During an extraordinary, peripatetic filmmaking career that spanned half a century and produced inimitably original and provocative work in three different countries and four languages, Luis Bun uel, who died Friday in Mexico City at the age of 83, secured a preeminent avant-garde position in movie history.

He was at once a stylistic pioneer and master at exploring the medium's potential for evoking the irrational and subconscious in instantaneous, graphic and often shocking terms.

The vast majority of movies reflect a genteel predisposition to ignore or trivialize this potential, and Bun uel himself lived long enough to indulge in occasional self-parody and inspire some excruciating imitations, notably the infamous "El Topo" of Alexandro Jodorowsky. Still, Bun uel's example will remain indispensable to any director seriously attracted to the medium's infinite flexibility and suggestibility, its barely developed affinity for revealing subjective, submerged feelings and emotions.

Not surprisingly, Bun uel's notorious early work caught the attention of Freud, and Bun uel remained the freest of cinematic free associators from the beginning of his career, when he contrived to offend conventional morality and illustrate the possibilities of a surrealistic vision in three inventive, scabrous, scandal-causing short films--"Un Chien andalou," "L'Age d'or" and "Land Without Bread."

Bun uel went to Paris in 1925 with a minor clerical job and hopes of somehow attaching himself to the filmmaking community. He served as an assistant to the expressionist director Jean Epstein on three productions before alienating his mentor by flatly refusing to be loaned to Abel Gance, whose grandiose style Bun uel found intolerable. Bankrolled by a gift of 135,000 francs from his mother, Bun uel cooked up the scenario of "Un Chien andalou" in three days of skull sessions with Salvador Dali and then shot the picture, which ran 17 minutes, in two weeks.

Years later Bun uel recalled his apprehension during the first screenings in Paris in 1928: "I was prepared for a public uproar and stuffed my pockets full of stones, just in case . . . I was peering out at the audience to see what the reaction would be, but the only people who came were aristocrats and artists . . . The enormous enthusiasm 'Un Chien andalou' aroused in them stunned me. When the showing was over, they got up and clapped and clapped. Those stones weighed pretty heavily in my pockets."

In fact, Bun uel was so shocked by the reaction of this unshockably appreciative audience that he later appended a sardonic note about his "success" to the published scenario: "What can I do about people who are crazy for anything new, even if the novelty outrages their inmost convictions, or about a venal or insincere press, or about that pack of imbeciles who found beauty or poetry in what is, in essence, nothing less than a desperate, passionate appeal to murder?"

After all, Bun uel had made his introduction by literally assaulting the eyes of his spectators. He himself appeared as the man with the razor in the indelibly shocking opening sequence of "Un Chien" who appears to slice open the eyeball of a young woman with that lethal phallic instrument.

Bun uel did get his belated Parisian uproar when "L'Age d'or," an hour-long expansion on the startling techniques and anarchic sexual themes of "Un Chien," appeared in 1930. Even the friends of his financial angel, Vicomte Charles de Noailles, recoiled at the anticlerical, antibourgeois ferocity of this second assault.

In his mid-sixties Bun uel's style had acquired a peculiarly mellow, nonchalant, discursive mastery of the interplay between objective and subjective episodes. It reached a droll pinnacle of perfection in the shaggy-dog social satire "The Discreet Charm of the Bourgeoisie," the 1972 Academy Award winner as best foreign language film. Bun uel would interrupt the action matter-of-factly, without making elaborate apologies or introductions. Minor characters entered to describe their dreams or traumatic incidents from the past, then quietly took their leave. The continuity rambled wittily from apparently conscious states to subconscious ones, from the central plot situation to digressions, subplots and dream sequences. At one point Bun uel deliberately kidded his own structural "looseness" by inserting a dream sequence inside a dream sequence.

Although it took on humorously playful forms throughout his career, this free association grew out of an abiding artistic conviction that subconscious life was not only as "real" as objective reality but that it also held the key to elemental passions and mysteries. Foremost among these is the sex drive, which often erupts in perverse or morbidly frustrated, thwarted behavior patterns in Bun uel's characters. Frustrated sexuality and undercurrents of emotional violence are thematic constants in his work from his first to last films. They link "Un Chien andalou," made in 1928, with "That Obscure Object of Desire," released in 1977. His protagonists are often prisoners of sex, and he doesn't ascribe to the idea that their condition lends itself to easy social amelioration or therapeutic massage.

Bun uel summarized his approach eloquently in a 1953 lecture called "Poetry and Cinema," delivered at the University of Mexico. "In none of the traditional arts," he said, "is there so great a disproportion between potential and achievement as in the cinema . . .

"The essential element in any work of art is mystery, and generally this is lacking in films. Authors, directors and producers take great pains not to disturb our peace of mind, and they keep the marvelous window of the screen closed to the liberating world of poetry . . . In the hands of a free spirit the cinema is a magnificent and dangerous weapon. It is the superlative medium through which to express the world of thought, feeling and instinct. The creative handling of images is such that, among all means of human expression, its way of functioning is most reminiscent of the work of the mind during sleep . . ."

The explosive impact of the early work did not result in an immediate directing career. After "L'Age d'or" had been hailed, condemned and then banned in Paris, Bun uel was briefly courted by MGM, but he spent most of the 1930s in executive roles--supervising dubbing for Paramount in Paris or Warner Bros. in Madrid, producing four features made by a newly formed Spanish company, representing the Loyalist government on propaganda missions to Paris and then Hollywood. In 1944 he went back to work for Warners as a dubbing supervisor on Spanish and French versions of their releases.

Financially solvent after his tenure with Warners, Bun uel emigrated to Mexico in 1947 and at last resumed his directing career. It was his second credit, a 1949 comedy called "The Great Madcap," that assured his reputation as a reliable commercial director in Mexico, and Bun uel became a Mexican citizen in the same year. However, it was his third credit, "Los Olvidados," a starkly unsentimental and psychologically powerful account of urban juvenile delinquency, that revived his international reputation as an uncompromising, revelatory original. Bun uel's characteristic themes were effectively embellished in other Mexican productions like "El," "The Adventures of Robinson Crusoe" (shot in English), "The Criminal Life of Archibaldo de la Cruz," "Nazarin," "The Exterminating Angel" and "Simon of the Desert."

He found a second filmmaking base in France during the 1960s and eventually made his two greatest international successes there, "Belle de Jour" and "The Discreet Charm of the Bourgeoisie." (The former can serve as testimony to his mesmeric influence within the movie intellgentsia. An elegant pornographic fable about the dirty secret life of a frigid beauty, embodied by Catherine Deneuve, its obvious psychological presumption as a male fantasy projection of feminine passivity or inscrutability has been willfully disregarded or excused by a remarkable number of customarily militant feminist critics.) He even returned to his native Spain for two major features, the 1961 "Viridiana," which ran into censorship problems, and the 1970 "Tristana," which drolly echoed the same story.

Bun uel's outlook remained staunchly unsentimental over 50 years. Even when he seemed to "mellow," it was on his own artistic terms, elaborating a permanent role for himself as the archridiculer of the bourgeoisie, which appeared likely to endure far longer than its anarchist and Marxist critics supposed back in the late '20s.

It's as if the elderly Bun uel had decided that while you can't beat the smug and overprivileged, and certainly shouldn't join or emulate them, you can still function honestly by giving them the needle. As compromises go, this seems fairly attractive and honorable. Satirists and moralists would be hard-pressed for subject matter without the enduring complacency and obliviousness of the human race, especially its better-placed representatives. Bun uel made them into his satiric pets and never lost sight of his guiding, intensely masculine perception that a vast, turbulent world of emotional aggression and longing can be found just beneath the surface of conventional behavior and socially respectable appearances.