Travis Tanner

Recent work on Mary Shepherd has largely focused on her metaphysics, especially as a response to Berkeley and Hume. However, relatively little attention has thus far been paid to the epistemological aspects of Shepherd’s program. What little attention Shepherd’s epistemology has received has tended to cast her as providing an unsatisfactory response to the skeptical challenge issued by Hume. For example, Walter Ott and Jeremy Fantl have each suggested that Shepherd cannot avoid Hume’s inductive skepticism even if she is granted her metaphysics. In this paper, I examine Shepherd’s epistemology and argue that her response to Hume is more successful than the current literature suggests. In particular, I argue that, if Shepherd is granted her metaphysics, she can answer Hume’s demand for a rational justification of ordinary inductive inferences via a deductively justified uniformity principle and an appeal to parsimony.

Descartes is often identified as having fired one of the opening shots of the scientific revolution: rejecting the four Aristotelian causes in favor of the efficient causes characteristic of mechanistic science. Scholars often write as if Cartesian science and corporeal metaphysics is best understood as a rejection of all causal notions other than the efficient. I argue that this is a mistake. On the contrary, Descartes endorses an avowedly Aristotelian notion of formal causality, inherited from Suárez, and this notion is central to his physics and corporeal metaphysics. I begin by tracing the history of the formal cause from Aristotle to Aquinas and Suárez. My main thesis here is that the Aristotelian notion of formal causation picks out two distinct explanatory modes. The first is linked to hylomorphic ontology, and so by rejecting hylomorphism Descartes rejects one sort of formal causation. Crucially, however, the Aristotelians also identify explanations from essence as a species of formal causality. Now, Descartes’s entire philosophical project is built upon the intellectual perception of the essences of God, mind, and matter; the uncovering and exercise of this broadly Platonic intellectual capacity is, as Descartes explained to Hobbes, a key raison d’être for project of the Meditations. So we might expect Descartes to embrace formal causal explanations from essence, which harmonize so thoroughly with his philosophical project. And indeed, this is what we find. This is most obvious in the case of the ontological argument. In the course of defending the claim that God is causa sui, Descartes explicitly appeals to formal causation and claims to be only be “following in the footsteps” of Aristotle. Thus, there is a Cartesian notion of formal causation that is both continuous with and distinct from its Aristotelian predecessors. Other cases are less obvious, but no less important. For example, one of the most strikingly “modern” aspects of Cartesian physics is its emphasis on quantitative laws. Yet Descartes’s official account of how these laws explain particular phenomena is puzzling: He claims that the laws are causes. This, however, is prima facie absurd; Descartes seems to claim that the law of inertia is literally pushing the moon forward along its orbital path. I argue that this is not and cannot be what Descartes means. On the contrary, he clearly takes the laws of physics to follow from the divine essence, especially immutability and simplicity. The laws are true and epistemically accessible to us because they follow from the divine essence. In other words, Descartes thinks nomological explanation in physics is formal causal explanation from (the divine) essence. Another central issue is the impenetrability, or solidity, of matter. I offer a close reading and reconstruction of Descartes’s argument that matter is necessarily but not essentially impenetrable, and I show how Descartes accounts for impenetrability without compromising his mathematical conception of the corporeal. Descartes argues that impenetrability follows from the nature of matter as geometrical extension, thereby reducing a paradigmatic quality of matter (its solidity) to quantity (extension). Note that the explanatory bite throughout is from essence. Thus, while solidity is not a genuine corporeal causal power, it does give bodies an ineliminable causal role in Cartesian physics and corporeal metaphysics. This role is as a formal cause, since every explanation from impenetrability is ipso facto an explanation from the corporeal essence, geometrical extension. This, in turn, shows that Descartes has a principled response to idealists, like Berkeley, who claim that matter’s lack of efficient causal power implies idealism; Berkeley’s mistake, Descartes would argue, lies in equating efficient causality with causality simpliciter. Thus, I argue that formal causal explanation from essence is both well-attested textually in Descartes and is consonant with some of his deepest projects and commitments, including his Platonic intellectualism and mathematization of the corporeal. All this in mind, it is shocking how little attention has been paid to formal causation in Descartes’s metaphysics. If I am right, a thorough re-thinking of Descartes’s physics and metaphysics is long overdue.

Descartes’s causal theory is often taken to announce modernity by radically breaking with the Aristotelian past. Specifically, Descartes is often taken to reject the full Aristotelian causal theory in favor of the efficient causes characteristic of mechanistic physics and the activity of minds. In this chapter, I argue against this view by showing that Descartes endorses an avowedly Aristotelian notion of formal causation. First, I articulate Cartesian formal causation in light of its Aristotelian background, and I show that Descartes endorses what Francisco Suárez termed metaphysical formal causal explanation. Then, I argue against taking formal causation to be a peripheral explanatory notion for Descartes by showing it to be both well-attested textually and part and parcel of his Platonic intellectualism. I conclude by suggesting some further contexts in which this Cartesian notion of formal causation could be profitably wielded.