Christian Wolff on the Mathematization of Ontology, Psychology, and Practical Philosophy

Abstract One of Wolff’s earliest and most distinctive ambitions was to turn philosophy into a mathematical science by integrating philosophical and mathematical cognition. This paper reconstructs the origins and development of an underinvestigated aspect of Wolff’s mathematization project and argues for its significance to Wolff’s mature system. Since, on his account, all that is finite has a quantity, Wolff thought it was possible to obtain mathematical cognition of the objects of all philosophical disciplines, including metaphysics and ethics. Inspired by John Craig’s application of mathematics to theology, Wolff soon envisaged the use of mathematical tools to reform ontology. He later justified the possibility of measuring non-extended objects by reviving the scholastic doctrine of degrees and intensive magnitudes. I argue that his groundbreaking interest in psychometry stems from this background.