Descartes and the Proof of God's Existence

The Existence of God

The problem Descartes faced was the possibility of an evil god, which threatened to invalidate all reasoning beyond his first discovered truth, "I think," since everything else could be false. Therefore, needing to rely on his reason, he attempted to prove the existence of God as a guarantee of goodness using three arguments based on the innate idea of perfection. He divided ideas into three categories:

• Adventitious: Seem to come from abroad.
• Factitious: Come from the imagination.
• Innate: Created spontaneously by reason.

Arguments for the Existence of God

• Epistemological Argument (St. Augustine): We are imperfect because we doubt, yet we possess the idea of perfection. Therefore, this idea must have been placed in us by a supremely perfect being (cause and effect): God.
• Causality Argument (St. Thomas Aquinas): We are contingent and imperfect, as our existence depends on others. Therefore, there must be a necessary first cause that is not dependent on another to start the chain: God.
• Ontological Argument (St. Anselm): God's essence implies existence, since the concept of "God" implies perfection, and existence is a necessary characteristic of perfection.

Having demonstrated the existence of God, Descartes proceeded to show His goodness. This equates to perfect truth, as lying is an imperfection; because God is perfect, He must tell the truth, which is Good.

Rebuilding Knowledge and Physical Reality

This allows for the reconstruction of the route followed in the process of doubt. After proving the existence of a good God, one can rely on reason, physical objects, and their qualities. Like Galileo, Descartes distinguishes between two types of qualities:

• Primary Qualities: Require two or more senses. We trust them because one sense can correct another if the information provided is false.
• Secondary Qualities: Require only one sense; therefore, we cannot trust them.

Finally, Descartes argues that the world is composed of three substances, each assigned a specific attribute:

• God: Infinity, as He has no limit.
• Soul: Thought, because it always produces ideas.
• Body: Extension, as it occupies a three-dimensional volume.