Descartes’ First Two Proofs of God’s Existence
Feb 1st, 2010 by Micah Tillman | Start the Discussion |
My lecture today was primarily on Descartes’ two proofs of God’s existence in Meditation III. They’re both fascinating proofs, and thus I thought I’d share them (translated more or less into my own terms).
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First Proof
The first argument goes basically like this.
The idea of God is the idea of an infinite substance (i.e., the idea of a thing that is completely unbounded and unlimited, completely perfect, omnipotent, omniscient, etc.).
The question is, “Where does the idea of infinite substance come from?”
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Descartes thinks either someone made it up, or it was caused in someone’s mind.
That is, either someone invented the idea (like when an author invents a new character), or something that someone experienced created the idea in the person’s mind (like when you first learn what a dog is as a child, by watching a bunch of dogs frolicking in a field or something).
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Descartes’ argument is twofold:
First, he argues that you couldn’t invent the idea of infinite substance (i.e., of God).
Second, he claims that only an infinite substance could cause the idea of an infinite substance in anyone’s mind.
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To invent the idea of infinite substance, you’d have to start with the idea of a finite substance, and then imagine expanding or augmenting the attributes (e.g., knowledge, power) of that substance forever.
But that just means you can only invent the idea of an infinite substance by imagining turning a finite substance into an infinite substance. And that means you already have to know what an infinite substance is.
(You have to say things like, “If I kept gaining knowledge forever. . .” or “If I always got just a little bit more powerful . . .,” or “If I kept gaining knowledge, and never stopped . . .,” etc. But words like “forever,” “always,” and “never,” are just different ways of talking about infinity.)
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So, if you can’t invent the idea of an infinite substance, then it must have been caused in your mind.
Descartes argues that nothing, besides an infinite substance, would have enough reality to cause the idea of an infinite substance in your mind.
Just like seeing red wouldn’t create the idea Mars in your mind, nor would seeing fastness create the idea of a cheetah in your mind, neither a “mode” (like red, fast, sharp, loud, etc.) nor a finite substance (like Mars, a cheatah, a tree, a book) could create the idea of an infinite substance.
(Red might be able to remind you of Mars, but not create the idea of Mars in your head. You’d already have to have the idea of Mars to be reminded of it by seeing red. Same goes for fastness and cheetah.)
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Therefore, the only thing that can create the idea of infinite substance is an infinite substance. And since Descartes has the idea of infinite substance, an infinite substance must have caused that idea. And therefore an infinite substance must exist.
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Second Proof
Descartes’ second argument for God’s existence goes like this.
Anything that has infinite power, and the idea of infinite substance, would turn itself into an infinite substance.
Descartes has the idea of infinite substance, but has not turned himself into an infinite substance.
Therefore, Descartes must not have infinite power.
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If Descartes does not have infinite power, then he could not have created himself out of nothing. Creating yourself out of nothing is impossible, and only something infinitely powerful could even come close to doing the impossible.
Therefore, either Descartes has always existed, or something with infinite power created him.
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If Descartes has always existed, then something is keeping him in existence (i.e., something is “sustaining” him). This would require infinite power, because “sustaining” a thing is the same thing as recreating it in each new instant.
Time is a series of discreet, disconnected moments, and the only way to get from one moment to the next is to be recreated in each new moment. If you’re not recreated in each new moment, then you will disappear when the present moment disappears.
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Therefore, the fact that Descartes exists proves that something is constantly recreating him out of nothing in each new instant. But this would require infinite power on the part of whatever is “sustaining” him.
Furthermore, it would require that whatever is “sustaining” him also either be an infinite substance (and thus be able to recreate the idea of infinite substance in his mind at each new moment), or at least have the idea of infinite substance (and thus be able to implant it in Descartes’ mind at each new moment).
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However, if the thing that is continually recreating Descartes has infinite power, which it must, and the idea of infinite substance, which it must, then it would have already made itself into an infinite substance.
Therefore, the fact that Descartes exists, and has the idea of infinite substance, proves that an infinite substance exists.
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Evaluation
I like the first proof a lot. I think it is fundamentally correct. It needs more working out than Descartes gives it — specifically with regard to the premise that only an infinite substance could cause the idea of an infinite substance — but I think he’s onto something important.
The second proof depends on two premises that one might question. First, there’s the claim that if a thing had infinite power and the idea of an infinite substance, it would make itself into an infinite substance.
This sounds right, but I’m not sure how certain it is.
Second, there’s the claim that time is a discrete series of points, and thus that everything must be created anew out of nothing at each new moment. This is a fascinating view of time, but I wonder if it is correct.
