The whole idea of the “Cartesian Circle” is an interesting case to look it. The main premise is that Descartes presupposes something, such as the existence of the all-perfect God, to prove that the premise is true, the existence of the all-perfect God. Many critics argue that he creates a circular argument, hence “Cartesian Circle” and with a circular argument nothing concrete is really being proven. According to the Stanford Encyclopedia of Philosophy, Descartes argument can be broken down into two main steps (Newman). The first step sheds light in the Third Meditations, where Descartes makes arguments for the existence of an all-perfect God. The second step is where Descartes takes the now established premise to argue that the all-perfect God exists. In short, Descartes is arguing that since he thinks, he exists and since he exists, an all-perfect God exists. Finally, since the all-perfect God exists, he thinks. This creates a circular argument according to his critics.
One of the objections to Descartes is in reference to the atheists. Descartes argument would lead us to believe that since atheists do not believe in the existence of the all-perfect God. The example used is the sum of the angles of a triangle equating to the angles of two right angles (Second Objections, DSW, p. 139). The critic would argue that under Descartes philosophy atheists, by default do not believe in the higher being, thus would not be able to have the knowledge to comprehend the idea that two right angles equal the sum of all the angles of a triangle.
Descartes somewhat concedes this point to dispute it. He points out that the atheists do not have true knowledge because they deny the existence of the all-perfect God. Descartes says they can garner awareness on topics such as the angles of the triangle, however true knowledge only lies within the believers who have the existence of God (Second Replies, DSW, p. 140). This is because an atheist can be deceived on matters and not realize this. Since they can be deceived they will always have doubt. An atheist could try and prove that God does not exist but “these proofs are quite unsound” and “will always be possible to point out their flaws to him” (Second Replies, DSW, p. 139-140). Essentially true knowledge only resides in those who believe in the existence of God.
Another objection is whether or not we can know for sure whether or not we are being deceived. How are we to know, as they say whether “their knowledge was as clear as the sunlight” (Second Objections, DSW p. 140). Some argue that this “clear and distinct knowledge” requires a sort of “clear and distinct explanation” (Second Objections, DSW p. 140). Based upon this how are we to know whether this is actual knowledge. For all we know it could be a very murky explanation thus creating a murky knowledge.
At the crux of Descartes response is the supreme being of God. He claims it is impossible for us to be deceived. If God is a supreme being as Descartes claims to have proved, then he “must be supremely good and true” (Second Replies, DSW, p. 140-142). A good and true God never would deceive us as people who believe in his existence. There is a reason God gives us this knowledge for he would not give it to us without a purpose. He would be a deceiver if it was his intention to cast some sort of doubt upon us. However, he has no such intention since he is an all-perfect and honest God.
A final objection is based off how we can be sure God exists because of our perception. Before we can even determine God exists, we need know what we perceive is actually true (Fourth Objections, DSW, p. 142). Essentially, Descartes argue that since what we perceive is true God exists. The critics would say that how are we sure what perceive is actually true in itself. For if God does not exist that is not true or if what we perceive is not true than God does not exist. In essence, Descartes argument is a circular one that uses the premise to eventually prove the premise itself.
Descartes claims that he is not making a circular argument. He claims to not be making the argument that because what we perceive is true that God exists. He actually is making the argument that only because what we perceive as true that the all-perfect God actually exists (Fourth Replies, DSW, p. 142-143). We are certain God exists because Descartes himself has proven this. He furthers his argument by saying that in order to perceive something as true we must perceive clearly. He claims this could be disputed except for the fact we know that the all-perfect God exists and that he is not a deceiver.
I believe it is apparent that Descartes does not make a perfect argument. However, he does make some valid points. While a circular argument may not be a perfectly valid argument it can still be a valid argument if it is applicable and true. Under the assumption of the all-perfect God we can decipher a lot of things. For if God was not perfect how would we know what we see before our eyes is actually true and not an illusion or trick played upon up by the evil demon? If God did not exist we would never be able to say with clarity that humans have two hands and that what we see is actual reality. Otherwise we could be in some sort of dream state as utilized in Inception where we do not realize that our world does not exist. Or we could be in some sort of computerized farm where the Matrix is only a figment of our imagination. We would be deceived in these cases and if we were deceived nothing we would know would be true and therefore God could not exist for a true God would never deceive us as such. Therefore if we take the premise of everything we perceive as true God must exist. And if this God does exist we are ensuring that was we perceive is absolute, clear, and true.
The “Cartesian Circle” is a debate that has been introduced and will continue to be utilized in the future. In brings into question the existence of God and the effect of denying this existence. Descartes is of the belief that for everything we perceive to be absolutely true God must exist, for if he did not exist, we could not perceive any truth. Critics would argue that this is a circular and thus invalid argument. While they have a point, if we can claim God exists then the argument does not become so circular. In fact it creates a fair and valid argument. Ultimately, Descartes is creating an argument with the purpose of proving the existence of God so that he can further solidify the world we live in as a reality and not a mere illusion.

Works Cited
Descartes, René. Descartes: Selected Philosophical Writings. Trans. John Cottingham, Robert
Stoothoff, and Dugald Murdoch. Cambridge: Cambridge UP, 1998. Print.
Newman, Lex, "Descartes' Epistemology", The Stanford Encyclopedia of Philosophy (Fall 2010
Edition), Edward N. Zalta (ed.), URL =
<http://plato.stanford.edu/archives/fall2010/entries/descartes-epistemology/>.