Descartes “Proof” of God




Finally! A rational equation for God’s existence! With Descartes algorithmic proof that God must exist, how could anyone remain an atheist after reading Descartes meditation five? Perhaps because, Descartes, through a series of flawed premises and erroneous foundations, made a proof in which it would be impossible to conceive of God as not existent. Descartes’ flawed reasoning is exposed through his implications of the essential properties of God, circular reasoning, clear and distinct ideas, and equating concrete ideas (mathematics) to be analogous to abstract ideas (God).


Descartes is able to conclude that God must exist based on the premise that “existence” is an essential property of God. By essential property, Descartes means that the idea (God in this case) could not be conceived of as not containing the property (Erikson). He claims that “God has all perfection and existence is a perfection” (Descartes 90). But is existence perfection? Could it just be our finite minds that believe it is better to exist then not to exist? Perhaps perfection is beyond our human understanding and it is, in fact, better to not exist. In other words, although we assume it is better to exist then not, perhaps a perfect being is one that is infinitely non-existent. After all, with out existence there would be no suffering and no pain.

Even if one were to agree it is better to exist then not to exist, perhaps it is only meant in the context that an object is better to exist as an idea than exist in reality. Kant argues,  “a being that exists as an idea is greater than a being that exists in reality” (Himmar). If it is more perfect for God to exist as an idea then reality, then (according to Descartes logic) the essential property of existence would enforce only the belief in the idea of God while simultaneously negating the conclusion of God’s existence in reality (Himmar).

Further more, even if one were to assume that it is better to exist then to not exist, why must this quality therefore be an essential property? Why must this property be such that God could not be conceived with out it? Kant would argue that existence may just be an attribute of God rather than an essential property. In this sense, even through Descartes’ reasoning, it may be possible to conceive of God as not existing (Himmar).

Yet, through Descartes definition of an essential property, when an atheist affirms that existence is an essential property, he or she falls into a contradiction. Descartes argues that existence as an essential property implies that to conceive of God, God must harbor its essential property of existence. In other words, under this premise one is unable to conceive of a God that is non-existent. However, that does not quite make sense any more so then if I were to apply the same logic to that of a perfect island (as in Gaunilo’s Island). I would be reasoning that a perfect island exists since I am accepting that it is better for this island to exist then not exist. Like Gods argument I would reason under the premise that “It is the island that which no greater can be conceived” (phl of religion). But realistically, a perfect island does not exist and similarly, one could not prove that such perfect island exists any more then one could prove of Gods’ existence.


As one may have noted, Descartes’ proof utilizes circular reasoning. He argues that perfect beings have the essential property of existing, and thus God must exist.   Descartes argues, “I cannot think of God except as existing, it follows that existence is inseparable from god. For that reason he exists” (Descartes 89). In a round about way, Descartes is claiming that God exists because he believes him to exist. He seems to argue that because the existence of God is essential to God, then God must exist. By using the premise of “existence of God” to prove the “existence of God,” Descartes is looping himself into a fit of circular reasoning.

This logical fallacy is further employed in another persuasion of God’s existence.  Descartes argues that because God exists, clear and distinct ideas are true, but Gods existence is also derived from the fact that God is a clear and distinct idea. Descartes is erroneously using the existence of God to prove the existence of God through the medium of a clear and distinct idea.


Besides the fact that Descartes, includes absolute premises such as: Clear and distinct ideas must be true and these ideas are also essential properties, Descartes also argues that his knowledge of these clear and distinct ideas are true because they were inborn with in him, by something independent of himself. He says, “this idea is not dependent upon my thought, but is an image of a true and immutable nature” (Descartes 90). However Descartes seems to be relying on the fact that these notions were inborn, with little foundation other than an unreliable analogy to mathematics. While Descartes argues these notions are true because they were inborn, others, like Hume would argue that such notions could just as easily be learned from experience. Descartes himself even admits he has seen, “triangle shaped bodies” and may have drawn knowledge of triangles from this experience (Descartes 88). If Descartes’ notion of the properties of triangles are not inborn, then, according to his logic, perhaps the idea of God came about by experience as well.  If this is so, then the idea was not inborn, not from God, and thus: the idea of God is not clear and distinct and therefore this idea of God can not be true and “immutable. ” As Hume might agree, whereas properties of triangles can be proven true (clear and distinct) objectively, the existence of God is based on assumptions that may differ based on ones epistemological perspective and are thus difficult to validate.



This faulty relationship between the properties of mathematics and that of God is one of the main pitfalls of Descartes argument. Whereas properties of triangles are objective and thus can be proven true for any scenario, “the existence of God” is subjective and thus one may come to a different conclusion based on ideas such as ones’ definition of perfection. Descartes reveals his subjective nature when he states, “God ought to have, for me at least, the same degree of certainty that truths of mathematics had” (Descartes 89). Not only does this exploit the supposed relationship of mathematic truths to abstract truths, it also exploits that Descartes is subjective in his reasoning. Whereas math is strictly objective, Descartes statement “for me” reveals the inability to separate ones perceptions from the logic of something so abstract. Clearly, mathematical properties such as that of a triangle are not analogous to something as abstract as existence or God. Moreover, existence is far more abstract then interior angles of a triangle that can be proved time again.

For example, when one thinks of or analyze a triangle, one knows that its internal angles add up to that of a straight line (180 degrees).  In any other three-sided figure that I think of, or have had experience with, this proof holds true. It would be impossible for one to conceive of a triangle that doesn’t have this property (Class Discussion). Although Descartes would argue that the internal angles of a triangle are analogous to existence in God in that both properties are essential to their respective idea, the existence of God does can not follow the same line of thought. Gods’ properties and its essential properties are subjective, causing unstable premises. One’s definition of perfection is tantamount to defining the essential properties of God, and essential to Descartes proof of the existence of God. For example, if one does not view existence as perfection, then Descartes argument is unable to prove Gods existence. Since ideas of perfection and the like are person relative whereas mathematics are objective, one can not easily equate something as abstract as existence to a property as clear as mathematical properties.



Under the premise of accepting existence as an essential property of God, Descartes made it illogical for the atheist by exposing the contradiction of conceiving in a God that must exist as non exist. However, Descartes’ own reasoning was flawed in its utilization of subjective essential properties, circular reasoning, faulty clear and distinct ideas, and illogical triangle to God analogy. It soon becomes clear why many remain unsatisfied by Descartes “logical” explanation. Descartes premises as well as his “logical” inferences are riddled with errors.


Philosophy of Religion. Web. 04 Oct. 201


Himmar, Kenneth. “Ontological Argument for the Existence of God [Internet Encyclopedia of Philosophy].” Internet Encyclopedia of Philosophy. 27 Apr. 2005. Web. 04 Oct. 2011. <;.


Robertson, Teresa. “Essential vs. Accidental Properties (Stanford Encyclopedia of Philosophy).” Stanford Encyclopedia of Philosophy. 28 Apr. 2010. Web. 04 Oct. 2011. <;.


Descartes, René.  Discourse on Method and Meditations on First Philosophy.  4th ed.  Trans. Donald A. Cress.  Indianapolis, IN: Hackett Publishing Company, 1998.

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