The natural law theory of Johann Gottlieb Heineccius was one of the most influential to emerge from the early German Enlightenment. Heineccius continued and, in important respects, modified the ideas of his predecessors, Samuel Pufendorf and Christian Thomasius. He developed distinctive views on central questions such as the freedom of the human will and the natural foundation of moral obligation, which also sharply distinguished him from his contemporary Christian Wolff.Heineccius’s work saw five Latin editions in thirty years as well as several French, Italian, and Spanish editions; and it had a long life in Latin America. The English edition presented by Liberty Fund is based on the translation by the Scottish moral philosopher George Turnbull (1698–1748). It includes Turnbull’s extensive comments on Heineccius’s text, as well as his substantial Discourse upon the Nature and Origin of Moral and Civil Laws. These elements make the work into one of the most extraordinary encounters between Protestant natural law theory and neo-republican civic humanism. Johann Gottlieb Heineccius (1681–1741) studied theology at Leipzig and later law at the newly founded (1694) University at Halle, where he became a pupil of Christian Thomasius.Thomas Ahnert is a Lecturer in History, at the University of Edinburgh, Scotland.Peter Schröder is Senior Lecturer in the History Department at University College London.Knud Haakonssen is Professor of Intellectual History and Director of the Centre for Intellectual History at the University of Sussex, England.