The existence of God is basic to the philosophy of Rene Descartes. Because Descartes’ philosophy depends on skeptical arguments which are essentially subjective, it is important for the thinker to not be deceived. A demon or devil would undoubtedly attempt to fool the thinker; however, God would not lead a person into false avenues. God is perfect, and a perfect Being would not deceive, or else God would lack perfection, which would be an impossibility.
Descartes’ proofs of God are primarily scholastic in their configuration. There are two proofs of God that Descartes uses: (1) The ontological argument for the existence of God, which was first developed in the eleventh century by Saint Anselm, who was perhaps the greatest theologian ever to have been the Archbishop of Canterbury; and (2) The first cause argument, which was one of the proofs developed by Saint Thomas Aquinas by way of Aristotle.
Besides being Archbishop of Canterbury, Anselm was a member of the Benedictine Order. Anselm describes God as a Being who is so perfect that further perfection would be impossible to imagine. Thus Anselm states: “So truly, therefore, dost thou exist, 0 Lord, my God, that thou canst not be conceived not to exist; and rightly. For, if a mind could conceive of a being better than thee, the creature would rise above the Creator, and this is most absurd” (Mavrodes and Hackett 95-96).
Rene Descartes reformulated Anselm’s ontological argument so that it is assumed that existence is a property or predicate. Descartes explicitly treats existence as a characteristic, the possession of which by a given x is properly open to inquiry. The essence or defining nature of each type of thing includes various predicates, and the ontological argument of Descartes insists that existence must be included among the defining predicates of God. In other words, God without existence would not be God. In Meditations V, Descartes asserts: “While from the fact that I cannot conceive God without existence, it follows that existence is inseparable from Him, and hence that He really exists; not that my thought can bring this to pass, or impose any necessity on things, but, on the contrary, because the necessity which lies in the thing itself, i.e. the necessity of the existence of God determines me to think in this way” (Wilson 205). This is the ontological argument for the existence of God.
Another theistic argument used by Descartes was initially developed by Saint Thomas Aquinas through Aristotle; and this is also a dialectical proof of God that is known as the first cause and cosmological conception of God’s existence. Aquinas arrived at five ways of proving the existence of God. First of all, there must be a Prime Mover; secondly, there must be a causation from a First Cause; thirdly, from a Necessary Being, there are contingent beings; the fourth proof is from degrees of value to Absolute Value; and the fifth proof arises from evidence of purposiveness in nature to a Divine Designer (Mavrodes; and Wilson 103-112).
Aquinas’ proofs commence from some general feature of the world around us that is revealed to our senses, and arrive at the conclusion that there could not be a world with this particular quality unless there were also the ultimate reality known as God. According to Aquinas, either there is a First Cause or the universe is ultimately unintelligible.
Descartes formulates a similar proof of God in his Discourse on Method. God would not deceive, or else He would not be perfect; deception would be an imperfection and could not be a part of the theistic purity of Infinite Wisdom. God, as the Prime Mover, has given us the ability to discern the true from the false. As Descartes states: . . . all the things which we clearly and distinctly conceive are true, is certain only because God is or exists, and because all that we possess is derived from him . . . . ” (Descartes 41). Descartes, Meditations III also contains a proof of God similar to that of Aquinas.
And so these two arguments for the existence of God form the basic foundation for Descartes’ philosophical conception of things. When God’s existence has been proven, the remainder of Descartes’ philosophy proceeds smoothly. Because God is perfect, He will not behave as a deceitful devil. God has given Descartes such a strong inclination to believe in bodies, that He would be perpetrating a falsehood if there were none; consequently, bodies exist. God also must have provided Descartes with the faculty of correcting errors; and he uses this faculty when he employs the concept that what is clear and distinct is true. This enables Descartes to understand mathematics, and physics also, if he remembers that he must know the truth about bodies by the mind alone, not by mind and body together.
Cartesian doubt, then, proceeds to be skeptical of everything except the thinker’s own thought. Thus Descartes arrived at the idea-: “Cogito ergo sum” or “I think, therefore
Although Descartes eliminates everything, he can at least think. Thought is the one thing that exists, and he has no doubt that he is thinking; and because God exists and is perfect, Descartes can be certain that God would not deceive him with regard to the truth of this. As Descartes says in his Discourse on Method: “. . . as I observed that this truth, I think, therefore I am was so certain and of such evidence, that no ground of doubt, however extravagant, could be alleged by the skeptics capable of shaking it, I concluded that I might, without scruple, accept it as the first principle of the Philosophy of which I was in search” (Descartes 35).
Descartes’ “I think, therefore I am” established the certainty of his individual self. From there, knowing that God would not deceive him, Descartes moves beyond himself to know that the world is real. There is an actual, material world; otherwise, God would be allowing us to live continually with a false concept. God, as a Perfect Being, would not fool us into believing something that is not true. Therefore, the existence of the material world is really true, and there is no need to have any doubts about it.
Thus Descartes moves from total doubt to complete belief in the existence of spirit and matter. However, another problem is raised: How can spirit move matter? Descartes answers this by affirming that God intercedes between the mind and matter.
This is Cartesian dualism in which the body and mind are like two clocks which operate independently of one another. When the mind wills an arm or a leg to move, the mind thinks the thought that seems to move the limb; however, the limb has already been programmed by God to move just at the same time the mind desires it to move. God plays an all important role as the foundation for Descartes’ system of philosophy.