Harnack, and the Luther scholar, Karl Holl. To the dismay of von Harnack, who regarded him as a potentially great church historian able one day to step onto his own podium, Bonhoeffer instead steered his scholarly energies to dogmatics, where his main interests lay in the allied fields of Christology and Ecclesiology. His doctoral dissertation, Sanctorum Communio (The Communion of Saints), completed in 1927, was hailed by Karl Barth as a “theological miracle.”3 Bonhoeffer was only twenty-one years