Descartes' methods in meditations are self-contradictory at the deepest level. On the one hand, he states that he will disconnect himself and his thoughts from all outside influence, forget his preconceptions, and proceed to think in a completely detatched fashion, using reason alone, to determine the true nature of reality. At the same time, he admits, (even boasts) that the purpose of the meditations is to prove, once and for all, the existence of god. The conflict between these two stated aims is never quite addressed.

He does attempt to prove that the existence of god is an innate idea with no root in external influence, and thus the idea of the existence of god is an innate idea, and hence his desire to prove this comes from internally, not externally. His argument here, however, is very shaky and is clearly coloured by his previous preconceptions. It also relies on the duality of mind and body, more of which later. His preconceptions are clearly illustrated in his letter to the Sorbonne, the faculty of theology at Paris;

His ideas about the duality of mind and body have also been completely discredited, for me, by modern neurology, and also by psychoactive drugs, which can both clearly show how thought processes can be affected by physical happenings in the outside world, without the senses themselves having to be decieved.

Actually, reading Meditations, I was shocked at how widely known and respected this work had become. There are two possible explanations for this. Perhaps the ideas behind the stated methods were strongly influential in western philosophy, even if the implementation of them in this case was dubious, to say the least.

Or perhaps it just goes to show the power of a good catchphrase!