Doubt and certainty › Reading the Arguments Critically

Descartes' reasoning becomes easier to assess if you separate its steps. The certainty that I exist while thinking is one claim. The claim that my essential nature is thought is another. The claim that I can exist without a body requires a further argument. Accepting the first does not automatically commit you to all three. The same discipline helps with the arguments for God. The Third Meditation needs a causal principle about the reality represented by ideas. It also needs the claim that the idea of infinity cannot be adequately explained by a finite thinker. A reader can understand the argument while rejecting one of those premises. Calling the argument a proof records Descartes' intention; it does not remove the need to examine its premises. The Fifth Meditation follows a different route. It asks whether necessary existence belongs to the nature of a supremely perfect being. Here the pressure falls on the relationship between conceiving an essence and establishing an actual existence. Kant's criticism addresses that relationship. It should not be treated as a criticism of the Third Meditation's causal argument simply because both arguments concern God. The proof of bodies introduces another distinction. Descartes argues that bodies exist; he does not conclude that every sensory impression accurately represents them. He later considers bodily error, including thirst in a person with dropsy. An ordinarily useful bodily signal can mislead in an abnormal condition. The role of sensation in preserving the embodied person helps explain why sensory information and geometrical knowledge have different purposes. His image of the pilot and ship matters here. Pain is experienced as something happening to me, not merely as information about a machine I observe from a distance. The Sixth Meditation combines a real distinction between mind and body with their experienced union. A reading that retains only separation misses part of the account.