Reversing the spiritual confusion evident among many evangelicals in the United States will require greater engagement with Scripture, more attention to discipleship and a commitment to attend church in person, leading pastors and scholars say.

“There’s a direct relationship between cultural relativism and the consternation regarding our social-political, cultural landscape and the lack of accuracy or affirmation of theological orthodoxy,” said Samuel Rodriguez Jr., pastor of New Season Church in Sacramento, California.

Trevin Wax, a columnist at The Gospel Coalition website and a former missionary to Romania, said Christians need to focus on what is true instead of just having “faith in faith” or a set of beliefs offering personal affirmation.

“The Christian faith is actually about particular things that we believe to be true about the world,” Mr. Wax said. “Not just true for me, not just true for you, not just my truth or your truth or just personal preference, but actual events that we believe actually happened.”

Along with Bible engagement, the Rev. Robert Jeffress of First Baptist Church in Dallas said people need to regularly attend church in person.

“I don’t think you can separate the lack of orthodox belief among Christians with the decline in church attendance that you’ve seen. I think one leads to another,” said Mr. Jeffress, whose book “18 Minutes With Jesus” about the Sermon on the Mount is set to be released next month.

Christian leaders are calling for a spiritual revival after a biennial survey of Americans’ theological attitudes showed great uncertainty about core religious beliefs, even among evangelicals, a group long known for faithfulness to biblical teachings.

The research indicated that adherence to doctrines such as the authority of Scripture, belief in the Trinity and the idea that only those who trust in Christ will be saved is undergoing a sea change in the U.S.

According to the “State of Theology” study conducted by Southern Baptist-affiliated Lifeway Research, beliefs about the Trinity — or one God expressed in three people, Father, Son and Holy Spirit — are equally confused.

About 52% agree somewhat or strongly with the statement “God learns and adapts to different circumstances,” the study found. The statement contradicts traditional understandings of an omniscient God who isn’t surprised by what happens in history.

Nearly 3 out of 5 said the Holy Spirit is not a personal being but rather an impersonal force.

When it comes to understanding Jesus, whom the Nicene Creed says is the “eternally begotten” Son of God, 53% of Americans surveyed said he was “a great teacher but not God,” while 55% said Jesus was the first “created being,” a view held by 73% of those who claim to have “evangelical beliefs,” as Lifeway defined it.

Many evangelicals’ theology is making a stunning shift while Christianity is losing its position as the majority faith in the U.S. A recent Pew Research Center study predicted that as many as 52% of Americans could identify as “non-religious” by 2070, as “religious switching” removes them from the faith in which they were raised.

“It’s not a coincidence that the world seems to be spiraling down the proverbial rabbit hole while the majority of Christians are not even privy to what makes us Christians,” Mr. Rodriguez said.

Mr. Rodriguez, president of the National Hispanic Christian Leadership Conference, said a shift in the past 30 years from sermons emphasizing doctrine to “a prioritization of psychology and sociology” has diluted congregants’ understanding of faith.

Sharon Ketcham, a professor of theology and Christian ministries at Gordon College in Wenham, Massachusetts, said consumer culture is also at play.

“In a consumer-based society, churches must morph into yet another consumable product, and this reduces the church’s role to be another service provider of spiritual experiences,” Ms. Ketcham said via email. “The pressure on pastors and church leaders is tremendous, and educating in the faith is a challenge in this environment.”

Ms. Ketcham has addressed the issue in a book titled “Reciprocal Church.”

Speaking to the Family Research Council’s Pray Vote Stand summit in Atlanta on Friday, Christian pollster George Barna presaged the study’s results by noting his research’s findings about how Americans, including many evangelicals, form their beliefs.

“The crisis is that our predominant worldview in America is syncretism,” the combining of different religions or beliefs, Mr. Barna said. “All of the problems that we have to encounter in America are a result of our unbiblical worldview in this country.”

An emphasis on Scriptural instruction is now essential, said Gregory A. Wills, dean of the theology school at Southwestern Baptist Theological Seminary.

“We who are called by the churches as pastors, teachers and elders must redouble our prayers, our labors and our love among the saints in order to teach the Word of God and in order to, by God’s mercy, deepen our faith in everything that God has spoken,” he said. “Every sin begins with a distrust of … God’s word, either in the truth of God’s word or in the practical benefits of that truth.”

Greg Laurie, an evangelist and senior pastor of Harvest Christian Fellowship in Riverside, California, said in an interview that the displacement of the Bible from society, in general, helps create confusion.

“There was a time when the Bible was taught in classrooms as literature — not theologically, but just as literature — just so you have a general knowledge of biblical stories or scriptural narrative,” he said.

“When I first started preaching 50 years ago, I would say something like Adam and Eve in the Garden or Noah’s Ark, and things of this nature, people would know what I was referring to,” Mr. Laurie said. “But now I don’t assume that my listener knows anything. It’s like a blank slate, which in a way is good because you don’t have to unlearn to learn. But the bad thing is, they know nothing.”

Two evangelicals said they found opportunities in the Lifeway data.

“It’s hard for people to form opinions on content that they’re not familiar with or are consuming secondhand,” said John Aden, CEO of David C. Cook, a 147-year-old publisher of Sunday School curricula. “My thoughts on some of the data points and insights is … there is an opportunity for biblical literacy in our churches today.”

Mark Gauthier, U.S. national director of Cru, a Christian evangelism and discipleship ministry formerly known as Campus Crusade for Christ, said the lack of understanding that the survey revealed “motivates us in Cru to do all we can to play our part in helping to present the message of the Gospel and then ground people through the process of disciple-making.”

He said the data “underscores the need to ground people in Scriptures. This is the most biblically illiterate generation that America has ever known. And so it underscores the need to teach those transformational truths from the Scripture.”

• Mark A. Kellner can be reached at