The Ontological Argument - valid or debunked?

[Edwardo Piet]

Even if it did not apply just as much to God's non-existence as his existence: For me the fallacy is one of equivocation. It's equivocating the mere logical possibility of God's existence with possibility in the sense of a "possible world". The fact something is logically possible doesn't mean it exists in any possible world, it just means it cannot be proved impossible.

"Not necessarily impossible" =/= "Necessarily residing in at least one possible world."

[Edwardo Piet]

1. The maximally great being is defined in such a way that if he is possible in at least one possible world world then he is by definition necessarily possible in all possible worlds.
2. The maximally great being is possible in at least one possible world.
3. Our world is a possible world simply because it isn't an impossible world.
4. Therefore the maximally great being exists in our world.

That's how I would describe the argument. Here's my critique of it.

1. The maximally great being is merely logically possible.
2. When something is merely logically possible that just means it isn't self-contradictory.
3. When something is merely not self-contradictory that gives you no reason to believe it is actually possible: it merely means there is no proof it is impossible.
4. Therefore there is still no reason to believe that the maximally great being is actually possible in any world at all.
5. Therefore there is still no reason to believe that the maximally great being actually exists.

So it is clear to me that it's equivocating "logically possible in a possible world" with "actually possible in a possible world". The equivocation fallacy within the argument was very implicit and hidden and I have tried to explicate its implicitly many times now... hopefully this time I have succeeded

[Neo-Scholastic]

Could you please point me to the exact reference from which you pulled this version of the argument? I don't recall ever seeing a comparison between souls and slugs in Aquinas. The term ultimate standard of being doesn't seem very Scholastic, what translation are you using?

This is a quote from MysticKnight #207 in this thread.

Everyone! Please, if you are going to attribute an argument to Aquinas please pay attention to the terms and how they were actually used by the Scholastics.

[Edwardo Piet]

...it's a link from a parody website.

[SteveII]

We know that there's something wrong with that logic because it can "prove" that gods do not exist just as easily as it "proves" that they do:

Premise 1: It's possible that a 'maximally great being' does not exist. 
Premise 2: If it's possible that a maximally great being does not exist, then a maximally great being does not exist in some possible world.
Premise 3: If a maximally great being does not exist in some possible world, then it does not exist in every possible world. 
Premise 4: If a maximally great being does not exist in every possible world, then it does not exist in the actual world. 
Premise 5: Therefore a maximally great being does not exist in the actual world.
Premise 6: Therefore a maximally great being does not exist.
Conclusion: Therefore God does not exist.

This second version is exactly as strong as the first version, yet it proves the exact opposite.  Any argument that proves both X and not-X is worthless.  In the scales of persuasion, its weight is zero.

We know, therefore, that the MOA (modal ontological argument) is worthless, absolutely refuted. 

Which brings us to P1.   

We're talking about necessary gods, gods that don't exist at all unless they exist in all possible worlds.  Can a god like that exist in some possible worlds? 

No.  Certainly not. 

We know that some possible worlds are godless.  We know this because of the definition of "possible world."  A possible world is any world without contradictions.  If a world doesn't have square circles or married bachelors, or anything other logical contradiction, then it is a possible world. 

There's nothing contradictory about godless worlds, so they are by definition possible. 

But a god existing in a godless world would be a contradiction, an impossibility.  Therefore, no god can exist in all possible worlds.  

Since P3 establishes that the god we are discussing, the god of the modal ontological argument, does not exist in any possible world unless it exists in all of them, it follows that this god does not exist in any possible world. 

Therefore, P1 is false. 

I'm sorry, but it makes no sense that this defeats the argument. What is the difference between Premise 1 and Premise 1'?

Premise 1: It's possible that a 'maximally great being' exists.
Premise 1': It's possible that a 'maximally great being' does not exist. 

So the real difference is in P4' (P2' and P3' are definitionally true). 

Premise 4: If a maximally great being exists every possible world, then it exists in the actual world. 
Premise 4: If a maximally great being does not exist in every possible world, then it does not exist in the actual world. 

When you apply the modal logic "if something is necessary in one possible world then it is necessary in all possible worlds" to a negative such as P4', you are saying it is necessary that something does not exist. Isn't that saying the same thing as a maximally great being is logically impossible? So to support P4', you are back to having to show that a greatest conceivable being is not logically possible--which was the original challenge of the original argument. 

[Neo-Scholastic]

And he was quoting it from me, and I was quoting it from here:

http://www.godlessgeeks.com/LINKS/GodProof.htm

So you reposted any atheist's summary of Aquinas without verifying the accuracy of the reference. That's not very rigorous of you. As a skeptic why aren't you equally skeptical of skeptics?

This seems to be another example of many who say that all the proofs of god have been debunked but who haven't done the heavy lifting to personally evaluate both sides fairly.

[GrandizerII]

We know that there's something wrong with that logic because it can "prove" that gods do not exist just as easily as it "proves" that they do:

Premise 1: It's possible that a 'maximally great being' does not exist. 
Premise 2: If it's possible that a maximally great being does not exist, then a maximally great being does not exist in some possible world.
Premise 3: If a maximally great being does not exist in some possible world, then it does not exist in every possible world. 
Premise 4: If a maximally great being does not exist in every possible world, then it does not exist in the actual world. 
Premise 5: Therefore a maximally great being does not exist in the actual world.
Premise 6: Therefore a maximally great being does not exist.
Conclusion: Therefore God does not exist.

This second version is exactly as strong as the first version, yet it proves the exact opposite.  Any argument that proves both X and not-X is worthless.  In the scales of persuasion, its weight is zero.

We know, therefore, that the MOA (modal ontological argument) is worthless, absolutely refuted. 

Which brings us to P1.   

We're talking about necessary gods, gods that don't exist at all unless they exist in all possible worlds.  Can a god like that exist in some possible worlds? 

No.  Certainly not. 

We know that some possible worlds are godless.  We know this because of the definition of "possible world."  A possible world is any world without contradictions.  If a world doesn't have square circles or married bachelors, or anything other logical contradiction, then it is a possible world. 

There's nothing contradictory about godless worlds, so they are by definition possible. 

But a god existing in a godless world would be a contradiction, an impossibility.  Therefore, no god can exist in all possible worlds.  

Since P3 establishes that the god we are discussing, the god of the modal ontological argument, does not exist in any possible world unless it exists in all of them, it follows that this god does not exist in any possible world. 

Therefore, P1 is false. 

I'm sorry, but it makes no sense that this defeats the argument. What is the difference between Premise 1 and Premise 1'?

Premise 1: It's possible that a 'maximally great being' exists.
Premise 1': It's possible that a 'maximally great being' does not exist. 

So the real difference is in P4' (P2' and P3' are definitionally true). 

Premise 4: If a maximally great being exists every possible world, then it exists in the actual world. 
Premise 4: If a maximally great being does not exist in every possible world, then it does not exist in the actual world. 

When you apply the modal logic "if something is necessary in one possible world then it is necessary in all possible worlds" to a negative such as P4', you are saying it is necessary that something does not exist. Isn't that saying the same thing as a maximally great being is logically impossible? So to support P4', you are back to having to show that a greatest conceivable being is not logically possible--which was the original challenge of the original argument. 

wiploc's argument shows that it can work both ways, that's the point. As you have yet to provide an argument that establishes the logical possibility of a maximally great being, then this argument is pretty much vacant at this point.

[Edwardo Piet]

And he was quoting it from me, and I was quoting it from here:

http://www.godlessgeeks.com/LINKS/GodProof.htm

So you reposted any atheist's summary of Aquinas without verifying the accuracy of the reference. That's not very rigorous of you. As a skeptic why aren't you equally skeptical of skeptics?

This seems to be another example of many who say that all the proofs of god have been debunked but who haven't done the heavy lifting to personally evaluate both sides fairly.

I originally quoted it from the parody site in the first place. After Stimbo linked it.

[Mister Agenda]

I think the most you can get from the argument is that God either necessarily exists or necessarily doesn't exist.

[Edwardo Piet]

It's funny because I conclude from it that it's possibily possible but we still have no reason to believe it's probable or even necessarily possible. If we spot the fallacy that is, if we fall for the fallacy then it seems to prove that "the maximally great being" necessarily exists by definition... but it is still extremely vague and unclear what that being actually is.