Letha Dawson Scanzoni, an evangelical author who argued, gently but persuasively, that the Bible considered women equal to men, inspiring a wave of Christian feminism and, perhaps inevitably, a backlash against it, died on Jan. 9 in Charlotte, N.C. She was 88.

Her death, at a skilled nursing facility, was from congestive heart failure, her son David Scanzoni said.

Betty Friedan’s “The Feminine Mystique” was already a best seller in the mid-1960s when Ms. Scanzoni began writing for Eternity, an evangelical Christian magazine that often challenged conservative attitudes on social issues. She had the same questions as her secular sisters: Should women be submissive to their husbands and stay out of leadership roles in the church, as many fundamentalist Christians believed?

Ms. Scanzoni did not think the Bible supported these views — and quoted scripture to prove her points in articles published in Eternity, like one titled “Women’s Place: Silence or Service?” and another on egalitarian marriage.

The articles didn’t accrue too much opprobrium at the time, though the editors did ask for a photo of Ms. Scanzoni and her husband to accompany the egalitarian marriage piece to show that he approved of her position. And there were a few outraged letters to the editor. One reader wrote that “Mrs. Scanzoni’s article is a prime reason the Apostle Paul told women to be silent.”

But as the women’s liberation movement gained momentum outside the church, Ms. Scanzoni felt that Christians were sitting on the sidelines, save for some mild carping about the decline of society, and decided to tackle the subject in a book. What resulted was “All We’re Meant to Be: A Biblical Approach to Women’s Liberation” (1974), which she wrote with Nancy Hardesty, who had been an editor at Eternity.

The book became a manifesto for evangelical feminism, using a hermeneutic analysis of the Bible, interpreting the text by noting the context in which it was written and extrapolating its tenets to modern life.

Eternity magazine declared it “the book of the year” in 1975, and Ms. Scanzoni became a sought-after speaker at Christian organizations and a founding member of the Evangelical and Ecumenical Women’s Caucus (now called Christian Feminism Today), a networking and social justice group for the movement that she had helped fire up.

The backlash was immediate, said Kristin Kobes Du Mez, a Christian historian and author of “Jesus and John Wayne: How White Evangelicals Corrupted a Faith and Fractured a Nation” (2020).

“Conservatives doubled down in their opposition to women’s rights,” Ms. Du Mez said by phone, “making male headship and female submission defining features of modern evangelicalism. Letha was such a threat because she presented her case for feminism in evangelical terms, making it hard for critics to depict feminism as a wholly secular movement intent on undermining traditional Christianity.”

Letha Marion Dawson was born on Oct. 9, 1935, in Pittsburgh and grew up in tiny Mifflintown, in central Pennsylvania. Her parents, James and Hilda (Koch) Dawson, owned a gas station-cum-diner and other small businesses. Her best friend was a preacher’s daughter, and with her parents working on many Sundays, Letha would accompany her friend to church. When she was 11, she had a conversion experience during an altar call and vowed to devote herself to Christian service.

Letha was a talented musician and excellent student, and after graduating early from high school, she enrolled at the Eastman School of Music in Rochester, N.Y., where she studied the trombone. There she joined a Christian youth organization and had another epiphany: There were many hypocrites in the group, she saw, and to her mind one jerk — the group’s director, who kissed her without her permission and who made racist and antisemitic comments, as she told Kendra Weddle and Jann Aldredge-Clanton, authors of “Building Bridges: Letha Scanzoni and Friends” (2018).

She transferred to the Moody Bible Institute in Chicago, where she met John Scanzoni. They married in 1956 and lived for a time in Oregon, where Mr. Scanzoni became the minister of a small independent church before earning a Ph.D. in sociology. Ms. Scanzoni had left school to care for their two young sons and began writing. Her first book was a dating guide for Christian teenagers.

The family was living in Bloomington, Ind., where Mr. Scanzoni was teaching at Indiana University, when she and Ms. Hardesty decided to write “All We’re Meant to Be.” Ms. Scanzoni used her research for the book to create her own independent curriculum in religious studies, earning her bachelor’s degree at Indiana in 1972. The couple divorced in 1983.

In addition to her son David, Ms. Scanzoni is survived by another son, Stephen; her brother, Robert Dawson; and five grandchildren.

In the mid-70s, Ms. Scanzoni began collaborating with Virginia Mollenkott, an evangelical English professor and Milton scholar, on a book about Christian ethics and social issues. Ms. Scanzoni was to tackle homosexuality and Ms. Mollenkott would take on divorce and censorship. But then Ms. Mollenkott, who had been living as a closeted lesbian, shared her secret with Ms. Scanzoni and watched with horror as her writing partner blanched with shock.

Despite writing theoretically about homosexuality for years, Ms. Scanzoni had, by her account, never knowingly met a gay person before.

Later, Ms. Mollenkott wrote her friend, saying “it is a terrible thing to be a person who has news to tell that can drain the blood from a good friend’s face.” Ms. Scanzoni wrote back — in tears, she said — that she was not condemning Ms. Mollenkott but coming to terms with new knowledge about her.

They scrapped their book on social issues to focus on another, one wholly on the now more urgent topic.

That book, “Is the Homosexual My Neighbor?” (1978), showed through meticulous, scholarly detail how the Bible, which had long been used as a cudgel to bash gay people and women, did not support the credo that homosexuality was a sin. It explored the suffering that that belief had worked on the world, and it marshaled social science to point out the complexity and range of sexual orientation.

“It is simplistic to presume,” they wrote dryly, “that when homosexuals become Christian, they automatically become heterosexuals.”

Their publisher at Harper Collins described the book as a “counter-market” title — meaning it probably wouldn’t sell very well (he was wrong) — but said he was proud to publish it anyway. While many evangelicals condemned its authors as heretics, many young gay Christians told Ms. Mollenkott and Ms. Scanzoni that the book had saved them from suicide.

Ms. Scanzoni was the author of nine books. Her most recent, “What God Has Joined Together: The Christian Case for Gay Marriage” (2006), was a collaboration with David G. Myers, who writes about faith as a professor of psychology at Hope College, a liberal Christian institution in western Michigan.

In 2006, the magazine Christianity Today included “All We’re Meant to Be” in its roundup of 50 books that have shaped evangelicals, along with touchstones like “Mere Christianity,” by C.S. Lewis, and Madeleine L’Engle’s “A Wrinkle in Time.”

“For better or for worse,” the editors wrote, “no evangelical marriage or institution has been able to ignore the ideas in this book.”