Why is it, knocking on Michael Moriarty's door, that one half expects him not to be in? Perhaps because, in so many of his roles, his character has in one way or another been out to lunch.

"Hi," Moriarty said, opening the door and sending another great interpretive theory down the drain.

Michael Moriarty, as it turns out, is more at home that ever as a result of a personal transformation he says has taken place over the past few years. Even so, that spacey quality that has invested his work from "Bang the Drum Slowly" to Col. Dorf in the NBC series "Holocaust," still subsumes his conversational presence. He has just opened at the Kennedy Center as the protagonist of Brian Clark's "Whose Life Is It, Anyway?" but as it happens, he has himself > written a play. It is called "Flight to the Fatherland," and it had a run at a theater in Rochester, N.Y.

"I had nothing to do with getting it produced," Moriarty said in that ethereal voice of his -- the friendly, somewhat vague, somehow mysterious voice that matches his water-clear eyes and the innocent roundness of his face. "But I learned a great deal. I learned, for example, that it's . . . not a play. It's halfway between catharsis and art."

"Flight to the Fatherland" concerns a son returning to his family in America after suffering a nervous breakdown while in England. Moriarty, after graduating from Dartmouth in 1963, won a Fulbright scholarship to study drama in London.

"Yes," he said, "areas of it are autobiographical. I had a bout with nervous breakdown over there myself. It was ultimately healthy, I think. The best thing that could have happened. It forced me to surrender."

Surrender?

"To the Force," he said, laughing. A large cigar lay burning on the table in front of him. "Have you seen 'The Empire Strikes Back?'" he said. "Gee, it's wonderful."

About the transformation, Michael . . .

His laugh is from "Who'll Stop the Rain," a laugh of submission to confusion, rather than the ragging, mocking laugh of the hotshot baseball pitcher in "Bang the Drum Slowly." "Uh, basically, it's a transformation from a belief that you have intellectual control over your life to a realization that you don't. The knowledge that despite what we've been taught we can't organiz e the world, or control it. That's what makes people commit suicide. They put the final piece of the intellectual logic puzzle together, and it spells The End."

It does not mean, however, that Moriarty has turned off his brain or abandoned ambition. On the contray, he retains a clear, if personal, picture of his career, and it is a candid one.His first break came in 1973, when he won an Emmy as the Gentleman Caller in the television production of Tennesee Williams' "The Glass Menagerie," opposite Katharine Hepburn. "Bang the Drum" followed shortly, as did the role of an agonized homosexual in "Find Your Way Home," for which he won the Tony award as Best Actor of 1974.

"I had success, all right," he said. "At first there was the natural euphoria of having done well, and then . . . there was emptiness."

The emptiness was not particularly apparent to his audiences, who got to see more and more Moriarty every year. The surrendering was perhaps more evident, since each of his characters seemed, in one way or another, already to have done that. In nearly every case, the choice of role had been his.

"I've tken only two parts for the money," Moriarty said. "One was 'the Last Detail,' where I played the Marine Lieutenant. I really wanted the Randy Quaid part, and I was quite disappointed not to get it. But Jack Nicholson was very understanding. The other was 'Who'll Stop the Rain,' which is a movie that I don't like.

That film of 1979, in which Moriarty appeared as a disillusioned and impotent war correspondent whose hapless smuggling efforts are taken over by a supervirile noble savage in the person of Nick Nolte, seems a metaphor for Moriarty's point of view.

"I believe in the gentle hero," he said. "The tradition of the lamb, the idea that the meek will inherit the earth. The basic structure of the novel of which the movie was based is that of a descent into hell, and there's lots of religious imagery. But my character -- well, it was hard to play, and I did't succeed. But at least there were glimpses of heaven in the book.

"The director was a humanist -- an agnostic -- and the result was that you got a 1950s existential theme placed upon this religious novel. The director's idea was that 'evil is ignorance.' So he had lots of hell in the film, but no heaven, and I don't think you can show one without the other. In its reliance on the Nolte character, the movie romaticized violence and drugs. What it really romanticized was American aggression and violence as a noble experience. And it got strangely sentimental, and inaccurate, about the nature of a heroine experience."

Moriarty picked up the long cigar, for a moment. The vagueness was altogether gone. Now 39, in his crew-neck sweater and jeans and loafers he looked like a philosophy professor in the student union, discussing somebody eles's film.

The transformation, Michael . . .

"I spent a year and a half with Zen. I learned a lot from it, but it only seemed to work up to a point. You had to assume the lotus position, which you can't do on stage much, when you think of it. And I kept thinking, what about the Zen Buddhists imprisoned in tiger cages in Asia? They can't attain the lotus position, so an important part of their belief is unattainable. Basically, I just sort of began to move back to Christianity. My family in Detroit are lapsed Catholics, and that's what I went back toward."

Moriarty's changing point of view -- the adoption of what he calls 'surrender' -- also helped color his view of the roles he has played. In 1976, for example, he played one of the Tyrone sons in Eugene O'neill's "Long Day's Journey into Night" in a Kennedy Center production directed by Jason Robards. The play is an American classic, but it is a far cry from light entertainment.

"I don't like O'neill that much," Moriarty said. "I just don't. The comic vision is the higher vision, even in Tennessee Williams, because Williams includes resurrection.I learned more from that cast than any other, though. For the first time I learned how to do a fourth wall play every night, with level of a realism appropriate to the style of the Play."

A "fourth wall" play, Moriarty explained, is one in which the audience is ignored by the playwright. They must sit like a fourth theater wall, obediently watching the action. Its antithesis is Shakespeare, in which the audience is presumed to be a participant, and may even be addressed directly by an actor from time to time. "Fourth wall plays are more voyeuristic," Moriarty said. "The other kind are ultimately more miraculous and certainly healthier."

The vagueness that attends Moriarty on stage was not present in his hotel room, but his sensitivity -- the word he uses himself -- was. "I'm just against violence, in all forms," he said. He includes violence perpetrated by critics, who he thinks can be barbaric. "Some of them make eating breakfast like going to the Coliseum." His method of coping is surrender; in order to reduce the necessity of surrender, he has given off reading newspapers.

How is it then that our subject, who picks and chooses his roles, has come to be known for the portrayal of Col. Erik Dorf, the enigmatic but finally monstrous Nazi of "Holocaust"?

"I got the role because I had just done the hockey player in 'The Deadliest Season.' I had had only three days to come up with that characterization, but I had long before personally learned the effect of success on one's sensitivity. That hockey player had learned to be mean -- a real goon -- because that was the way he was taught to be. But I thought the role analyzed the conglomerate responsibility for increasing violence."

"Holocaust" was a controversial large-scale treatment of Nazi genocide, but Moriarty thinks it worked, and was a role suitable for his point of view.

"Shall I give you my response to The New York Times?" Moriaty asked, dredging up a memorized rebuttal to a complaint of oversimplification and careless research. "For The Times to attack 'Holocaust' for low artistic standards is like Martin Luther King attacking Harriet Beecher Stowe for the low literary quality of 'Uncle Tom's Cabin.' It's a little demeaning, and it misses the point. In terms of what the market for an unsavory message will bear, 'Holocaust' definitely succeeded."

Moriarty, more and more, is taking the business of drama into his own hands. His own potters' Field Theater Company, which is based at New Yorks's Cathedral of St. John the Divine, is now 3 Years old. Potters' Field and the Stratford Shakespeare Festival are co-producing a "Richard III" that will open the Kennedy Center's subscription season here on Sept. 4.

And he has an idea for a new play by his own hand.

"It has to do with pride," Moriarty said. "Man is proud of his sensitivity, and a woman is proud of her love for him. But they're both in the process of being destroyed by their own pride. Pride is the insidious disease. It's the basis of Greek tragedy, and it's a particular problem in the religious world."

Ah, the drama of the Moriarty transformation.

"But it's not dramatic," he corrected, grinning in that wavery but compelling voice."Not too long ago Guideposts magazine came to see me in New York. An interview and a photographer who took a lot of pictures. The interviewer heard my story, and he kept asking me: Just when did it happen? Just when did it occur? I did't hear anything about the interview for a while, so I called them up. 'Oh,' they said. 'We're not using it. It wasn't dramatic enough.'"

"So I guess you could say when I auditioned for religion, I didn't get the part."

The anecdote seemed to please Moriarty, and he let it hang in the air a moment, surrendering to the contradiction.

"The best work you do," he said, his eyes round, "is always on the other side of intention."