Analysis of Descartes Third Meditation

The next step in the pursuit of knowledge, then, is to prove that god does indeed exist. Descartes's starting point for such a proof is the principle that the cause of any idea must have at least as much reality as the content of the idea itself. But since my idea of god has an absolutely unlimited content, the cause of this idea must itself be infinite, and only the truly existing god is that. In other words, my idea of god cannot be either adventitious or factitious (since I could neither experience god directly nor discover the concept of perfection in myself), so it must be innately provided by god. Therefore, god exists. (Med. III)

As a backup to this argument, Descartes offered a traditional version of the cosmological argument for god's existence. From the cogito I know that I exist, and since I am not perfect in every way, I cannot have caused myself. So something else must have caused my existence, and no matter what that something is (my parents?), we could ask what caused it to exist. The chain of causes must end eventually, and that will be with the ultimate, perfect, self-caused being, or god.

As Antoine Arnauld pointed out in an Objection published along with the Meditations themselves, there is a problem with this reasoning. Since Descartes will use the existence (and veracity) of god to prove the reliability of clear and distinct ideas in Meditation Four, his use of clear and distinct ideas to prove the existence of god in Meditation Three is an example of circular reasoning. Descartes replied that his argument is not circular because intuitive reasoningвЂ"in the proof of god as in the cogitoвЂ"requires no further support in the moment of its conception. We must rely on a non-deceiving god only as the guarantor of veridical memory, when a demonstrative argument involves too many steps to be held in the mind at once. But this response is not entirely convincing.

The problem is a significant one, since the proof of god's existence is not only the first attempt to establish the reality of something outside the self but also the foundation for every further attempt to do so. If this proof fails, then Descartes's hopes for human knowledge are severely curtailed, and I am stuck in solipsism, unable to be perfectly certain of anything more than my own existence as a thinking thing. With this reservation in mind, we'll continue through the Meditations, seeing how Descartes

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