Abstract

In their book on Descartes’s Changing Mind, Peter Machamer and J. E. McGuire argue that Descartes discarded dualism to embrace a kind of monism. Descartes famously proposed that there are two separate substances, mind and body, with distinct attributes of thought and extension. According to Machamer and McGuire, because of the limitations of our intellect, we cannot have insight into the nature of either substance. After reviewing their argument in some detail, I will argue that Descartes did not relinquish his favorite doctrine but may have actually fooled himself about the nature of his dualism. It is my contention that the problem with Cartesian dualism stems from the definition of mind and body as substances and the role of their respective attributes—thought and extension—in the definition of substances.