Abstract

The aim in this chapter is to expound and (if possible) resolve two problems in Spinoza’s theory of mind. The first is how Spinoza can accept a key premise in Descartes’s argument for dualism—that thought and extension are separately conceivable, “one without the help of the other”—without accepting Descartes’s conclusion that no substance is both thinking and extended. Resolving this will require considering a crucial ambiguity in the notion of conceiving one thing without another, Descartes’s principle that each substance has a principal attribute, and the prospect of neutral monism as a theory of the mind. The second problem is how Spinoza can maintain that each mental event is identical with some physical event while denying that there is any causal interaction between mental and physical events. Resolving this problem will require looking into the reach of opacity in Spinoza’s philosophy and considering whether there are ever any legitimate exceptions to Leibniz’s Law.