The multitude of Jewish responses to the Holocaust and the creation of the modern state of Israel—twentieth-century events that profoundly impacted contemporary Jewish beliefs, practices, cultures, and identities—illustrate both the gifts and the challenges of Judaism's profound heterogeneity. This chapter provides an overview of Judaism and contextualizes streams of Jewish thought that set the stage for Jewish responses to the developments of the twentieth century. The latter half of the chapter is devoted to investigating Jewish theological innovations that fall broadly into six categories: Auschwitz constitutes a new revelation; the covenant has been broken; God must be redefined; God is dead; a renewal of ethical obligation is required; and mystery and silence are our best response.