Descartes claim of ‘Cogito ergo sum’ marked a sharp departure from what philosophy was in his time. He started from the basic principle of rationalism and he concluded that ‘I think, therefore I exist’. In his Meditation II, Descartes hits an epistemological ground zero. Here it is that Descartes begins his startling point, “And thus, having reflected well, and carefully examined all things, we have finally to conclude that this declaration, Ego sum, ego existo, is necessarily true every time I propound of mentally apprehend it.” In this statement he affirms his existence and later concludes that he was a res cogitans -- a thinking thing, “that is to say a mind, an understanding or reason-terms of significance of which has been hitherto been unknown to me. I am a real thing, and really existent.” Descartes broke with old philosophy and gave it a new beginning. In particular, because his system of truth originated from his own thinking and analysis, he no longer desires to rely on ideas of previous philosophers. He is clearly determined to find out the basis of intellectual certainty in his own reason. In proving Descartes ‘Cogito’ I will use to prove God’s existence.
Descartes intuits this self-evident proposition and at the same time simultaneously infers his own existence. By an act of simple mental vision, he clearly and distinctly perceived that he exists from a clearly and distinct premise about what he thought. The Cogito for him meets the criterion of truth that he previously formed. This proposition cannot be undermined because it is a privileged truth and is not subjected to the ‘evil genius’. Such a truth is also indubitable. It should be stated out here that he was thinking not so much in the order of existence but rather in the order of knowing.
While taking the cogito ergo sum as an indubitable truth, Descartes then needed ‘to prove the existence of a God who was not a deceiver to be able to apply universally and confidently the criteria of truth that is to say the propositions which he perceives clearly and distinctly cannot be subjected to doubt.’ Thus the existence of a non-deceiving God becomes the guarantor of all the truths that he apprehends. Descartes is also stymied from proving God’s existence using senses or for that matter anything extra-mental since at this stage he is simply a “thinking thing’
I agree with Descartes when he states that he does not see any reason to believe that there is a God who is a deceiver. To prove this he examines those ideas that he has in his mind. For him, some are innate and others he deems as adventitious-meaning that they are foreign to him and come from the outside. The other kinds of ideas are the ideas which he had invented. There is a distinction between the ideas that exist formally and those that exist eminently. Something that exists formally as the cause of the objective reality of an idea has an exact correspondence of the idea of it in the mind; on the other hand things that...