The story of Franz Rosenzweig’s life is among the most moving in the history of twentieth-century thought. Rosenzweig was born on Christmas Day 1886 into an assimilated Jewish family in Kassel, Germany. Although there was a long tradition of religious learning in the family, Franz acquired only a superficial introduction to Jewish life at home, where the Sabbath was not celebrated. His family hoped he would pursue a medical career but at the University of Freiburg his interests shifted to philosophy and modern history under the influence of the distinguished scholar Friedrich Meinecke, who supervised his doctoral dissertation. A gifted student, Rosenzweig gave every appearance of being a conventional academic in the years leading up to the First World War.
Internally, though, he was tormented by religious and philosophical questions that scholarship could not help him address. A number of his close Jewish friends and relatives had converted to Christianity, not for the usual social reasons but out of spiritual conviction. They had come to the conclusion that the relativism of contemporary philosophy was false and that all existence depended on divine revelation. They were also convinced that the Christian conception of revelation was the purest and had made the modern world possible. Rosenzweig was susceptible to these arguments. He was particularly taken with his friend Eugen Rosenstock, a convert who was already established academically and would later have a career as a historian in the United States. After several long, heated discussions with Rosenstock in the summer of 1913 Rosenzweig announced his intention to convert, telling his astonished mother that the New Testament was true and that “there is only one way, Jesus.”
What happened next is now part of legend. Before converting to Christianity, the story goes, Rosenzweig decided to attend Yom Kippur services one last time, and there he experienced what might be called a preemptive counter-conversion, deciding on the spot to devote himself to Judaism. That, in any case, was the account Rosenzweig’s mother gave. He himself never wrote about the incident and it is doubtful he would have described such a melodramatic, quasi-Christian awakening. Still, we know from his letters that something important did happen in the fall of 1913, making it possible for him to write to one of his converted cousins, “I have reversed my decision. It no longer seems necessary to me, and therefore, being what I am, no longer possible. I will remain a Jew.”
Rosenzweig was as good as his word. That fall he began to meet with the eminent neo-Kantian philosopher Hermann Cohen, who after his retirement from Marburg taught philosophy at a Jewish institute in Berlin, where Rosenzweig was studying Hebrew and Talmud. He also met Martin Buber, who would become a lifelong friend and collaborator, and began writing essays on the nature of Judaism. When the war broke out Rosenzweig was sent to an antiaircraft unit on the Macedonian front, which was relatively quiet. That left him time to pursue his studies and even to …