 Arnauld’s treatment of the union of mind and body shows that he was not a docile follower of Descartes, and was prepared to develop “the philosophy of Descartes” in ways that Descartes would probably not have accepted. It also shows that Arnauld was prepared to modify Descartes’ philosophy in a way that increased its similarity to Augustine. It is well known that Arnauld pointed out similarities between Augustine and Descartes from the beginning of his published work, in the “Fourth Objections.” In the present case, however, Arnauld changes the philosophy of Descartes in a way that increases its similarity to Augustine. Arnauld did not mention Aquinas, though he could have done so, as another authority who held that a material thing cannot produce an immaterial effect. It was only a few years later, in Ideas, that Arnauld began to claim an affinity between the views of Descartes and those of Aquinas. But in his development of the Cartesian position on the union of mind and body, one can already see Arnauld attempting to make of Descartes a Christian philosopher standing in continuity with his great patristic and scholastic predecessors. (This attempt on Arnauld’s part is explored in the journal Dix-Septieme Sciecle, 2013/2 no. 259.)