Jack Gannone was about to have a defining moment, one that would unite him with more than a billion people of 200 nations and 600 languages.

Like most of them, he never saw it coming.

The day was April 23, a Sunday, and inside the sparely modern sanctuary of St. Eleanor Roman Catholic Church in Collegeville, 6-month-old Jack squirmed on his mother's lap.

"Parents, do you understand what you are about to do?" the Rev. Andrew Brownholtz asked. John Gannone and Sara Benton nodded.

Suddenly Jack found himself tilted head-back over a marble font. He did not howl, but gave a what-in-the-world roll of his eyes toward the vaulted ceiling as holy water streamed onto his downy brown hair.

"I baptize you," the priest intoned, "in the name of the Father and of the Son and of the Holy Spirit."

In that instant, Jack Gannone became a Roman Catholic, a member of the largest Christian church on Earth, one of an estimated 67 million adherents in the United States and nearly 1.5 million in the Philadelphia Archdiocese.

Statistically, he probably will remain in the fold for life. Although American Catholics have a higher dropout rate than Protestants of any major denomination, 80 percent stay at least nominally in the church from cradle to grave.

But what kind of Catholic might Jack - and indeed, any of his 21st-century soul mates - grow up to be?

If today's strong trends are an accurate compass, they point to someone whom the hierarchy has never gladly embraced: a Catholic who lives the faith on his or her own terms.

From baby boomers through Gen-Xers and Millennials, a streak of spiritual autonomy is growing more pronounced among those who count themselves as practicing Catholics. Religious scholars scan the horizon and see little that might reverse the slow drift away from not only the dictates of Rome but also some core teachings of the faith.

"My sense is that this is an enduring condition, not just an anomaly," said Chester Gillis, chairman of the theology department at Georgetown University in Washington and author of Roman Catholicism in America, a 1999 portrait of the U.S. church.

"There's a tension between Catholicism and American culture," he said. "American culture is winning out."

With that comes a deepening dilemma that the church has long faced in Europe, where institutional Catholicism is in near-collapse and Pope Benedict XVI has decried a "dictatorship of secularism."

"What can the church do? If she stands by her moral teaching, then she will be seen as standing in judgment" of a sizable portion of the membership, said the Rev. Timothy Radcliffe, former master general of the religious order of Dominicans. "If she does not, then she will be seen as surrendering to modernity."

Some of that "modernity" is evident in a Zogby International telephone poll of 1,901 Catholics nationwide, conducted in March for The Inquirer and Le Moyne College in Syracuse, N.Y. Of young adults ages 18 to 35, fewer than half said they:

Attend Mass weekly (46 percent).

Go to confession at all (31 percent).

Consider it important that priests be unmarried (48 percent).

Think that the church alone has the final say on sex outside marriage (25 percent).