Even when leaders of different Christian traditions find theological agreement, “the churches don’t really know what to do with the results,” said Father Frans Bouwen, a member of a Catholic order called the Missionaries of Africa, or White Fathers, who run Saint Anne’s Basilica in Jerusalem. In his years overseeing a journal on ecumenism, Proche-Orient Chrétien, Bouwen has found that theologians and top Church leaders have more energy for ecumenical work than local religious leaders. “This is in some way disappointing,” he said. “The priests say, ‘We have done the work, but the churches do nothing.’”Ecumenical efforts may find most difficulty in the parts of the world where Christianity is changing and growing most quickly. Bouwen said ecumenism is low on the list of priorities for missionaries who work on evangelization in Africa, where Catholicism has seen its greatest rate of expansion over the last couple of decades. Younger churches, including the Pentecostal and evangelical congregations that have seen similar success in Africa in recent years, are often underrepresented in ecumenical movements, Bouwen added: They don’t carry the same history of intra-Christian conflict and don’t necessarily view ecumenical problems in the same way as more established churches. Plus, he said, they’re busy evangelizing their particular brand of Christianity.

Meanwhile, Christian denominational families continue to fracture. The United Methodist Church, which claims 12 million members around the world, and the Anglican Communion, which claims 85 million, have both experienced bitter conflicts in recent years over LGBT issues. These divisions have been driven in part by the different orientations of relatively progressive American churches and their relatively conservative counterparts in Africa and other parts of the global South.

While these disagreements have led to painful splits—both denominations face the possibility of schism in the coming years—they also suggest that a growing number of Christians are organizing themselves based on ideological convictions, rather than a shared confessional tradition. “As a lot of denominational traditions are experiencing pressure and even fracture,” said Noll, “so also [is] interdenominational cooperation amongst like-minded people growing in leaps and bounds.”

Some of the ecumenical reformers of the 1970s and ’80s imagined they’d see full Christian communion in their lifetimes, Bouwen told me; he himself was part of that generation. Clearly, that has not come to pass. He’s a bit more jaded than he was as a student in Rome during the heady years of Vatican II; he’s spent too much time in Jerusalem, where, he said, “unity is a scandal.” Despite himself, though, he still holds out hope that the church can become whole again.

“Ecumenism is a microbe,” he said. “You either have it or you don’t have it. And if you have it, you can’t get rid of it.”