Baptists and Lutherans often define the tension of being in the world, but not in terms of two separate realms: the kingdom of God and the kingdom of the world. However, their understanding of these realms and their delicate connection is quite nuanced. Within the Lutheran tradition, the two kingdoms are held in tension, which in turn leads to a precarious interaction of state and church. In the (Ana)Baptist tradition, a much stricter duality is emphasised, resulting in a more radical and separatist stance. ‘Dietrich Bonhoeffer and Arnold Koster’ analyses and compares the historical development of these two viewpoints, and to discover how these traditions, represented in the lives of two individual followers, responded to the ideological onslaught of neopaganism and the enforced political conformity of the Third Reich. Compared with Dietrich Bonhoeffer, little is known of the Baptist preacher Arnold Koster. His ministry as a pastor of the Baptist church in Vienna lasted from 1928-1960. During the Nazi regime, he consistently preached critically and prophetically against its underlying ideology.