Descartes on Causation (review)

How does Descartes think causation operates? His definition of matter as mere geometrical extension, along with his rejection of the scholastic apparatus of substantial forms and real qualities, does not make it easy to see how there can be dynamic causal interactions in the universe. According to an influential reading, championed, for example, by Dan Garber in his Descartes’ Metaphysical Physics (Chicago, 1992), Descartes “rejected the tiny souls of the schools only to replace them with one great soul, God, who . . . manipulates the bodies of the inanimate world.” Tad Schmaltz’s aim, in this wonderfully detailed and intricately argued book, is to reject this tendency to move towards an occasionalist reading of Descartes, and to show how the Cartesian system permits things in the world to have a genuine, if derivative, kind of causal power: “Descartes’s intention is to allow for a physical world that has an internal source of activity” (128).

Of course, it is important that, for Descartes, God is always in the background. But this does not mean that he is busy shoving things around. Instead, in the Cartesian system, the laws (whether of bodily interaction or of psychophysical interaction) are, on Schmaltz’s view, “most immediately” related by Descartes to “conserved natures” (162). Explaining what this “conservationist framework” (219) amounts to leads Schmaltz into a fascinating exposition of some of Descartes’s scholastic forebears, notably Suárez, the fourteenth-century Dominican philosopher Durandus, and also more distant Islamic and Jewish precursors (Ghazali, Maimonides). In the end, though, it is Aquinas who (as so often in Descartes) is the key. St. Thomas’s “causal compatibilism” aims to show how actions can be attributed to both God and his creatures, thus avoiding the extremes of divine monocausalism and complete creaturely causal independence. God is a cause of things secundum esse, but not secundum fieri; very roughly, he generates their original and continued existence, but not the precise way their potentialities unfold. So in Descartes, “there . . . seems to be room for a derivative sort of causation of the modifications of substance,” so that “such causes educe from material substance modes that are contained in it merely potentially” (76–77).

As for body-mind causation, we certainly find a certain amount of occasionalist language in Descartes (e.g., in the 1648 Comments on a Broadsheet). But Schmaltz argues that Descartes “is in fact closer to Aquinas in attempting to make room for a genuine causal role for body in sensation” (149). He claims that bodily motions (transmitted via the nervous system) “emit the features that are contained objectively in our sensory ideas” (153). This seems very hard to make sense of, especially given Descartes’s frequent insistence that there is no resemblance at all between, for example, our visual sensation of redness and the corresponding corporeal motions of the objects we see as red. But Schmaltz’s ingenious suggestion is that, albeit with the assistance of an innate mental faculty, the corporeal motions “bring it about . . . that the mind has sensory ideas that direct it to certain bodily features rather than others” (ibid.).

Among the book’s many riches, a nicely-judged chapter convincingly argues that Descartes’s final account of human freedom is “fundamentally ‘incompatibilist’ in nature” (179). Along the way comes one of the most helpful discussions I have read of the notorious Cartesian doctrine of the divine creation of eternal truths, where Schmaltz ends up underlining what is (for both theological and logical reasons) a highly welcome restriction on that doctrine, namely that it is not supposed to apply to those truths that necessarily flow from God’s essence (189).

Overall, Schmaltz sees himself as partly deconstructing a standard narrative of Descartes’s view of causality, namely that it replaced the scholastic framework (based on the four Aristotelian causes) with the efficient causes required for his new mechanistic physics. Yet, although Schmaltz’s book does indeed brilliantly show how deeply the language in which Descartes expressed himself was indebted to his scholastic predecessors, we should not allow...