God's existence cannot be proven logically!

Actually, a logical argument, by definition, is a collection of statements (called premises) and another statement (called the conclusion). What you are stating here is a method for determining whether an argument is valid (that is, whether the conclusion must necessarily follow from the premises).But the "real" way of determining whether an argument is valid is to construct its truth table. Now it is true that it takes time for a person to do this, but any argument consists of only a finite number of simple statements and so can (in principle) be done in a finite amount of time, and the results are, unlike the linear proof you are talking about, unambiguous.The reason that you don't see truth tables very often is that in real arguments, consisting of a very large number of premises (most of which are not even explicitly stated in the proposition), and so it is actually impossible to do a truth table in a reasonable amount of time.-The real reason that logic cannot prove that God exists or that God does not exist is that logic cannot prove anything about the real world. All logic does is determine whether or not a conclusion does necessarily follow the given premises. In the linear method of proof that you mentioned (the only one available in practice), one can (one hopes) show that a conclusion does follow the premises, and, in some cases, one might show that the conclusion does not necessarily follow from the premises.But that says nothing about the real world since there is no guarantee that the premises are accurate statements about the real world. As one example, given Newton's laws of motion and the law of gravity, scientists of the 19th century proved that the orbit of Uranus will follow a particular path. In actuality, Uranus did not follow this path. Clearly this meant that one or more of the premises were wrong: it could be that the law of gravity was incorrect, or that the laws of motion were not correct. Well, what actually happened was that the unspoken premise that there were only seven planets was changed to explicity state that there is an eighth planet...and Neptune was subsequently discovered. In fact, the history of science is really the history of how our premises about the real world have changed. Some of these changes were so profound, using Kuhn's ideas of paradigm shifts, that our very definitions and conceptions ended up changing.So the problem with the proofs for or against the existence of God is that, just like in the sciences, we cannot be certain that our premises, the assumptions that we make about the nature of God or reality, are correct. In reality, God either exists or he does not, and all we can do is try to come to the most reasonable conclusion whether he does or does not based on what we know or what we think we know about the real world around us. Logic is merely a tool to help us draw the correct conclusions based on what we know or what we think we know, but it will never be definitive since at all times our knowledge about the real world is limited and usually inaccurate to some degree.

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Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine

That is more or less correct, pd. There are two things needed for an argument (like the example you gave) to be sound. One is that the argument must be valid, that is, the conclusion must be true whenever the premises are all true. The other is that the premises must all be true.Logic itself does not concern itself with whether the premises are true or false; as I tell the class when I teach this subject, the truth or falseness of the premises are the subjects of the other courses in history, physics, biology, and so forth. Logic is concerned with determining whether, assuming the premises are true, we can be certain that the conclusion is true.The example you gave is a variation of what is called in modern logic Modus Ponens. The typical Modus Ponens looks like this:p -> q
p
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Therefore, qIn modern logic, we know that this form is valid when we construct the truth table for it (it's a bit awkward to describe truth tables for arguments on the internet without being able to draw stuff -- if you're interested, you can look it up. If it's still not clear then I'll give a shot at explaining it).The exact form you gave is more of an ancient classical form:All P are Q.
X is a P.
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Therefore, X is a Q.This form actually has a name in the classic system, but I forget what it is, and I don't feel like digging out my logic text book to look it up. In the older classical systems of logic, I think these standard forms were determined to be valid or invalid simply by using common sense. But I think that you can see that we can rewrite this in the modern form of Modus Ponens if we wanted to.Now given that Modus Ponens is a valid argument, it is only left to show whether or not the premises are true. If the premises are true, then we can be confident that the conclusion is true (taking into account my earlier caveat that there may also be unspoken premises of which we are not consciously aware, at least not until we find out the conclusion is actually false!). If either or both of the premises are false, then we can't make any determination one way or the other about the truth of the conclusion.Does this help?

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Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine

Well, you know, there isn't any evidence whatsoever that the Flood ever occurred.Hey, wait a minute....

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Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine

Thanks.I actually thought of that one a long time ago, back when Randman was doing his "God can go back in time and fix things -- that's why carnivores have sharp teeth" schtick.

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Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine

Actually, if one truly can't logically prove the existence of god, then it means that the premises are not sufficient to reach the desired conclusion. That means that either we don't have the data to formulate reasonable premises, or that our conception of god is inadequate to come to reasonable premises. Of course, that might be because no god actually exists.As I've previously explained, one cannot logically prove anything about real facts (like whether or not a god exists). All logic allows us to do is to determine whether or not certain conclusions must follow our initial premises and assumptions.

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I've done everything the Bible says, even the stuff that contradicts the other stuff! -- Ned Flanders