Meditation III In Descartes Third Meditation, he establishes arguments to prove the existence of God. Descartes believes in "Cogito Ergo Sum" this means I think therefore I am. The "I" in this sentence means the soul. Descartes believes the existence of the mind is better known than the existence of the body. If my soul thinks then I exist. The Cogito proves the existence of self or the mind; this is not the same for the theory of God.
Descartes has two arguments in the Third meditation. The arguments are the cause of his idea of God and the cause of his existence now. In the third meditation Descartes uses his existence as an example to find out whether God exist. Descartes explanation is whatever he perceived clear and distinct is true.
The idea of the existence of God could have been caused by something out side of himself. Something had to put the idea of God in his mind for him to think about the existence of God. Descartes says, "I must examine whether there is a God, and, if there is, whether he can be a deceiver. Descartes has to prove that God exists and that he is no deceiver. Descartes then explains that the idea of God is the idea of a perfect or Supreme Being. A perfect being could have set this idea in our minds.
He discovers that a perfect thing exists and that perfect being is defined as God. Descartes says, "All these attributes are such that, the more carefully I concentrate on them, the less possible it seems that they could have originated from me alone. So from what has been said it must be concluded that God necessarily exists." Descartes also reveals that God is not a deceiver. Descartes knows that a perfect being has no faults. Deception depends on some defect or fault.
Therefore, if a perfect being has no faults then that perfect being can not be a deceiver. In Descartes Third Meditation he believes, that the idea of God exists. An eternal being is a positive concept. If we have an idea of a perfect being then some how this perfect being must exist. Example: "I know that a million dollars exists even though I have never seen a million dollars, I have an idea of it." Descartes concludes that God is not a deceiving being because a perfect being is pure.