Franz Rosenzweig, the religious existentialist, was born in Cassel, Germany. From 1905 to 1912 he studied natural sciences, modern history (under Friedrich Meinecke), and philosophy (under Heinrich Rickert) at the universities of Göttingen, Munich, Freiburg, and Berlin. At Berlin he earned a doctor of philosophy degree in 1912 with a dissertation on G. W. F. Hegel's political doctrines; later, he expanded this study. In the fall of 1913, after a spiritual crisis, he turned to religious, especially Judaic, philosophy. In 1918–1919 he wrote Der Stern der Erlösung (The Star of Redemption), a three-part religio-philosophical system; in 1920 he founded the Freies Jüdisches Lehrhaus (Independent House of Judaic Studies) in Frankfurt. Two years later he was appointed lecturer for Jewish religious philosophy and ethics at the University of Frankfurt, but the onset of progressive paralysis prevented him from accepting the appointment. Despite his affliction, he continued his scholarly...