''I've always played an idiot,'' says Steve Martin. As if we didn't know. After all, this is ''The Jerk'' talking - the wild and crazy guy of ''Saturday Night Live,'' the star of ''Dead Men Don't Wear Plaid.''
But don't count on more of the same. Yes, farces are hot nowadays, and the surest way to a fast buck is to peddle another ''Bachelor Party'' spinoff. Still , says Martin, ''I just can't bring myself to do that anymore. I'm the wrong age , and my emotions are completely somewhere else.''
Don't get him wrong. He isn't auditioning for ''Long Day's Journey into Night ,'' at least not yet. But he sees his current role, opposite Lily Tomlin in the comedy hit ''All of Me,'' as a step in a new direction.
''This man is not an idiot,'' Martin told me over lunch recently, describing his ''All of Me'' role as a lawyer whose body is invaded by the transmigrating soul of a rich, daffy woman.
In fact, says Martin, this character is ''a contemporary person with some brains. The movie is wildly comic, but he's not naive or a victim of circumstances. He's an intelligent man who happens to get caught in a disaster. That's a big difference between this role and any other part I've played.
''And believe me, I really liked it,'' he adds with a grin. ''I liked not having to say 'What's happening to me?' all the time. After a certain age you can't act adolescent anymore. I'd love to play James Bond!''
Besides giving him a well-rounded role for a change, ''All of Me'' showcased Martin's talent in a less chaotic setting than usual. ''For the first time,'' he says, ''I'm in a story with a beginning, middle, and end. It's old-fashioned and solid, like a drawing-room comedy. The hardest thing to do is tell a story straight. That's why I'm happy I made this little movie that works, not some extravaganza that overwhelms the senses. This movie was like going to school. I learned a lot about structure and character.''
''All of Me'' pleases moviegoers as well as Martin, judging from the box office. Some may be drawn by the movie's raunchy moments and bathroom humor, which push the PG rating pretty far. Speaking before the film's premiere, though , Martin insisted that the solid story and characters were salable in their own right.
''People wonder how it'll fare in a market where there's nothing but guys peering through peepholes at naked girls,'' he said. ''Yes, those films do well, but other kinds also do well: 'Tootsie' and 'Heaven Can Wait.' I don't want to call this 'adult comedy,' because I think 'All of Me' hangs in with the younger people, too. It has what Lily calls a naughtiness about it. But there are rebels even in the huge 10- to 16-year-old market - kids who like something a little older, more mature. . . .''
Even before his move to ''All of Me'' and ''more mature'' work, Martin took on some risky and interesting projects. ''Pennies From Heaven'' may have been an artistic failure, but it's among the most experimental movies Hollywood ever made, mingling sober drama with bizarre comedy and surreal musical numbers. ''Dead Men Don't Wear Plaid'' might have been a flop, but its format - new comedy scenes intercut with clips from old detective pictures - is one of a kind for a feature film.
Why has Martin tested such uncertain waters instead of basking in the tried-and-true success of ordinary farce?
''I did 'Pennies From Heaven' because - in my mind - my career had sort of peaked with 'The Jerk' and a concert tour I did,'' Martin recalls. ''I knew I couldn't go on being just a stand-up comedian, because there's a bell curve to this stuff. Pretty soon you aren't playing 15,000 seats anymore - you're playing 10, then 3, then none. You're back in the clubs and doing TV commercials. Even though I was at the top of things with my act, I knew that was over. I was at the end of my rope emotionally.''
So he made the ''painful'' decision to move fully into movie work. The big prize he wanted from Hollywood was ''longevity'' - the ability to ''make a movie , lay off for three years, then make another one.'' His model was ''someone like Warren Beatty. He's always around even when he doesn't make a picture for four years.''
Martin thought that would be paradise after his years of stand-up work. ''Doing my act night after night was like always going up in smoke,'' he complains. ''You do it - and it might be great, it might be lousy, but it's completely gone. I don't know if this is an ego thing, but you wish it would stay around. You work so hard on something that you'd like to be able to visit it again, instead of having it be a vague memory.''
Since he had one successful film already behind him - ''The Jerk'' - he found he was ''already a star'' when he knocked on Hollywood's door. ''It gave me an entree into the movies,'' he recalls. This felt good, but had its disadvantages. ''It wasn't like I had 10 films to get my feet wet and understand how movies are made and what they're about,'' he says. With hindsight, he would have managed some things differently - such as making 'Pennies From Heaven'' after ''Dead Men Don't Wear Plaid,'' not before it. Coming at the peak of an ''increasing bizarreness'' trend, he feels, the daring ''Pennies'' might have worked better commercially.
How does Martin choose his roles? He isn't quite sure. ''All those questions are still being answered in my mind,'' he says. ''I still don't have a total grasp.''
He's certain about one aspect, though: He enjoys variety. ''I liked doing 'All of Me,' but to go out and repeat it isn't tempting,'' he says.
''Because they're complicated they stand repeated viewings,'' he says. ''But I'd be just as happy making a warm movie like 'It's a Wonderful Life.' That's the business I'm in - try to make 'em laugh and cry. I'm not in the art business.''
Martin entered the entertainment world as a southern California teen-ager, doing a magic act ''in folk clubs where anyone could get up on Monday night.'' Later he got a TV writing job for which he was ''really ill-equipped,'' worked on material for ''The Smothers Brothers Show,'' went back to stand-up work, and finally joined the ''Saturday Night Live'' cast -which, along with a successful record and appearances on the ''Tonight'' show, launched him for good.
Though television was important to his early career, Martin feels ''TV is isolated - a place where you show off rather than learn.'' The transition to film was not smooth. ''I had to learn how to calm down a little,'' he recalls, ''because the screen's real big. You have to speak from your heart. When a character got mad in my act, I really exaggerated it. But when people in life get mad they sometimes get very quiet. There's a big process to learning these things.''
At the core of the process is ''learning to use your own personality,'' he continues, naming Jack Nicholson as a master of that art. ''He's a great actor whatever he plays,'' says Martin. ''He's really an oddball, and that always makes him interesting. I'm not too much of an oddball in real life, but I am normal, and I think there's a place for normal people on the screen!''
How does he assess his movies so far? ''There's not a great film in my background,'' he says with reasonable modesty, ''but there's no clinker to be ashamed of. There are at least good moments or good intent in each one.''
This isn't a bad track record, Martin thinks, given the mediocrity of today's comedy. ''A friend said recently that the old comedies - by Chaplin and Keaton - were really clever and funny and you really laughed,'' he muses. ''I realized that was true. Those pictures didn't just skim along the surface with a funny situation every now and then. There's something we've forgotten, lost sight of.''