In his Discourse on Method and Meditations on First Philosophy, Descartes looks back on his life and realizes that a great number of his opinions have been false. Subsequently, the knowledge he has built up over his life must also be markedly false, seeing as it is based upon such incorrect opinions. He resolves to restart his quest for knowledge from the bottom, building a philosophy to be the foundation upon which all further intellectual knowledge can be built. Descartes proposes that there is a distinct difference between truth and belief, and that all he can know o be true is the existence of his own mind.
Descartes plans to remove all uncertain beliefs, making sure that the beliefs constituting his philosophy are absolutely true. He calls this the Method of Doubt, and says that to go through his opinions and reject them one by one would take too long and be futile. Therefore, he dismisses all of his opinions that have something about them of which he is not one hundred percent sure (can be doubted). More specifically, Descartes suggests the rejection of the doubtable foundations and basic principles upon which all his other opinions are founded.
In the examination of his beliefs, Descartes first argues that one cannot trust the senses. Everyone has at some point been deceived by his/her senses into thinking that something seemed good looking from a distance, but was actually very ugly when seen up close, or food that looked very tasty turned out to be disgusting. Descartes doubts his senses because he knows that they have tricked him before and gives the example of something looking small from a distance but large when up close. In addition to doubting his senses, Descartes also doubts whether anything he is experiencing is real.
He claims that he might be dreaming everything, because sometimes dreams seem as real as our “waking perceptions. ” Descartes realizes that while dreaming, he is often convinced that he is sensing real objects. He feels certain that he is awake and sitting beside the fire, but contemplates that he has often dreamed this very sort of thing and been fully convinced by it. If there is no way to determine whether he is dreaming or not, then he has no way to determine if anything he is experiencing is real. The third and final argument in the Method of Doubt is that of the evil, deceiving demon.
Assuming that he may be dreaming, Descartes first suggests that even dream images are drawn from waking experiences, just as paintings are representations of real things. He thus concludes that we can doubt complex things like paintings, physics or medicine but cannot doubt the simple things from which they are constructed like shape, geometry, quantity, size, arithmetic and time. Upon further thought however, Descartes concludes that even simple things can be doubted, because there could be a malicious God controlling his perceptions and making him hallucinate or dream that he is experiencing reality.
Based upon this, supposed “truths” of reason, such as mathematics (e. g. 3+7=10) may be wrong because of an evil God trying to trick us all. Thus, Descartes cannot be certain that any of his beliefs are true because there is always the possibility that an evil demon is constructing such illusions to fool him. If we suppose there is no God, then there is even greater likelihood of being deceived, since our imperfect senses would not have been created by a faultless being. By doubting everything, he can at least be sure not to be misled into falsehood by this demon. Following his arguments in Meditation I, Descartes starts Meditation
II with the assumption that he has no senses, and that body, movement and place are all non-existent. He then declares that he has found a belief that holds up to the Method of Doubt. This belief is that he exists; “Cogito, ergo sum” – I think, therefore I am. Though Descartes is assuming that his physical body does not exist, his mind does exist because it is thinking. Also, based upon the idea that a God is putting the thoughts in his head, Descartes says that while he may indeed be misled by an evil demon, there must first exist something for the demon to mislead.
This seems to contradict Descartes’ Method of Doubt. If he says that everything can be doubted, why can’t he doubt also that he exists? One way to understand this is to say that just articulating the words “I exist” proves his existence. If he did not exist then he would not be able to say that he did. However, he can only say that he exists; he can not say that anybody else exists because he has no way to know, and he can only say that he exists right at this moment in time. It is not possible for him to say, “I thought, therefore I was,” because he does not know whether he really did think previously.
Descartes cannot doubt that he thinks either, because doubting is a form of thought. How does Descartes know that this “I” exists, if he cannot trust his senses or his imagination? If he exists only as a thinking thing, then why does he have such a grasp of what his body is and yet have so much trouble identifying what this “thing” is that thinks? To answer this question, Descartes describes the way in which he comes to know a piece of wax. He knows that it is still wax, no matter whether it is warm and melted or cold and hard, whether rolled in a ball or melted flat like a puddle.
Descartes does not come to know this through the senses because the wax looks and feels different in each instance. He also recognizes that he cannot know it through his imagination either, because he cannot imagine all the different shapes that wax can change into. Therefore, he reasons that he must know the wax through clear and distinct intellectual perception alone. Without the intellect, we would not be able to make sense of what we perceive. From the wax argument, Descartes goes on to say that although he cannot know that what he perceives is real, he can know that he exists ecause sensory perception is a type of thought.
Every perception he has validates his existence, while further casting doubt on the existence of objects outside his mind. Descartes thus concludes that he knows the mind better than he knows the body. The second meditation raises several questions. Firstly, how does Descartes know that all thinking things exist? He does not give an argument for the proof of the existence of thinking things. How does every sensory perception validate Descartes existence but cast doubt on material objects? Also, what does Descartes define as clear and distinct perception nd how does it yield its epistemic guarantees?
According to Descartes, all beliefs based upon experiences and perceptions are doubtful because we can never be sure that they are not illusions or hallucinations. It is not possible to say that my backpack is full, or even that the backpack exists at all, or that my bedroom which it is in exists either. I can not even know that my body is typing this paper, because my senses could be deceiving me, I might be dreaming, or a misleading god may be tricking me. The only thing I can truly know is that I think and that I exist.