Descartes set out to build a set of arguments designed to prove God’s existence. On those, he constructed all of his other arguments. His goal in proving God’s existence was dual; he wanted to build ground to base his arguments on, that is that he exists ...etc. That goal will not be discussed in too much depth in this paper. It is his other goal to prove beyond a doubt God’s existence to all non-believers.

Descartes starts by rejecting all his beliefs, so that he would not be misleaded by any misconceptions from reaching the truth. He notices that by doubting all of his previous ideas he is thinking in. Descartes determines that in order for him to think, he must exist. He states that he knows that to be the case beyond any doubt, and that this is the first principle of the philosophy he is seeking. From that single observation he deduces a rule that he will build his entire argument upon. Descartes notices that the idea of his existence is very clear and distinct in his mind; based upon this clarity, and the fact that he has just determined his own existence, he infers that the things that he sees as very clear and very distinct are all true.

Descartes employs another interesting rule for his logic, or way of thinking: an objective reality cannot exist without formal reality. That is to say that an idea cannot originate without a cause. The ideas can be less perfect than their cause, but they cannot be more perfect. He also explains that those ideas in us that apparently do not have formal reality, such as a mermaid, are merely combinations of other formal realities- in this case a woman and a mermaid -- and thus do not invalidate the rule.
Descartes also explains the difference between being an idea and being merely an opposite of an idea. He uses heat and cold as his example; whereas heat is an idea, cold is simply non-existence of heat. That is a very important idea that he uses in his argument to exclude a potential critique of his argument.

Descartes, after establishing his rules, explains that he knows that he is not perfect. He knows that because he doubts, and he can clearly see that knowing is more perfect than doubting. From that he determines that within him lies this idea of a perfect being, and that he is unable to come to such an idea by himself. Descartes concludes that such an idea must have a formal reality, a cause. This cause, he explains, could not have originated from a less perfect reality or being, since he has already established that ideas can be less perfect than their cause but never more perfect. He then determines that this idea could not have been composed of several ideas or causes because \"composition attests to dependence and that dependence is manifestly a defect\". And since God, or the idea of God, contains within it all perfections, God was not composed this way. Descartes also determines several qualities he deduces that God possesses simply by observing himself. He determines that whatever ideas he had, if they contained perfections then God would possess them, and if they were marked by any imperfections then God would not possess them.

Descartes’ next point is that the idea of God contains within itself God’s existence in much the same way that geometrical arguments contain their own proofs and properties. He explains that although the idea of a triangle contains within itself certain properties, such as having three sides and that the summary of all angles equals one hundred and eighty degrees. There was nothing within that idea that proves the triangles’ existence. By applying that logic, Descartes determines that since the idea of a God contains within itself existence, and as much as existence being perfect, then the existence of God, or the idea of God is at least as certain as geometrical arguments. Combining that with his ideas of objective reality he determines that God’s existence is at least as certain as anything else’s existence. God’s existence, to Descartes is at least as certain as the existence of the stars, the sky, the earth, or indeed, even more than having a body. It is unclear whether he believes God’s existence to be more certain than his own thinking.

Descartes’ main reason for proving God’s existence is this: whatever perfections he possesses are deduced from and followed by God. From that he can say that his precision and distinctness of thought derives from God such that it is certain that whatever he sees very clearly and distinctly is true.

If Descartes or I for that matter exist is certain, then the fact that I study my existence proves it. What is not clear to me is the conclusion that can be drawn from this fact. Descartes observed a quality within that truth, that is he observed that his existence is very clear and distinct, and he used that quality as a rule. Therefore, all things clear or distinct are true. That is no truer than saying that all ideas that are unclear or confusing to me are not true no matter what. Also, the existence of God depends on the precision and distinctness with which we perceive the idea of God, for if it was not clear and distinct then it would not necessarily be true. But the precision and distinctness of our thoughts depends on the existence of God. That is no less circular and argument than the one applied by the more traditional worldview mentioned in the second paragraph.

Descartes also establishes that he does have within him an idea of a perfect being and that he is imperfect. Then he uses his imperfect judgment to observe and examine ideas within him and respects them or removes them from the idea of God. By doing this he is assumes that his judgment, as to what is perfection and what is not, is as perfect as the idea of God is. For if he did not think that his judgment was as perfect as the idea of God, he would not have used it to determine the qualities that God has. Moreover, Descartes declares that he has an idea of a perfect being that is not composed, and then he examines his own ideas of perfection to compose an idea of that perfect being’s qualities.
Another problem that I found studying Descartes was his use of the concepts of formal and objective reality. For me to have an idea, it would have to necessarily exist. It is difficult to understand because just as we can think of a God, we can think of a being so absolutely imperfect that it does not exist, since existence is perfection. But since it has an objective reality, according to Descartes, it must have a formal reality, what is almost impossible.

Descartes was obviously a man of great intelligence, who influenced the course of progress of Western Civilization. His inventions in the fields of Philosophy, Mathematics, Geometry, and science as a whole are undeniable. In his work he was very modest, always states himself no more gifted than anyone, but we can feel arrogance in his conclusions. For example, only his method would deliver humanity, he will complete the debate of God’s existence, his judgment is right to describe characteristics of God, etc. I think Descartes succeeded in some parts of his proof for the existence of God, but failed in proving God’s existence from a logical point of view. The fact that there are educated men of all religions proves that anybody can be right in his own description of existence of God.

Rene Descartes, Discourse on Method and Meditations on First Philosophy.