English summary: The work of Basel theologian Karl Barth (1886-1968) is unique in the history of theology of the 20th century. In thought and in writing, he often communed with contemporaries or personages from earlier centuries. He was guided by people he found interesting - such as Joseph Ratzinger, Friedrich Durrenmatt, Franz Rosenzweig and Nicholas von Zinzendorf - and answered them, learned from them, but also disagreed with them. That was his...