Abstract:

Several ambiguities plague Émilie du Châtelet’s deployment of the Principle of Sufficient Reason (PSR) in her Institutions de physique. The first concerns the modal scope of the PSR. On the one hand, du Châtelet claims that the Principle of Contradiction [PC] distinguishes the possible from the impossible (IP 1.5), restricting the scope of the PSR to explaining why possibles are actual (IP 1.8-9). On the other hand, she occasionally invokes the PSR in pursuit of the possibility of certain phenomena (IP 7.120-121; IP 8.142; IP 3.49). The second ambiguity concerns whether the PSR is a constitutive metaphysical principle or a regulative epistemic one. On the one hand, the PSR implies that there are grounds or causes of existences (e.g., IP 2.19, IP 3.42-44; IP 7.120-124), supporting a metaphysical reading. On the other hand, there are passages that are more naturally read as epistemic (e.g., IP 1.8-1.9, IP 7.120), and there is growing scholarly support for regarding du Châtelet’s PSR as a methodological principle (Brading 2019) or even as an epistemic principle that is restricted to human understanding (Wells 2021; Wells 2023; Amijee 2021; Amijee forthcoming). Finally, there is an apparent ambiguity in the kinds of reasons demanded by the PSR. In some instances, du Châtelet seeks ‘how come?’-type (Dennett 2017) reasons, in the form of causal or grounding explanations (IP 8.146; IP 2.19, IP 3.42-44; IP 7.120-124). In other instances, she seeks ‘what for?’-type reasons, in the form of final causes or practical reasons (IP 1.8; IP 2.27-8; IP 5.74; IP 8.139).

In this paper, I defend an interpretation of du Châtelet’s PSR that makes sense of the passages that generate the ambiguity concerns, while defending the consistency and univocity of her account. With respect to modality, I argue that while the PSR is restricted to actuals, a sufficient reason for actuals must account for their possibility, not in the sense of strict logical possibility (established by the PC), but in the sense of showing how it is causally possible (e.g., by evincing the mechanism), or metaphysical possible, by establishing its constitutive ground (IP 7.120-121; IP 8.142; IP 8.162 IP 11.227-9). I defend a metaphysical and constitutive reading of the PSR, which, I argue, is perfectly consistent with the passages that suggest that reasons must be intelligible, since the (mind-independent) facts that constitute reasons are themselves intelligible. Finally, with respect to the ambiguity about kinds of reasons, I argue that there is a unity to du Châtelet’s notion of reasons: they are just those facts (about things, essences, determinations, forces, wills, etc.) in virtue of which a phenomenon can be understood. Nevertheless, what counts as a sufficient reason will vary across domains of inquiry (e.g., physics, metaphysics, natural theology, morality), each of which have their own criteria of explication. This reading preserves the internal coherence of du Châtelet’s use of the PSR, while challenging widely held scholarly claims that lead interpreters to ascribe to du Châtelet an unduly restricted and attenuated version of the PSR.