Spinoza and the cosmological argument according to Letter 12

In this paper, I discuss Spinoza's conception of the cosmological argument for the existence of God (hereafter CA), as it can be reconstructed taking departure from Letter 12. By a CA, I understand, quite broadly, an argument which infers a posteriori the existence of a necessary being, usually identified as God, from the experience that there exists some other being, often oneself, the existence of which is contingent upon the existence of this necessary being. The difference between various versions of the CA stems from differences in the way in which the relation of existential dependence is understood. The aim of this paper is to reconstruct a version of the CA which would be valid on Spinoza's principles. I argue that such a version must be understood in the context of Spinoza's causal rationalism. By such causal rationalism, I mean a doctrine committed to the idea that everything is rational and thus explicable and that causal explanations are somehow fundamental. Moreover, I hold that, in Spinoza's causal rationalism, there is one form of causation through which all other types of causation are ultimately understood. This ‘archetype’ of causation is self-causation.