In the Third Meditation, Descartes sets out to create and argument for the existence of God. The purpose of this argument was for Descartes to fulfill his quest to have only true beliefs. Questioning things whenever possible in order to achieve this goal, Descartes breaks down existence from the very beginning leading into the third meditation. Descartes starts off his argument by noting that if there is a God, God may be deceiving him into "matters that seems most evident". The notion that God is a deceiver is against the traditional Christian philosophy as noted throughout the bible. Judeo-Christian traditions teach that God has a Canaan with man that he has never broken so it seems as though Descartes discards this theory. Going by these traditions, Descartes has no reason to believe God is a deceiver so he inquires as to whether there is a God at all. This question leads Descartes to inquire if God does exist, is it possible for God to be a deceiver?
The argument Descartes puts forth in the Third Meditation is not only about proving the existence of God but rather to prove his own existence. As with what was spoke about in class, Descartes can doubt his body is real but he cannot doubt his soul's reality. Descartes belief basically boils down to him not being certain of anything unless all clear and distinct perceptions can be certain. This is the logical reasoning for Descartes to question the reality of God.
Descartes notes there are three sources for ideas. Ideas can be innate, adventitious coming from outside us, or they can be invented through us like our imaginations. Although Descartes cannot determine which ideas come from where yet, or if they only fall into the three categories listed above. What Descartes is most concerned about is where adventitious ideas come from, and since they are coming from outside of us, are they coming from God? Questioning this, how does Descartes even know if the ideas he speaks of are adventitious at all? How does Descartes know if these thoughts are clear and distinct perceptions as he wrote earlier?
Another clear argument Descartes makes in the Third Meditation is that no effect can be greater than the cause of it. This is another bold statement from Descartes like "I think therefore I am". To from an idea, one must have a cause of action or an effect in the brain...