 1943, settled down as a stevedore in San Francisco, where he completed "The True Believer."

"All mass movements . . . irrespective of the doctrine they preach and the program they project, breed fanaticism, enthusiasm, fervent hope, hatred and intolerance . . . " he wrote. "Absolute faith," he once said, "corrupts absolutely." Readers found his book lucid and lean, filled with ideas, difficult to summarize, easy to admire.

Other books included "The Passionate State of Mind" (1955) and "The Ordeal of Change" (1963).