In Meditations on First Philosophy by Rene Descartes, he discusses his doubt, his existence, and the existence of God. In the First Meditation, Descartes sits by a fire and thinks about things he believed but came to know were false. After this he clears his mind so he can build his opinions back up again from the ground. "Accordingly, I have today suitably freed my mind of all cares, secured for myself a leisurely tranquility, and am withdrawing into solitude. At last i will apply my self earnestly and unreservedly to general demolition of my opinions."(Descartes. 13). Descartes states that he has accepted that most of what is true he can perceive through his senses. But he states that at times your senses can deceive, but with only regard to objects that are small or at a distance. He believes that you can not doubt simple or universal things such as arithmetic or geometry, but you can doubt things such as "physics, astronomy and medicine"(Descartes, 15) because they are dependent on other things unlike arithmetic and geometry. Lastly in Descartes Meditations One he states that a God must exist because if God didn't exist there is a greater chance of us being deceived by our senses since they would not be created by a perfect being.
I can mostly agree with Desecartes on his concept of doubt with regard to the senses, mathematics, and science. What we see, feel, touch taste, and smell (without regard to those that suffer from hallucinations, delusions and things of that sort) must be true because that is how it is perceived the world. If we doubt our senses then the world we live in and everything around us would be subject to question. As for his thoughts on mathematics, I believe he is correct because they are based on concrete structure, for example two and two will always be four. I also agree with Descartes that science can be doubted because science is based on theory, subjects that are not based on a solid structure or truth.
In Descartes' Second Meditation he takes up the subject of his existence. He recalls on his first meditation asking what if his senses are defective and if what he sees does not actually exist. He also pretends that he lacks a body and senses . He discovers that since he is thinking these things, he must exist. "Here i make my discovery : thought exists, it alone cannot be separated from me . I am; i exist - this is certain."(Descartes,19). He also questions what is "I", what does that make him. He doubts all of his aspects except for one, that he thinks, and decides the he is only a thinking thing.
I agree that as human being an important part of our existence is our thought . But i feel that to say we only exist because we think is absurd. For example, if a person gets into an accident and is brain dead, this person may not think, but still exists in the real wold.
