Descartes' Ontological Argument in Meditation V

This article shows that Descartes' ontological argument in Meditation V is needed to ground essential distinctions, particularly the mind/body distinction. It does this by tracing out Descartes' distinction between two types of falsity, and therefore truth, and the implications for the claim that all clear and distinct ideas are true. Clear and distinct ideas are formally true insofar as they represent true and immutable natures (actual essences). I argue that Descartes' ontological argument shows that existence is an essential property of God, rather than simply that God exists, a point supported by the potential objections Descartes himself raises. Insofar as God is perfect, God is unchangeable; insofar as existence is an essential property of God, God always exists. Insofar as God is the cause of true and immutable natures, the perfection and essential existence of God are necessary and sufficient to ground the real distinction between mind and body.