Johannes de Raey on subtle matter: a medical synthesis of Aristotle and Descartes

This paper examines how the seventeenth-century Dutch Cartesian Johannes de Raey sought to reconcile the philosophies of Descartes and Aristotle. It focuses on De Raey’s identification in Aristotle of a doctrine corresponding to Descartes’s subtle matter and asks which strand of the Aristotelian tradition he relied on for this identification. The study centres on De Raey’s 1652 disputation De materia subtili and also draws on his lecture notes preserved in manuscript form, his earliest disputation, and the disputations of his teacher Henricus Regius, in which De Raey often served as respondent. The analysis shows, first, that De Raey interpreted Aristotle as positing a subtle body analogous to the element of the stars. Second, it argues that De Raey arrived at this reading by relying on the interpretation of the Generation of Animals by the Wittenberg medical professor Daniel Sennert, whose works De Raey encountered early in his career while studying medicine under Regius. Finally, De Raey gave Sennert’s interpretation a decisively materialist turn, thereby making it possible to read Aristotle within a corpuscular, Cartesian framework. In this respect, he can be placed within the broader seventeenth-century movement to reinterpret Sennert’s Aristotelianism in corpuscular terms.