Abstract

This article discusses the impact of Descartes’s substance-dualism on his account of discursive reason. Taking the presentation of deduction in the Rules as a paradigmatic case of thought’s extension and movement in time, I analyze the relation between intuitive and discursive understanding and that between intellect and imagination. I focus specifically on the mediation of corporeal impressions and of intellectual ideas by ingenium. As intellectual, ingenium is a faculty of understanding; as joining with phantasia, ingenium has access to corporeal affections, images, and memory. Deduction involves both of these aspects of ingenium, and Descartes’s dualism complicates efforts to clarify the operations and nature of ingenium. Thus the dynamics of dualistic psychology account for some of the limitations of deduction in particular and discursive rationality in general.