Descartes was a great thinker, philosopher. To be honest, I have no idea about his philosophical idea until I read this article, I must admit to feeling ashamed. “I am thinking, therefore I exist” (15) which is the main idea through his whole article. Descartes tried to find a thing can above of the individual senses, universal point of view, even in science, mathematics theory of the “absolute truth”. And he found that in all these human cognitions can be reasonable to doubt. My personal understanding about “doubting” is the way of thinking, when I doubt whether I was, I had been thought. Therefore, I absolutely cannot doubt myself if I am thinking. Thinker is a subject, so the main body of thought of “I” must be exist. “Where did I get my ability to think of something more perfect than I am?”(15). Descartes’s answer is “[so] the only possibility left was that the idea had been put into me by •something that truly was more perfect than I was •something indeed having every perfection of which I could have any idea, that is—to explain myself in one word—by •God To this I added that since I knew of some perfections that I didn’t myself have, I wasn’t the only being that existed” (16). Through that quote, Descartes’s idea of perfection is coming from God. For me, it’s hard to agree and understand his belief. I was grown up in Buddhism culture, but right now I am an atheistic man since I began touching science knowledge in school. In my opinion, we can use Descartes’s doubt theory to doubt and assume that God exists. In fact, the result of our assumptions are we don’t have any proofs to prove that god exists. Since we are human being, we absolutely cannot be a perfect man, the God, who is the perfect being in Descartes’s mind. Whereupon we can say that the perfection does not exist, just like I am doubt the God does not exist.