What’s in a Dream? Leibniz’s Response to External World Skepticism

In this paper, I compile and compare Leibniz’s answers to the skeptical challenge of how to distinguish dreams from reality, relying mainly on a series of texts from the 1670s, as well as some later writings such as the Theodicy, that offer responses to Descartes’ well-known treatments of skepticism in the Meditations. In doing so, I aim to unearth a central part of Leibniz’s nuanced and life-long engagement of skepticism, which so far has received little attention in the literature. In reconstructing Leibniz’s response, I show that while to a certain extent, Leibniz’s and Descartes’ arguments run parallel, a number of crucial differences emerge. Importantly, while for Descartes our knowledge of the external world can have metaphysical certainty, according to Leibniz, our certainty can only be moral. Indeed, Leibniz seems to introduce an altogether different, “pragmatist” sense of certainty here.