 We can see Desgabets adoption of the new Cartesian philosophy in his adherence to the core Cartesian metaphysics of dualism, mechanism, and union, and his critique of the Scholastic doctrines. However, his development of the doctrine of matter in the Eucharist controversy, his development of the interaction of mind and body as essential for all operations of the human mind, his development of the doctrine of indefectibility especially with respect to matter, and his defense of the “Creation Doctrine” led to many controversies in his day. Each of these, particularly the metaphysics of the human being as a substantial union of mind and matter whose interaction underlies all our thoughts has some interesting epistemological consequences. It is not surprising that Desgabets was known for his spirit of reform and earned Regis’s title as “one of the greatest metaphysicians of our century.” 