Hermann Cohen’s magnum opus, “Religion of Reason Out of the Sources of Judaism” appeared in print posthumously in 1919. The work is widely considered to be one of the most consequential articulations of Jewish thought in the period of the nineteenth and twentieth centuries. Some have even placed its importance in first position. Cohen was the leading neo-Kantian thinker in his day. Not surprisingly, he set out to formulate a concept of religion based on reason. What makes the work decidedly Jewish, nonetheless, is how it presents fundamental concepts of Judaism, as they are revealed in the Torah and in classical Hebrew texts, as the original sources of that religion of reason.