Irena Backus offers the first study in over four hundred years that characterizes Leibniz as both scholar and theologian. She explores his treatment of the key theological issues of his timepredestination, sacred history, the Eucharist, efforts for a union between Lutherans and members of other Christian traditionsilluminating his unique integration of theology into philosophy. Drawing on a wide range of Leibniz's writings, Backus carefully examines the philosophical points and counterpoints of his positions. She shows how Leibniz's Lutheran theology was reconciled with his philosophy, and demonstrates that the solutions he sought to the problems of confessional division were more philosophical than theological. Despite his attempts to merge the two fields, Backus reveals, many of Leibniz's ideas were met with resistance by both theologians and philosophers of his time. Using a wealth of previously unexplored material, Backus also includes the first-ever English translation of the Unvorgreiffliches Bedencken. This study will be an important contribution to the history of ideas, and to understanding Leibniz's place in the mainstream Protestant theology of his time.