Jesus prayed that the church’s unity would reflect the unity of the Father and Son. Paul urged the Ephesians to cultivate the virtues of peace that would express the sevenfold unity of the church (Ephesians 4). That demand is a perennial one.

But we’ve been divided for a long time. Even if unity is a demand of the gospel, is it an urgent demand today? Don’t we have other, perhaps bigger, fish to fry? Why now?

I doubt there are any bigger fish, but I admit that my conclusion that it’s a propitious time to intensify our efforts at unity is a judgment call. That judgment rests in part on the perception that Christians have a rare opportunity today, and that opportunity arises largely from the ways in which the churches have changed over the past half century. I’m addressing an evangelical Protestant audience, so let me start there.

Presbyterian churches are not united doctrinally, practically, morally. There are clusters of Presbyterian churches, or a spectrum, but we can no longer assume that a Presbyterian church will have a significant commitment to the Westminster Confession or to Scripture or to traditional Christian morality. The global Anglican communion is splintered, with new continuing Anglican churches springing up regularly.

As a result, in terms of belief, practice, and ethics, Evangelical Protestants have more in common with churches outside our denominational boundaries than we do with churches within. In terms of women’s ordination, for instance, the Presbyterian Church in America and the Orthodox Presbyterian Church have more in common with Orthodox and Catholics and conservative Lutherans than with any other Presbyterian body. The same is true on a range of issues: Abortion, same-sex marriage, and other issues concerning sexuality. Even in areas where we traditionally differ from Catholics, we are sometimes closer to them than to other Protestants. We often have more in common with Catholics in our understanding of Scriptural authority than we do with liberal Protestants.

One of the massive changes is the eruption of new forms of Christian faith and practice, and the accompanying geographic shift in Christianity’s center of gravity. At the beginning of the 20th century, neither Pentecostals nor the charismatic movement existed. Now there are nearly 300 million classical Pentecostals around the world, in over 700 denominations. And that does not include the many in nearly every traditional denominations that are associated with the charismatic movement. (There are 117 parishes in the Charismatic Episcopal Church in the US, and 1700 congregations outside the US.) Philip Jenkins has said that Pentecostalism was the most successful social movement of the 20th century.

In many parts of the global South, new religious movements have spring up that have tenuous connections with traditional forms of Protestantism, Catholicism, or Orthodoxy. As Jenkins has pointed out at length, demographically, the center of gravity in Christianity has already shifted from Europe and North America to Africa, Latin America, and Asia.

All this means that the global configuration of the church has shifted. Is this as massive a shift as the shift that came with Constantine? Or the great schism? Or the Reformation? I have a hunch that it is. We are living in a time of epochal change in Christianity.

Protestants often assume an essentially Catholic account of the Catholic church—or, better, an old Catholic account. According to that account, Catholicism is monolithic and unchanging. It has always taught what it now teaches; it has always been the church it now is. This view of the church is not favored these days by Catholics themselves, but Protestants cling to it. For many, Catholicism—no matter what happens, no matter what changes are made—is the permanent other to Protestantism.

But the Catholic church is a very different church from what it was at the beginning of the twentieth century. There was a deliberate, massive shift from a “juridical” understanding of the church to an ecclesiology rooted in the idea of communion. Look at Lumen Gentium’s description of the church as “people of God” and body of Christ, and compare that to late nineteenth-century Catholic ecclesiologies.

Catholics regard Protestants differently than in the past. We are no longer considered simple outsiders, but are brothers, though “separated ones.” In the language of Vatican II, the church “subsists” in the Catholic church. It does continue to say that the church exists in fullness only in those churches that are associated with the Roman church, but Vatican II no longer identifies the church with the Roman Catholic church.

These ecclesiological shifts have been accompanied by liturgical reforms. Some Catholic churches have trended in a pop-Evangelical direction, but many have retained much of their traditional structure, though much simplified and with much more emphasis on the word and the Supper as Supper. Communion in both kinds is normal in many parishes.

The Bible plays a much larger role in Catholic life, especially in Catholic theology, than it did before Vatican II. The Catholic church has many of the leading biblical scholars of our time (Raymond Brown, Gary Anderson, Luke Timothy Johnson, Joseph Fitzmeyer, Harold Attridge). Catholic theologians who are not biblical scholars engage the biblical text in some depth (see the works of Hans Urs van Balthasar; de Lubac; Congar; or, today, Matthew Levering and Rusty Reno, among many others).

Admittedly, these changes are more apparent in some parts of the Catholic church than in others. Polish Catholics aren’t the same as American Catholics. Catholic theologians have a more nuanced grasp of both Catholic doctrine and of differences with Protestantism than parish priests, much less lay Catholics or converts-turned-apologists. Admittedly too, Catholics have to do some strange dancing to explain how they still conform to the dogmatic statements of Trent. Catholicism still has some features of sectarianism.

These qualifications don’t undermine the basic fact: Catholicism has changed in ways that open new possibilities for engagement with Protestants. Catholics have made generous offers of fellowship. Protestants would be churlish, perhaps faithless, to refuse.

(This is drawn from a lecture on “Protestant and Catholic in Late Modernity,” delivered at Covenant Seminary, St. Louis, March 6, 2015.)