‘Procedes Huc’: Voltaire, Newton, and Locke in Lettres Philosophiques

In Lettres philosophiques, Letter XIII is devoted to Locke, as are Letters XIV–XVII to Newton. The ordering of these letters is not adequately explained by comparing the dates of birth or death of the two thinkers. For the Letter on Locke not only precedes but also ‘frames’ those on Newton, in the sense that it provides the reader with a guide through the philosophical intricacies of Letters XIV–XVII. This works in two ways. On the one hand, in order to defend Newton against his detractors Voltaire broadly adopts Locke’s perspective on the relation among words, ideas and things. On the other hand, he subtly and misleadingly grafts Locke’s epistemology onto the Principia, though it differs from Newton’s epistemology in significant respects. For Locke, unlike Newton, holds that we can identify fixed, permanent limits concerning what kind of thing humanity can know of matter and the universe. Voltaire presents Newton’s ideas as though they respected Locke’s limits. However, we can glimpse Voltaire’s own attitude in the final words of Letter XV: ‘Procedes huc, et non ibis amplius’: Voltaire agrees more closely with Locke than Newton concerning the limits of epistemology.