Is Judaism a religion, a culture, a nationality--or a mixture of all of these? In How Judaism Became a Religion, Leora Batnitzky boldly argues that this question more than any other has driven modern Jewish thought since the eighteenth century. This wide-ranging and lucid introduction tells the story of how Judaism came to be defined as a religion in the modern period--and why Jewish thinkers have fought as well as championed this idea. Ever since the Enlightenment, Jewish thinkers have debated whether and how Judaism--largely a religion of practice and public adherence to law--can fit into a modern, Protestant conception of religion as an individual and private matter of belief or faith. Batnitzky makes the novel argument that it is this clash between the modern category of religion and Judaism that is responsible for much of the creative tension in modern Jewish thought. Tracing how the idea of Jewish religion has been defended and resisted from the eighteenth century to today, the book discusses many of the major Jewish thinkers of the past three centuries, including Moses Mendelssohn, Abraham Geiger, Hermann Cohen, Martin Buber, Zvi Yehuda Kook, Theodor Herzl, and Mordecai Kaplan. At the same time, it tells the story of modern orthodoxy, the German-Jewish renaissance, Jewish religion after the Holocaust, the emergence of the Jewish individual, the birth of Jewish nationalism, and Jewish religion in America.