The relationship between Reformed orthodoxy and the Cartesian Enlightenment remains a central question in the study of post-Reformation theology. Through the first comprehensive study of Campegius Vitringa (1659-1722), this volume argues that he represents a distinct middle position between Reformed orthodoxy and rationalist Reformed theology. Drawing on many untranslated Latin theological and philosophical works and comparing Vitringa with dozens of Reformed contemporaries across Europe, this study offers a more precise account of theological certainty in Reformed thought between 1600 and 1750 and its engagement with early modern philosophy.