Doubt as a Method, and the Proofs That Follow

Descartes wanted a foundation that could not be shaken, so he set out to reject anything open to the least doubt, and pushed the doubt as far as it would go: the senses deceive, dreams are indistinguishable from waking while they last, and even mathematics could be the work of a powerful deceiver bending the mind at every step. What survives is that the one being deceived must exist in order to be deceived. From that single point the Meditations builds outward, and the first thing it builds is God.

There are two arguments and they are different. The first observes that a finite mind contains the idea of something infinite and perfect, and holds that such an idea cannot have been produced by the mind that contains it, so its cause must be what it represents. The second, in the fifth meditation, argues from the concept of a perfect being to its existence in the manner of the older ontological proof. Both are load bearing, because the reliability of clear and distinct perception is what the whole reconstruction rests on and God is what guarantees it. Contemporaries objected at once that this is circular, since the proofs themselves are known clearly and distinctly, and the objection has never been fully disposed of. He dedicated the work to the theology faculty of the Sorbonne and meant it to serve them.