Hermann Cohen's Religion of Reason, Out of the Sources of Judaism (first published in 1919) is widely taken to be the greatest work in Jewish philosophy and religious thought since Maimonides' Guide to the Perplexed. It is at once a Jewish book and a philosophical one: Jewish because it takes its material from the literary tradition that extends from the bible to the rabbis to the great medieval philosophers; philosophical because it studies that material in order to construct a worldview that is rational in the broadest sense of the term. This edition reprints a 1972 introduction by Leo...