This article studies the academic context in which Cartesianism was absorbed in Germany in the mid-seventeenth century. It focuses on the role of Johann Clauberg (1622-1665), first rector of the new University of Duisburg, in adjusting scholastic tradition to accommodate Descartes’ philosophy, thereby making the latter suitable for teaching in universities. It highlights contextual motivations behind Clauberg’s synthesis of Cartesianism with the existing framework such as a pedagogical interest in Descartes as offering a simpler method, and a systematic concern to disentangle philosophy from theological disputes. These motivations are brought into view by situating Clauberg in the closely-linked contexts of Protestant educational reforms in the seventeenth century, and debates around the proper relation between philosophy and theology. In this background, it argues that Clauberg nevertheless retains an Aristotelian conception of ontology for purely philosophical reasons, specifically, to give objective foundations to Descartes’s metaphysics of substance. In conclusion, Clauberg should not be assimilated either to Aristotelianism or to Cartesianism or, indeed, to syncretic labels such as ‘Cartesian Scholastic’. Instead, he should be read as transforming both schools by drawing on a variety of elements in order to address issues local to the academic milieu of his time.