Descartes discusses the deception of human senses, and how things sometimes seem different than what they really are, in the third and fourth paragraphs of Meditation 1. Descartes explains how he is sitting near a fire and he is holding a newspaper. Here, he questions our senses. He says that our senses have deceived us before, but they only deceive us with things that are unclear. He says that our basis for some of the things we know and understand come from a reference due to our past sense experiences. He presents the question of whether or not his hands and his body are really real. He knows that he is in front of a fire, and holding a newspaper, but how do you know. Is it from a frame of reference, or just from past knowledge? Since our senses sometimes deceive us, do we trust them, according to him we must. He then goes on to comparing himself with the mentally insane. Maybe their minds are not distorted. Maybe their senses see things in a different way. What seems right to someone may seem inverted to another. He then states that they are demented and that if he were to take their side or accept their views, then therefore that would make him demented too. (p.232-233) .
Descartes makes reference to the mentally insane while posing the question of if something or someone is really what they seem to be. Why Descartes talks about the mentally insane, is that, he shows how the senses can deceive us. Mentally insane people may look at a person and say that that person is made of clay. Where as a "normal person" may say that they are made of flesh and bone. Who is right? This is a good example of how things can be seen or experienced through our senses. Is one person wrong, or does it depend on the eye of the beholder. Descartes presents this paradox in order to show us that what may be observed in one person can be totally different in another. He later goes on to say that he would not take the same views of a mentally ill person because they are demented, and therefore; he would then be demented too.
