Such an approach can easily be a recipe for self-indulgence, but with Cassavetes, an actor who became a director conducting 'method' workshops with unemployed actors in the 1950s, it led to a style of improvisational cinema that achieved an astonishing immediacy and was capable at its best of touching emotions of riveting intensity and truth. His movies grew out of feelings rather than production values. His camera was like another person in a room: part of the company. Everything happened around it rather than for its sake, sometimes even out of vision or only glimpsed in the corner of the frame.

Cassavetes, who is rightly seen as the pioneer of today's vibrant American independent cinema and whose work is celebrated this month with a major retrospective at the IFI, made his breakthrough in 1959 with Shadows, an exploration of the relationships of two brothers and a sister and their friends and lovers in a squalid New York of nightclubs and drunken parties.

Developed out of his workshops and financed by his pay as the lead in the TV series Johnny Staccato, Shadows with its handheld photography and naturalistic dialogue is as much a cinematic landmark as Godard's French New Wave Breathless, which came out the same year and launched the French New Wave, although the influence of Shadows took much longer to become apparent.

Opinion has always been divided on Cassavetes, the son of affluent Greek immigrants whose father lost money as fast as he amassed it. While directors claim him as an inspiration . . . in particular Martin Scorsese, John Sayles and Jim Jarmusch . . . some critics are less sure, with David Thomson doubting that he was as good a filmmaker as he wanted to be. "He was courageous, unruly, an enemy to Hollywood for many good reasons, yet he was a tyrant, too, a man who had to be right, " Thomson argues.

Perhaps there is truth in this, but his movies stand above his personal shortcomings. "He was possibly the handsomest man I had ever seen, " says actress Gena Rowlands . . . the daughter of a Wisconsin senator . . . who married him in 1954 and stayed with him despite his alcoholism until his death from cirrhosis of the liver in 1989. "I soon saw he was a good actor, but I was totally unprepared for him to turn into a director."

So much so that when he cast her as a femme fatale in Faces, a depiction of the disintegration of a marriage over the course of an evening of anguished dissection of emotional wounds, she at first found his direction . . . or the lack of it . . . confusing. When she asked about her character, he'd simply tell her, "I've given it to you, you own it now." She recalls the experience as "rough going, but after I saw it put together, I realised I was wrong."

Faces was made in 1968 following a brief flirtation with Hollywood. He'd been lured there by Paramount after Shadows won the Critics Award at the Venice Film Festival. Studios were desperate for edgy new talent to counter the challenge of television. Directors like Arthur Penn, John Frankenheimer and Franklin Schaffner revitalised the industry with Bonnie And Clyde, The Manchurian Candidate and Planet of the Apes.

With his distrust of conventional production values and reliance on unstructured narrative, Cassavetes didn't fit in. His two studio movies, Too Late Blues and A Child Is Waiting, which starred Judy Garland and Burt Lancaster with Gena Rowlands in a supporting role, both flopped leaving him resentful and unhappy. He fared better before the cameras, winning an Academy Award nomination as best supporting actor as a nervy private for The Dirty Dozen. Critically-acclaimed performances in Rosemary's Baby and Don Siegel's The Killers launched him in a career as a screen baddie that would provide the financial independence to make films largely free from studio interference. Faces won three Academy Award nominations, and Cassavetes returned yet again to the theme of marital discord in Husbands, teaming up with his friends Peter Falk and Ben Gazzara to play a trio of husbands who go on a drunken spree in New York and London after the funeral of one of their friends.

During this month's IFI retrospective, various guest speakers will introduce their favourite Cassavetes movie. For me there are at least three favourites . . . A Woman Under The Influence, The Killing of A Chinese Bookie and Gloria . . . although his entire body of work is so richly rewarding it hurts me to omit Shadows, Husbands and Faces. As a critic back in the 1960s and 1970s, when censorship was rife and there were so many extraordinary new directors to discover and to fight for . . .

Scorsese with Mean Streets, Coppola with You're A Big Boy Now, Bogdanovich with Targets, Pollack withA Slender Thread, Spielberg with Duel, Ashby with Harold and Maude . . . I can still feel the tingle of anticipation triggered by the often belated arrival of each Cassavetes movie.

"I made films, got drunk, stayed away from home, " he said after his 1974 masterpiece, A Woman Under The Influence. "I destroyed my wife yet she stood by me through child after child.

So I made this film as a tribute to Gena for all the lousy things I've done to her." Rowlands was rewarded with a best actress Oscar nomination for her portrayal of a middle-class wife overwhelmed by the responsibility of trying to hold together her volatile family and keep the love of a husband . . .

Peter Falk . . . who finds at work and with his friends relief from his frustrations.

A Woman Under The Influence was edited in Cassavetes' garage. The cast is largely made up of family and friends, including his mother and children, the ultimate home movie. Although it feels improvised, the improvisation was all done in rehearsal and then worked into the script, an approach that later found a disciple in Mike Leigh. "Oh, our whole life was a wild life, " Rowlands said in a 1999 interview. "But I thank God we met each other. We both had a lot of temperament and a lot of opinions. But I don't think I ever saw him depressed, and I never saw him fearful. Now, I saw him angry a lot."

By normal Hollywood standards his next movie The Killing Of A Chinese Bookie (1976) ought to be a thriller. A Los Angeles strip-club owner is coerced into assassinating a Chinese underworld boss in order to pay off a Mafia gambling debt. But the thriller is only incidental for Cassavetes, a way of making us feel part of the seedy Californian porn world of Ben Gazzara's Cosmo Vitelli.

The girls at the Crazy Horse Club are as familiar as typists chatting at lunch hour. Every moment is so alive with humorous immediacy and casual compassion that the so-called dramatic climaxes occur almost as asides. Even the shootout is routine: just one of those things that happen. What you remember is the expression of the victim, innately courteous even in death. Gazzara comes across as a born survivor, prepared to make the best of every disaster: not so much a performance as the revelation of a human being which, indeed, is true of all the characters in this compulsively watchable film.

As in The Killing Of A Chinese Bookie, nearly all the killing in Gloria (1981) . . . and there is much of it . . . takes place off camera.

Cassavetes has created a film about violence that avoids being violent itself. Gena Rowlands, playing a one-time chorus girl and gangster's moll, is trapped against her own nature ("I'm not the mother type, I hate kids") into becoming protector of a macho little Puerto Rican boy who somehow escapes the carnage when Mafia hit-men methodically massacre the family of a man caught grassing to the FBI. What might have developed into a conventional chase thriller opens out under Cassavetes' free direction into an offbeat odyssey through the back streets of South Bronx and Times Square. Nobody behaves and nothing happens the way genre movies have conditioned us to expect although Gloria remains in the Hollywood mould in one respect: it is dominated by a bravura Oscar-nominated performance of intriguing ambivalence by Rowlands, who manages to convey vulnerability even when she talks tough ("It's nothing to me to blow somebody's head off, I just hope it's somebody I know").

The Cassavetes retrospective opened last week with Faces. It continues with Shadows and closes with a re-mastered print of the little-seen Opening Night with Rowlands as an ageing film star going through a breakdown brought on by fear of being left alone and unloved. "People in independent film have a passion, they're not in it for the money, " she once said. "I'm very proud that John had a part in it."

The John Cassavetes Retrospective continues at the IFI, Eustace St, Dublin 2 with 'Shadows' (today, tomorrow and Tuesday), 'Husbands' (13 July), 'Mikey & Nikey' (14/15 July), 'The Killing Of A Chinese Bookie' (14/15 July), 'Minnie & Moscovitz' (16 July), 'Gloria' (19 July), 'Love Streams' (21/22 July), 'A Woman Under The Influence' (28/29 July) and 'Opening Night' (27-31 July)