God's diplomat, the pope of the ecumenical movement, but also an acerbic theologian and a difficult person: this is how journalists characterised Willem Adolf Visser 't Hooft (1900-1985). He was one of the best-known Dutch theologians outside the Netherlands and he left his mark on the world church. Even at an early age he made profound efforts in support of international ecumenical youth and student organisations (Dutch Student Christian Movement, YMCA and World Student Christian Federation). He led the World Council of Churches during its formative stages (from 1938), and after its formal establishment in 1948 became its first general secretary, serving until 1966. To Visser 't Hooft, the unity of the church was both an article of faith and of a pragmatic organisation of church influence in a disunited world.

Jurjen Zeilstra (1961) is a historian and theologian. The biography served as a dissertation in the humanities at the Amsterdam Free University in order to receive the degree of Ph.D. in 2018. Earlier, in 1995, Zeilstra earned the degree of Th.D. with his thesis European Unity in Ecumenical Thinking, 1937-1948, in the Theological Faculty at Utrecht University. His current job is as a Protestant minister in Hilversum.Jurjen Zeilstra (1961) is a historian and theologian. The biography served as a dissertation in the humanities at the Amsterdam Free University in order to receive the degree of Ph.D. in 2018. Earlier, in 1995, Zeilstra earned the degree of Th.D. with his thesis European Unity in Ecumenical Thinking, 1937-1948, in the Theological Faculty at Utrecht University. His current job is as a Protestant minister in Hilversum.

Introduction: The Importance and Limitations of a Biography-1 Subject and Background-2 Existing Biographies-3 Method1 The World Opens Up, 1900-19242 The School of International Encounter: Working with Youth and Students, 1924-19393 Church Unity in Wartime, 1939-19454 From 'Spiritual Contact' to Political Involvement: The Swiss Road, 1942-19445 Towards a World Council of Churches: Reconciliation and Restoration, 1945-19486 General Secretary of the World Council of Churches, 1948-19667 The Cold War, the Unity of the Church and Eastern Orthodoxy, 1948-19668 Roman Catholic Contacts: 'Nostra Res Agitur', 1948-19699 Obsolete Institutionalism? The Twilight Years, 1966-198510 In the Mirror of Rembrandt and the Perspectives of OthersTaking Stock: An Assessment of a Life Lived for the Unity of the Church Sources and Literature Consulted-1 Archives and Unpublished Primary Sources -2 Oral Sources -3 Digital Sources -4 Published and Unpublished Works by W.A. Visser 't Hooft -5 Published Sources and Secondary Literature 6 Newspapers and Magazines *A - Persons Quoted*B - Other References Index