This volume brings together 138 of Leibniz's writings on four key areas of philosophy–metaphysics, natural philosophy, ethics, and jurisprudence. His metaphysical writings trace the development of some of his most distinctive doctrines such as the complete concept theory of substance, pre­established harmony, the nature of human and divine freedom, and the infinite analysis of contingent truths. Leibniz's writings on natural philosophy reveal a conviction that the principles of physics ultimately depend on those of metaphysics and his efforts to develop a rational physics grounded not in experiments but in an a priori investigation of intelligible and sensible qualities, such as figure, motion, and colour. The ethical writings focus on happiness, the role of virtue, and the importance of adopting others' perspectives. Meanwhile, Leibniz's jurisprudential works centre on his ambition to create a systematic, rational foundation for law and his plan to reform legal codes by integrating Roman law with modern European jurisprudence. This collection traces the evolution and interconnection of these ideas and projects during Leibniz's formative first decade in Hanover (1677–1686), and is the most extensive collection of such writings in English to date. Strickland has returned to Leibniz's original manuscripts to produce accurate, carefully annotated translations that document textual variations, deletions, and marginalia. Of the 138 texts included, 88 appear in English for the first time, and one has never been published in any language. In addition to the translations, the volume features a substantial introductory essay on Leibniz's life, work, and writings on metaphysics, natural philosophy, ethics, and jurisprudence from 1677 to 1686, along with detailed explanatory notes on each text, providing context, background, and the rationale for their dating.