A priori philosophy of nature in Hegel and German rationalism

Hegel’s many remarks that seem to imply that philosophy should proceed completely a priori pose a problem for his philosophy of nature since, on this reading, Hegel offers an a priori derivation of empirical results of natural sciences. We show how this perception can be mitigated by interpreting Hegel’s remarks as broadly in line with the pre-Kantian rationalist notion of a priori and offer reasons for doing so. We show that, rather than being a peculiarity of Hegel’s philosophy, the practice of demonstrating a priori the results of empirical sciences was widespread in the pre-Kantian rationalist tradition. We argue that this practice was intelligible in light of the notion of a priori that was still quite prominent during Hegel’s life. This notion of a priori differs from Kant’s in that, while the latter’s notion concerns propositions, the former concerned only their demonstration. According to it, the same proposition could be demonstrated both a posteriori and a priori. Post-Kantian idealists likewise developed projects of demonstrating specific scientific contents a priori. We then make our discussion more concrete by examining a particular case of an a priori derivation of a natural law, namely the law of fall, by both Leibniz and Hegel.