Christia Mercer has exposed for the first time the underlying doctrines of Leibniz's philosophy. By analyzing Leibniz's early works she demonstrates that the metaphysics of pre-established harmony developed many years earlier than previously believed and for reasons that have not been understood. A much deeper understanding of some of Leibniz's key doctrines emerges. Christia Mercer's study will force scholars to reconsider their basic assumptions about early modern philosophy and science. This is a very significant contribution to the history of early modern philosophy that will be of special importance to philosophers, historians of ideas, historians of science and those in religious studies.