Descartes and the Metaphysics of Causality in the Material World

Abstract

The debate about the causal status of Cartesian matter has been steadily brewing for the last few decades. In particular, there has been renewed interest in the question of whether Cartesian bodies can cause changes in motion in other bodies. Pitted against each other are two camps. The first consists of broadly causalist interpreters, who ascribe some sort of causal or active power to bodies; the second consists of occasionalistic interpreters (of body-body interaction), who maintain that bodies are devoid of all causal or active properties. There has been a notable pendulum swing in the last two decades, with the majority of recent publications favoring the causalist view. I aim to rebut these causalist interpreters and offer a new defense of occasionalism about body-body interaction. Along the way, I will break new ground in sorting out the details of Descartes’ views.The components of my dissertation can be viewed in two main groups. Chapters 1 through 4 will mount four independent arguments against the causalist view. Each of these chapters investigates Cartesian bodies at a different level of metaphysical analysis: in turn, I assess bodies in terms of their principal attribute or essence, in terms of their modes, in terms of physical forces, and in terms of God’s concurrent action. At each level of analysis I will argue on textual and philosophical grounds that Descartes does not ascribe active or causal powers to bodies. In chapter 5 and in the appendix, I will change gears and outline the details of my own occasionalist interpretation. In particular, I explain the basis and manner of God’s action on bodies. Here follows a detailed overview of each chapter. The first chapter focuses on extension as a principal attribute. I argue that Descartes neither does nor could ascribe causal properties to extension considered as a principle attribute. This is supported on two bases. First, I argue that the textual evidence does not favor a causalist reading of matter, but favors an occasionalist reading. For one thing, Descartes never ascribes secondary causality to matter itself; for another, Descartes appears to distinguish the causal status of bodies as “external causes” from the notion of secondary causality. This latter point will be shown to track the later distinction between occasional causes and secondary causes. Second, I argue that it would be impossible on metaphysical grounds for Descartes to claim that extension is causal. This is shown by first establishing the conditions for secondary causality in Descartes’ physics: a secondary cause determines changes in motion in a functional way (i.e. there is a necessary connection between specific pre-collision and specific post-collision states). Then I argue that none of the propria or properties of matter jointly satisfy this condition. The second chapter focuses on the modifications of matter. This is to block any suggestion that Descartes could attribute modes to matter which add properties not already contained in matter considered as a substance. I first establish the more general metaphysical thesis that no mode can add properties to a substance which are not already contained in that substance’s principal attribute. I infer secondly that Descartes therefore could not consistently attribute causal modes to matter, given that matter’s principal attribute is itself not causal. Third, I then have to explain in general how the properties of modes are contained in their substances. I argue that Descartes is committed to the thesis that the properties of modes are contained eminently in their substances. The third chapter focuses on a central concept of Cartesian physics: force. The results of collisions are determined by the forces of the colliding bodies. So if it turns out that force is a per se feature of Cartesian bodies, then scholars would have good reason for thinking that bodies are causal. I will argue that force is not a per se feature of bodies, but is rather a per aliud feature directly grounded in God’s causal action. In order to defend this thesis, I make a negative and then a positive argument. The negative argument takes aim at current scholarship. Over the past two decades there have been four distinct interpretive camps which all converge on the same interpretive thesis—namely, that force is indeed a per se property of bodies. I argue against each camp individually and then generally. My general argument is a significant and especially novel contribution to the literature, in that I show that the per se reading of force is inconsistent with Descartes’ formulations of the laws of nature. As for my positive argument, I present a new interpretation of Cartesian force which entails that force is ascribed to bodies per aliud by God’s direct, law-governed action. I argue that forces in particular, and physical tendencies in general, are best understood as (non-real) relations. A tendency for Descartes is the conditional relation between a mode’s instantiation in one instant and its continued instantiation in the next. I argue that this conditional relation is established by God’s direct action, in conformity with the laws of nature. Force is the comparative measure of tendencies which is used by God to determine which modes to preserve or instantiate after collisions. The fourth chapter considers a loose end, namely Descartes’ appeal to the scholastic notion of concursus. For the scholastics, the theory of concurrentism brought together the disciplines of theology, metaphysics, and physics by maintaining that natural creaturely operations depended upon direct and cooperative divine operation. Importantly, Descartes uses the terminology of concursus when explaining material change, which has led some scholars to argue that Descartes is committed to scholastic concurrentism. If this is true, then Descartes would be committed to the view that for every material change there would be a divine efficient cause and a creaturely efficient cause. But if there is a creaturely efficient cause, this by definition entails that bodies are efficient causes. My fourth chapter blocks this causalist reading on two grounds. First, I show that textually Descartes does not use “concursus” consistently with scholastic usage. Rather, as is the case with many technical terms which he appropriates, he subtly changes the meaning of this term. He uses “concursus” as a synonym for divine conservation or preservation. Second, I show that Descartes could not have been a concurrentist in the scholastic sense (which would be necessary for the causalist argument to go through). One thesis of concurrentism is the claim that the primary cause actualizes the secondary cause. But given Descartes’ ontology, he lacks the distinctions requisite for bodies to be capable of actualization. To be specific, he lacks any distinctions remotely analogous to a distinction between potency and act. The fifth and final chapter explains how God causes motion and changes in motion. This will involve clarifying the role of the laws of nature in explaining change. I will argue that the laws are general formulae describing how God causes motion in bodies. God’s action is thus the truth-maker of the laws. I will furthermore argue that God does not cause changes in motion because he wills the laws, but rather that the laws obtain because of the way that his nature leads him to redistribute the motion which he chose to create. I will also sort out some of the technical details of God’s decision to produce motion. The appendix makes a minor point about the nature of causality in body-body interactions. Based on conclusions from chapters 1 and 2, it is necessary to explain what sort of causality is involved in material changes. I argue that it is misleading to describe change on the model of efficient causality. Instead, it is best described in terms of “modal causality.” I will explain what upshots this has for understanding the radical departure of Descartes’ natural philosophy from scholasticism.