As show business couplings go, the marriage of Ruth Gordon, 84 this month, and Garson Kanin, 67, is remarkable—for productivity as well as longevity. When they met in 1939, he was an experienced film director with such credits as A Great Man Votes and Bachelor Mother. She was already one of the leading actresses of the century, having played her first role—Nibs in Peter Pan—in 1915 and gone on to star in Serena Blandish and A Doll's House. After they were married in 1942, Gordon and Kanin collaborated on the screenplays of the Spencer Tracy-Katharine Hepburn hits Adam's Rib and Pat and Mike, among other films. Gordon won an Oscar for best supporting actress in Rosemary's Baby in 1969 at age 72, and starred in the cult film Harold and Maude with Bud Cort, two years later. She has also written plays (Years Ago) and her memoirs. Kanin is the author of some 38 novels (Moviola), plays (Born Yesterday) and nonfiction works (Tracy and Hepburn). This year, they each have a new publishing venture. Hers is Ruth Gordon: An Open Book (Doubleday, $11.95), the third volume of her memoirs. Kanin's is his eighth novel, Smash (Viking, $14.95), the chronicle of a musical comedy's journey to Broadway. The couple divide their time between Martha's Vineyard and an apartment overlooking Central Park in Manhattan. There, in a rare joint interview, they spoke with Eric Levin of PEOPLE.

What has enabled your marriage to endure for 38 years?

Garson: I think the key is that we don't always agree. Agreement is deadly dull. For instance, we went to see The Tin Drum, and I found it brilliantly conceived and executed, not like most book adaptations. I have never read the book, but I don't see how it could be any more powerful.

Ruth: I could just throw up over that film. The children peed in the soup and made the little boy drink it. Disgusting. The worst thing I ever saw like that was in Rosemary's Baby. Roman Polanski, the director, wanted Mia Farrow to be terribly sick, so he had her eat a raw chicken liver. Well, it was just awful. He could have gotten the effect without making her do that.

Garson: Ruth also can't stand sushi—Japanese-style raw fish—which is my idea of absolute heaven.

Ruth: Raw octopus! Horrible stuff. But then, I hate the whole Japanese nation because they didn't treat us right.

When? During World War II?

Ruth: Sure.

You mean you've never forgiven them?

Ruth: Why should I? I haven't forgiven the Germans either. Actually, Garson took me to this Japanese restaurant one day, and I was the wow of the place because it turns out Harold and Maude just slayed 'em in Japan. So I changed my feelings a little. You like anybody who likes you, I guess.

You two collaborated successfully on Pat and Mike, Adam's Rib and other screenplays. Don't your professional tastes coincide sometimes?

Garson: Not at all. When we wrote together, I would say a line and laugh hysterically, and she would look at me stonily and say, "What's funny about that?" Sometimes we'd compromise, which never satisfied either of us. Sometimes, because I was much more experienced than Ruth in directing, she would defer to me. But I wasn't always right, you see. Or I'd hold back my opinion because she's very sensitive. She could always tell anyway. So we stopped collaborating.

Ruth: We don't read each other's books either, until they are published.

What motivated you to write your latest books?

Garson: On this, we did agree. Now that we have reached a certain age and experience, we feel impelled to pass on something of what we've learned, something possibly helpful.

Ruth: To have a career you've got to be selfish, put the blinders on, no question about it. After you make it you can't very well go back and help the people that you stepped on, but you can help somebody.

What do you want to pass on?

Garson: Well, at some point you figure out that what you really know, as opposed to what you may desire or believe, is very small.

Ruth: Somebody once asked me, "What do you actually know?" I said, "I know how to put on straight makeup, and that's all I'm sure about."

Garson: Anyway, one thing I realized I knew about show business is that somewhere along the line most of the people quit, drop out, give up. Why? Because it's hard, that's why. For every play we see there must be 550,000 first acts lying around unfinished. But if you stick with things, so I have learned, they work out. I'd like to pass that on.

Ruth: Gar, remember that scene in Kramer vs. Kramer where Dustin Hoffman is pushing the boy on the bicycle? Now that was a movie we both liked. Well, the boy is teetering and wobbling, and Dustin calls out to him, "Keep going! Keep going!" I love that. In fact, I wrote Dustin, who I don't know very well, to tell him so.

Garson: That's the lesson, all right.

What keeps the two of you going so energetically?

Garson: Everybody wants to know that. "What is Ruth's secret?" I live with her, so I know. It's absolute flexibility. She might walk in a week from now and say, "Please let's go to Japan for a month and eat sushi every day."

Ruth: And raw octopus. Oh, give me a raw octopus!

Garson: It wouldn't surprise me. For instance, I adore Gilbert and Sullivan operettas. Ruth hates them. Well, we went to see The Pirates of Penzance in Central Park, with Linda Ronstadt. Now, Ruth has a way of going off into her own thoughts, into the horse latitudes, if she's bored by what's happening onstage. But five minutes into the show I looked over at her and she was...transported. I can hardly believe this myself, but we went to see it five more times.

Is there more to it than flexibility?

Ruth: My doctor, Dr. Fred Plum, has a great saying: "Enthusiasm in maturity—that's the secret of life."

Garson: We went to see Arthur Rubinstein a few weeks ago. He is 93, ill, going blind, has a little difficulty hearing. But, my God, he had been to all the new movies and he had a stack of new recordings he was all excited about—operas, string quartets, symphonies, things he never had time to listen to when he was playing piano.

Ruth: And what he was really enthusiastic about was that his secretary was going to a deli every day and bringing him back enormous bags of everything they have.

Which of your books and movies would you save if you could only save one?

Ruth: There's no answer to that. When Janet Gaynor's house burned down I said to her, "Janet, my God, when you ran out of the house what did you take with you?" And in that wonderful cracked-china voice of hers, she said, "Well, Ruth, I took all my stills." She was right, of course, but I'm not going to take any of that stuff.

As you grow older, how do you deal with the passing away of your closest contemporaries and the issue of your own mortality?

Ruth: Cheerful subject. Well, I'll tell you: Thornton [Wilder] didn't die, for me. He's with me when I make decisions and at many other times.

Garson: You've just taken away my answer. The really great ones don't die. Across the room there is Felix Frankfurter's oak rocker, which used to be in his study. When I look at it, I can see him in it, surrounded by mountains of certiorari. As for us, Ruth is a truly religious woman. I, on the other hand, am an atheist. I see organized religion as the scourge of mankind, the cause of all its wars and friction. I wish it could be eradicated.

Ruth: Oh, what a crock. When you've been in a jam I didn't hear you say, "Oh, President Carter, if I just get through this I'll vote for you." You said, "Oh, God!"

Garson: I know, but that was just an expletive.

Ruth: I'm not so sure. I asked Thornton once if he believed in God, and he said, "Well, we all know something's going on out there."

Garson: Look, the most basic aspect to this question is whether you believe in an afterlife—Heaven and Hell.

Ruth: I used to. I used to figure it out that Thornton and Alex Woollcott and Harpo Marx would meet me there and help me over the first days. Then I'd come back—oh, I had a whole scenario worked out—and look and see Garson sleeping by himself. And I'd think, "Oh, boy." One day I came and looked in and there was a pretty girl in bed with him. Then I never came back anymore, and got used to Heaven.

Garson: I think if people believe in God, or gods, they're less inclined to believe in people.

Ruth: I believe in people, but that doesn't mean I don't believe in God too. I don't go to church, but I got invited to preach a couple of times, and I think I would have done it well, but that wasn't the way I intended to go.

Garson: You know, we have a true intermarriage. A Jew—even though I'm not religious—and this lovely little WASP—

Ruth: But I'm not a WASP.

Garson: You're not a WASP?

Ruth: Of course not.

Garson: Well, you're a white Anglo-Saxon Protestant, which is what it stands for.

Ruth: I don't like the connotation. I admit, I am white—I can't help that. I'm Protestant—I'm wearing a St. Christopher's medal on my bracelet. I'm also wearing a charm of my Academy Award, so that kind of counterbalances the other.

Is it true that Katharine Hepburn hasn't been speaking to you two since Garson wrote Tracy and Hepburn?

Garson: No, we're as close as ever. That rumor got started when the book first came out and she said to me, "As a favor, please don't ever ask me to read it." I agreed, and later I told the story to an interviewer, who distorted it, and it got steadily built up. Kate never said anything to anybody about the book, yet the rumor persists.

You've known many famous people. Are there any you haven't met that you would like to?

Ruth: Reggie Jackson. He's a superman. My maiden name is Jones, so we have the same initials—RJ—which I think gives us a kind of affinity. If you're careful and cautious you'll never be great. Reggie lets 'em fly. Sometimes he strikes out and just nothin's goin' right. Then zingo! He hits one and it's history. You've got to take wild, flying chances in life. People may say, "My God, how awful," but you're aiming for something. Reggie's aiming for something, and he is among the greats.

Is there one question you would like to ask each other?

Garson: That's intriguing. Let's see. Why do you think, Ruth, that when you get scripts you instinctively say no?

Ruth: That's a wonderful question. I guess I don't really get intrigued by many things, although Every Which Way but Loose I was wild to do, and Harold and Maude I had to fight for. Take the other week. Jule Styne asked me at a party if I would play Peter Pan on the stage. "I'm 84 years old," I said, "and that's the first play I ever appeared in, in 1915." He said, "Are you worried about flying, the wires and belt and all?" I said, "No, dear, I'm just worried if you're a nut or what, and I'm not going to talk to you anymore."

What would you like to ask Garson?

Ruth: Are you in love with anybody except me?

Garson: The answer to that question is yes! I have a lot of love in me, and it's spread around. I would hate to think I loved one person and didn't love anyone or anything else.

Ruth: I didn't say "love," I said "in love."

Garson: I've never quite gotten that distinction, to tell you the truth. I've heard it used, but I really don't know what it means.

Ruth: Oh.