A formalization of Descartes’ causal argument for existence of God

In this paper I attempt a formalization of Descartes’ causal argument for the existence of God presented in the Third Meditation. By taking into account the philosophical setting of Descartes’ Meditations, I argue that the best logical theory to carry out the formalization is quantified modal logic where free logic is used for the first-order axioms. This fact is related to Descartes’ distinction between formal and objective reality which — to my mind — suggests both the adoption of modality (e.g. true in formal vs true in objective reality) and the possibility of using empty names (i.e. names which lack reference in “formal reality”). After presenting the formal system and the reconstruction of Descartes’ proof, I will discuss some issues related to the philosophical import of the formalization, such as the understanding of rigid designation and lack of reference. I will argue that the formalization of Descartes’ argument has an intrinsic philosophical value for it sheds light on the structure of argument, its implicit difficulties, and the use of logic itself to understand the philosophical tradition.