How does Descartes try to prove his own existence? Does he succeed?

Knowledge impregnable to doubt has always been associated with Descartes’ philosophy. However, Descartes knew that even the a priori truths of Mathematics were not indubitable. Descartes allowed it to be that a malignant demon should deceive him even with regards to those things of which he was most certain. This demon, deceiving his senses, would delude him into believing falsehoods. Descartes raised the question of whether there could be any propositions which were certain and indubitable, which could possibly have escaped the demon’s reach.

Descartes’ answer was that there was only one thing he could be absolutely certain of: his own existence. His attempts to prove his own existence involve some hilarious assumptions which make for some shaky arguments. Descartes uses these arguments to arrive at the famous cogito ergo sum: I think, therefore I exist. Although the arguments with the cogito ergo sum as their implied conclusion are weak, the cogito ergo sum itself is strong enough when finally stated in its entirety to be entirely convincing. On the whole, I believe that Descartes was very successful in proving his own existence, simply because of the water tightness of the cogito ergo sum, which far outweighed the ridiculous assumptions he made in trying to arrive at it.

First, Descartes’ arguments which lead to the cogito ergo sum will be examined. Descartes begins by doubting the existence of everything in the world. He then says that God could have put these thoughts in him, or he might have created these thoughts himself. He then implies that whether or not God or himself created the thoughts he was now thinking, the fact that he existed would follow on directly from the fact that he was thinking these thoughts. This argument is a short one and its lack of any definitions whatsoever (e.g. of God or a higher being) make for some loopholes. Firstly, if God had put these thoughts into Descartes, God would also have the power to manipulate him into believing he existed when in fact he didn’t. Secondly, Descartes seems to veer towards the notion that the thoughts he thinks have been created by himself and not God, as being essential to his final conclusion that he exists because he thinks. However, he never shows us why he is partial to that notion in the first place, which leaves the reader unconvinced of his conclusion.

The next argument Descartes uses to lead to the cogito ergo sum involves the malignant demon mentioned in the introduction. He assumed the existence of an evil demon who was always working to deceive him. He then concluded that he had to exist in order to be fooled by the evil demon in the first place. In an attempt to reinforce his conclusion, he hastily added another argument: that the evil demon could not deceive him with regards to thinking that he existed, as long as he thought he existed. Hints of his strongest argument, the cogito ergo sum, are seen here, but I think this is a rather weak argument because of the rather ridiculous concept of the existence of an evil demon who would deceive him in everything other than his own existence. Although this argument seems perfectly valid, I do not think that it is Descartes’ best proof of his own existence. It seems to be rather juvenile perhaps because of the assumptions it involves or the simplicity it represents.

The last argument for his existence Descartes presents us with is his most successful one, and the one I will discuss most in detail. Some might not even say its structure was that of an argument, but it is entirely convincing. Descartes states it in its entirety in his Principles:
“We cannot prevent ourselves from believing that this knowledge, ‘I am thinking, therefore I exist’, is the foremost and most certain that occurs to anyone who philosophizes methodically’.”[1]

The strength of this argument lies in the way Descartes made the premise, “I think”, irrefutable. Descartes could not doubt that he was thinking, he said, because the very act of doubting itself was thinking. Thinking was conceived by Descartes as a mode of which doubt was an extension. “I think” would thus necessarily be true as doubting a thought would be contributing an extension of that mode, thought, in the first place. Having a doubt would be having a thought, so to doubt that one was thinking would be to think. Hence, according to Descartes, “I think” would be a logical necessity and irrefutable.

The way Descartes defined thought was also to his advantage here. Personally, I am not so sure that doubt and thought are extensions of the same mode, thought. I can also conceive of doubt and belief simply being states of consciousness, where thought belongs in another mode altogether. Perhaps if I wanted to quibble about semantics, I could refute Descartes in that way, and restate his argument as “I am conscious, therefore I exist”. However, Descartes, having defined doubt as an extension of thought, left no room for argument there, which is one of the reasons why this argument for his existence succeeds. Descartes uses “think” to define a wide range of mental processes, including belief, so much so that the reader is misled to believe that doubt that one is thinking is in some way the opposite of thinking, and if doubt that one is thinking means that one is thinking anyway, then there can be no argument against the fact that one is always thinking and it is a logical impossibility for one not to be thinking. This only serves to make us very convinced of the truth of the premise, and should I bring up my argument about doubt and thought being different states of consciousness, I would probably have been refuted by Descartes saying that “consciousness” was what he meant by “thought” in the first place. Again, only a minor matter of semantics.

Descartes, having proved that “I think” was a logical necessity, went on to say that a thought could not have been conceived without a faculty for conceiving it. Hence, it would be a natural conclusion to make that if there was a thought, there would have been something to think it. Descartes thus concludes that his own existence follows on directly from the fact that he thinks.

The success of this argument, I think, stems not from the fact that its premise is logically true. “I am not thinking” is a logical impossibility. However, it may not be a physical impossibility. There could be a state of mind somewhere in between thinking and doubting that one thought, which could be perhaps the state of nothingness nirvana is said to represent. But Descartes seems to have the suppressed premise that one is either thinking or doubting, and that doubting and thinking belong to the same mode – thinking. He implies that there is no such thing as a state of nothingness where one is neither thinking nor doubting that one was thinking. Hence he has not considered all the factors that come into play when proclaiming “I think” to be an eternal truth. However, his argument is still very successful as “I think, therefore I exist” is in itself a logical truth. “I exist” must always follow on from “I think”, and since it is logically impossible to doubt that one thinks (note: Descartes carefully avoids mentioning the non-process of not thinking itself), “I exist” must be true.

In conclusion, I believe Descartes was successful in proving his own existence, even in the light of the ridiculous assumptions he used in the process, simply because the cogito ergo sum, being a logical truth, is immensely convincing; not least because of the way Descartes chooses his definitions of belief and doubt as well. Even though I can see a little loophole in the cogito ergo sum, it is nothing that cannot be argued away with a little semantics. After all, who would want to believe that Descartes had not existed?

[1] Rene Descartes, Meditations and other metaphysical writings, Pg 114