One of Peter Cruikshank's two unfinished novels takes place in a science-fiction future that programs robots to complement their human masters. Titled Companions Forever, the manuscript has for its hero a robustly bodied but meekly souled young human trying to live a simple life and stay out of trouble. He is furnished with a robot that is short, snotty and mean, and keeps getting into trouble. The human meets and falls in love with a woman who is outgoing and assertive. Her robot is introverted.

The novel explores two types of companionships: the one between human and robot, which results in a gradual assimilation of each other's personality traits; and a traditional love affair, also with mutual assimilation of characteristics, that lasts forever.

Peter embraces both ceaseless change and permanent romance. "I believe in love and communications," he says.

For him, the key sentence in the marriage ceremony is his vow to "love her and respect her as the person she is and will become."

"It's the biggest problem in marriage: after a while she is not the same person you married, and you aren't the same person yourself," he says. "You change, which is all right as long as it is gradual. Drastic change is hard to take. But you should be able to cope with change if you realize from the beginning that this is how it will be. If you are shocked when someone changes, you won't be able to cope with it."

Peter was born in Fort Benning, Ga., and lived most of his life in Arlington, Va. At 30, he has an associate of arts degree in management from Montgomery College and works as a management analyst with the Navy. His middle-level civilian job is to study procedures and policies and to recommend improvements. The issues he deals with, outsiders find dull, he says, but he finds his job "challenging." He intends to pursue a career working for the Navy, though, he says with a dreamy look in his eyes, "if given a chance, money and time, I'd like to be a writer."

Peter is a cheerful companion; he says what he looks for in people are a sense of humor and good conversation. A solid team player, he is one of the boys. He is the type of person likely to make the best barbecued chicken wings in the neighborhood (actually, his specialty is lasagna). He is the neighbor one wouldn't hesitate to ask for the loan of a lawnmower or a chain saw.

"Pete seems like your average outgoing friendly guy, but he is more than that," his sister Joey says. "He has depth. He can be hurt deeply, and he can be happy deeply. That first marriage of his hurt him a lot. He's had it real rough. But in Carol he found his true love. I have no doubt about that. I wish I could be so certain of my choice for a partner."

Built like a quarterback, Peter works with computers, which, he says, fascinate him. He has a beer belly, which embarrasses him, and if someone mentions it, he pledges to "work on it."

He loves movies and finds himself thinking visually: he considers how something he plans--his wedding, for instance--would look on the screen. He likes comedies and love stories, and his favorite actors are Alan Alda--"that's the kind of guy I would like to be"--and Jimmy Stewart, whom he admires for his "elegance," "flair" and "down-to- earth humor." Humphrey Bogart is "too macho" for him.

His absolute, number one film is "E.T.," which he calls "a classic which we'll watch year after year." He acknowledges that "E.T." made him cry --even the second time.

"'E.T.' drags a lot of emotions out of you," Peter says. "Every time you see it, you get a really good feeling. The only bad thing about it is that it ends."

When he got married the first time, he was 18, and he describes himself as having been "popular, with a ton of casual friends, but with no close friends. I couldn't get real close to anybody. I dated around, but never more than a month."

Yet after only a few dates he fell in love with Elizabeth Aitken, also 18, also a Roman Catholic, also an Army brat, also from Northern Virginia. When they decided to get married, both families pleaded that they wait. Four months after their first meeting and tired of planning a wedding that their families frowned upon, Elizabeth and Peter eloped to South Carolina, where they were married by a justice of the peace. Peter says: "It was in 1971, and the Vietnam war was in full force. It was a turbulent time, and marriage was a way of stabilizing ourselves. A lot of people I knew were getting married then. I thought marriage would take good care of me, and I thought I was in love--neither one was true. At 18 you don't know who you are and what love is. You don't have anything to compare against.

"Marriage stabilized us for a while. We thought of marriage as forever. But shortly after we got married, we knew it was not going to work. We knew it in the first year. We both kept trying; we hoped it would work out."

After marriage came graduation from high school; then Peter signed up with the Air Force for four years.

"Looking for a career and looking for something in life, I thought military service might help," he says. "Where I was stationed, nobody was thrilled about going over to Vietnam. But I would have gone if I had to.

"Everybody of our age was rebellious. When I went into the Air Force, I thought I knew more than the others. If we went ahead and got a divorce, that would have proved that the adults were right."

The marriage lasted seven years and produced Beth, now 11, and Billy, now 10. After the second child--both by a caesarian section--the doctor advised them that having more children would be dangerous for the mother's health.

"It was easier for me to have a vasectomy than to have her tubes tied," Peter says. "I don't regret doing it."

He says he does not consider having his vasectomy reversed. He says he has heard that the surgery is unreliable and much too expensive.

Peter admires closely knit families. Having a father and a brother--and his first father-in-law--in the military, influenced his decision to enlist, though his own father left home when Peter was 14, and his parents no longer communicated.

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A few weeks after he met Carol, the woman who became his second wife last month, Peter started calling her parents "Mom" and "Dad" and established a routine of playing golf every Saturday morning with his future father-in-law and brother-in-law.

In the wedding ceremony Peter wrote, the minister asked the parents to give their "blessings" and "pledge" their "acceptance" of the marriage.

One of Peter's intense disappointments is that his father did not answer his letters and spoke only in short, clipped responses when approached on the telephone. The last time father and son met was in 1969, when the father came home from Vietnam for a brief visit. Or perhaps that happened in 1967. The son is not sure.

After his divorce, Peter dated a lot of women and lived for awhile with a few of them. But, he says, he knew with each that it wouldn't work out in the long run.

It was different with Carol.

"A couple of days after I met Carol, I knew she was for me," he says. "From the beginning I was totally convinced we were made for each other. We don't argue a lot. We discuss. We are adults."

During the Vietnam war, Carol marched for peace. Peter had no objection to serving in that war. In 1979, Peter voted for Ronald Reagan and Carol voted for Jimmy Carter.

"For a couple of nights we stayed up discussing politics," Peter says. "Now both of us are moving toward the center.

"I never had problems talking to women, but after 15 minutes I ran out of things to say. But not with Carol. From the beginning we could talk for hours, easily.

"She doesn't have to say anything, and I know what she means.

"We hope that our decision is for the rest of our lives. At 18 you can't make such a decision."