Abstract

In the Principles of Philosophy, Descartes makes a remarkable claim that has never received the proper recognition it deserves. He asserts that there is merely a "rational distinction" between a substance and each of its attributes. I argue that, properly understood, this claim means that a substance and each of its attributes are numerically identical in reality, and distinguished only within our thought by means of reason. I then use this central insight to resolve a number of apparent inconsistencies and interpretive puzzles that have plagued Descartes' philosophy. ;The most important of these problems concerns Descartes' theory of essences. In the Fifth Meditation, Descartes claims that certain objects such as geometrical figures have "true and immutable natures or essences" that do not depend on the mind, yet have being even if there are no such things existing in the world. On the basis of this statement, a number of influential scholars have concluded that Descartes is a Platonist regarding essences and in the philosophy of mathematics. One problem with this seemingly natural reading is that it contradicts the conceptualist, anti-realist strain that one finds in his other works. I enlist the theory of rational distinction to show decisively that Descartes is a conceptualist regarding essences and all universals. ;The theory of rational distinction illuminates several other features of Descartes' ontology as well--including the status of attributes and their distinction from modes, the notion of substance, the relation between essence and existence, the nature of space, the doctrine of divine simplicity, and the notion of a principal attribute. ;My central thesis also reveals that the so-called ontological "argument" is not a formal proof but the assertion of an intuition akin to the Cogito. I confirm this interpretation by investigating a poorly understood method called "analysis" employed in the Meditations. Descartes holds that the greatest impediments to knowledge are various philosophical prejudices that obscure and confound our innate ideas, particularly our innate idea of God. Analysis is the method for dispelling these prejudices. Once they are removed, God's existence is more self-evident than the simplest mathematical truth