Descartes occupies an important place in western philosophy. He starts philosophy at a time when it had dried out by the end of 1600 AD. He wants to find a foundation on which other knowledge could be built. Thus, he can be thought of as a foundationalist. He believes in the Plato’s idea that ‘knowledge requires certainty’. But at the same time, Descartes rejects Plato’s ideas that the physical world is not knowable. In fact, he tries to build a certain and stable foundation to know the physical world.
At the time when there was rejection of Aristotle by the contemporary western philosophers, Descartes remains a rationalist. While the contemporary philosophers like Locke, Berkely, Hume and others started and became a part of the empiricist movement; Descartes is still in Aristotleian tradition. Descartes is the champion of what is called as mechanistic philosophy. He argues that the world is a giant machine. Objects do not move themselves, rather one movement leads to another. Thus Descartes focuses on causality.
As stated earlier, Descartes believes in certainty. He is looking for a stable foundation which is certain and which cannot be doubted so that he can use that as a base to build upon knowledge. In this process, Descartes comes up with the ‘Method of Doubt’. According to the method of doubt, anything which can be doubted is false and hence that cannot be used as a foundation for building knowledge:
“For the purpose of rejecting all my opinions, it will be enough if I find in each one of them at least some reason for doubt
However, it must be noted here that Descartes does not actually believe that the things which can be doubted are literally false. It just means that Descartes discards them of being capable of providing a foundation or being used in a valid argument. Descartes believes that if he can find something which is not doubtable in this sense, it can be used in a valid argument to build the knowledge of the physical world.
In order to search the ‘undoubtable’, Descartes starts with doubting the three faculties by which we come to know the world and the things. These faculties are the senses, the imagination, and the reason or understanding. He starts off by doubting the senses. His argument is that the senses are unreliable and hence cannot be used as foundation. We might get into an illusion by our senses. For example, the scientific experiments of optical illusion prove that we might be misled by our vision. Similarly, we can be misled by other senses. Since the senses are unreliable, they cannot be the foundation.
Now Descartes moves on to doubting the physical world. To doubt the physical world, he uses the argument that he could be dreaming that he is in the physical world. And thus, the physical world becomes an imagination of the mind. Similarly, he extends this argument by saying that this possibility cannot be ruled out anything or any experience in the physical world.
Further in order to doubt the physical world, Descartes introduces the idea of the ‘Evil Genius’. The evil genius has the powers of the God but he is not God. The evil genius can deceive us about the physical world. It is possible that the evil genius created illusions all around. Even the stars, the sun and all the celestial bodies are illusions created by the evil genius. However, it must be, once again, noted here that Descartes does not believe that the evil genius really exists but he is just using this argument to doubt the physical world. According to him, this is a possibility which cannot be ruled out.
Finally, Descartes doubts the disciplines like physics, astronomy, medicine and all the others which are based on the study of composite things. He doubts the simple and general disciplines like geometry, arithmetic on the grounds that these are study of things whose existence in this world is doubtful. He takes the example of a math problem and says it is possible that everyone is making a mistake in solving the problem and no one in the world is aware of the mistake. To understand this argument better, let us look at the following math example:
Let us assume, x=1
ð x = x^2 -1
ð x-1 = (x-1)(x+1) [Expanding the RHS]
ð 1=x+1 [Dividing both sides by x-1]
ð 0=x [Subtracting 1 from both sides]
ð x=1 & x=0.
Hence, it is proved that 0=1.
However, there is a mathematical error (dividing both sides by x-1) in the above example, it is very difficult to figure that out for someone who is not adept at mathematics. Similarly, it is possible that we all are doing some mathematical errors everyday without realizing it.
Thus, Descartes rules out all the truths which are derived from senses or imagination and eliminates almost all the truths which are derived from logical reasoning or understanding. And this elimination takes places by doubting those truths. However, he says that there is one thing which is certain. He cannot doubt his own existence. When he doubts, he must exist. Even if there is an evil genius who is deceiving him into illusions, even if all the mathematical reasoning has got some unknown mistake, but the fact that he is able to think about these means that he exists. The evil genius cannot deceive him till he is not there in existence. So when he is thinking, he knows that he exists which cannot be doubted. Hence, he finally concludes
As stated earlier, Descartes is looking for a foundation on which he can build other knowledge. ‘Cogito ergo Sum’ is the foundation on which he can build all that he doubted. This piece of knowledge has the quality which he calls as being clear and distinct. He says that an idea is clear if it manifests to an attentive mind. This means that if one is awake, attentive, well fed and not distracted, one would be able to see that it is true. He further adds that an idea is distinct if it contains nothing but clear ideas. ‘I think, I exist’ is self evidently clear and distinct.
In the next step, Descartes extends what he has discovered till now. He knows that he exists and the essential characteristic or requirement of his existence is the fact that he thinks. This means that it is possible for him to exist without a body but existence without a mind is not possible. However, it must be kept in mind that by thinking, Descartes means anything which is a mental activity. It may include seeing, feeling pain, believing that two plus two is equal to four etc. Thus, when Descartes says that ‘I exist’, he actually talks of the existence of his mind.
The proposition ‘I exist’ comes from the fact that ‘I think’. It means that Descartes has assumed that I exist before he could prove the existence of ‘I’. Moreover, there is another assumption in this case which says that thinking things exists. There is no reason given by Descartes on why or how thinking things exist.
There is some certainty in the proposition ‘I exist’ but there lie many ambiguities on the grounds of assumptions taken in the proposition ‘I exist’. The first one comes from the argument that I exist because I think. This means that Descartes has assumed that the thinking things exist in the world. However, he has never mentioned or proved the existence of ‘thinking things’ in his arguments. The second assumption is that the process of thinking is believed to be done by ‘I’. By saying that it is ‘I’ who is thinking, Descartes has not considered the fact that the thought which is passing through ‘I’ might be something which is put in it by the evil genius. Thirdly, as Soren Kierkegaard says, Descartes has inherently assumed the existence of ‘I’. It is also possible that this ‘I’ is something which is part of the evil genius which is controlling the body and our experiences of the physical world. This means that there might be no existence of ‘I’. Thus it is wrong to assume that the ability to think is in the mind as it can be a part of the evil genius. Moreover, Descartes says that ‘I’ can exist without a body but ‘I’ cannot exist without a mind but he has not shown how the mind can exist without a body. This is something which Hobbs also points out in his argument.
Using Descartes principles of Cogito, we can also think of the existence of man-made robots and computers. Since robots are capable of thinking and taking their own decisions in different situations, so we can assume that robots also exist. But it becomes difficult to explain how a machine exists which was assembled by human body whose existence is doubtful.
Though the above arguments question the existence of ‘I’ but these arguments also accept the existence of something in which the thoughts are being put by the evil genius. And if we consider the possibility of ‘I’ being a part of the evil genius, we also arrive at the certainty of the existence of the evil genius. If we consider the existence of ‘I’ with a mind, it is unclear how it can exist without a body. Thus, it can be concluded that there is something which exists but its nature is unclear and arguable.
Brown, Dr Richard. Descartes-1, Method of Doubt. 29 July 2012, youtube
Descartes, Rene. Meditations on First Philosophy [Meditations de prima philosophia, 1641], Meditation I and part II. Trans. J. Cottingham. Cambridge: Cambridge University Press, 1986, rev, edition 1996.