Causation and the Cartesian Reduction of Motion: God’s Role in Grinding the Gears: William Eaton and Robert Higgerson

Abstract

Louis de la Forge’s occasionalist explanation of local motion provides a way to reduce motion to other modes of extension. Such a reduction is favourable to the Cartesian scientist both in terms of parsimony, by reducing the total number of primary modes of extension, and in terms of intelligibility, by explaining the nature of motion at a deeper level than rival explanations.1 Furthermore, it suggests an approach to the problem of reconciling problematic but important elements of Cartesian metaphysics and science. We will argue that what makes La Forge’s reduction of motion possible is a commitment to solid Cartesian principles that, when taken as a whole, imply occasionalism, at least regarding body-body causation. We hold that this is both true and signifi cant for Cartesianism in general, whether or not Descartes himself was aware of the entailment. So the fi rst part of this chapter involves the reduction of local motion to other modes of extension, as well as the signifi cance of this reduction, while the second part explores how the solid Cartesian principles required for this reduction entail occasionalism. In doing this we are, in part, defending the position of Daniel Garber against recent interpretations of Descartes advanced by scholars such as Helen Hattab and Tad Schmaltz.2 In the end, we argue that despite signifi cant evidence to the contrary, the entailment of occasionalism from solid Cartesian principles is so straightforward that it’s hard to see how Descartes could not have been an occasionalist, at least regarding body-body causation. Our view is that occasionalism is the best way for a Cartesian to reconcile the transfer of power necessary for genuine causation with the essentially passive nature of matter.