René Descartes is known to be the ultimate skeptic. He believes that nothing we experience can be trusted, because our senses do not show us the truth and we do not have the physical characteristics necessary to observe the truth. He concludes that everything he experiences is inaccurate. Yet he discovers that there must be an existence within him. This is because he sees a distinction between the physical world and the non-physical world. In the Descartes Meditations, he explains the fundamental differences between the mind and the physical world. The difference is that matter is an unreflective, doubtful, extended substance, which means that it extends in space. Whereas the soul is a thinking and unextended substance which cannot be doubted. My thoughts take up no space, have no mass, and cannot be divided, unlike matter. Descartes concludes that the mind and the body are two distinct things, because the mind could exist without a body and the body without a mind. Even if my body was just the product of my senses alone, I know for a fact that my spirit, or my soul, must exist in this universe. This leads to Descartes' belief that it must exist. Because he has the ability to think that he exists, this proves that he has some existence at least in the non-physical world. “I have convinced myself that there is nothing in the world: neither heaven, nor earth, nor spirits, nor bodies. Does it not follow that I do not exist? No, I surely exist if I am the one who is convinced of something” (Norman 341). This existence in the non-physical world is accessible through one's mind. Furthermore, because he has the ability to be deceived by his senses, he must therefore exist. Thought is the only necessary factor for existence. If I am a thing that "doubts, understands, affirms...... middle of paper ... like the brightness of the screen, I always have the understanding that it is the same computer with the same shape . Even though my mind, thinking of these words, is independent of the fingers typing them, they still interact to write this article. With this physical essay, I can then share the realities that occur in my mind through the physical world and into the mind of another person, the reader. Because of this interaction between extended and non-extended substances, humans can influence each other and exist together in both realities. Without this interaction, we would not have the beauty of what we call a "human", a being who can exist in both realities, sharing our ideas in order to progress towards understanding the truth. Works CitedMelchert, Norman. The big conversation. New York: Oxford University Press, 2011. Print.