 If there is one part of Descartes’ philosophy that met with Arnauld’s enthusiastic approval, it is Descartes’ mind-body dualism. Yet even here Arnauld’s version of the Cartesian philosophy departed in important ways from Descartes’ own views. Arnauld’s departure did not have to do with the distinction between mind and body; here he largely contents himself with endorsing what Descartes  says.[8]  It had to do rather with the union of the mind and body in a human being. Arnauld rejected a claim at the core of Descartes’ position, namely, that the union of a person’s mind and body makes it possible for the mind and the body to exercise real causal action on one another. Arnauld explicitly says that a person’s body cannot act causally on his mind, and had at least some difficulty with the notion that a person’s mind can act causally on his body.