It was the breakup of the millennia. Now, 500 years later, Catholics and Protestants find common ground.

Holly Meyer
The Tennessean

Carl McKelvey is the only Protestant in the Bible study group he attends every Tuesday at Christ the King Catholic Church in Nashville. Everyone else is Catholic. 

Bob True, a Catholic deacon at Christ the King Catholic Church, left, stands next to his friend, Carl McKelvey, director of Lipscomb University's Center for Spiritual Renewal, at the Longview Mansion on Tuesday, Oct. 24, 2017, in Nashville.

While the theological differences are insurmountable, McKelvey and the other members focus on what they have in common as Christians instead of what divides them.  

"Why would I not jump at the chance to study the Bible with anybody? It's my calling in life," said McKelvey, who leads Lipscomb University's Center for Spiritual Renewal. "It has been a learning experience." 

Their collegiality is a far cry from the deep divisions that splintered the Catholic Church half a millennia ago when Martin Luther and his 95 theses sparked the Protestant Reformation. Tuesday marks the 500th anniversary of the start of the schism and birth of Protestantism.   

► More:A lawyer, priest, professor and brewer walk into a bar. Bartender says 'Hi Martin Luther'

► More:What would Martin Luther do? Atheists' project lets you compile your own 95 theses to post to church doors

► More:How a central Pennsylvania group is reforming what 'church' looks like

Protestant and Catholic relations have improved dramatically since the 16th century and the tumultuous times that followed. Michael Root, a systemic theology professor at The Catholic University of America in Washington, D.C., compared their ecumenical relationship to that of "friendly cousins."

"They're not quite brother and sister. There are still some significant differences," Root said. "There is a strong recognition that we are all children of Christ, but also the recognition that there's a real separation."

Theological differences continue to divide

Views on church authority, communion and ethical questions continue to divide the groups, Root said. But nearly six in 10 Protestants and two-thirds of Catholics in the U.S. think the two Christian groups have more similarities than differences, a recent Pew Research Center survey shows. 

Shared beliefs sparked a friendship between McKelvey and Catholic Deacon Bob True, who facilitates their Bible study at Christ the King every week. 

The two men sat in McKelvey's office at the Church of Christ college's historic Longview Mansion one week before the anniversary of the Reformation and explained the roots of their friendship. They had just come from their Tuesday Bible study at the Catholic church. 

"Our friendship has been built on a relationship of stressing likeness rather than difference," McKelvey said. "We will never agree on everything." 

True, who lives near the mansion, met McKelvey by chance about 15 years ago when True and his curious grandson decided to visit the historic home in Nashville.

During their first meeting, True spotted a framed prayer on McKelvey's desk written by Thomas Merton, who was a Catholic monk in Kentucky, and it spurred a conversation. It surprised True, but McKelvey explained that he thinks clergy in the Churches of Christ can learn from the past writings of religious leaders, including Catholic theologians. 

As their friendship grew, so did their understanding of each other's religion. They dispelled personal misconceptions about Catholics and Churches of Christ, worked on ecumenical projects and studied Scripture together. 

"There's always a tendency to defend our beliefs. We tend to get bogged down in the icing rather than digging into the cake," True said. "There's so much in the cake, so much in the Scripture, that we have in common."

Marking 500 years since the Reformation around the world

Catholic and Protestant leaders at local and global levels have come together in recent decades, recognizing shared beliefs, like Baptism. Many are marking the 500th anniversary of the Reformation, too.

A major shift in ecumenical relations came in the 1960s with the Second Vatican Council, which ushered in major reforms in the Catholic Church. It opened the door to improved relations between Catholics and other religions.

"We've seen the Catholic Church now with some limits significantly engaging in cooperation and ecumenical discussions with other churches where that seems possible," Root said. 

But 500 years ago, the division was sharp.

Historians dispute whether Luther actually nailed his 95 grievances to the church door in Wittenberg, Germany, on Oct. 31, 1517, but he did share them. Luther's lengthy critique of the Catholic Church, including its selling of indulgences, became a catalyst for the Protestant Reformation, a pivotal moment in Christianity's history.

Martin Luther's 95 Theses, visualized in a word cloud.

"Up until the Reformation, the notion that you could have multiple churches in the same place was unthinkable to everybody," Root said. "There was simply the church."

► More:Who was Martin Luther? What you need to know about him 500 years since the Reformation

► More:A Q&A with Martin Luther impersonator

The German monk believed that faith alone was enough for salvation; good works were not required. He also believed the Bible was the sole source of religious authority; guidance from church teachings and traditions were unnecessary. 

Wars broke out. The Protestant and Catholic theological tensions in Europe became wrapped up in the toxic mix of the national and ethnic tensions of the time, Root said. 

"You have a series of religious wars throughout Europe, which were very, very violent," Root said. 

Religion was split along geographical lines. Northern Germany was Lutheran and Southern Europe was Catholic, Root said. That changed with modern mobility.  

"America is sort of the cutting edge of that, where you have from early on multiple churches in the same place," Root said. "That's now the reality everywhere."

Coexisting and the easing of tensions

Protestants and Catholics coexisting helped ease tensions, Root said. They got to know one another, and concerns over once controversial topics, like marriage between Protestants and Catholics, subsided.

While relations have improved, Root does not expect Protestants and Catholics to budge on their significant differences, like views on church authority and ethical questions. 

"I am not that optimistic about really significant change in the immediate future. I think we've made some significant changes. I see the problems that now exist as ones we have to learn to live with," Root said. "On the other hand, change is impossible to predict." 

Reach Holly Meyer at hmeyer@tennessean.com or 615-259-8241 and on Twitter @HollyAMeyer.