An ontological argument is one that attempts to prove the existence of god using reason and intuition alone. In his book, Meditations, Descartes provides his own argument for God’s existence and was the first person to do so since Anselm of Canterbury, due to St. Thomas Aquinas’ critique. Descartes later provides two objections to his argument and resolves both of them. In this paper, I will provide an explanation of Descartes argument for God and explore how he resolves each of these objections he raises against his own argument.
Descartes believed the existence of God could be derived from his nature similar to how a geometric idea can be derived from the observation of shapes. Descartes explained that his idea of God, or rather the essence of God (in the medieval definition, something can have essence yet not exist) is that of a perfect being, similarly to how he thinks of a triangle in his head as containing two right angles. However, in order for something to be perfect, it must have always existed, as existence is a integral part of perfection.
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Descartes then came to the conclusion that the existence of God and the essence of God go hand in hand. Descartes describes it as “Hence it is just as much of a contradiction to think of God …. lacking existence (that is, lacking a perfection), as it is to think of a mountain without a valley” (Pg. 46). Descartes admits that this is not a undeniable logic for the existence of God, just as sound as his previous arguments for mathematical truths. Immediately after finishing his argument for the existence of God, Descartes presents his first objection.
He returns to the metaphor of the mountain and the valley, stating that just because he has never seen a mountain without a valley, doesn’t necessarily mean one does not exist. Likewise, just because he thinks that God exists does not necessarily mean that he does. His begins his rebuttal to the objection by stating “… I cannot think of a mountain without a valley, it does not follow that a mountain and valley exist anywhere but simply that a mountain and a valley, weather they exist or not, are mutually inseparable” (Pg. 6). Descartes uses this same logic when referring to God, saying that it is not his thought that makes God exist, but rather that existence and God are as inseparable as are a mountain and a valley. He can think of God not existing just as he can think of a horse with wings, neither of which would be true. After proving the existence of God, Descartes returns to his original statement to begin his second objection. How does he know of this perfect being, regardless of its existence?
To resolve this objection, Descartes returns to the idea of geometric shapes. It is not necessary for Descartes to imagine a triangle, but if he were to ever think of a geometric shape with three angles, it would be necessary to give it all the attributes of a triangle. He claims a similar logic should be followed when determining the origin of existence. With this in mind, Descartes says “… there is the fact that, apart from God, there is nothing else of which i am capable of thinking such that existence belongs to its essence” (Pg. 47).
Descartes is saying that existence is only possible because of a being, who has existed before everything else and, since he cannot imagine two such Gods, it is necessary for this being to exist for eternity. Since there is only one being with the essence of existence, a sign of perfection, this being must then have all the other perfections that Descartes originally gave to him. Descartes began with a simple one paragraph proof for the existence of God and expanded on this by providing two of his own objections and reasons for why the proof stayed true.
He came to the final conclusion of “for what is more self-evident than the fact that the supreme being exists, or that God, to whose essence alone existence belongs, exists? ” (Pg. 47). Since Descartes used a similar method for mathematics, to him, the existence as God is as much a truth as mathematical truths. His logic was derived from an ontological argument which for God is based on intuition and reason alone. Starting with the notion of God as being fully perfect, Descartes embodied such arguments in his thinking expressed in his book.