Descartes’ Proof for The Existence of God and Its Importance

Descartes’ Philosophical Quest for Certainty

Method of Doubt and the Evil Genius Hypothesis

In Meditations on First Philosophy, Descartes describes his philosophical quest to find absolute, certain knowledge. His method for finding this knowledge is to start from the most basic truths, systematically working through them and trying to establish some sort of doubt about them. If he is able to create doubt about something, anything that follows from that thing will also contain doubt and therefore be eliminated. To create as much doubt as possible, he comes up with the “evil genius hypothesis,” in which there is a higher being that exists who deceives all sensory perceptions that Descartes has. In going through this process, the only thing that Descartes is able to determine as true is that he is a thinking thing that exists; he is unable to prove the existence of anything else. At this point, he also establishes a general rule for truth, which states, “everything I [Descartes] very clearly and distinctly perceive is true” (line 35). In order to prove anything else beyond that he is a thinking thing, he must disprove the idea of the evil genius and he does this with his proof for the existence of God. For Descartes, proving the existence of God is absolutely crucial; without this proof, he would have been unable to go any further on his quest to attain unconditional knowledge.

The Structure of Descartes' Argument in Meditation Three

In Meditation Three, Descartes presents his proof for the existence of God. Before discussing God, Descartes declares that an effect cannot have more reality than its cause—everything that comes into being had to be made by something that has an equal or greater amount of reality. The initial cause of an idea must contain at least as much formal reality as the idea has objective reality. Here, Descartes posits that if he can conceive of an idea that has more objective reality than he could possibly possess formally, it follows that something else exists in the world that is the cause of this idea. It is from this that he bases his argument for the existence of God.

Arguments for God's Existence: The Infinite Substance

His proof for God’s existence contains a number of different arguments. From the name “God” Descartes says he understands a certain substance “that is infinite, independent, supremely intelligent and supremely powerful, and that created me along with everything else that exists—if anything else exists” (line 45). In examining the idea of an infinite substance, he says that the fact he is also a substance is not sufficient to explain having the idea of an infinite substance, because he is finite. Therefore, the idea must have proceeded from an infinite substance. He next says that while he can doubt the existence of other things, he cannot doubt the existence of God, because it is an idea “utterly clear and distinct” (line 46), a reference to his truth criterion mentioned above. Following this, he then proposes that he himself may be supremely perfect, that he possesses all of God’s perfections as potentialities and is constantly improving—meaning the idea of God could have come from himself. However, he dismisses this idea with three reasons: God is all actual and not at all potential; because he is always improving his knowledge will never be infinite; and a potential being is nothing, the idea of God must come from an actual infinite being. Lastly, Descartes argues that if his parents or some other imperfect being created him, this creator must have also possessed this idea of God. Whoever created them, then, must also have had this idea. Tracing the chain back, one must ultimately conclude that the idea of God can originate only from God.

Proving God's Non-Deceptive Nature

Knowing that the cause of his idea of a perfect, infinite God is actually God allows Descartes to prove that God is not the “evil genius” he previously hypothesized him to be. He can clearly and distinctly perceive that God is not a deceiver, because all deception relies on some sort of defect, and God (who is the cause of the idea of a perfect, infinite God) has no defects. This is the key to continuing his quest. Proving that God exists and is not a deceiver enables him to move out from just his thoughts and prove the existence of things outside of himself. He is now able to use his reason, which he believes is man’s natural endowment, to find truths because he knows he is not being deceived.

Critiques Surrounding Circularity in Descartes' Proof

Critics, both during Descartes’ time and in modern times, have found in Descartes’ proof a number of faults, most notably charging it with circularity. This circularity critique revolves around Descartes’ “a clear and distinct perception equals truth” rule. For Descartes’ proposal that something that is clearly and distinctly perceived is necessarily true to hold, god must exist and not be a deceiver. However, he also uses as part of his proof of God’s existence the reliability of a clear and distinct perception. As God’s existence must first be established in order to rely upon a clear and distinct perception, it can be easily seen that if a clear and distinct perception is used in the proof of God’s existence the argument appears to be circular. Descartes did respond to these critiques from his peers, but his defense was not completely convincing, as the critiques still exist today.

The Legacy and Impact on Knowledge Pursuit

In Meditations, Descartes presents a number of groundbreaking, revolutionizing ideas about the pursuit of knowledge. His proof for the existence of God is an integral part to his concepts. However, because of the holes that critics have found in this proof, many find it to not be very convincing, which in turn negatively affects the rest of his ideas.