Leibniz's Optics and Contingency in Nature

It has been tempting to suppose that the central theses of Leibniz's mature understanding of the laws of nature are forged in the domain of physics and opportunistically carried over to the domain of optics. This essay argues that that tempting story gets things essentially the wrong way around. Each of its three main sections accordingly takes up one of the defining features of Leibniz’s mature understanding of the laws of nature and argues that it is best understood as arising from his increasingly sophisticated attempts to show that the laws of optics can be thought of as selecting one uniquely determined actual path from an infinite family of possible paths. Collectively the three sections aim to show that the crucial nexus of views at the heart of Leibniz’s mature philosophical understanding of the laws of nature has its most intelligible roots in his optical derivations, which appear to have paved the way – both historically and conceptually – for the philosophical significance he assigns to his discoveries in the domain of physics. Optics the horse, as it were, physics the cart.