Why does Descartes think it is so important to prove that God exists?  What does he think depends upon coming up with such a proof?  Pick whichever one of his attempted proofs you think is his best shot, and discuss it.  If no such proof turns out to work, what (in his view, and in yours) are the consequences?

Rene Descartes (1596-1650 CE) is one of the greatest philosophers that has ever lived.  He’s one of the greatest mathematicians that has ever lived as well—perhaps even more amazingly—developing what is now known as Cartesian geometry (helpfully named after himself in homage) and other advances in the field of mathematics before leaving his “study of letters,” as he called it, to pursue philosophy exclusively at a rather young age.  His experience in mathematics is evident in his philosophical writings, as he believed very strongly in the use of unabashed logic to convey his views on “life, the universe, and everything” to others.  In order to facilitate this, Descartes decided to remove all his assumptions about the world (as best he could) from his mind—starting at square one.  From here, he tries to explain everything about his world using logic as his only tool.

His first baby step is to prove that he exists.  His simple argument: “I think, therefore I am.”  Although even this point could be argued, because of the limitations of this paper we shall assume the logic here holds water.  After a few more steps concerning his body and soul, in quite a change of pace, he decides to prove the existence of God.  One may find it rather unusual that he decides to tackle the question of a supreme being so early in his meditations, but by analysis of his writings in whole, his path turns out not to be very surprising at all.  This essay will attempt to show that Descartes places great importance in being able to prove God’s existence because he in fact believed in God himself, that many of his proofs after his God existence proof rely on that proof (giving him added incentive to prove such a supreme being exists), and that at least one of Descartes’ proofs of God’s existence may not be as airtight as he believes.

So, first we examine Descartes’ writings.  It is abundantly clear that Descartes believed in God.  All references to God are positive—Descartes imagines this entity as being utterly omnipotent, omniscient, and omnibenevolent.  Even the thought that God could exist as a being just as powerful but not infinitely good in nature, in fact, causes Descartes greats pains.  In a moment of agitation trying to disprove this notion (cast adrift in a sea of broken logic, perhaps), he says he felt “…as if I had suddenly fallen into a deep whirlpool, I am so disturbed that I can neither touch my foot to the bottom nor swim up to the top.” (Note Packet, 54)  Also, all references Descartes makes to skeptics and doubters—those who doubt or do not believe in God’s existence—are overwhelmingly negative.  One gets the impression Descartes feels listening to the arguments of these “non-believers” are not worth his time: “…none of the objections, among the questions I received, were worth noting, except two, and I will respond to them here…” (Note Packet, 49) Although he doesn’t specifically mention who these “unworthy” questions were written by, it is a good bet that a large number of them came from atheists and skeptics since Descartes’ discussion of God’s existence is, by far, the most controversial portion of the book.  It is somewhat suspect that Descartes doesn’t even mention what these arguments were, if only perhaps to show how silly he feels them to be.

Thus, we arrive at a motive for not only why Descartes wants to prove his existence, but also why he does it so early: A world without God would be incomprehensible to such a believer as Descartes appears to be.  In fact, once he has “proven” God to exist, he basically skims over the rest of his proofs for the laws of nature—basically, how and why the universe works in the fashion it does—by saying that those laws are what they are simply because God wanted an ordered universe and made it that way: “Moreover, I showed what the laws of nature were, and, without supporting my reasons on any other principle but the infinite perfections of God, I tried to demonstrate that all those laws…even if God had created many worlds, there could not be any of them in which these laws failed to be observed.”  (Discourse, 24)  Without being able to prove God’s existence, his subsequent arguments topple like a deck of cards blown over by the wind.

Now that Descartes’ motives for proving that God exists have been examined, as well as what rides on him being able to demonstrate such a thing, we can finally start analyzing one of Descartes’ proofs and see whether it truly holds water.  The one to be discussed in this essay deals with man’s conception of perfection.

Consider the definition of a circle: the set of points equidistant from a single point in space.  We can conceive of a perfect circle in our minds simply by closing our eyes and imagining it.  However, no such circle exists in the world!  Any circle drawn by a man will have its flaws, no matter how steady the hand.  The paper the circle is drawn on has its flaws as well, with microscopic bumps and ridges to further contaminate our perfect circle.  The pen or stylus with which the circle was drawn also has its own defects.  A clever sort might argue that a computer can display a perfect circle on the screen, but, alas, even a computer is limited by the resolution of the monitor—if we were to examine a computerized circle on a pixel level, we would see that the circle has rough edges caused by a series of finite points (pixels, in this case) being necessarily unable to produce a perfect curved line.  Only a computer monitor with infinite pixels would be able to depict a true perfect circle, not to mention the infinite processing time needed to render such an object.  Both infinities are impossible in our universe—or at the very least, well beyond the capacity of anything that has existed or currently exists to create.

Now comes the philosophical part of the argument: Descartes freely admits that man is an imperfect being.  Man errs, man stumbles, and man makes mistakes.  How, then, is man able to conceive of a perfect circle?  No man has ever seen one, drawn one, or stumbled upon one in any place other than in his or her own mind.

Descartes argues that man could not conceive of perfection unless there was such a thing.  Since man is flawed, this means that there must be something more perfect than man in order to place the notion of perfection into man’s mind.

Another clever sort might point out that perhaps an entity more perfect than man exists, but that this being is not all perfect. By the same logic he used earlier, Descartes postulates that some being more perfect than that less-flawed-but-still-flawed being would need to exist to put the idea of total perfection into its mind, and by recursively repeating that idea, Descartes arrives at the hypothesis that there must therefore be a supreme, perfect being: God.

The author of this paper, however, does not agree with Descartes’ conclusions on this matter.  Descartes is of the belief that since we are flawed and we can conceive of something more perfect than ourselves, it must exist.  He does not, in the author’s opinion, adequately support this idea with empirical proof—he simply claims in his theoretical proof that since we are flawed creatures, we couldn’t conceive of perfection unless it existed.  He simply says that since we can conceive of perfection, it must exist.  To that, the response is simply: Why?

The Wright Brothers had an idea—to create a flying machine.  This flying machine was better (closer to perfection) than any that had come before, primarily because it worked whereas all prototypes developed to that point had failed to provide permanent air propulsion.  It is fair to say, then, that the Wright Brothers created something closer to perfection than anything that existed in that time, and they went out and created it themselves.  Themselves—without help from a being closer to perfection than themselves.  Descartes would probably make the counter-argument that the Wright Brothers couldn’t have conceived of the idea unless God or some other superior being had placed the idea in their minds for them and that they would not have been able to build it without being “pushed” in the right direction by this being.  While this would simply be conjecture on Descartes’ part, let us assume for the moment that he might be right.

So, to provide a more concrete counterpoint to Descartes’ original line of reasoning, we turn our attention to something that absolutely does not exist in our world: a time machine.  (The same clever person who has been trying to catch the author in a fallacy throughout this paper may pick a substitute non-existent object instead of a time machine in case he or she contends that a time machine really does exist somewhere in secret.)  Time machines have been hypothesized, but none have been successfully made.  How, then, can Descartes explain the fact that we have a concept of a time machine if none exist?  Descartes has claimed that for man to have a notion of perfection, it must exist.  Since there are no time machines, by his same argument, a time machine must exist.  None do.

Descartes might say that the concept of a time machine isn’t out of our grasp, since the components of a time machine do exist, and putting them together in the proper way yields a time machine.  He might even point to a unicorn, saying that we can imagine a unicorn because both horses and horns exist in our universe, and making a unicorn is as simple as putting a horn on an unicorn’s head.  That logic follows fine for a unicorn, since we can visualize both of the necessary components coming together to form it, but the same logic is shaky when applied to a time machine—not only can’t we visualize the components being attached in the proper way to form one, we don’t even know what any of those components are.  All we have is the abstract concept of a time machine.  If the concept didn’t come from its parts, where did it come from?

We could even go way back to our perfect circle: if the perfection associated with the perfect circle must exist according to Descartes, then mustn’t the perfect circle itself exist as well.  We can conceive of it, after all, just as we can conceive of perfection!

It was recently pointed out to the author by a rather philosophical fellow that Descartes attempts to dismiss this entire line of reasoning in a single paragraph in the preface to his Meditations: “For, just as the objective ingeniousness of this idea must have some cause (say, the knowledge possessed by the artisan or by someone else from whom he has received this knowledge), just so, the idea of God, which is in us, must have God himself for its cause.” (Note Packet, 51)  This really doesn’t seem to be a dismissal, just a reiteration of his previous ideas—he still doesn’t clearly explain how he feels inventors are able to truly innovate, to go beyond their own empirical knowledge (and sometimes even the sum of knowledge of all those who have gone before them) to create their inventions.  He can’t empirically prove that God or some other more perfect being placed the idea in the inventor’s mind, and so we are left with some doubt at the very least.

Since Descartes’ argument in favor of God’s existence now is cast into some uncertainty, the burden of proof necessary to conclusively prove his point is not met.  Thus, since the laws of nature proofs following his God existence proof rely on it (as stated earlier), they all fail as well since one of their assumptions is possibly false.  This doesn’t necessarily mean that the laws of nature cease to exist—obviously—only that Descartes has failed to adequately explain them.  Likewise, it is by no means certain that the views presented here are correct—just as Descartes has no empirical evidence showing the existence of God, the author has none refuting his existence.  It is simply presented as an alternate viewpoint to the one Descartes presents, with some nitpicking of his theories in an attempt to weaken them somewhat.  The full and true answers, after all, may never be known.


Descartes, Rene. (ed. Cress, Donald)  Discourse on Method and Meditations on First Philosophy.  Indianapolis: Hackett Publishing Company, 1998.

Philosophy 101 Note Packet (Schacht).  University of Illinois, Fall Semester 2000.

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