This chapter considers the medieval and scholastic context of Descartes's theory of causation. It starts with a brief account of the origins of occasionalism in medieval Islamic theology, and then turns to two different alternatives to occasionalism in the later medieval period, namely, the “concurrentism” of Thomas Aquinas, according to which God “concurs” in the action of secondary causes, and the “mere conservationism” of Durandus of Saint-Pourçain, according to which God merely creates and conserves secondary causes that act on their own. The chapter concludes with a discussion of the metaphysical framework for efficient causality in the work of the early modern scholastic Francisco Suárez that prepares the way for a transition from a more traditional Aristotelian view of causality to what we find in Descartes.
Keywords: medieval occasionalism, concurrentism, mere conservationism, efficient cause, Thomas Aquinas, Durandus, Suárez