IN THE Second Meditation, Descartes discovered that his own existence is a condition of his engaging in inquiry guided by the method of doubt, and he used the doubts of the First Meditation to discover new ways to describe his nature and his states. In the Third Meditation, he goes on to argue that, ultimately, the existence of God as his creator is a condition of his engaging in inquiry guided by the method of doubt. This enables him to judge with complete certainty that God created him, and thus that everything he understands clearly and distinctly to be true, is true.
The existence of God, then, is an outer condition of Descartes's doubt. Of course, God is not outer in the sense of occupying a space that is somehow outside the doubter: God does not occupy any space at all. Rather, God is outer in the sense that he is something distinct from Descartes and his states. In most of this chapter I will be concerned with the argumentative steps that lead Descartes from doubt to God, but at the end I will look briefly at the character of the argument that leads Descartes to absolute certainty that extended things exist. Like God, extended things are “outer” objects in the sense that they are distinct from the meditator and his own states; unlike God, they occupy space.
Descartes's argument in the Third Meditation for God's existence is a sort of cosmological argument, moving from a contingent premise about what exists to the conclusion that this could not exist unless it were caused to exist by God. Descartes actually gives two somewhat distinct cosmological arguments in the Third Meditation, the first inquiring into the origin of my idea of God, and the second into the origin of me. But my idea of God cannot exist without me, and the second argument turns on the point that I must have an idea of God. So both arguments have much the same (compound) contingent premise: I exist and have an idea of God. Both arguments are powered by principles concerning causality; it is those principles that, when applied to the contingent premise, yield