This essay explores the difficulty of reconciling Spinoza’s ontological monism; his thesis that mind and body, extension and thought, are two different and mutually irreducible way of describing the universe; his insistence on the reality of the mental; and his denial of mind-body interaction. According to Spinoza, while a particular event described in one vocabulary may cause a particular event described in the other, a fully adequate explanation of a mental event cannot be given in physical terms and vice versa. This thesis is what Spinoza had in mind in denying mind-body interaction.
Keywords: Spinoza, monism, theory of affects, mind-body interaction, extension, thought