Nadine Gordimer arrived here 12 days ago full of trepidation, knowing she would have to insist on a polite but principled protest at Mount Holyoke College and wishing that she didn't have to. "I thought they might think it very rude of me, you know," she fretted.

She is not by nature a firebrand. Gordimer, the South African writer whose opposition to apartheid goes back more than 30 years, whose novels have several times been banned in her own country, stands barely five feet tall, is elegantly thin and silver-haired at 61, and would not look out of place graciously presiding over the cucumber sandwiches at a garden party. Accepting an invitation, then discomfiting one's hosts without warning, was simply poor manners.

The exigencies of life in South Africa are such, however, that Gordimer would not trust either the telephone or the mail to alert Mount Holyoke to her plans for yesterday's commencement ceremony. "One simply doesn't correspond about such things," she said. Not until she was on this side of the Atlantic could she explain to college officials that she couldn't exactly accept the honorary Doctor of Letters degree the college wanted to bestow.

"I was so embarrassed," Gordimer sighed in her throaty alto. "But I needn't have been. They understood totally."

The school had planned to honor both Gordimer and her countrywoman Winnie Mandela, the black activist whose husband Nelson Mandela has been imprisoned since 1964. But the South African government would not permit Winnie Mandela, banished to a remote village, to travel to South Hadley, Mass., to receive a Doctor of Humane Letters degree.

"I thought, 'How can I go take a degree if Winnie can't be there?' " Gordimer recalled, pacing her son's West Side apartment. "But for me simply to refuse to go -- then no one knows about it. It doesn't do Winnie any good. It doesn't do anyone any good."

Gordimer had contacted Winnie Mandela to discuss strategy, itself a difficult undertaking. Mandela cannot have a visitor unless the government grants a permit, and she has no telephone. Gordimer reached her on the public phone she comes to each morning and afternoon to receive monitored calls. Mandela agreed that Gordimer should go to Mount Holyoke to explain why she could not and -- before Mandela's empty chair in the college amphitheater -- gently decline the hood and diploma.

" . . . I must ask to delay my investiture until such time and place as she and I may receive these honors freely together, as was your intention," Gordimer said yesterday. In response, the audience of 3,000 faculty, family and graduates, carrying single flowers in Mandela's honor, rose in a sustained ovation.

Mount Holyoke President Elizabeth T. Kennan has said that she's applied for a visa to visit South Africa so that she could personally present the degree to Mandela.

Even several days before the event, Gordimer seemed to be girding herself. She did not relish holding a press conference, confronting what she calls "the usual political questions." She dislikes being described as a political novelist, a phrase which to her suggests that "you go out to illustrate a certain precept. You don't start with the mystery of life; you see yourself as a teacher and your books as something didactic."

Gordimer, on the other hand, was a writer while still in grade school, published at 15 -- "not even knowing what politics were. I was quite retarded, I sometimes now think." She had never known blacks who were not servants until she was a university student. "I was living in an extraordinary sociopolitical situation that to me was quite natural. I wasn't made a writer out of indignation and social outrage, but out of a sense of wonder and curiosity."

Indeed, one of the pleasures of visiting abroad, Gordimer added, simply is being able to talk literature with friends like Susan Sontag and Elizabeth Hardwick. "It's a joy to be able to talk writer to writer," she said. Social evenings in Johannesburg, by contrast, invariably become political discussions. "We might be able to talk about books or theater, but it comes round to politics," Gordimer said, smiling. "So many of my friends are active, even in professions that wouldn't seem to be. In South Africa, they become so."

"As a child it was dinnertime conversation forever," her 30-year-old son Hugo, a New York film maker, said. (Her daughter and two grandchildren live in France.) "It was a revelation, when I left, to see that in more normal societies one can have a different life."

Gordimer professed to be a reluctant radical. "By temperament, going to meetings, speaking in public, even talking this way to you is something I would never have done if I lived elsewhere," she said. "But I find it impossible if I want to stay -- and I do -- to sit back and say, 'I'm just going to write.' Even though I believe my writing is the best thing I can do for my country, I can't make myself an entirely private person. Perhaps, to my shame, I limit this side of my duties as a South African," she considered. "It's not something I do best."

It is an internal debate out of a Nadine Gordimer novel, a theme and variation on power and privilege and how they compromise and distort the lives of the beneficiaries as well as their victims. Because of apartheid, Gordimer believes she lives differently. She even, to a degree, writes differently.

"When you deal with big, complicated themes, many strands of reality, you have to develop strong narrative power," she explained. "My first stories were very sensuous, tastes and smells and feelings. It's a wonderful stage for a writer, but I was weak on narrative in my first couple of novels. Maybe because so much was happening, I had to develop this muscle," she said, clenching a small, delicate fist. "You couldn't hover sensitively around some of the things preoccupying me."

Politics does preoccupy Gordimer now. Simple questions call forth long, detailed history lessons about apartheid legislation; tributes to resisting churchmen (the film Gordimer coproduced about a "colored" minister who persuaded an international church council to declare apartheid a heresy, "Allan Boesak: Choosing for Justice," will air on public television stations here, probably in the fall); denunciations of the new constitution and other supposed reforms. "These are all the paroxysms and convolutions white supremacy goes through to try to accommodate black power without really giving black power," she said.

She has been heartened by the recent wave of college demonstrations for disinvestment and protests over apartheid, though she's conscious of the far greater risks taken by South African dissidents of both races. "You live so very safely here," she said somewhat wistfully. "To make a protest and to be arrested for a couple of hours can make you a hero. In my country, it's quite different." To have read a message from Mandela at Mount Holyoke yesterday, for example, would have been a treasonable offense under South African law. "I don't sneer at that safety ," Gordimer added. "It's an enviable kind of innocence. The world should be like that."

Will the demonstrations abroad make any difference? "When people live thousands of miles away there is the feeling that there will be a decisive riot, a decisive year, a decisive change in policy, all happening at once," said Gordimer. "Since the 1976 uprisings, there has never been a single week when there hasn't been some sort of riot or uprising somewhere in the country. It has never really stopped. The country's been in a state of revolution all this time.

"The walls of Jericho are not going to fall because people demonstrate. But it's not true, as South Africa says, that the outside world has no influence. South Africa is very concerned about its image in the rest of the world. It wants, for a million cultural and political and economic reasons, to belong. That's why I believe public opinion in this country is important."

She feels encouraged, too, by the nascent reintegration of South African protest after the black separatism of the 1970s, a phenomenon she thought necessary yet found painful. Like a character in her own fiction, she saw sociopolitical change mirrored in her friendships, in her dinner parties.

In the 1950s, she and her art dealer husband and their black friends, artists and intellectuals and journalists, "thought it was a political gesture to ignore apartheid. We thought by thumbing our noses the law would break down. We moved around freely. Love affairs between blacks and whites were illegal -- and common.

"But, of course, it was always an illusion. As soon as our friends left the house, or the university, they had to travel with passes in their pockets, on a train for blacks or a second-class taxi. At home we could eat and drink together. But the black wasn't free at all and the white wasn't free. I'm not decrying it; it had a spillover in understanding on both sides. But it never had any impact on the millions of people who never had contact with whites except to call them 'boss' or 'missus' and to do their bidding. They weren't helped by our freedom."

By the 1970s, Gordimer recalled, "it became very difficult for blacks to have white friends. They were told, 'You can't go running in and out of white houses. You've got to concentrate on our struggle. When it's all over you can have drinks and dinner.' Though some friendships did endure, some did not, and new ones weren't formed. In every level of life there was this move toward separation."

The Southern African chapter of PEN, the writers' organization, "had an extraordinary meeting where the blacks said, 'We'll have to resign, en bloc.' One was our chairman." It was a "jolly good" group that fought censorship and promoted black authors, Gordimer added. "It was a great pity that we died, killed off by history," yet now that black and white student organizations and trade unions can belong to the same umbrella group, "we may make it come back. It's not impossible."

She sounded weary after talking politics for an hour and a half. After Mount Holyoke, later in the week, she will accept a degree from City College of New York before going home to Johannesburg.

She has only rarely thought of living elsewhere. "I had a terribly romantic idea once to go and live in another African country," Gordimer confessed. "I saw it was mad when I moved around Africa and saw that anywhere else I was just a European. At home, we were never rejected completely."

Tired as she has grown of her public role, "as long as I'm fortunate enough to have a voice, I can't just sit here. I must speak out. It's little enough to do," she said, somewhat apologetically. "I have a great sense of inadequacy, always."