A fateful Yom Kippur experience in 1913 transformed Franz Rosenzweig from a German intellectual on the brink of converting to Christianity into one of the twentieth century's most influential Jewish philosophers. Standing at the crossroads of German Jewish assimilation, Rosenzweig developed a revolutionary theological framework that bridged German idealist philosophy with Jewish tradition, addressing Judaism's perceived lack of systematic metaphysics. Through analysis of "The Star of Redemption," his correspondence, and educational activities, this study reveals how his "New Thinking" positioned Judaism and Christianity as complementary yet distinct paths to divine truth. Rosenzweig's practical innovations, particularly the Frankfurt Lehrhaus, revolutionized Jewish education by integrating secular scholarship with traditional texts. Even as amyotrophic lateral sclerosis progressively paralyzed his body, his mind remained fierce - he continued producing translations and philosophical works until his death in 1929 through extraordinary determination. His successful synthesis of philosophical rigor with Jewish observance provides a compelling model for modern Jewish intellectual engagement, offering particular insight into twentieth-century Jewish responses to secularization and assimilation pressures in Western Europe.