Well i have been having a discussion with a theist and he has just brought up the modal ontological argument.  I have now  done some research on modal logic and have sites marked to further educate myself on it, but i am still way to new to it to have any clue whether my argument holds water or not, and i would really apreciate some help.

the argument he used goes like this
"1. It is possible that a maximally great being exists.
2. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.
3. If a maximally great being exists in some possible world, then it exists in every possible world.
4. If a maximally great being exists in every possible world, then it exists in the actual world.
5. If a maximally great being exists in the actual world, then a maximally great being exists.
6. Therefore, a maximally great being exists."- him

to which, after very little research i replied with


 "Now the modal ontological argument is not proof of anything .The modal ontological argument applies a string of logic but fails to test the logic. If the same string of logic can be used to come to an opposite conclusion, then the logic has been disproven through contradiction.

1) It is possible that a maximally great being does not exist.
2) If it is possible that a maximally great being does not exist, then a maximally great being does not exist in some possible world.
3) If a maximally great being does not exist in some possible world, then a maximally great being does not exist in any possible world.
4) If a maximally great being does not exist in every possible world, a maximally great being does not exist in the actual world.
5) If a maximally great being does not exist in the actual world, then a maximally great being does not exist.
6) Therefore maximally great being does not exist.

This uses the exact same logic to reach an opposite conclusion that is at odds with the original conclusion. This proves that the logic of the MOA is completely faulty and as such, illogical."-my reply

To which he replied


 "The issue I hold  that you does not effectively deny the rationality of there existing God. Here I would re-enter the absence of evidence ,does not, = evidence of absence argument. Due to the nature of the atheist's presuppositional base for the arguments against the existence of God, it undermines the evidences that are provided for the existence of God because to say there is no evidence for the existence of God suffices to say that the atheist's knows all possible proofs that God exists, which is logically absurd. This is what I meant with my ontological argument as a preface for the evidence of absence. There is enough rational proof for the existence of God and that's where Plantinga's argument comes into play. Philosophically, it is possible. Yes, you can flip the logic but I don't believe that's sufficient enough to prove the argument holistically false.  The difference here is I am saying that a maximally great being is necessarily possible and not simply possible. The reason for providing Plantinga's argument in the first place is because I am meaning to exhibit that there are no logical objections to the maximally great being unless the objector can prove that to be false. Rendering us back to premise 1. that it is possible. " - hes reply


Now this is where i am at the moment. now form my limited understanding it seems the major problem with this argument is that it uses two different meanings for the word possibility and only gets away with this argument by confusing them. the one type of possibility has to do with something that is either true or false but which the laws of logic cannot say one way or the other  . such as the possibility england will win tomorrows rugby match.
The other possibility seems to be a logical possibility, something that has always been either true or false and always will be either true or false and so then has to be neccesarily true or false. and the only reason we can call it a possibility is because we do not have the answer yet.
Now this is what i have come up with so far to answer back to what he replied just  and i would like to know if it is valid or not


 "  what i am  saying is that this  argument proves nothing. lets us  replace god with some other proposition which is possible and  if true is neccaserily true for all possible worlds  , but that we do not know the answer to. lets call it (x) and (x)=  the statement that the 12 billionth and first digit of pi is a 7. now we dont know the answer so it is possible that (x) is true  , and if true in any world it would be true in all worlds,so  if true it is neccaseraly true. now i will use your exact same argument
1. It is possible that (x) is true
2. If it is possible that(x) is true , then (x) is true  in some possible world.
3. If (x) is true in some possible world, then it true in every possible world.
4. If (x) is true  in every possible world, then it true in the actual world.
5. If (x) is true  in the actual world, then (x) is actualy true
6. Therefore, (x) must be true

Now we do not need to know the actual answer to be able to say this does not prove (x) is true. yes it is possible (x)  true, there is a 1/10 chance it is, but this does not prove it is true and we do not need to be able to prove  (x) is untrue to be able to say this does not prove anything."


Now this seems fine to me and the only objection i can think of is if , in modal logic, it is possible for worlds to exist where logical and mathematical truths are not true any longer. ie if there is a world where 2+2=563 or something

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Thank you for that. the only problem is i dont yet have near enough knowledge of modal logic to argue something that is so controversial. atleast not without just parroting what some one else says, and while most chistians have no problem with that i feel it is intelectualy  dishonest.

But then lets just for arguments sake take axiom s5 to be true, does the argument i made with (x) not stand up to scrutiny?

The other question is. Is it possible in modal logic for worlds to exist that dont follow our rules of logic or mathematics. is it possible for there to be  worlds where pi =2 or 2+2= 563

And yes i would actualy love some reading suggestions upon this so i can start to educate myself on this topic

Here's my response (didn't read it all, TL;DR)

1. It is possible that a maximally great being exists.

Really? Demonstrate how...

It's also fun to replace "maximally great being" with "Captain Kirk" or some equally fictional character. Shows the logical stupidity of such a logical argument.

I feel like this fails right off the bat.

1. It is possible that a maximally great being exists.
2. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.

Actual or conceptual world? Obviously, just because one could say that something is possible doesn't automatically mean that it actually exists somewhere.

1) It is possible that I won $1m.
2) If it is possible that I won $1m, then I won $1m on some possible world.
3) If it is possible that I won $1m on some possible world, than I won $1m on every possible world.
4) If I won $1m on every possible world, then I won $1m in the actual world.
5) If I won $1m in the actual world, then I actually won $1m.
6) Therefore, I won $1m.

Obviously (to me at least) I did not in fact win one million dollars. This whole string of logic simply doesn't hold up and just makes one baseless jump after another. Plus, as others have pointed out, you can cut and paste to explain anything into apparent existence no matter how silly or contradictory.

Here I would re-enter the absence of evidence ,does not, = evidence of absence argument.

True... Except for where there should be evidence. When there are specific claims that should have left evidence behind, and there is none. Such can certainly cast serious doubt on the veracity of the claim.

to say there is no evidence for the existence of God suffices to say that the atheist's knows all possible proofs that God exists, which is logically absurd

True, I wouldn't say that I know every every argument ever raised or that will ever be raised, but that misses the point. The important fact is that thus far, every so called proof or argument brought forth has been empty, ill conceived or absurd. One mustn't know every possible claim to come to a conclusion. Say you enjoy living in the town you reside in and haven't seen any reason to think you'd like somewhere else better. Have you lived in every single town in the world? Have you at least visited or researched every single town? It would be absurd to say that you would need to be privy to every claim to say which town is for you. Quite simply, I as an Atheist have not seen any evidence for an deities. After years of personal study, I've found nothing. Nothing in the historical record or the writings of the many who came before me. In light of this lack of evidence I can say that I see not logical reason to accept such an outstanding claim. Then add on top of that lack of evidence that there is evidence expressly contradicting specific god claims and I'd say that at the very least that doubt is quite justified.

Logically speaking why would 3 [X is true in all possible worlds] follow from 2, [X is true in some possible world].

This seems to me would only makes sense if X defines what is possible in the first place. Easy to overlook if you define or assume X in such a way. Take X to be the exact mass of the up quark, which unlike an unknown digit in pi is as far as we know not necessarily what it is in our Universe in another possible or even equally probable Universe.

You could turn it around too and claim that since we live in a possible world (2), every X in our world applies to all possible worlds (3). Then let him modally bicker away with a Fine Tuning Theist.

It's really sort of irrelevant when you consider the nature of logic's origin. Ask him how his thoughts were formed and what they're made of. Or, hey, we can just philosophize all day and pretend we've made no advancements in physics and neurology doesn't exist. That's cool too.

1. It is possible that I win the lottery.

2. If it is possible that I win the lottery, then I win the lottery in some possible world.

3. If I win the lottery in some possible world then I win the lottery in every possible world.

4. If I win the lottery in every possible world then I win the lottery in the actual world.

5. If I win the lottery in the actual world then I have won the lottery.

6. Therefore I have won the lottery.

No it wasn't a reply to you, I just plugged it in here. And no I see no way by which I could possibly have concluded that you agree with it's validity.

I just thought maybe my suggestion of substituting the mass of an up quark is (apparently) still too abstract to show what it I think what is wrong with this particular form in addition to premise 2 not necessarily following, premise 3 does not follow, except in the singular case that this is actually true. This is the clearest example by which to show this that I could think of.

Okay that is where I am wrong, within modal logic as far as I understand it now, you are right.

If the set of all possible worlds is infinite, it must necessarily be true. (edit: removed objection that I doubt is valid.)

The obviously flawed form here used:

1. It is possible that a maximally great being exists.
2. If it is possible that a maximally great being exists, then a maximally great being exists in some possible world.
3. If a maximally great being exists in some possible world, then it exists in every possible world.
4. If a maximally great being exists in every possible world, then it exists in the actual world.
5. If a maximally great being exists in the actual world, then a maximally great being exists.
6. Therefore, a maximally great being exists."

Or from 1 follows 6, what's in between is just a ritualistic formula and doesn't really matter: whatever you fill in at 1 will come out at 6.

Is a derived form, with copy of terminology, of that of Plantinga:

1. A being has maximal excellence in a given possible world W if and only if it is omnipotent, omniscient and wholly good in W; and

2. A being has maximal greatness if it has maximal excellence in every possible world.

It is possible that there is a being that has maximal greatness. (Premise)
Therefore, possibly, it is necessarily true that an omniscient, omnipotent, and perfectly good being exists.
Therefore, (by axiom S5) it is necessarily true that an omniscient, omnipotent and perfectly good being exists.
Therefore, an omniscient, omnipotent and perfectly good being exists.

In this form the objection to wrongful use of modal logic is much more in place. In the first argument it isn't pointed out that a "maximally great being" is only a "maximally great being" if and only if premise 3 is true, a tautology. Then indeed you are just begging the question and it isn't an argument at all.

dumb question, and may open a can of logic worms that none may want to bother with, but...

...in this context, what does the phrase "in some possible world" mean?  Any imaginable space which we cannot prove impossible?

Thanks.  I guess what is hanging me up is the word "possible".  By Greg's definition, "some is logically possible if it is not logically impossible," wouldn't a "possible world" then be any world that is not logically impossible?


For example, unicorns are not logically impossible, therefore they exist in some possible world. Yes?


Is the argument here then that if a "A maximally great being exists" in one world, then, by virtue of its maximal greatness, spans all possible worlds, and therefore exists in our actual world?

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Posted by Quincy Maxwell on July 20, 2014 at 9:37pm 28 Comments

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