As ever, Bonhoeffer cagily maintained a certain distance. He wished to learn from the old master, but would preserve his intellectual independence. In the end he would not choose church history. He respected that field, as he demonstrated by mastering it, to Harnack’s delight, but he disagreed with Harneck that one must stop there. He believed that picking over the texts as they did, and going no further, left behind “rubble and fragments.” It was the God beyond the texts, the God who was their author and who spoke to mankind through them, that fired his interest [Metaxas in Bonhoeffer, 62].
By September he made his decision: he would write his doctoral dissertation under Seeberg after all, but it would be on a subject dogmatic and historical. He would write about the subject he had begun puzzling over in Rome, namely, What is the church? It was eventually titled Sanctorum Communio: A Dogmatic Inquiry into the Sociology of the Church. Bonhoeffer would identify the church as neither a historical entity nor an institution, but as “Christ existing as church-community.” It was a stunning debut [Metaxas in Bonhoeffer, 63]
I myself find the way such a decision comes about to be problematic. One thing is clear to me, however, that one personally – that is, consciously – has very little control over the ultimate yes or no, but rather that time decides everything. Maybe not with everybody, but in any event with me. Recently I have noticed again and again that all the decisions I had to make were not really my own decisions. Whenever there was a dilemma, I just left it in abeyance and – without really consciously dealing with it intensively – let it grow toward the clarity of a decision. But this clarity is not so much intellectual as it is instinctive. The decision is made; whether one can adequately justify it retrospectively is another question. “Thus” it happened that I went [to Barcelona] [brackets mine] [Metaxas in Bonhoeffer, 70].