To improve his knowledge of Christian theology, Covenant Life Church pastor Josh Harris announced Sunday that he is heading to Regent College in Vancouver, B.C. (Katherine Frey/The Washington Post)

For most of his career, Joshua Harris was the kind of evangelical pastor who chuckled at the joke that “seminary” should really be called “cemetery.”

The son of a national home-schooling leader — home-schooled himself — Harris by his mid-20s had become a prominent pastor as well as a best-selling author on religion and sex, despite having no formal theological training. He immediately became a darling of a movement that took off in the 1990s called nondenominationalism, largely made up of conservative evangelicals who view religious institutions and denominations as often lifeless and unopen to God’s spirit.

And for 17 years, Harris preached the power of outsiderdom as pastor of Covenant Life, a 3,000-member church in Gaithersburg that is well-known — and sometimes controversial — on the national nondenominational scene.

That is, until Sunday, when the 40-year-old announced that he is leaving to go to seminary, saying he needs formal education and training and more exposure and connection to other parts of Christianity.

“That, my friends, is a crazy, backwards life!” Harris said in his sermon about his career.

In an interview, Harris said the isolation of Covenant Life, and of a small cluster of churches of which it was a part, may have fed leadership mistakes, including the decision of pastors — himself among them — to handle a child sexual abuse case internally instead of going to police.

A former Covenant Life member who helped with the youth group was convicted last year of molesting three boys in the 1980s. Trial testimony showed that the victims or their families had gone to church leaders for help and that the church officials did not call police. Harris said the thinking of the church was that such allegations should be handled as an internal, spiritual issue, though church spokesman Don Nalle noted that Covenant Life has contacted civil authorities in other abuse cases in the past.

A lawsuit filed by different alleged victims was dismissed largely because the statute of limitations had expired.

It is not a given that being part of a denomination or having more academic training would have fixed all errors, he said, but they would have had much more outside input.

The church “was sort of a mom-and-pop structure that grew exponentially,” he said.

Now, he added, “I’m looking at my own training and saying: ‘I want to get a broader perspective. . . . I want to learn other ways of how pastors and other leaders deal with all these things.’. . . We need to learn from the historic church about ways that there is better accountability and responsibility.”

Experts on American religion say Covenant Life in some ways is a case study of nondenominationalism — a part of U.S. religion that can be difficult to measure but that experts believe is expanding — and the possible ramifications of the dissolution of religious structures. Such communities believe passionately in the effectiveness of evangelizing and the idea that God — not man or some academic credential — bestows control.

About 10 percent of U.S. churches are nondenominational evangelical, research shows.

“One of the significant problems is that it’s left to the church or the individual pastor or leadership board to in essence police themselves or create relational ties. That is a real challenge,” said Scott Thumma, a sociologist at Hartford Theological Seminary who studies nondenominationalism. “In the long run, . . . there will be so many excesses that the pendulum will swing back the other way.”

Of course, being part of a denomination doesn’t guard against institutional scandal — witness sex abuse coverups at high levels of Orthodox Judaism and Catholicism, among other places.

Harris also praises the benefits of independent churches like Covenant Life.

“If I had been seminary-trained with established convictions about church polity, pastoral leadership and other topics, I don’t think I would have been chosen to lead our church. But I believe that it was God’s purpose for me. I think it was God’s will for me,” Harris said in his Sunday sermon. Now, however, “we have needed to repent and change in many ways and that is an ongoing process. . . . We’re like an overweight guy who goes to the gym. It feels like the trainer is killing us, but we’re actually just getting healthy.”

Covenant Life was the flagship congregation of Sovereign Grace, a cluster of churches founded in the 1980s by a former hard-core partier named C.J. Mahaney. The church’s theology is charismatic and imagines God as disciplinarian and man as needing oversight. Followers called Mahaney “apostle,” and critics said he behaved like a cult leader.

Building criticism from other evangelicals over Mahaney’s leadership style and the sex abuse allegations brought national controversy to Sovereign Grace, which in 2011, Harris preached, was “being publicly spanked . . . humiliated and being brought low.” He removed the Gaithersburg church from Sovereign Grace the next year, but the sex abuse allegations and criticism about the way pastors had treated victims continued at Covenant Life.

All of this led Harris, he said, to reconsider his own journey and whether formal education might help him.

Harris is the oldest of seven children of Gregg Harris, one of the early national leaders of the Christian home-schooling movement and a strong advocate of independent learning. Joshua was 21 when he wrote “I Kissed Dating Goodbye,” a memoir that became a cult classic to young evangelicals by urging them not only to hold off on sex but even dating — saying it was a form of promiscuity to spread around one’s emotional intimacy.

In the years since, nondenominational Christianity became more popular and loose. Informal networks of churches, groups and individuals have formed, such as the Vineyard, Willow Creek and the Gospel Coalition — the last of which Mahaney and Harris were leaders. But these are akin to social groups and not meant to hold one another accountable as denominational organizations often do.

About half of nondenominational pastors have a seminary or theology degree, compared with 72 percent of all Protestant pastors, according to Barna Research. Mahaney, like Harris, had no formal theological training.

Harris went on to write several other books about dating, and his stance is more nuanced now, no longer opposed to dating but in favor of deeper commitment in relationships. But he has had a hard time shaking the label of “dating expert” as he has sought to be taken more seriously as a theologian. This month, he let loose this self-deprecating tweet: “Read ‘I Kissed Dating Goodbye’? #FiveWordsToRuinADate,” which was favorited dozens of times.

His family, like home schooling, has moved to the mainstream. Two of his brothers — twins Alex and Brett — wrote a best-selling self-help book for parents called “Do Hard Things.” Alex is now at Harvard Law School. Joshua Harris said that when he moves his family to Vancouver, B.C., for seminary school, his children will probably go to public school.

Harris said he expects that studying at Regent College, a graduate school of theology, will broaden his perspective, including on accountability.

There are also theological issues to be worked out, he said. For example, the Old and New Testament call for believers to be “special, distinct” from society, he said, so how does that meld with adopting corporate America-like­ management practices? And if their focus is on a radical God capable of transforming and changing anyone, how important in that picture are nonreligious experts, such as social workers or police?

Ed Stetzer, executive director of Lifeway Research and an adviser to evangelical churches, said Harris and the cluster of Sovereign Grace have been on an evolutionary journey — one that other nondenominational congregations might learn from.

“There has been a move from what’s been a historically unhealthy and insular Christian movement to kind of engaging in a broader evangelical world with some more healthy preparation. Josh said he did these things in reverse, and I think he’s right,” said Stetzer. “You have this explosion of nondenominational movements, and the question is: How do we educate ourselves? How do we evangelize? Some are answering well, some badly. Josh just announced to the world what he thinks the answer should be.”