IBELIEVE firmly that a filmmaker's entire work is contained in his first film," wrote Francois Truffaut 15 years ago. "Not that it can all be foreseen, but it can afterward be verified."

Six years later he enlarged on this belief in an essay about Jean Vigo:

"Just as we say a person is fully formed between the ages of 7 and 12, so we can also say that a filmmaker shows what his career will be in his first 150 feet of film. His first work is himself, and what he does later will also be himself, always the same thing, sometimes a masterpiece, sometimes something less good, even some failures... Like all artists, filmmakers search for realism in the sense that they search for their own reality, and they are generally tormented by the chasm between their aspirations and what they have actually produced, between life as they feel it and what they have managed to reproduce of it."

The American Film Institute Theater's auspicious new series, "Truffaut on Truffaut," offers the rare opportunity of tracing an important filmmaker's career in its entirety -- from the beginning to the near future in Truffaut's case. All 18 features, including two that still haven't opened theatrically in the United States, and his two significant dramatic shorts are scheduled to be shown. In addition, the series is augmented by films Truffaut considers personally influential and/or irresistible. Finally, Truffaut himself has consented to star in this retrospective, appearing at the opening program today at 7:30 p.m. in the Eisenhower Theater and two programs later this week at the AFI Theater in the Kennedy Center.

The Truffaut series will nearly monopolize AFI Theater programming between now and the end of March. This evening Truffaut is scheduled to introduce and discuss his latest feature, "Love on the Run," a romantic comedy that may or may not conclude the avowedly autobiographical group of films, beginning with "The 400 Blows" and extending through "Bed and Board," in which Jean-Pierre Leaud has portrayed Antoine Doinel, Truffaut's fictionalized self-portrait.

The American release of "Love on the Run" is still several months away, a factor that enhances the specialness of this special preview. "The Green Room," an adaptation of the Henry James story "The Altar of the Dead," which Truffaut shot just before "Love on the Run," will be previewed at the AFI Theater on Mar. 21 and 22, a few weeks in advance of its American theatrical release. Truffaut plans to introduce a showing of Ernst Lubitsch's impeccable boudoir farce, "Trouble in Paradise," Tuesday night at the AFI Theater. He also will preside at a showing of his own "Mississippi Mermaid" on Wednesday night, exhibiting the original 145-minute version of the film, which lost about half an hour here. Since "Mermaid" seemed peculiarly listless and misbegotten in its abbreviated form, it remains to be seen if this restoration will prove a glorious revelation or prolonged disappointment.

Annette Insdorf, an assistant professor at Yale and the author of a new scholarly study of Truffaut's movies, will translate and moderate during his personal appearances. It's conceivable that the death of Jean Renoir early last week could necessitate last-minute changes in Truffaut's schedule of appearances, although no changes had been announced at press time.Truffaut was very close to Renoir, who will be buried in the small French town of Essoyes on Tuesday. Three of Renoir's films -- "The Rules of the Game," "La Marseillaise" and "Toni" -- are included in the AFI Theater series.

Truffaut regards Renoir as one of the most profound influences on the filmmakers who emerged 20 years ago on the crest of the French New Wave. Since they shared obvious temperamental and stylistic affinities, it became a critical commonplace to describe Truffaut as Renoir's legitimate artistic heir. Truffaut has written that "along with 'Citizen Kane,' 'The Rules of the Game' is certainly the film that sparked the careers of the greatest number of directors. We look at this movie with a strong feeling of complicity; I mean that instead of seeing a finished product handed to us to satisfy our curiosity, we feel we are there as the film is made, we almost think that we can see Renoir organize the whole as we watch the film projected."

Truffaut's characterization of Renoir as "the quintessential moviemaker of the personal" could be aptly applied to Truffaut. From the outset he demonstrated a flair for personalized cinematic expression, reflected in both his autobiographical subject matter and fluid, spontaneous style of depiction. He seemed to take to the medium like a duck to water. His first three features -- "The 400 Blows," "Shoot the Piano Player" and "Jules and Jim" -- evoked fresh, heartening notes of pathos. They were potentially shameless tearjerkers transformed by a fundamentally realistic, resilient attitude toward life. They were survival stories, tinged with melancholy but never despairing or humorless.

For example, the delinquent Antoine introduced in "The 400 Blows" was patronized by some reviewers but not by Truffaut himself, who recognized the boy's essential resourcefulness. The character began to soften up later on. The adolescent Antoine seemed more capable and quick-witted than the young man he theoretically matured into when an increasingly innocuous Jean-Pierre Leaud recreated the role in "Stolen Kisses" and "Bed and Board," pictures which exposed a coy streak that hadn't surfaced in Truffaut's earliest features.

Nevertheless, Truffaut himself seemed to corroborate the stability and resilience one perceived in the original Antoine. At the age of 47, he remains the most consistent, durable, productive and likable veteran of the New Wave. He's indulged some unrewarding brainstorms like "The Bride Wore Black," "Bed and Board" and "Such a Gorgeous Kid Like Me" but invariably renewed himself with a "Wild Child" or "Day for Night" or "Small Change."

Truffaut is almost certainly regarded with more affection by knowledgeable moviegoers than any other active, illustrious filmmaker. An ingratiating personality emerged from the earliest photos of him and interviews with him, but his personal appeal has been vastly enhanced by the roles he played in his own films -- the dedicated teacher Itard in "The Wild Child" and the patient director Ferrand in "Day for Night" -- and the role he played in Steven Spielberg's "Close Encounters of the Third Kind." In addition to valuing Truffaut as a filmmaker, and probably their favorite filmmaker, many people must think of him subconsciously as a mentor, an authority figure who quietly commands respect.

The structure of the AFI Theater series reflects Truffaut's dual roles as a movie critic and movie director. In league with Jean-Luc Godard, Jacques Rivette, Claude Chabrol and Erich Rohmer, Truffaut prepared for a filmmaking career by serving an apprenticeship as an ardently opinionated, polemical reviewer, principally for the weekly magazine Arts and the monthly Cahiers du Cinema between 1954 and 1958.

Truffaut had been encouraged to write by the late, widely respected film critic Andre Bazin, who founded Cahiers in 1950. In "The Films in My Life," an anthology of old and new critical pieces published in English translation last year, Truffaut recalled, "It was the first happy period of my life; I was going to the movies and talking about them, and somebody was paying me to do it. I was finally earning enough money to do nothing from morning to night but what I enjoyed, and I appreciated it all the more because I had just gone through seven or eight years of trying to find enough money to eat every day and pay my rent."

Bazin came to Truffaut's rescue on several occasions. They first met in 1947 when the movie-mad Truffaut organized a neighborhood film club and discovered that its screenings conflicted with an established club run by Bazin. When Truffaut got into debt, Bazin helped bail him out. He also helped extricate the runaway teenager from a reform school after Truffaut's father had discovered his where-abouts and turned him in to the police. Later, when Truffaut went AWOL shortly before his army unit was scheduled to be sent to Indochina, Bazin persuaded him to turn himself in. When the army finally rid itself of Truffaut for "instability of character," Bazin again took charge of him. In Truffaut's words, "I became his adopted son. Thereafter, every pleasant thing that happened in my life, I owe to him."

Truffaut's conviction that children are vulnerable but think-skinned -- the theme of "Small Change" -- obviously grows out of his own hand-to-mouth existence as a kid. To some extent the relationship between Itard and the wild child must also reflect his gratitude to Bazin for helping rehabilitate a scroungy urban kid. According to James Monaco's account in "The New Wave," Truffaut lived with his grandmother until he was 8 and his parents took him back only reluctantly when she died. "They weren't bad people," he quotes Truffaut as saying, "just nervous and busy." A runaway at 11, Truffaut was evidently supporting himself with odd jobs and petty thefts before he was in his teens.

In the introductory essay to "The Films in My Life" Truffaut explains, "I have included very few bad reviews, even though I had the reputation at that time of being 'the demolisher of French cinema.'" The book preserves a few demolition jobs, including a well-deserved and astutely argued one on Jules Dassin's "He Who Must Die," which was sort of the "Midnight Express" of its day. Despite the preponderance of appreciative pieces, one can imagine that Truffaut earned his reputation. The Cannes Festival was one of his favorite sources of ridicule. Banned from the festival in 1958, he returned in the role of novice filmmaker in 1959 and won the best direction award for "The 400 Blows."

Truffaut recalled, "I always thought of the director while writing my article. I wanted to influence him (but when I attacked him, my way of influencing him could become very offensive).... That's why my last year on Arts was less valuable. I would forget about the script the director had filmed and end up by suggesting the one he ought to have filmed."

Truffaut also was encouraged to make the transition by his father-in-law, a prominent film distributor named Ignace Morgenstern, who was occasionally angered by an unfavorable review. He put up a third of the $100,000 that it cost to produce "The 400 Blows." Two years earlier he had formulated a manifesto: "The film of tomorrow appears to me as even more personal than an individual and autobiographical novel, like a confession, or a diary. The young filmmakers will express themselves in the first person and will relate what has happened to them... and it will be enjoyable because it will be true and new...." Happily, he wasn't forced to eat his words.

Truffaut's comments on many of the supplementary films in the series may be found in "The Films in My Life." The judgments run the gamut from the sublime to the ridiculous, but they suggest that Truffaut was probably stimulating to read even at his most quixotic and outrageous. There are some shrewd pieces on a number of pictures that haven't been booked in the series: "You Only Live Twice," "Jet Pilot," "Baby Doll," "Paths of Glory," "Bonjour Tristesse," "Love Me or Leave Me," "Stalag 17," "A Man Escaped," "Le Mystere Picasso," "Assassins et Voleurs," "The Two of Us."

Truffaut's appreciation of "Assassins et Voleurs," the glorious last comedy of Sacha Guitry, renewed an old unfulfilled desire of mine to see his earlier work, which hasn't been revived for years. Truffaut seems to have been particularly alert to the fresh qualities in several young performers: His descriptions of Jean Seberg, Brigitte Bardot, Marilyn Monroe and James Dean are admirably vivid and perceptive. The traps he has occasionally fallen into when trying to make genre movies that recall Hitchcock or Lubitsch or Cukor may be foreseen in this observation about "Love Me or Leave Me": "Indeed, it often happens that searing flashes of truth, nuances whose sincerity is beyond doubt, creative and sublime mimicry of all sorts are injected into the most conventional Hollywood sequences. It sometimes seems that the element of truth is all the more powerful as the framework, ambience or genre of the film are all the more phony and artificial."

Truffaut must have been putting this theory to the test in experiments like "Mississippi Mermaid," "Such a Gorgeous Kid Like Me" and "The Man Who Loved Women." The sort of kitsch revelation that sometimes worked for Hollywood has never really worked for Truffaut, whose genius resides in straightforward, unemphatic evocations of emotion.

At any rate, "Truffaut on Truffaut" promises to be an exceptionally interesting series. Some casual reading in "The Films in My Life" may help to put it in perspective and simplify viewing preferences. It's a trifle sobering to think that the New Wave began 20 years ago, but a pleasure to have one of the movement's original agitators and stoutest spirits to Washington.