Causal Powers in Cartesian Physics: Descartes’ Laws of Nature in La Forge and Clauberg

Andrew Platt

Stony Brook University, NY

Gary Hatfield (1979) and Daniel Garber (1993) have argued that Descartes’ physics entails that mere bodies are intrinsically passive, and thus do not have any active causal powers or any intrinsic motive force. On their reading, Descartes thinks that the motions of bodies are grounded in God’s activity of continual recreation: the only “force” in Descartes’ physics comes from God. Thus they take Descartes to be a kind of partial Occasionalist: he thinks that the natural motions of bodies are caused by God alone, not by any action of bodies upon one another. A similar reading is suggested by Thomas Lennon (1974), who argues that Occasionalism follows from two metaphysical theses implicit in Descartes’ works. The first thesis is that modes are not really distinct from the substances in which they inhere. The second thesis is that the act of conserving a finite substance in existence is identical to the act of creating it. The Cartesians Louis de la Forge and Gerauld de Cordemoy appeal to these principles, says Lennon, to argue for Occasionalism. Thus we can think of these authors as showing how Descartes’ metaphysical views can be interpreted to entail an Occasionalist physics. La Forge argues for Occasionalism about natural motion in his Traité de l’esprit de l’homme (1665). He presents his treatise as a reconstruction of Descartes’ own views. And as an early follower of Descartes --with ties to Descartes’ literary executor, Claude Clerselier -- La Forge’s interpretation seems to have some authority as a guide for how we should understand Cartesian physics. Thus the textual evidence from La Forge seems to support the Hatfield-Garber reading, on which Cartesian bodies do not have causal powers. I agree with (among others) Tad Schmaltz (2007) that Cartesian physics does not entail Occasionalism about natural motion. I argue that we can interpret Descartes’ physics in a way that is consistent both with the metaphysical theses Lennon identifies and with the claim that bodies act causally on one another. The result is a non-Occasionalistic version of Cartesian physics, according to which bodies have active powers that are partially grounded in their intrinsic natures. Thus I suggest that Descartes himself would not have accepted La Forge’s arguments -- and I argue that at least one of Descartes’ early followers interprets Descartes’ physics in this way as well. This non-Occasionalistic Cartesian physics in found in Johann Clauberg’s Disputationes Physicae (1664). I present Clauberg’s exposition of Descartes’ laws of nature, and argue that on Clauberg’s interpretation they imply that bodies have motive force or power. This shows that La Forge’s reading is not the only natural way to develop Descartes’ physics -- and gives us reason to question the idea that Occasionalism is a logical consequence of Descartes’ views about the metaphysics of body and the laws of nature.