The Many Faces of Spinoza’s Causal Axiom

Abstract

“Cognition of the effect depends on and implies cognition of its cause,” announces Spinoza in 1a4 of his Ethics. This axiom, known as “Spinoza’s causal axiom,” is one of the most important in the Ethics. It plays a central role in Spinoza’s arguments for some of his most significant doctrines, including (1) that things with nothing in common cannot causally interact; (2) that we have sense perception of the external causes of our bodily states; (3) that we have adequate knowledge of God’s eternal and infinite essence; and (4) that the order and connection of ideas is the same as the order and connection of things. It would, thus, appear that a single axiom bears a tremendous amount of weight in Spinoza’s metaphysical system. In what follows, I will explore how Spinoza uses the axiom to argue for the four doctrines mentioned above, and I will argue that it cannot be given a consistent interpretation that allows it to play all the roles that he assigns to it. In particular, whereas there is a single interpretation that makes sense of (1)–(3), there is no way to make the causal axiom consistent with both those three doctrines and the role Spinoza assigns it in securing (4). I will argue, however, that this does not present an insuperable problem for Spinoza, because he has a better argument for the parallelism that relies not on the causal axiom but rather on mode identity. I conclude by considering the underlying