I remember a proof of the existence of God my old 1st year logic prof brought up that seems to use the StolenConceptFallacy.  The proof goes something like this:

	Definition:  God is the greatest conceivable being.
	We can conceive of beings as existing.
	It would be greater for God to exist, than to not exist.
	Therefore the greatest conceivable being (aka God) exists.
The prof's counter was that "existence cannot be predicated".  Essentially "existence" and "greatness" are orthogonal qualities so it makes no sense to apply them to each other.
--AndyPierce

This is known as the Ontological Argument, originally proposed by St. Anselm of Canterbury.  See:

http://members.aol.com/plweiss1/anselm.htm (very concise)

http://plato.stanford.edu/entries/ontological-arguments/ (lots o' stuff)

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I remember reading that. And I bet that like me you were rolling your eyes at how crushingly unconvincing an argument it was. Is there some voodoo magic that makes it "inapplicable"? Apparently so. It's only when you delve into the meaning of the term existence that you discover that existence is a '''meta'''-predicate. Existence of an object is not a property of an object but a property of the corresponding sentence in relation to its system. That an object exists means that a sentence belongs to the system under discussion. And of course, what this shows is that existence is the ''sole exception'' and talking about the "applicability" of normal predicates or sentences is nonsense. You can turn existence into a predicate by creating a new formal system to discuss your original system, at which point you've invented a completely new type of existence. As I'll have to explain all over again, the only valid separation between different "domains" is that between level and meta-level. The 'sun' and 'food' are not on different levels of abstraction. -- RichardKulisz

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I read this in a slightly different form: "God is that than which no greater can be conceived. A being that exists is greater than one that does not. Therefore, God exists."

From that, I constructed a parallel argument: "God is that than which no greater can be conceived. A being that has a web page is greater than one that does not. Therefore, God has a web page."

Furthermore, "A being whose web page is very popular is greater than one whose web page is not. Therefore, God's web page is very popular."

Slashdot is God. (Warning: There was sarcasm in the preceding, and little else.)

My point, stated more directly, is that, using the initial statement, "God is that than which no greater can be conceived," you can ascribe just about any "good" quality to God. But if you can find two mutually exclusive good qualities, you can ascribe them both to God and create a contradiction. Since an object cannot be two things at the same time and in the same respect, God cannot exist, or else, he cannot have all the greatest qualities.

But the argument begs the question. When it says, "God is" -- just that much -- it is asserting the existence of God. If it said, "If God existed, he would be the greatest being conceivable," then the rest of it would go, "It is greater to exist than not to exist, therefore, if God existed, then he would exist." It begs the question. -- EdwardKiser