Bill Murray takes on a new role; Francois Truffaut always did

The idea of Bill Murray starring in ''The Razor's Edge'' sounds pretty silly - more like a ''Saturday Night Live'' sketch than a real Hollywood project. Yet there he is at our neighborhood theaters, all dressed up as the philosophically questing hero of W. Somerset Maugham's weighty novel. And he's not half bad, giving the role a nicely balanced blend of dignity and humor.

Unfortunately, the picture as a whole doesn't measure up to his standard. Maugham's basic story is there, tracing the adventures of a young American who seeks enlightenment from Eastern gurus after World War I combat shatters his illusions. But the action is ponderous, rarely rising above the trite screenplay by Murray and director John Byrum, whose previous losers include ''Inserts'' and ''Heart Beat.''

What's a comic like Murray doing in a serious yarn like this? I was impressed enough with his performance to meet him in Manhattan the other day and ask.

''I wanted to change the way I was perceived by people in Hollywood,'' he replied. ''I didn't want to keep getting the same kind of parts. A comedian has to know how to play it straight, or you could never set a situation up. So I felt I could do 'The Razor's Edge' without problems.''

That didn't mean Hollywood would agree, and sure enough, Murray says the project met resistance and skepticism. But he had an ace up his sleeve: a movie called ''Ghostbusters'' that Columbia Pictures was eager to make. The star and the studio agreed on a package deal, and the two films (starting with ''The Razor's Edge'') were shot back to back. ''Ghostbusters'' was released first - with its large budget, it needed to hit the market during the peak summer season - and became a smash success.

Approaching his ''Razor's Edge'' role, Murray decided immediately to leaven the plot with humor. ''When I read the book,'' he recalls, ''I thought there could be more laughs in it. It's like this Larry guy is in a trance every time he speaks - you blow smoke in his face and he talks a certain way for a couple of hours. That kind of seriousness and piety wouldn't play in the '80s. The story is great, but you have to make the characters accessible.''

He also had ideas about Larry's quest. ''I've known people who got involved in some kind of spiritual search,'' he says, ''and my experience is that their sense of humor improved a great deal. They're able to laugh at themselves - for the first time in their life, perhaps - and it makes everything much funnier. I thought that was worth putting into the movie. And I thought it would help us, too, because you can't sit for two hours and listen to someone go to heaven. It's too boring.''

In all, he enjoyed the challenge of his first drama, despite the physical difficulties of shooting in all kinds of conditions on locations from England to India. ''It's harder to make people laugh than to make them cry,'' he says, defending his usual work as a comedian. ''I cry at Burger King commercials. But weighty themes are fun, too - they sort of tickle your mind.'' Truffaut's influence

At a New York press conference a few years ago, a questioner confronted Francois Truffaut with a highly critical remark by Jean-Luc Godard, another French filmmaker of the same generation and background.

''I know he thinks all my films are bad,'' Truffaut answered. ''As for me, I think all his films are good.''

This response indicates why Truffaut, who passed on Sunday, was among the most warmly regarded of all cineastes, and why his films continue to exert a keenly positive influence on world cinema.

His career was propelled by a love for directing, a love for his characters, and a love for cinema that led him to champion not only his own approaches but those of many other filmmakers, including some whose views diverged sharply from his own.

The tone of Truffaut's work was established in his first movies (notably ''The 400 Blows'' and ''Shoot the Piano Player'') as he showed his sympathy for the young, the timid, and other outsiders. His sensitivity to children is clear in such films as ''The Wild Child'' and ''Small Change,'' which explore the difficulties of adjustment to an arbitrary world, a theme close to his own youth. His series on the life of Antoine Doinel - a Truffaut surrogate played by Jean-Pierre Leaud - is a feat of indirect autobiography with no cinematic peers.

Other currents in his career include a passion for literature and a view of romantic love as complex and even perilous, as in the masterpiece ''Jules and Jim.'' A lifelong affection for suspense movies pervades films like the freewheeling ''Confidentially Yours.'' His continual delight in the moviemaking process shines through ''Day for Night,'' which won the Academy Award for best foreign-language picture of 1973.

A man for all cinematic seasons, Truffaut started his career as a critic, a practice that has become ever more common in his wake. He directed his first feature in 1959, helping to launch France's hugely influential ''new wave'' - a movement dedicated to spontaneity and immediacy - at the expense of a stifling ''correctness'' that he and his colleagues felt was smothering European film.

I met and spoke with Truffaut many times, and I found him an unfailingly warm and responsive man, whose enthusiasms for life and cinema were so intertwined they were indistinguishable. In both arenas the achievement that moved and fascinated him most was what he simply called ''survival'' - the act of persevering, whether the foe be physical danger or (much more often in his films) emotional aggression and moral confusion.

In his most purely personal movie, ''The Green Room,'' the enemy was death itself; yet even here the last, lingering image was the face of an undaunted woman gloriously illuminated by what Truffaut considered the life-affirming light of cinema. His persistent faith in film's power to uplift the human spirit has proved a strong and ongoing inspiration to the movie world.