Fortunio Liceti on Mind, Light, and Immaterial Extension

Almost half a century before Henry More, the Padua-based natural philosopher Fortunio Liceti (1577–1657) formulated a distinction between material extension and immaterial extension. While More’s version of the distinction is seen as one of the most characteristic features of his metaphysics—underlying both his theory of individual spirits and of absolute divine space—Liceti’s metaphysics of immaterial extension has not received much attention by commentators. Liceti ascribes immaterial extension to light and the human mind and, like More, he uses the analogy between light and mind to explicate the structural differences between material and immaterial extension. In this article, I explore how Liceti—following some aspects of Albert the Great’s eclectic Aristotelianism—tries to combine broadly Aristotelian accounts of light and mind with the Platonic concept of emanative causation. I argue that, in Liceti, the notion of existential independence from matter lies at the heart of his conception of extended, but actually indivisible, immaterial beings: Such beings cannot be divided through the division of matter because their existence, due to the role of emanative causation, does not depend on the potencies of matter.