Second Response to Descartes
Descartes’s chief reason for rejecting an Aristotelean view of existence is that he does not trust his senses. He says that they often deceive him, particularly when he is attempting to perceive objects from a distance or when he is dreaming. These discrepancies lead Descartes to construct an entirely new philosophy, rationalism, in which the only thing of which man can be sure is his mind and the existence of God. Descartes’s arguments against trusting the senses are unconvincing because he misunderstands the natures of the senses and sleeping.
The senses sometimes deceive us, but this is not because they are flawed. For physically normal people, they are infallible tools merely for giving us raw information about things like light rays and sound waves. We must use our mind to process this information for ourselves.
Descartes’s most compelling argument against the senses is that the world of dreaming, when we are in it, seems just as real as the world when we are awake. At the end of his sixth Meditation, however, Descartes notes that sleeping is clearly different from reality because in our dreams, we cannot use our memories. Thus, he undermines his own argument that we cannot trust the senses and can believe this is the real world.
When one eliminates dreams as a source of information about the real world, one loses the most compelling argument that man’s senses are fallible. The only doubt one can raise is arbitrary. If I cannot provide any evidence to support my claim, I have no reason to make other people believe it. This is a problem for Descartes’s philosophy.