If she thinks she can do it, if she can stop being frightened by the idea that so many grown-ups will be looking right at her, a 7-year-old girl will sit today in the benches that face the justices of the United States Supreme Court.

She will know, because she is smart and her family is fairly straightforward, that the talk has something to do with her life. She will hear a lot of complicated language about "denial of equal protection" and "best interests of the child" and "termination of the parental rights of an unwed father," but the main thing she will know is that the judges have the power to change her adoption in some way -- to make it final, so that the family she has lived with since she was 5 weeks old will be permanently and unchangeably hers; or to make it different, so that new people might come and make themselves family too.

She knows a little, but not much, about the legal record that began to gather when the name at the top of the papers was not Katie but Baby Girl M, which is the kind of name American courts give to infants caught up in the emotional collisions of adults around them. In this record are arguments about fact and arguments about fairness and arguments about the natural order of things, arguments that try to jam complicated questions into precise corners of American law.

Here's a question: How much weight is the American legal system to give to the fact of biological fatherhood?

Here's a question: What are the parental rights that society and the law ought to guarantee a man whose child was the product of what the documents refer to as "casual dating"?

Here's a question: How many adults can an emotionally healthy 7-year-old girl understand to be her father?

Her name is Moses, Katie Moses. Where she lives, in the West, there are horses in a pasture out back. During a television program the other day she and her brother asked their mother about blood, whether her blood ran in their veins, and their mother said no, that this was something that happened when babies were in people's wombs and that they had grown in other women's wombs but that she, their adoptive mother, had carried them in a different way. "In my heart," Pamela Moses said.

Katie Moses thought about that and went back to the television program.

While she's in Washington, she would like to see the White House.

Eight years ago, at a sales convention in San Diego, a carpenter and part-time cleaning products salesman named Edward McNamara met a young woman he liked. They dated for a while, and then didn't anymore, and eight months after their brief romance had ended the woman called McNamara and asked him to dinner: There were some things, the woman said, that McNamara needed to know.

On Aug. 1, 1981, in a restaurant in San Diego, McNamara learned that he was the father of a 2-week-old baby girl who had been placed for adoption with the County of San Diego Social Services Department. The mother had no ambivalence about this at all, McNamara says; she was barely 20 and entirely unprepared to be a single parent, and as soon as McNamara added his signature to the papers, she told him, an adoptive family could take the baby home.

Edward McNamara was 34 years old, living in a mobile home and father already to two boys who lived with his former wife, and he says he was stunned, that he had not even known his friend was pregnant. He knew almost nothing about adoption or what a man in his position was supposed to do, and when he saw a county social worker four days later, the worker told him the county was preparing family profiles for the baby's mother to choose from. All that was necessary, the social worker said, was for McNamara to formally relinquish his parental rights.

The one thing he knew, McNamara says now, was that he did not want to do that. He says that at that point he did not want custody of the baby, but he wanted some role in her life, and he was thinking of a couple from his church group who had been unable to have children but had often baby-sat for his sons. "The worker told me that if I did not sign a relinquishment, they would take me to court to have my rights terminated," McNamara says. "My thought was, if she was going to be adopted out to someone, why not have it go to someone I know, so I could be involved in my daughter's life?"

The county's briefs say the social worker told McNamara he had several options -- that he could relinquish the baby, or sign a statement denying that he was the father, or begin a legal action to establish the parent-child relationship. McNamara says nobody ever told him those things, he had no money for a lawyer and was still bewildered by the four-day-old news that he had fathered a third child. "When you're a criminal, they give you your Miranda rights," he says. "When you're a father, nobody tells you what your rights are."

On Aug. 17, under the supervision of workers at the county adoption agency, McNamara was allowed to spend half an hour with his infant daughter. He had given the agency the names of the childless couple he knew, but the baby's mother had chosen another family instead; McNamara had been told she wanted the baby raised by someone neither of them knew, and he says he thought about that as Baby Girl M was brought to him in a small blanket and he was able, for the first time, to hold his daughter himself. "It was great," he says. "I decided I wanted her, and could raise her ... And I informed the county that I wanted her, and I was not going to agree to the relinquishment."

McNamara says this mildly, without much apparent rancor; it is obvious that he has said it many times before, and as he leans back in the desk chair in his small windowless office east of Los Angeles, one fat briefcase is loaded with the bound documents he will carry with him to Washington. He works as an estimator for a general contractor. He has a big belly and graying light hair and a pencil jammed behind one ear, and beside him, tacked to the small bulletin board above his desk, is a photograph of the child whose name for the last seven years has been Katie Moses. The photograph is copied from a picture that appeared in the Los Angeles Times. The rest of the family, Robert and Pamela Moses and Katie's older brother Joshua, have been cropped out.

The baby the San Diego County adoption workers brought to Robert and Pamela Moses was from the beginning labeled what the adoption people call a "high risk" placement. She was placed with the Moseses on Aug. 24, 1981, and Robert and Pamela Moses say they were told that the mother had liked the description of their family -- a working father (he is now a business consultant), a mother who was not working outside the home, another child who was also adopted. They were told the county had begun legal proceedings to terminate the parental rights of the baby's father, but that the father was fighting those proceedings and wanted custody himself. There was a chance, in other words, that in a matter of months the county of San Diego would have to take Baby Girl M back.

"They were straight about saying that at the end of the six-month period, should anything wild happen -- because they still didn't think that would happen -- that we would have to relinquish her," says Pamela Moses, who is usually called P.J. "I think they still felt -- their emotional and legal interpretation was, if you carried this child for nine months -- "

P.J. Moses hesitates; she is imagining, she says, how she would have felt if "casual dating" had left her single and pregnant. "And then this man walks in, whom I know nothing about, with whom I have had no long-term relationship, and I have carried this child for nine months and made a very tough decision -- and he can walk in and say 'No'?" Moses emphatically shakes her head. "Forget it," she says.

She is blond and animated, perched on the edge of the living room couch in her home, which abuts a hilltop in a western suburb whose location the Moseses have asked be kept private. Her face looks so much like Katie's that an outsider walking into the Supreme Court today would instantly assume that the 7-year-old girl is the biological child of Edward McNamara and P.J. Moses; P.J. Moses says it has made her smile when strangers have looked up and said brightly to Katie, "Well, you certainly know who your mom is."

In August 1981, the Moseses say, neither of them was new to the emotional hazards of adopting a child. Four years earlier, knowing that P.J. Moses' endometriosis was going to prevent her carrying a pregnancy, they had signed on to the lengthy adoption agency waiting lists in San Diego, where they lived then, and at the same time learned of a Wyoming teen-ager who had one son already and was pregnant with a second child she wanted to place in an adoptive home. They met by telephone, and for three months the teen-ager and her son lived in the Moses house; P.J. Moses took the young woman to childbirth preparation classes and braced herself, she says, for the possibility that the baby would end up going back to Wyoming.

"We really were very firmly committed to the idea that if we could help her get through this pregnancy, and it was the best thing for her to keep this baby, that that was really the primary thing," she says. "She was wonderful when Joshua was born. She turned around, and they handed me the baby ... and she said, 'I want you to go tell Robert he has his son.' "

It was clear to them, P.J. Moses says, that the woman who gave birth to Joshua had a right to participate in the baby's life; they corresponded by mail, sent photographs, and at intervals arranged meetings between Joshua and the woman they had always identified as his "birth mother." And when they were told that Baby M might be taken from them within six months, they baptized her, named her Catherine and decided that six months of uncertainty, after what they had already managed, was something they could bear.

In December 1981, Edward McNamara got his day in court. He was a good and loving parent, McNamara argued; he was able to care for this baby, she was biologically his child, and the county ought not to be able to terminate his parental rights simply because the mother wanted the child placed out for adoption. But Baby Girl M had by that time been living for four months in the Moses house, and when the trial judge finally issued her opinion in February 1982, she ruled that the baby was already "bonded" -- that it was, in the legal language that was to confront Edward McNamara for the next seven years, in the "best interests of the child" to leave the baby with the people a county bureaucracy had effectively turned into her parents.

Robert and P.J. Moses had for six months worked hard at a careful kind of feeling toward this baby, they say; they had never decorated a room for her and had told their friends they wanted no baby shower. Now, by judicial order, Edward McNamara's parental rights had been terminated -- and the baby shower plans began. "The day of the baby shower, we get a phone call that he's appealed," P.J. Moses says. "And we said, 'What do you mean, appealed?' "

Twenty years ago, the American legal system had a particular and long-established way of thinking about unwed fathers. Unwed fathers ran from paternity suits; unwed fathers were almost by definition ill-suited parents; unwed fathers had no parental rights that permitted them to block adoption or override the wishes of the women who had borne their children. Then in 1972, the U.S. Supreme Court was presented with the dilemma of Peter Stanley, an Illinois man who had fathered three children while living off and on with their mother for 18 years. The couple never married, and when the children's mother died, all three children immediately became wards of the state -- because Stanley, under Illinois law, had no legal parental rights to his own children.

The Supreme Court, in language that former American Bar Association family law section chairman Sanford Katz calls "revolutionary," ruled that the Illinois statute was unconstitutional and that even though Stanley was unmarried, the state had to give him a hearing to show that he was fit to be a parent and keep his children. And over the next 12 years, as three more unwed fathers came to the Supreme Court seeking paternity rights to children adopted by others without their consent, the court began to narrow down just what it is that gives a man parental rights the Constitution can protect.

Biology, the court has said, is not enough. If an unmarried man wants federally protected parental rights -- if he wants to be able to veto an adoption or demand custody of his biological child -- he cannot show up years after the child's birth and demand to be heard. He has to act like a father, the court has ruled, and that means more than proving the child is genetically his; it means making efforts at developing a real relationship with the child, by visiting regularly, for example, or making certain state-prescribed gestures like listing himself with a state registry of unmarried fathers claiming responsibility toward their children.

For seven years, Edward McNamara has been trying to convince the court system that he wanted to do just that. He is the first unwed father ever to reach the Supreme Court with a claim that it was adoption procedure and the law itself that kept him from developing the kind of fatherly relationship the justices have talked about. From the day he first held his baby, McNamara says, he did everything legally possible to get custody of her; what blocked him, he says, was the state of California, which like a number of other states makes distinctions among different kinds of unwed parents -- distinctions McNamara contends are unconstitutional.

Look, McNamara has said in his many briefs and pleas to the courts, you used an unjust standard when you decided that Katie belongs with the Moses family. If I had been living with her mother, or if I were a woman and had actually given birth to her, the simple language "best interests of the child" would not have been legally enough to keep her away from the parent who gave her half her genes; you would have assumed, unless somebody proved me unfit, that I was a better parent for her than an adoptive family with no biological ties to her at all.

He is arguing, in other words, that the state let his daughter be taken from him because she is the product of a casual affair -- and that, McNamara says, is unfair to both of them. "That's my daughter," McNamara says. "And I'm her father. And it's my opinion, and has been my opinion, the whole way, that the natural parents should have the first right to bring up their children before the government steps in and starts telling people who their kids should live with."

For many years, McNamara says, he listened to the Moseses and other critics declare that if he really did have fatherly feelings toward this child, he could not have suggested she be moved from the only home she had ever known. "I disagree," he says. "I wasn't going to shut the Moseses out. I think probably they would have had a harder time dealing with it than Katie would have."

But she is 7 years old now, McNamara says. No one has ever suggested to him that the Moseses are anything but admirable parents, and although he wanted for a long time to have his daughter live with him, he says it seems unlikely at this point that a court would give him physical custody. What he wants instead is a formal recognition of his rights as Katie Moses' father, a procedure that would mean undoing the adoption, which was completed last year, and making legal arrangements for regular visitation.

"The type of relationship I have with my boys," McNamara says, meaning the two sons who now live with their mother and stepfather in Northern California. "I go and visit them once a month. I fly up, spend the weekend ... There's a whole extended family that Katie has. She has aunts, and uncles, and grandparents. She has two big brothers."

What would McNamara like his daughter to call him? "Dad," he says firmly. "Kids can have more than one dad -- or mother. My kids have done that. I know it's difficult for me, because I was a father. But I accepted it."

"She's got aunts," Robert Moses says. "She's got uncles. She has a full set of these people. You want to bring another set of all those people in to confuse her? I'm not sure that's enrichment."

The Supreme Court, should the justices rule in favor of Edward McNamara, might send the case back to a lower court to retry -- to use different standards, for example, to see whether the adoption should be reversed and McNamara made Katie's legal father. What that could mean for California and other states is still under debate; the American Civil Liberties Union has urged in a friend-of-the-court brief that the high court see this as a sex discrimination question and require state laws across the country to grant unwed fathers and unwed mothers the same rights and responsibility toward the children they conceive.

Adoption agencies, for their part, have warned in their friend-of-the-court briefs that a broad finding in favor of McNamara might threaten the entire adoption process by giving veto power to all unwed biological fathers, regardless of their genuine relationship with their children. "Adoption agencies all over the country want the county to win," says family law expert Katz, now a professor at Boston College, "and preserve the difference between fathers who have no relationship to the newborn -- and have done nothing to establish it -- and fathers who do. Just think of the rapist, for example, or incest. Or the one-night stand."

In the Moses house, where the man from the legal papers is referred to with studied formality as "Mr. McNamara," there is no comfort any longer in the notion of Katie living as the child of two families rather than one. Three years ago, the Moseses say, they still thought that possible; when McNamara successfully appealed his first termination of parental rights and returned the case to a trial court for rehearing in 1985, he and the Moseses left the courtroom one day to go to a coffee shop together and talk about Katie. It was the first time they had ever met without lawyers hovering around, and all three remember the conversation as awkward but polite. Katie Moses was a happy child, the Moseses said. She was healthy, and she loved her big brother, and they were willing, they said, to arrange a visitation program so McNamara could see her sometimes.

But at that point McNamara wanted custody, not visitation. "Any visitation program would have been at the total whim of the adoptive parents," he says. Robert and P.J. Moses began to have a different feeling then about Edward McNamara, they say; they had sympathized with him when the legal conflict first began, but now it began to seem to the Moseses that this man was pursuing not a child but a cause.

"We're talking about a property issue here," Robert Moses says. " 'You stole my car. Give it back.' "

Their feeling about visitation was changing too, the Moseses say, and not simply because they resented what McNamara was trying to do. P.J. Moses had already written a letter to her son's birth mother in Wyoming; she hoped the young woman would understand, Moses wrote, but she believed Joshua was growing confused about loyalties and who the children's real families were supposed to be. She promised to keep sending pictures of Joshua as he grew, but until he was older, Moses wrote, she wanted the birth mother to refrain from contacting him.

P.J. Moses says the birth mother did not protest. It is all too much to ask of a child, P.J. Moses says; she believes now that adoptive children should certainly be helped to contact their birth parents when they are older, but that small children should not be asked to cope with the presence of two families at once, with a father who is a real father because he has always been there, and a father who is a real father because biology made him so. "Mr. McNamara's beliefs and value systems are very different from ours," she says. "It does not mean either is any better. But it does mean Katie does not need both."

Children of divorce do something like this all the time, of course, but that does not reassure the Moseses much. Children of divorce, they say, are damaged by the pull in two directions too -- and they at least are usually pulled, even after the arrival of stepparents, by two people they have always understood to be their mother and father.

"She knows I'm out there," Edward McNamara says. He says he sent his daughter a birthday card last year, and signed it "Love, Your Dad." He says he wrote a letter to the Moses family, too; he was trying to be conciliatory, he says, and suggested in the letter that they all meet once more to talk.

The response he got was from the Moses family attorney. The Moseses had found McNamara's letter objectionable, the attorney wrote, and any further correspondence would be returned unopened. "He just wanted to pop up here this summer," P.J. Moses says. "With his two sons."

She taps a finger to her forehead. She thinks it would have been a very bad thing, this sudden arrival of a second family; she thinks it will be very bad if the legal system now orders that on them, too, but she is prepared, she says, to ready some complicated emotional passage for her 7-year-old daughter if that is what the law says the Moses family must do. "I don't think anything is insurmountable," P.J. Moses says. "I just don't think it's healthy."