To sum up the passage from above:
- I know that I exist since I can think.
- When I think I have ideas.
- I have an idea of God which I did not cause; my idea is an effect.
- My idea of God is of God as perfect.
- Perfection entails existence.
- A cause must have at least as much reality as an effect.
- The cause of my idea is not me since I am imperfect.
QED, God exists.
Descartes' Proof for the Existence of God, defined in Meditation III in his "Discourse on the Method," is one of the most studied of all of his ideas. It is more respected than the proof offered by Anselm in his "Proslogion," since Descartes removes the premise of "I believe in God," isolating theological nature from his argument.
Descartes began his meditations with four procedural rules:
- Doubt everything
- Break all ideas down into the simplest form
- Start from the simple and move to the complex
- Omit nothing
Soon afterward, he had emerged from his meditations with the statement, "I think, therefore I am." He began to build on that, and eventually, came to his proof.
In short, Descartes states his cogito, that when he thinks, he has ideas, and he has an idea of God which he did not cause - The idea is an effect. He says his idea of God is of a perfect being, and that perfection entails existence. He finally states that a cause must possess as much reality as its effect, and the cause of his idea of God is not himself, since he is imperfect. Therefore, reasons Descartes, God exists.
It is a worthy argument, and when you assume all of the premises are valid, the conclusion must be true. This is why this is indeed a compelling argument that could convince your non-believer of average intelligence. However, it fails to impress me.
Descartes' first two premises are valid. There's no reason to discuss them then. Where Descartes' argument falls short is on his third premise. His idea of God existed previous to him sealing himself off and performing the meditations that led him to this proof. Even if he truly was able to get rid of all ideas obtained prior to the meditation, the fact remains he was still thinking in human language - Something which, by adolescence, would have become nearly hard-wired into his brain's language and thought centers.
In that language there were words - one of which was "God." Had he successfully forgotten everything he had learned, he would have no idea of the word "God," let alone of the concept of him. His bias in this area shows through.
Further, he states that his idea of God is an effect, which obviously, must have a cause. He rationalizes that this cause is God's very existence. I put forth that the cause was the information gene of religion being implanted in his brain. This information gene, or meme, gained enough of a prominence to remain even after he had "forgotten" everything else that he obtained through his senses, and thus, its existence and prominence led him to create this proof.
This peg knocked out, one no longer needs to spend time finding flaws in his fourth, fifth, and sixth premises, because the seventh immediately becomes an invalid one. With at least two flawed premises, the conclusion is no longer true. So it is my opinion, that, when interpreted sans analysis, the proof appears to be readily valid. But like a coin fresh off the mint which has the appearance of perfection, it doesn't look the slightest bit perfect when examined with an electron microscope. The magnification of intellectual analysis will find the weaknesses in any argument that appears true on the surface.