This paper addresses a chapter of Third World church history and the need for an ecumenical perspective in the study of church history. Ludwig I. Nommensen is a part of the history of the church in Indonesia. He - like other Western missionaries - has identified himself with the Batak people of Sumatra in unfailing dedication. His life and work in Sumatra have been of great impact. In the memory of Indonesian Christians he lives on as the venerated "apostle of the Batak." In Europe, the region of his origin, however, his legacy has as yet to be interpreted more widely. Nommensen, the Westerner, has lived "solidarity as a missionary principle." In this approach to the mission of the church he has built a bridge between Christians in Indonesia and in Europe. Moreover, in the encounter between European and Indonesian cultures and religions, Nommensen's ideas and the Batak Christianity can contribute to a relevant partnership of churches, and to a renewed understanding of the apostolate of the church.