IN 1971, three years before the socialist revolution hit Portugal, three women in Lisbon were planting the seeds of a feminist revolution. Meeting twice weekly, they were sharing and recording their innermost feelings--the kinds of feelings that women, and particularly women in Latin countries, have been taught to keep innermost. When these feelings became public in the form of a book called New Portuguese Letters in 1972, the authors were immediately arrested on charges of "abuse of freedom of the press" and "outrage to public decency." The trial dragged on and on until finally, in April 1974, the three Marias--as the authors had become known--were about to face sentencing. Then came an eleventh-hour reprieve in the form of the Revolution of April 25. The judge said "Go in peace," and all the women in the courtroom shouted. "Women, united shall never be defeated!"

Meanwhile, the case had become an international cause celebre, and the authors had attracted so much attention that they threatened to eclipse their own book. On the cover of the English-language edition, the original title is relegated to a subtitle in thin black letters, while the words. "The Three Marias" are emblazoned in bold red across the top. But it is really quite fitting that the authors should get this kind of star billing, because the book is really about them--or rather, about their shared experience of writing it.

None of the essays, poems, stories, or letters in the book is signed. It is a collective production, but three individual voices can be heard distinctly throughout, raised sometimes in unison and sometimes in opposition, sometimes bouncing off and echoing one another. The result is, as one of the authors has said a "trialectic."

The authors have taken the thematic framework of the book from the story of a 17th-century nun, Mariana Alcoforado. Sent to a convent at the age of 16 because her parents could not afford to provide her with a dowry, she was seduced and impregnated by a dashing French cavalier, who then abandoned her and returned to France with Napoleon's army. Mariana poured out her love and her bitterness in a series of five letters addressed to her seducer--the original Portuguese Letters, which were published in Paris in 1668.

No matter that the story is perhaps spurious and that scholars have proved that the actual author of the letters was the Vicomte de Guillereagues, a Parisian man-about-town who dabbled in the study and analysis of passion. The metaphor still holds. "What woman is not a nun, sacrificed, self-sacrificing, without a life of her own, sequestered from the world?" the three Marias ask.

THE STORY of Mariana serves the authors the way a grain of sand serves an oyster. It acts as an irritant to which they return again and again, a stimulus to the creation of an entire world--a world constructed from materials extracted painfully from within themselves. Through letters supposedly written to and by Mariana, they invent a cast of characters and unfold a baroque plot full of passion and intrigue. Interspersed with these letters are vignettes of other Marianas. Marias and Maria Anas, all trapped in some kind of "convent"--of marriage, of motherhood, of passion--and all somehow seduced and abandoned. And scattered throughout are poems and letters in which the authors speak in their own voices, voices that are surprising both in their explicit eroticism and in their unsparing honesty and self-doubt about the work they are engaged in.

At times, the book comes perilously close to taking itself too seriously, but it is this honesty that saves it. The opening letters establish a tone of self-conscious dedication to a revolutionary literary experiment, to the creation of a sisterhood, to the stripping away of all masks and to the exposure of women's true feelings about love and passion. And then, in Letter Three, there is a subtle, slightly self-mocking shift:

Ponder the fact, my sisters, as our flesh today is warmed by this gentle sun shining down on everyone and bringing in flocks of tourists, that this literary novelty of ours is going to sell well.

Occasionally the authors carry their objective analysis of themselves onto a more serious level. A recurrent nagging question is summed up in one letter that consists of the two sentences:

My sisters: But what can literature do? Or rather what can words do?

An even more nagging question is whether or not the problems these women authors see themselves confronting--isolation, abandonment, the pain of love--are actually women's problems or human problems. One of the Marias argues that the reason they see Mariana as a sympathetic character is "not because she was a nun and a woman put behind bars, but because she was different," and any artist--male or female, has a "love of violating taboos."

Perhaps so. But the specific problem that all the Marias in this book face is the impossibility of loving someone who is seen as your enemy--who is supposed to conquer and possess you--and that is specifically a woman's problem. Eroticism becomes inextricably linked with masochism: women are fruits waiting to be sucked dry, their bodies are battlefields about to have flags implanted upon them, they are eager to "impale themselves upon an enormous pleasure." That women themselves find such images erotic is proof that they have been robbed of their own pornography.

IF THE ACID test of sexual equality is the act of sex itself, then it seems that women--and men--have a long way to go. And the inescapable question--one that the Marias ask with a faint horror--is whether they will ever get there. Sometimes the answer seems to be yes, sometimes no. And as far as what happens with the way things are now and have been for centuries, the Marias seem to offer two alternatives for women: either give yourself to your enemy and go mad or commit suicide like Maria, or else harden yourself like Joana, an invented character who coolly sends her lover suggestions for improving his technique in bed.

And what about men? The Marias make a rather half-hearted attempt to present their side of the story, but all the male characters fall into the pattern of the callous and insensitive French cavalier with a monotonous sameness. There is one exception--a sympathetic cousin whom Mariana calls her "guardian angel"--but he proves to be an unstable character and, like her, commits suicide.

If the book should be faulted for anything, perhaps it should be for putting things in terms that are too black and white. Not everyone who falls in love becomes heartless or goes crazy, and the excess of madness in the book almost reaches the point of being ridiculous. Here too, the ability of the Marias (or at least of one of them) to see themselves objectively just saves them, and they stick in an intentionally ridiculous vignette of a woman who is committed to an asylum after her parents find her locked in copulation with a large dog.

Some of the pieces in the book go on too long, some are redundant, some are too crude and unsophisticated and some are too finely polished. But the book as a whole is successful. To read it is to share in the excitement and the fear that the three women participating in this "experiment" felt.

The experiment itself was not so successful. What these women were trying to do was to break down the separation that exists not just between man and woman but between human and human, to create a new family. But the conflicts between the three stubbornly become sharper and sharper, and the moments of unity shorter and shorter. By the end of the book, the letters convey no bitterness but only a sense of disappointment and exhaustion. Not all was in vain, though. On the contrary, there seems to be something very precious even in that shared disappointment. As one Maria says in her final letter:

...in all sincerity I say to you: we shall go on alone, but we will feel less forsaken.