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James

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Van Inwagen's "Knowno's"
« on: May 31, 2016, 04:10:17 pm »
Prof. Van Inwagen proposes a problem with modal ontological arguments, particularly with the premise, "possibly a maximum greatest being exists."  Would it not be accurate to say that, "possibly a 'knowno' exists" where a "knowno" is a being that knows that no maximally great being exists?  The problem should be pretty evident: if a maximally great being possibly exists, then it necessarily exists, yet if it's possible that a knowno exists, then it's impossible for a maximally great being to exist.

It seems we're stuck on evaluting the truth of 2 rival premises:

a) possibly, a maximally great being exists
or
b) possibly, a knowno exists.

Thoughts?


- http://www.amazon.com/Metaphysics-Peter-van-Inwagen/dp/0813349346/ref=sr_1_1?ie=UTF8&qid=1464729045&sr=8-1&keywords=peter+van+inwagen+metaphysics

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Atheist in Louisiana

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Re: Van Inwagen's "Knowno's"
« Reply #1 on: June 02, 2016, 04:06:14 pm »
The idea of a maximally great being is not clear.  Necessary existence can't be demonstrated to be somehow greater than non-existence.  The way I see it, a being that doesn't exist, and yet has some effect is greater than one that does exist, regardless of the effect that existent being has.  Non-existence is just as likely to be greater than existence, as existence is likely to be greater than non-existence.

Also, the concept of the MGB as used on this forum attempts to define the MGB into existence by defining it as being necessary.
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joncantey

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Re: Van Inwagen's "Knowno's"
« Reply #2 on: June 12, 2016, 01:09:50 pm »
Quote
The way I see it, a being that doesn't exist, and yet has some effect is greater than one that does exist, regardless of the effect that existent being has.

Clarify how something that doesn't exist can have any effect (isn't that some kind of contradiction in terms)?  Or are you trying to say that a MGB has no effect?


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joncantey

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Re: Van Inwagen's "Knowno's"
« Reply #3 on: June 12, 2016, 01:33:06 pm »
James, I'm curious if Inwagen's knowno is a necessary being.

The ontological argument says that if it is possible the MGB exists, then MGB exists.  It therefore can't be possible for something to exist that contradicts the first premise unless it is impossible for the first premise to be true.  It doesn't seem like Inwagen's argument comes at this from the right angle.  It seems like Inwagen's proposal begs the question by assuming that MGB isn't possible.  Adding a premise that is logically incompatible with the first premise doesn't really do that as far as I can see.

I think to defeat the ontological argument you have to prove that an MBG is logically not possible.  I don't see how Inwagen's argument does that, but perhaps I'm missing something.

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aleph naught

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Re: Van Inwagen's "Knowno's"
« Reply #4 on: June 12, 2016, 02:19:23 pm »
Prof. Van Inwagen proposes a problem with modal ontological arguments, particularly with the premise, "possibly a maximum greatest being exists."  Would it not be accurate to say that, "possibly a 'knowno' exists" where a "knowno" is a being that knows that no maximally great being exists?  The problem should be pretty evident: if a maximally great being possibly exists, then it necessarily exists, yet if it's possible that a knowno exists, then it's impossible for a maximally great being to exist.

It seems we're stuck on evaluting the truth of 2 rival premises:

a) possibly, a maximally great being exists
or
b) possibly, a knowno exists.

Thoughts?


- http://www.amazon.com/Metaphysics-Peter-van-Inwagen/dp/0813349346/ref=sr_1_1?ie=UTF8&qid=1464729045&sr=8-1&keywords=peter+van+inwagen+metaphysics

That's a brilliantly simple way of getting around the typical (and, imo, rather silly) point that they're only talking about the possibility of a thing existing, and not of a state of affairs.

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aleph naught

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Re: Van Inwagen's "Knowno's"
« Reply #5 on: June 12, 2016, 02:27:38 pm »
James, I'm curious if Inwagen's knowno is a necessary being.

It wouldn't be nor would it have to be a necessary being. If a being that knows no MGB possibly exists, then no MGB exists. This follows from the same sort of S5 inference that Plantinga's modal ontological argument uses.

Quote
The ontological argument says that if it is possible the MGB exists, then MGB exists.  It therefore can't be possible for something to exist that contradicts the first premise unless it is impossible for the first premise to be true. It doesn't seem like Inwagen's argument comes at this from the right angle.  It seems like Inwagen's proposal begs the question by assuming that MGB isn't possible.  Adding a premise that is logically incompatible with the first premise doesn't really do that as far as I can see.

I think to defeat the ontological argument you have to prove that an MBG is logically not possible.  I don't see how Inwagen's argument does that, but perhaps I'm missing something.

The first premise is that "if God possibly exists, then God exists". Did you mean the second premise, that "possibly, God exists"? Because yes, the point is precisely that maybe that second premise is impossible.

Just as God's possible existence entails his existence, God's possible non-existence entails his non-existence.

Neither the possibility of God's existence or his non-existence are any more plausible. So to infer that God exists because he possibly exists is special pleading, because we have just as much reason to think it's possible that he doesn't exist and that therefore he does not exist.

Or, as Peter Van Inwagen is saying, it's no more plausible that God possibly exists, than that a Knowno possibly exists.
« Last Edit: June 12, 2016, 02:31:38 pm by aleph naught »

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joncantey

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Re: Van Inwagen's "Knowno's"
« Reply #6 on: June 12, 2016, 03:15:17 pm »
I think part of the answer here might have to do with the difference between epistemological possibility and ontological possibility, but I'm not an expert on the difference -- maybe someone can help me out.  As I understand it, epistemological possibility is depicted in statements like "for all I know ___ exists or ___ doesn't exist".  But ontological possibility identifies whether it is logically consistent for ___ to exist.  Ontological impossibility requires something like logical incoherence, and I don't think that's been shown here regarding MGB's existence. 

For those interested, there's also a distinguishing between conceivably and epistemic possibility:

http://maverickphilosopher.typepad.com/maverick_philosopher/2010/01/coceivability-and-epistemic-possibility.html

Regarding my question about necessity, is it logically possible for a contingent, non-necessary being to exist if that entails that a necessary being can't exist?  That doesn't seem like a coherent solution.  So, perhaps it is being implied that either the knowno is a necessary being, or that there is a quasi-MGB that knowno does know.  Is that where this is going?

Furthermore, I'm not sure how you can state that it is equally plausible in light of the other arguments for theism.  I think Craig's position is that while these arguments are independent, they work together to increase the warrant for each other, thus reducing the charge of being ad hoc.  I've never heard other arguments for knownos.

As a side question what is the understanding behind "know" in Inwagen's argument?  Does it entail the usual "justified/warranted true belief" idea?  It seems like it would have to, because otherwise the knowno is simply wrong if MGB exists and they aren't logically incompatible.  I've probably answered my own question, but there it is anyway.  I just want to make sure we're all using the same terms here.

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Atheist in Louisiana

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Re: Van Inwagen's "Knowno's"
« Reply #7 on: June 12, 2016, 09:10:27 pm »
Quote
The way I see it, a being that doesn't exist, and yet has some effect is greater than one that does exist, regardless of the effect that existent being has.

Clarify how something that doesn't exist can have any effect (isn't that some kind of contradiction in terms)?  Or are you trying to say that a MGB has no effect?

You understand surprisingly well.  That's why a non-existent thing that does have an effect would be greater than one that does.  Would you not agree that a thing capable of instantiating a contradiction would be greater than a thing that is incapable of such an act?  It's trivially easy to pick up a brick if you exist, but it's far harder if you don't exist.
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aleph naught

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Re: Van Inwagen's "Knowno's"
« Reply #8 on: June 12, 2016, 10:59:03 pm »
I think part of the answer here might have to do with the difference between epistemological possibility and ontological possibility, but I'm not an expert on the difference -- maybe someone can help me out.  As I understand it, epistemological possibility is depicted in statements like "for all I know ___ exists or ___ doesn't exist".  But ontological possibility identifies whether it is logically consistent for ___ to exist.  Ontological impossibility requires something like logical incoherence, and I don't think that's been shown here regarding MGB's existence.

The difference is that metaphysical possibility (or ontological possibility, as you say), simply refers to possibility. It's what we're talking about when we say things like, "the Nazi's could have won WW2". In this way metaphysical possibility refers to some way things actually could be, or could have been. Epistemic possibility isn't actually a sort of possibility, rather it refers to a state of unknowing. To say that something is epistemically possible is simply to say that, for all we know, it is the case. We sometimes use "could" in this way to denote uncertainty, e.g. "there could be extra-terrestrial life, who knows".

Metaphysical possibility doesn't refer to logical possibility or coherence, that's something else entirely. Logical possibility simply refers to consistency. There are a lot of things that are consistent but impossible (note that both atheism and theism are both consistent, but only one could be true).

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Regarding my question about necessity, is it logically possible for a contingent, non-necessary being to exist if that entails that a necessary being can't exist?

Yup, it's possible. When we say God is a necessary being, we're saying that by his nature he has the property of existing necessarily. Similarly, we would say that a triangle by its nature has three sides. But, there have to actually be triangles for there to be three sided triangles. It doesn't make any sense to talk about non-existing things having properties. Likewise, God has to actually exist if he exists necessarily. And, whether or not he exists is exactly the question being debated.

As such, defining God as a necessarily existing being only entails that: if God exists, then God exists necessarily. Similarly, if there is a triangle, then it has three sides.

Quote
That doesn't seem like a coherent solution.  So, perhaps it is being implied that either the knowno is a necessary being, or that there is a quasi-MGB that knowno does know.  Is that where this is going?

Hopefully I've explained clearly enough why it's not incoherent. No one would want to say that a Knowno necessarily exists or that there is a quasi-MGB (especially not the atheist!).

Quote
Furthermore, I'm not sure how you can state that it is equally plausible in light of the other arguments for theism.  I think Craig's position is that while these arguments are independent, they work together to increase the warrant for each other, thus reducing the charge of being ad hoc.  I've never heard other arguments for knownos.

But there are also some very strong arguments against the existence, and even the possibility, of God. Think of the problem of evil, divine hiddenness, poor design and so on.

Quote
As a side question what is the understanding behind "know" in Inwagen's argument?  Does it entail the usual "justified/warranted true belief" idea?  It seems like it would have to, because otherwise the knowno is simply wrong if MGB exists and they aren't logically incompatible.  I've probably answered my own question, but there it is anyway.  I just want to make sure we're all using the same terms here.

Yes, I think that's exactly what Van Inwagen wants to say. It's possible for a Knowno to exist, and if a Knowno exists then God does not (since knowledge requires true belief).

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joncantey

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Re: Van Inwagen's "Knowno's"
« Reply #9 on: June 13, 2016, 05:21:23 pm »
Quote
The way I see it, a being that doesn't exist, and yet has some effect is greater than one that does exist, regardless of the effect that existent being has.

Clarify how something that doesn't exist can have any effect (isn't that some kind of contradiction in terms)?  Or are you trying to say that a MGB has no effect?

You understand surprisingly well.  That's why a non-existent thing that does have an effect would be greater than one that does.  Would you not agree that a thing capable of instantiating a contradiction would be greater than a thing that is incapable of such an act?  It's trivially easy to pick up a brick if you exist, but it's far harder if you don't exist.

So, I'm admittedly lost now.  It looks like I need to go read up on the various theories of existence, because I would have assumed that something that doesn't exist can't, by definition, have an effect.  But until I read the current literature I can't yet tell you that you are wrong.  You could save me some time if you could point to a definition/theory of existence that would entail a non-existence being's ability to affect the world in which it doesn't exist.

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James

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Re: Van Inwagen's "Knowno's"
« Reply #10 on: June 16, 2016, 10:31:29 pm »
James, I'm curious if Inwagen's knowno is a necessary being.

I don't think it is or needs to be in order for him to make his point.

Quote
The ontological argument says that if it is possible the MGB exists, then MGB exists.  It therefore can't be possible for something to exist that contradicts the first premise unless it is impossible for the first premise to be true.  It doesn't seem like Inwagen's argument comes at this from the right angle.  It seems like Inwagen's proposal begs the question by assuming that MGB isn't possible.  Adding a premise that is logically incompatible with the first premise doesn't really do that as far as I can see.

If I'm understanding him correctly, I think he's just presenting a sort of counter argument to demonstrate an inability to evaluate the truth of the premise "possibly a MGB being exists."  His argument seems to present an alternative, rival premise "possibly a knowno exists." 

Yes, if it's possible a MGB exists, then the argument demonstrates a MGB is necessary.  However, if it's possible that a knowno exists, then a MGB is impossible.  It seems that he points out that whatever method used to establish the truth of the premise "possibly a MGB exists" can also be used to establish the premise that "possibly a knowno exists."  So, if Van Inwagen is correct, then I think his point is that we can't evaluate the truth of the key premise of the modal ontological argument.  So it's not that it's wrong, it's simply that we don't have reason to accept it as true either.

Quote
I think to defeat the ontological argument you have to prove that an MBG is logically not possible.

I think that's correct as long as you accept the premise that a MGB possibly exists.  However, I think Van Inwagen casts doubt on the ability to evaluate that premise as being true.  Not that he demonstrates it as false though; simply that we might not have a reason to accept it.

Quote
I don't see how Inwagen's argument does that, but perhaps I'm missing something.

No worries, I could be missing something too.
« Last Edit: June 16, 2016, 10:34:05 pm by James »

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Atheist in Louisiana

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Re: Van Inwagen's "Knowno's"
« Reply #11 on: June 19, 2016, 06:46:04 pm »
Quote
The way I see it, a being that doesn't exist, and yet has some effect is greater than one that does exist, regardless of the effect that existent being has.

Clarify how something that doesn't exist can have any effect (isn't that some kind of contradiction in terms)?  Or are you trying to say that a MGB has no effect?

You understand surprisingly well.  That's why a non-existent thing that does have an effect would be greater than one that does.  Would you not agree that a thing capable of instantiating a contradiction would be greater than a thing that is incapable of such an act?  It's trivially easy to pick up a brick if you exist, but it's far harder if you don't exist.

So, I'm admittedly lost now.  It looks like I need to go read up on the various theories of existence, because I would have assumed that something that doesn't exist can't, by definition, have an effect.  But until I read the current literature I can't yet tell you that you are wrong.  You could save me some time if you could point to a definition/theory of existence that would entail a non-existence being's ability to affect the world in which it doesn't exist.

I don't believe that non-existent things can have effects.  That's why such a thing would instantiate a contradiction, making it more powerful than something that is incapable of such an act.
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joncantey

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Re: Van Inwagen's "Knowno's"
« Reply #12 on: June 19, 2016, 09:17:56 pm »
I don't believe that non-existent things can have effects.

OK, good, because I wasn't finding anything helpful along that route.

That's why such a thing would instantiate a contradiction, making it more powerful than something that is incapable of such an act.

So, you are asserting that an all-powerful being would be able to do the logically absurd?  If you are, then he could create a knowno, and Inwagen's argument has no teeth.  But, I don't think that omnipotence entails the ability to do the logically impossible.  For example, square-circles and married-bachelors are absurdities and not "things", so not being able to make them doesn't mean that God can't do "any-thing".  Similarly, an MGB can't make himself non-necessary or a quasi-MGB.

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Atheist in Louisiana

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Re: Van Inwagen's "Knowno's"
« Reply #13 on: June 19, 2016, 10:06:37 pm »
When talking about logical impossibilities, I should clarify that I'm only referring to things that are logically impossible in the universe in which we find ourselves.  I know it's not a common idea, but I don't know if the logic that works in our universe, is actually universal.  I can imagine other universes that are so wildly different from our own that there could exist things that we consider to be logically impossible.

For example, here in our universe, 2 dimensional molecules cannot exist.  The third dimension may be small, but it would still exist.  Such an object is easily possible in a universe with only two spacial dimensions.  In that same way, other universes could yield possible, objects that are impossible in our universe.  Instantiated contradictions (according to the laws of our universe) may be one of those things
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joncantey

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Re: Van Inwagen's "Knowno's"
« Reply #14 on: June 20, 2016, 11:33:29 am »
When talking about logical impossibilities, I should clarify that I'm only referring to things that are logically impossible in the universe in which we find ourselves.  I know it's not a common idea, but I don't know if the logic that works in our universe, is actually universal.  I can imagine other universes that are so wildly different from our own that there could exist things that we consider to be logically impossible.

For example, here in our universe, 2 dimensional molecules cannot exist.  The third dimension may be small, but it would still exist.  Such an object is easily possible in a universe with only two spacial dimensions.  In that same way, other universes could yield possible, objects that are impossible in our universe.  Instantiated contradictions (according to the laws of our universe) may be one of those things

I think you are referring to nomological possibility, not logical possibility. (See the Wikipedia page on Subjunctive Possibility.  Don't ask me to explain the difference between logical possibility and metaphysical possibility, because I don't get it quite yet.)