When the Rev. Wesley Granberg-Michaelson was younger, the bad blood between Christian denominations made the notion of a modern-day ecumenical movement seem far-fetched.

Now, the recently retired general secretary of the Reformed Church in America says American Christianity has reached “a new frontier.”

“We have a chance of bringing in more around the table the way God really intends,” said Granberg-Michaelson, who stepped down in June after 17 years in the post. “The missional church needs the unity of the church. How else do we think we can do useful things for the world if we’re divided amongst ourselves?”

Amid a culture too often lost in its own self-importance, it’s a unity that’s sorely needed, Granberg-Michaelson argues in his 288-page memoir, Unexpected Destinations: An Evangelical Pilgrimage to World Christianity.

Known in many Christian circles as the elder statesman of the contemporary ecumenical movement, Granberg-Michaelson traces his four decades of journal writing to urge Christians of all denominations to forge a new path of unity that requires them to do more than hold hands and sing “Kumbayah.”

While loyal to his Reformed tradition, Granberg-Michaelson’s book makes it clear he’s grateful he wasn’t tightly tethered to his denomination.

He recalls the first time he profoundly experienced God’s love was at a Trappist monastery; explains why the once Dutch-dominated RCA must morph into something more inclusive; and describes why the National Council of Churches and the World Council of Churches have lost their way.

Granberg-Michaelson’s road to an inclusive Christianity started in a small way in 1950, while growing up in a suburb in northwest Chicago where he rode bicycles with two neighborhood friends who were Catholic.

Raised in an evangelical household where being “born again” was paramount, Granberg-Michaelson’s mother encouraged her son to “witness” to his two Catholic friends about Jesus’ saving grace since they prayed to Mary and the saints.

But evangelistic fervor turned into a mild case of envy when he noticed his two friends had medals of St. Christopher ― the patron saint of travelers ― on their handlebars.

After many conversations with his boyhood friends, Granberg-Michaelson concluded the doctrinal chasm between them wasn’t as wide as he once thought.

“The main difference was they had St. Christopher medals on their bikes, and I didn’t,” he said.

When it came to quieting his 60-hour workweeks, Granberg-Michaelson often found solace at a Trappist monastery. He still remembers his 1972 visit to the Holy Cross Abbey, a Trappist monastery in Berryville, VA, that enveloped him with God’s presence.

“I had one of those deep and profound life-changing encounters where God’s presence and love had simply overtaken me, and has stayed with me ever since,” Granberg-Michaelson said. “To this day, when I want to go on a retreat, what I often do is head to a Catholic monastery.”

Ethnic diversity also is vital to the body of Christ, added Granberg-Michaelson. During his tenure as the RCA’s general secretary, 230 new churches were established since 1993 ― more than half of them composed of people of color.

“The most important change is the change in the culture of the RCA,” Granberg-Michaelson said of his 177,500-member denomination. “Deep change isn’t just changes in structure and programs, but changes in values, habits and the style of the way we meet with one another, and bringing people into the RCA who don’t know how to play Dutch bingo.”

Granberg-Michaelson writes that he is most proud of navigating the denomination through some still-thorny issues.

“Homosexuality comes to mind,” he said. “I think we’ve been able to say this is an issue we’re not going to let divide us, but figure out how to talk and keep our focus on the main things and not let us get off track.”

Granberg-Michaelson also takes aim in his book at some long-held ecumenical partnerships: the NCC, he says, has suffered from “strategic incoherence” and “inept management.”

“One problem with the modern ecumenical movement with the National Council of Churches and the World Council of Churches is it ended up, not by design, excluding huge parts of the Christian family,” said Granberg-Michaelson, who served for six years on the WCC staff in Geneva.

“It’s made up of historical Protestants and Orthodox but not Pentecostals or Roman Catholics. As good as an organization as the World Council of Churches is, one-quarter of all Christians are outside their membership. There are more Pentecostals today than those who are members of the World Council of Churches.”

Ultimately, Granberg-Michaelson hopes his book spurs others to take the plunge and make a difference.

“I would hope by sharing my story someone else would have the courage and intentionality to take the next step in their own journey, and know how to take it,” he said.

Paul R. Kopenkoskey writes for “The Grand Rapids Press.”