We aren’t sure what to call it. A celebration? A commemoration? Regardless, Lutherans and Catholics will mark the five-hundredth anniversary of the Reformation in 2017. Our uncertainty of what to call this year has not slowed down our event planning. Countless lectures, readings, and conferences are being planned across the United States and Germany. For Lutherans and Catholics alike, it promises to be an engaging and inspiring year. Yet a greater question remains: where will we go in 2018?

Over the past five decades, Lutherans and Catholics have made significant ecumenical advances. Our greatest success, The Joint Declaration on Justification, voiced agreement on the theological question which sparked the Reformation and was adopted by the Pontifical Council for Promoting Christian Unity and the Lutheran World Federation in 1999. Next year will see the American publication of From Conflict to Communion, the latest product of Lutheran-Catholic dialogue. Yet the anniversary of the Reformation comes at a time of transition for the institutional ecumenical movement. While great progress is being made among theologians and church leaders, ecumenical institutions no longer enjoy the same influence they once had. Many in the pews wonder what another statement can accomplish.

The ecumenical movement is strongest not when issuing statements of theological accord but when engaging in a shared commitment to mission. Ecumenical statements are necessary but not sufficient for true church unity. Indeed, we would be wise to remember that the ecumenical movement is rooted in the missionary project of the nineteenth century, coming into its modern form out of Edinburgh’s World Missionary Conference in 1910. While some think that the ecumenical progress of that era was no more than a logistical compromise to make missions more efficient or convenient, it actually came from a deeper conviction that a divided church betrayed the gospel of reconciliation that the missionaries preached. Missionaries could not preach that God had reconciled humanity to one another if they hadn’t even been reconciled to their own Christian brothers and sisters. A shared commitment to mission made ecumenical unity a necessity.

Some may say that this “scandal of disunity” is no longer a burden on the church. We have become so used to denominationalism and disunity, they argue, that they are no longer a stumbling block to anyone. Some even claim that the shift of the church’s center of gravity toward the Global South proves that there is no need for mission. To make matters worse, mission has become akin to a four-letter word in many of our churches, something enlightened Christians don’t do anymore. Yet the truth remains that our desperately needed ecumenical agreements will not bring Lutherans and Catholics into greater unity without a renewed attention to common mission.

For inspiration on how Lutherans and Catholics can engage in mission together, we would be well served by looking outside our own churches to the life and work of Presbyterian theologian, missionary, and bishop Lesslie Newbigin. In 1936, a young Newbigin was sent to Madras, India to serve as a missionary for the Church of Scotland. It soon became clear to Newbigin that the disunity of the church was stunting its ability to engage in mission. Reflecting on this experience in a series of lectures given in Glasgow in 1952, Newbigin noted that “when the Church ceases to be one, or ceases to be missionary, it contradicts its own nature.” Newbigin envisioned a church that went beyond de facto denominationalism toward a deeper organic unity. Seeking a better way forward, Newbigin was integral in the formation of the Church of South India, a new church comprised of Anglican, Methodist, Congregational, and Presbyterian churches. After intense debate, particularly around the role of bishops, the Church of South India was founded in 1947, mere weeks after India gained its independence. Newbigin served as one of the Church of South India’s first bishops, a sign of the ecumenical progress that had been made within the Church of South India itself. Far from being a mere ecumenical triumph, the Church of South India has also been a success in its mission. Today it has over five million members and is the second largest church in India, second only to the Catholic Church.

The success of the Church of South India would be enough to cement Newbigin’s legacy as one of the twentieth century’s most important missionaries and theologians, yet what happened after he left India may be the most instructive for Lutherans and Catholics today. In the mid-1970s, Newbigin served as a professor of missiology and ecumenism at Birmingham’s Selly Oaks Colleges. After teaching for five years, Newbigin served Winson Green United Reformed Church, a small parish of twenty members in a derelict section of Birmingham. In returning to England, Newbigin was startled to find how the culture he had left in the 1930s had become increasingly hostile to the Christian faith. He found that the mission field was no longer an ocean away but outside his door. Newbigin analyzed and responded to this new situation in Foolishness to the Greeks (1986) and The Gospel in a Pluralist Society (1989). He criticized the attempt to create a more “reasonable Christianity,” advocating instead for a more eschatological understanding of the church, emphasizing the church’s calling to serve as a sign, foretaste, and instrument of the kingdom of God.

These concerns were not limited to Newbigin’s writing; they also manifested themselves in his work as a pastor. Geoffrey Wainwright’s Lesslie Newbigin: A Theological Life (2000) recalls how Newbigin responded with the same zeal for creative proclamation that he had shown fifty years earlier in India. Though church institutions were too engrained to be realigned, Newbigin was able to foster ecumenical partnership among Pentecostal and black churches aimed at asking what the unity of the church meant for the community of Winson Green. After race riots in nearby Handsworth, for example, Newbigin organized church, municipal, and law enforcement officials in community meetings. Newbigin’s presence became so vital in the neighborhood that even ten years after he left Winson Green people who had never worshipped at his church were still asking the church secretary about his health.

Reflecting on the mission of the church, Newbigin once noted that “the world provided the agenda.” When the five-hundredth anniversary of the Reformation is over, Lutherans and Catholics will have to figure out what direction our life together will take. The next five hundred years have great potential for Catholic and Lutheran unity, but our ecumenical progress will only reach its potential when we commit to greater mission together. It is time to let the world write our agenda.

Joseph Schattauer Paillé is a candidate for ordination in the Evangelical Lutheran Church in America and lives in New York City.