This is the first book-length study of two of Descartes's most innovative successors; Robert Desgabets and Pierre-Sylvain Regis; and of their highly original contributions to Cartesianism. Relating their work to that of fellow Cartesians such as Malebranche and Arnauld, the book establishes the important though neglected role played by Desgabets and Regis in the theologically and politically charged reception of Descartes in early-modern France. This major contribution to the history of Cartesianism is of interest to historians of early-modern philosophy and historians of ideas.