Descartes' Ontological Argument: From Radical Doubt to the Existence of a Supreme Being

    Descartes’ argument is grounded in what is predicated of God. For example, the predicate of existence is derived from idea of a supremely perfect being and such a being must have the predicate of being a necessary existence. Descartes often compares his ontological argument to a geometric demonstration by arguing that necessary existence cannot be excluded from idea of God any more than having three sides can be excluded from the idea of a triangle. Therefore, the existence of God is ‘a priori’ for Descartes, or is axiomatic, or known without experience. It seems like it is a counterfactual dependence, or by definition. For example, if one has a pair of birds, it is by definition that if there is one bird, there must be another to complete the pair. In the same way, if there is a supremely perfect being, it must have the predicate of necessary existence otherwise there would be a contradiction of terms. 

    For Descartes, the premises and the conclusion had to be a priori due to his ‘radical doubt’. Descartes aims to doubt anything that can be doubted. The idea is to strip away all beliefs that might be based on faulty reasoning or unreliable senses, in order to arrive at a foundation of knowledge that is certain and indubitable. He doubts things such as the physical world, his imagination, and even mathematics. However, Descartes concluded that despite all these errors with senses, reason, reality, and math, as long as there is the first-person experience of thinking, he exists. “I think therefore I am” (Cogito, Ergo Sum). As long as one is thinking, they exist. 

    How can one have the concept of eternality if no human has lived forever? Descartes concluded that something greater than him exists, God. Then he assumes that if a powerful being created him, the powerful being would not create him in deception, therefore reasoning, math, reality, and senses return. He did not begin with God to philosophize about the self, he began with the self to reach God. 

One is able to attain knowledge of God’s existence by apprehending that necessary existence is included in the idea of a supremely perfect being. As Descartes writes in his Fifth Meditation,

 

“But if the mere fact that I can produce from my thought the idea of something entails that everything which I clearly and distinctly perceive to belong to that thing really does belong to it, is not this a possible basis for another argument to prove the existence of God? Certainly, the idea of God, or a supremely perfect being, is one that I find within me just as surely as the idea of any shape or number. And my understanding that it belongs to his nature that he always exists is no less clear and distinct than is the case when I prove of any shape or number that some property belongs to its nature.” (paragraph 66) 

 

    Whatever I clearly perceive to be predicated of something is true of that thing. Therefore, if I clearly perceive that necessary existence pertains to the idea of a supremely perfect being, then such a being truly exists.

If this were to be put in a syllogism:

P1: I have an idea of a supremely perfect being.

P2: A supreme being has all perfections.

P3: Necessary existence is a perfection.

C: Therefore, a supremely perfect being exists.

    This argument will hold true for any of the attributes of God such as omnipotence, omniscience, and eternality. Furthermore, there is a connection between all of God’s attributes and His necessary existence. If one thinks of an omnipotent being, one is already prescribing for them the predicate of existence. Furthermore, if an omnipotent being exists, it must have the attribute of aseity, or self-existence as if it were caused by something else it would not be omnipotent. To be all-powerful, the being must exist by its own power.