BOSTON - Professor Leonard Saxe sits in his room at Brandeis University and sketches his family tree in the air. His grandparents, Saul and Sophie, came to America as children in the late 19th century and married in 1910.

Their three sons, who were raised in a traditional Jewish home, became doctors. All three married Jewish women. They had eight children. The eldest had four, the second two and the youngest another two.

The eldest son's four children, unlike the other four, did not receive a Jewish education. Altogether, six of the eight married non-Jews, though one of the wives converted to Judaism.

At the end of 2006, Saxe, who heads the Cohen Center for Modern Jewish studies at Brandeis, conducted a study of Boston's Jewish community and found that it was expanding. He also found that most of the mixed couples - some 60 percent - were bringing their children up as Jews. This is almost double the rate measured in other communities - 30 percent in New York, 36 percent in Pittsburgh, and 33-39 percent in the American Jewish community overall.

Those who advocate keeping "mixed" couples in the community saw this as proof that intermarriage can work. It is not necessarily a disaster leading to assimilation.

Edmund Case, president of the interfaithfamily.com Web site, believes that the focus must be on how people raise their children. To the coffee shop in Cambridge he brings a damning statistic: Only 0.1 percent of the American Jewish community's budget is allocated to "outreach" programs - an attempt to reach interfaith Jews. He is convinced that Boston has succeeded because it multiplied spending on these activities tenfold to 1 percent.

Saxe is not sure that these figures reflect a huge success. Perhaps it is merely a coincidence. Barry Shrage, president of the Combined Jewish Philanthropies of Boston, is also very cautious. It is hard to isolate a single factor from the study as the cause of the high percentage of Jewish children in mixed families. Shrage believes that a good, strong and vibrant community is the key.

In a few weeks, a follow-up study with "astounding" conclusions is to be released, says a person familiar with the research. The study found, among other things, that when it comes to Jewish identity, the difference between mixed couples and non-Orthodox in-married ones is not that substantial.

Sudbury

The first girlfriend of Alan Corinne, a 53-year-old Jewish American, was of Syrian decent and he thinks that she was Christian. He recalls that his parents didn't really care. Corinne's parents were not especially religious, but they celebrated Jewish holidays and held a bar-mitzvah ceremony for him. Alan, who lived in Boston, sang in the synagogue choir. He studied, worked and lived overseas for several years, married and eventually returned to Massachusetts. When a friend asked him to sing with the choir, he found that he remembered everything. This gave him a significant push back into the Jewish community.

Alan, his wife Pat and their three children - a 13-year-old girl and younger twin boys - live in a large, isolated house surrounded by trees. His wife, a Catholic, agreed to raise the children as Jews. They promised as much to the rabbi who married them - a rabbi that was not easy to find. She did not mind, he said. She does not believe Jesus is the son of God.

They are members of the Beth El Reform synagogue in Sudbury, attend prayers and lessons, and the children take classes at the synagogue. Cara, the eldest, is not so pleased. Sometimes she says she hates being Jewish. The twins, who started younger, are used to it.

They have certain advantages that not every Jewish child has: In mid-winter, they will hang Christmas lights on their house and have a Christmas tree with presents. Some things, you don't give up, said Pat. It is not a religious thing; Christmas is a sort of national holiday for them. Alan is comfortable with that now, although at first, he admitted, he felt a little guilty about it.

Nobody told Alan not to marry a Catholic. Almost half of American Jewish youngsters marry non-Jews. The younger they are, the more likely they are to marry out of the faith.

You cannot treat it like a disease, said Saxe, or cure it (i.e. by conversion). He believes intermarriage is not a problem that must be solved. Many disagree.

The "outreach" advocates' real or imagined foe is Professor Steven Cohen of Hebrew Union College. Cohen recently released a study that attracted coast-to-coast attention. He found that the identity chasm between in-married and intermarried Jews is so wide that there are actually "two Jewish nations." He politely dismissed Saxe's study, saying "it does not prove that outreach works."

Cohen cited several other Jewish communities where 60 percent of the children in mixed families are raised Jewish, such as Cleveland (66 percent), Miami (65 percent), Baltimore (62 percent) and Hartford (59 percent).

Part of the argument between him and Saxe is purely professional - how to ask the questions, how to quantify the results, what to check. In his writings and remarks, Cohen presented himself as someone who always found the data matched the negative side of the interfaith dispute.

"Intermarriage independently depresses Jewish involvement," he once wrote.

Boston's Jewish community leaders disagree. Saxe also criticizes the attempt to create an atmosphere against intermarriage. Both he and Shrage believe that a vibrant community can shape the next generation's life more than any other factor. Saxe wrote that the Boston study again proves that long-term Jewish education is effective as a strategy and can make the difference.

Cambridge

In Professor Noah Feldman's office the boxes have yet to be unpacked. He has just arrived, beginning a new life as a law lecturer at Harvard University. People say he is a rising star, and even those who do not like him admit that he is brilliant.

Feldman angered many Jews when he wrote in The New York Times two months ago about the "Orthodox paradox." The contentious article accused the modern Orthodox education, on which he was raised, of racism and separatism.

He says that he simply pointed out that the objection to marrying non-Jews is un-American. If a Catholic told his son he did not want him to marry a Jewish woman, Feldman says, we would call him an anti-Semite. Therefore, in his view, accusing in-marriage advocates of racism is not groundless. From an "American" point of view, marriage between people of different religions is an essential part of social life, he says.

There is no agreement in the Jewish community on how to deal with intermarriage. Time is pressing, and the next generation is already at the threshold, half of them holding the hand of a non-Jewish partner.

The STAR (Synagogues: Transformation And Renewal) rabbis' organization released a survey of 200 rabbis, mostly Reform and Conservative, this week. They are concerned over the difficulty of recruiting new members to their congregations. Some 70 percent said they plan to locate gay Jews and bring them to their synagogues.

But STAR's executive director, Rabbi Hayim Herring, said that the increasing number of intermarriages is a challenge for the synagogues. The rabbis are realizing that their role is not just to increase existing community members' involvement, but also to reach out to a more varied public beyond the community.

Israelis who have grown accustomed to treating intermarriage humorously ("they have a Christmas tree and a menorah"), or to seeing it as a tsunami threatening to destroy American Jewry, will now have to get used to a more complex picture. Intermarriage is a fact of life to most Jewish federation heads, not to mention the largest contributors. The community is learning to live with it and even gain from it.

The opposing sides invoke floods of studies and data to prove their arguments. One side looks at the statistics and moans "gevalt"; the other side sees the same figures as an opportunity to win over these couples' hearts and minds.

One way or another, a great experiment has started - perhaps the most daring in Jewish history. Communities like Boston declared years ago that they want to draw mixed couples closer. Others, slowly but surely, are joining in, forever changing the face of American Jewry.