Abstract

The fourth chapter analyses the establishment of Cartesianism at the University of Leiden in 1650s and 1660s. This was carried out by De Raey, who provided a defence and teaching of Descartes’s physics in his Clavis philosophiae naturalis (1654), although not based on Descartes’s metaphysics: physical principles, indeed, are presented by De Raey as self-evident truths, and consistent with Aristotle’s theory of scientia or universal and necessary knowledge. This was not the only peculiar characteristic of Leiden Cartesianism, as De Raey also provided a differentiation between philosophical and practical knowledge (including medicine and revealed theology), as these are based on different sources of knowledge, namely, intellect and sensory experience. In the hands of Christopher Wittich, the separation thesis became the standard in conceiving the place of Cartesianism in the university, which was confined to natural philosophy in 1650s and strictly secluded from revealed theology. At the same time, the need to develop a moral philosophy consistent with the Reformed creed became the centre of the debate between Revius and Heidanus, a Reformed theologian who saw in Cartesianism a philosophy more consistent with Calvinism than Scholasticism. Accordingly, he was eager to support the appointment in Leiden of Arnold Geulincx, who was developing a philosophical ethics independent of revealed theology but consistent with the Reformed creed. For this purpose, besides the relation of body, soul and world, Geulincx considered those relations of man, world, and God from which moral duties follow. Accordingly, he provided his ethics with a foundation in rational theology. In turn, this foundation entails a reflection on the type of knowledge that constitutes physics and determines its very method. Given the inscrutability of God’s reasons in creating the world, Geulincx could claim that physics has to proceed by hypotheses based on experience rather than by a deduction of natural laws from metaphysical principles. In this way, the epistemic consequences of his foundational theory refuelled a reflection on the method of natural philosophy itself, making his foundation a sample of the transformation of Cartesian foundationalism – dominated by Descartes’s metaphysical physics – into a reflection on physics itself. In other words, Geulincx provided, together with De Raey, a de-metaphysicisation of physics.