BOB ABERNETHY: Now, a look at a controversial phenomenon in America's Jewish community -- the secular Jew. After centuries of persecution, two great concerns of Jews are how to preserve their religion and their numbers. Intermarriage and low birthrates are a threat, and so is another trend, perhaps more serious: loss of faith. Nearly half of all American Jews say they are not religious. Betty Rollin has our story.

BETTY ROLLIN: It's Friday evening in New York City, and like so many Jews around the world, the Bloomberg family is celebrating the Sabbath. The difference is the Bloombergs are in the company of other families, all of whom feel intensely Jewish, but don't believe in God.

The usual prayer over the challah bread is: "Blessed are you our God, King of the Universe, who brings forth bread from the earth" -- but in this room, prayers contain no mention of God.

Although most secular Jews do not join groups like this, the International Federation of Secular Humanistic Jews has 71 chapters. This is one. Myrna Baron is the director.

MYRNA BARON (Director, New York Chapter, International Federation of Secular Humanistic Jews): Just because some secular Jews are not comfortable in a traditional temple or synagogue doesn't mean that we have to give up the wonderful aspects of Jewish community. And that's what we have. We can share holidays, birth of babies, the bar and bat mitzvahs of our children; we can give each other solace.

ROLLIN: Bar and bat mitzvahs are coming-of-age ceremonies.

JILL BLOOMBERG (Member, City Congregation for Humanistic Judaism): Really what pushed us to join is our daughter, who wanted a bat mitzvah.

SONIA LESSUCK (Daughter of Jill Bloomberg): All my cousins are being bat mitzvahed and my mom and her sisters were bat mitzvahed. And it was something that I would enjoy. It's nice to be brought into a community. So you could still feel Jewish without having to believe in God.

ROLLIN: Shirley Ranz is a long-time member of the congregation.

(to Ms. Ranz): If you don't believe in God, then why be Jewish?

SHIRLEY RANZ (Member, City Congregation for Humanistic Judaism): Because Judaism really doesn't -- for me, doesn't have anything to do with a deity. It's about a people, it's about a sense of a culture, values, and a common history.

ROLLIN: Shirley's parents survived Nazi concentration camps.

Ms. RANZ: How can I be religious? My parents had gone through the worst hell on Earth. How could I believe that a good, powerful God would allow this to happen, allow the murder of one to one and a half million children? And all the explanations that I heard from rabbis and philosophers make no sense to me at all.

ROLLIN: Forty-five percent of American Jews are secular -- the highest rate of any religion. But "secular" includes people who may not practice their religion but who believe in God. Of secular Jews, 34 percent don't believe in God. Still, they consider themselves Jewish.

Meet Michael Steinhardt, one of the nation's major Jewish philanthropists devoted to Jewish causes -- among them Birthright Israel.

(Birthright Video): The biggest, most ambitious project in the Jewish world has begun. Its goal is to send 100,000 Jews from all over the world to Israel.

ROLLIN (to Mr. Steinhardt): What is your ultimate goal?

MICHAEL STEINHARDT (Jewish philanthropist): That the values that I cherish will be instilled in the next generation as it has been for lo these past centuries.

ROLLIN: The continuation of the Jewish religion is very important to Michael Steinhardt, even though he, himself, is not a believer.