The Instigator
orangutan
Con (against)
Losing
0 Points
The Contender
Philocat
Pro (for)
Winning
28 Points

The Plantingan Modal Ontological Argument is sound

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Post Voting Period
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after 4 votes the winner is...
Philocat
Voting Style: Open Point System: Select Winner
Started: 5/4/2015 Category: Philosophy
Updated: 1 year ago Status: Post Voting Period
Viewed: 619 times Debate No: 74762
Debate Rounds (4)
Comments (9)
Votes (4)

 

orangutan

Con

Resolved: The Plantingan Modal Ontological Argument (or a logically equivalent formulation) is sound.

This is a challenge to Philocat.

The burden of proof is on Pro to show that his argument is sound.

Pro will make his presentation in the first round. Pro will waive his last round. The debate will last four rounds.

Sources are fine as long as they are properly cited. TinyURL links do not count as sources.

I wish my opponent the best of luck in this debate. If Philocat does not desire to debate this topic at this time, I will consider allowing others to accept this challenge.
Philocat

Pro

Thanks Orangutan, I accept the debate.

Sound = 'based on valid reason' (1)

So I have the burden of proof to uphold the validity of the argument's reasoning.

____________________________________________________________________________________________________________________________________________________________

The Argument

Note: when I say 'possible' in this context, I am essentially saying 'logically possible'. This is because we are discussing ontology (that is, whether things exist), and hence we are discussing whether it is logically possible that such and such exists. In other words, when discussing ontology, logical possibility is the form of possibility most appropriately considered (2).

P1: God = The greatest possible being/maximally great being (the definitions are interchangeable)
P2: God exists in at least one possible world
P3: If God exists in at least one possible world, He exists in all possible words
P4: The actual world is a possible world
C: God exists in the actual world.

This argument is deductively valid, inasmuch as the premises deductively entail the conclusion. The only point of contention is regarding the veracity of the premises.

Defence of P1

This is an uncontroversial premise - it accords with the traditional understanding of God so this is a suitable definition. Even if one denies that God is the greatest possible being, the argument is still sound insofar as it proves that the greatest possible being exists.

Defence of P2

This logically follows from P1, the greatest possible being is, by definition, possible. Otherwise it wouldn't be the greatest possible being.

Defence of P3

From P2, we have two possible options:

1. God exists in some possible worlds, viz. He exists contingently
2. God exists in all possible worlds, viz. He exists necessarily

The latter is greater than the former, since necessary existence is 'greater' existence than contingent existence, insofar as necessary existence entails a greater 'amount' of existence than contingent existence. If X exists in more possible worlds than Y, then X has greater existence than Y.

As the former is therefore less great than the latter, it contradicts the definition of God. As if He only existed contingently then he wouldn't be maximally great, yet he is defined as being so. Reductio ad absurdum, the negation of an absurd conclusion must be true. Ergo, God must exist necessarily.

Defence of P4

Uncontroversial. If the actual world was not possible, then it wouldn't exist. But if it doesn't exist then it isn't actual. Hence the contradiction present if one attempts to negate this premise.

Conclusion

This logically follows from P4.




I have upheld the argument and hence I affirm the resolution.

Over to Con.




(1) Google: 'Define sound'
(2) https://www.bu.edu...;
Debate Round No. 1
orangutan

Con


I thank Philocat for accepting my challenge.



The common philosophical definition of a sound argument is an argument in which the argument is logically valid and the premises are true [1]. So Philocat must show that not only is the Modal Ontological Argument (MOA) deductively valid but that the premises are true.



First, I would like to clarify the definitions of two modal operators that are very important in the MOA.


“Possibility: A proposition is possible if and only if it is true in some possible world. A being is possible if and only if it exists in some possible world” [2].


“Necessity: A proposition is necessarily true if and only if it is true in every possible world” [2].


These definitions are expressed via possible world semantics [3]. Another way to express them is the following. A proposition is necessarily true if it was logically impossible for the proposition not to be true. In other words, a proposition is necessarily true if, if the proposition was false, a logical contradiction would result. In contrast, a proposition is possibly true if it is not logically impossible that the proposition is true. Given these definitions, I think my opponent can agree with me that “God necessarily exists” is equivalent to “It is necessarily true that God exists.” The latter is a preferable expression since the former gives the impression that necessity is a characteristic, when it is in fact a modal operator.



Argument Against MOA



The argument against MOA that I will present is not my own invention; I found it on a blog post made by a user named Rayndeon [4]. Many of the following ideas are his own, not mine, but I will present the argument in my own words.



Consider the following argument (I pick up the numbering from where Philocat left off)


(6) It is necessarily true that God exists.


(7) If it is necessarily true that God exists, then God exists. (S5 axiom)


(5) God exists


This argument is unimpressive, since it commits the fallacy of begging the question [5]. No atheist would agree that it is necessarily true that God exists, since that would mean that it is logically impossible that God exists, and the atheist clearly thinks it is logically possible that God does not exist. It is unclear how the theist would be able to demonstrate premise 1 to be true. However, I contend that this argument is logically equivalent to the MOA, and hence the MOA is question-begging. Given proposition 1 and the S5 axiom, we have the following deduction.



(6) It is necessarily true that God exists.


(8) If it is necessarily true that God exists, then it is possible that it is necessary that God exists. (S5 axiom)


(9) It is possible that it is necessary that God exists.



So (6) and (9) are logically equivalent. So a modal argument starting with (9) would be, despite appearances, begging the question. But the truth of (9) is exactly what my opponent’s argument requires to be true.



Look at my opponent’s formulation of the argument. Since this formulation is slightly sloppy, I will rephrase the premises. P3, that “if God exists in at least one possible world, He exists in all possible words” means (3) if it is possible that God exists, then it is necessary that God exists. How does my opponent justify (3)? In his argument for (3), he is using premise (9) as justification for (3), and (3) is in fact an application of the S5 axiom. But since (9) and (6) are logically equivalent, what he is really trying to do is argue that it is logically impossible for God not to exist, which is question-begging. So when my opponent says that necessary existence is “greater” than contingent existence, he is saying that it is possible that it is necessary that a maximally great being exists. We can thus more clearly formulate my opponent’s argument as follows.



(9) It is possible that it is necessary that God exists.


(3) If it is possible that it is necessary that God exists, then it is necessary that God exists (S5 axiom)


(6) It is necessary that God exists.


(7) If it is necessarily true that God exists, then God exists. (S5 axiom)


(5) God exists.



As I showed, (9) and (6) are logically equivalent, so the argument is question-begging. To accept the first premise is to accept that it is logically impossible for God not to exist. But we have not actually been given a real argument that it is logically impossible for God not to exist- that would refute atheism by itself! My opponent claims, “As if He only existed contingently then he wouldn't be maximally great, yet he is defined as being so. Reductio ad absurdum, the negation of an absurd conclusion must be true. Ergo, God must exist necessarily.” But this does not follow. At best, this shows that “If God exists, then it is necessary that God exists.” But the argument is supposed to prove that God exists!



It also seems, by the way, silly to say that “necessary existence is 'greater' existence than contingent existence, insofar as necessary existence entails a greater 'amount' of existence than contingent existence.” There is no such thing as an amount of existence. The confusion comes from assuming that necessity and possibility are properties, rather than modal operators. Possibility and necessity refer to propositions, not beings. “God is a necessary being” might be a useful shorthand for “It is necessary that the proposition that God exists is true,” but it does not follow that necessity is a property- my opponent has to prove it.



Now, suppose my opponent claims, “We should assume that ‘(9) It is possible that it is necessary that God exists’ is true unless we prove otherwise. A reasonable rule is to assume the possibility of a thing or a proposition unless we have evidence that such a thing is possible.” A rule like that might work in regards to epistemic possibility, but we are talking about modal possibility. Rayndeon has an answer to this sort of objection- “However, one honestly wonders how such an approach would consistently apply to necessity. Recall that a proposition is necessary if and only if its negation is impossible, that is, its negation entails a contradiction or some metaphysical absurdity. If one were indeed to consistently apply the maxim ‘modal propositions are innocent until proven guilty,’ one ought to inquire, with respect to a purportedly necessary proposition if the negation of a proposition is really impossible. It seems that one is ruling the negation as ‘guilty’ and as impossible” [4]. Rayndeon makes the point that if you apply an “innocent until proven guilty” rule to propositions of necessity, you are making a big claim which requires justification, namely that it is logically impossible for the proposition to be false. So in order to prove that his argument is sound, Philocat must prove that it is logically impossible for God not to exist.



Besides, as Rayndeon points out, if we applied an “innocent until proven guilty” rule to propositions of necessity, we can make absurd arguments proving that, for example, unicorns exist [4]. Here is an example of one such argument.



(10) It is possible that it is necessary that Superman exists (after all, it is logically possible that denying the existence of Superman is a logical contradiction, right?).


(11) If it is possible that it is necessary that Superman exists, then it is necessary that Superman exists. (S5 axiom)


(12) It is necessary that Superman exists.


(13) If it is necessary that Superman exists, then Superman exists.


(14) Superman exists.



Clearly, something has gone wrong here, but what? The answer is that propositions 10 and 12 are logically equivalent, and the argument is question-begging in favor of Superman’s existence. But just as we have no reason to believe that it is necessarily true that Superman exists, so has my opponent failed to show that it is necessarily true that God exists.



Conclusion



The resolution is “The Plantingan Modal Ontological Argument is sound,” and the burden of proof is on Pro to affirm the resolution. I have shown that Pro has not given any reason for believing that the premise that it is possible that it is necessary that God exists is in fact true. In order for Pro to uphold his burden, he must show that denying God’s existence entails a logical contradiction. If he fails to do this, then he fails to meet his burden of proof, and the debate goes to Con.



[1] http://philosophy.hku.hk...


[2] http://plato.stanford.edu...


[3] http://plato.stanford.edu...


[4] http://analyticabstraction.blogspot.com...


[5] http://www.nizkor.org...


Philocat

Pro

I will now defend the argument.

Begging the question?

I maintain, that the argument is not question-begging if I manage to argue soundly that it is possible that God necessarily exists. If I do not manage to do this, then I concede that the argument is indeed question begging.

So, is it possible that God, as a necessary being, exists? Firstly, I must establish whether God is necessarily necessary.

Consider the definition of God as 'a maximally great being'. Such a definition entails that it is necessary that God is necessary, as otherwise God would not be maximally great (and hence present a contradiction). Logical contradictions are necessarily false, so the negation of a logical contradiction is necessarily true. Therefore, God is necessarily necessary.

Something is possible if it is true in at least one possible world. God being necessarily necessary entails that God is necessary in all possible worlds (as per modal logic). Hence God is necessary in at least one possible world.

In other words, it is possible that God is necessary, which is the premise upon which S5 modal logic concludes that God necessarily exists. This is because if it is possible that God is necessary, then God is necessary in at least one possible world. Therefore, in some possible world, it is true that God exists in all possible worlds - but this can only be the case if God exists in all possible worlds. Therefore God exists in all possible worlds if it is at least possible that he does.

I think Con's issue with the argument is that he does not realise that the argument is essentially a demonstration, insofar as it demonstrates, as opposed to argues, that it is necessary that a maximally great being exists by logical necessity and implications of the definition. The argument would be fallacious if the initial premise (that it is possible that God necessarily exists) is unsupported, but it is not. It is a logical implication of the concept of a maximally great being that such a being is necessary, otherwise there would be a logical contradiction.

The reason it exists as, and is perceived as, an argument is that, prima facie, the proposition:

'It is possible that a maximally great being exists'

does not seem to entail that this being necessarily exists, but this is only because of the intricacies of modal logic.

But when thought about, it becomes clear that the above proposition logically entails that a maximally great being necessarily exists, for the reasons explained above.

One may ask whether I am justified in presenting this proposition as true. Just to make sure, I will reiterate why it is possible that a 'maximally great being' exists.

P1: Something is logically impossible if, and only if, it 'violates the laws of logic, and is therefore inconsistent or self-contradictory' (1)
P2: A maximally great being does not violate the laws of logic
C1: A maximally great being is not logically impossible.
C2: A maximally great being is possible.

P1 is uncontroversial, and I do not have the burden of proof to argue that P2 is correct. This is because P2 is a negative premise and it is impossible to prove a negative. Con has the burden of proof to demonstrate that a maximally great being violates the laws of logic.

Therefore the conclusion is justified, that it is possible that a maximally great being exists.

Finally, my opponent argues that the argument can be used to prove the existence of fictitious entities such as Superman. However, the parody does not work because nothing in the definition of 'superman' entails that he is necessary. In contrast, the very definition of 'maximally great being' entails that this being is necessary, otherwise there is a contradiction.

In order for Con to refute the argument, he must either:

1. Prove that it is not possible that a maximally great being exists, by proving that such a being violates the laws of logic

or

2. Refute the argument that:

'it is possible that a maximally great being exists'

logically entails that:

'it is necessary that a maximally great being exists'


Con has done neither so far, hence I affirm the resolution.


Debate Round No. 2
orangutan

Con

orangutan forfeited this round.
Philocat

Pro

I extend all arguments.
Debate Round No. 3
orangutan

Con

orangutan forfeited this round.
Philocat

Pro

Vote pro please :)
Debate Round No. 4
9 comments have been posted on this debate. Showing 1 through 9 records.
Posted by tejretics 1 year ago
tejretics
Why is orangutan's account not active??? :(
Posted by tejretics 1 year ago
tejretics
Hmmm ... no reductio ad absurdum?
Posted by Philocat 1 year ago
Philocat
metaphysical possibility could be a separate thing, but it need not be discussed. I give a source in my argument that confirms that logical possibility is the most suitable form of possibility to be discussed when discussing ontology.
Posted by tejretics 1 year ago
tejretics
Or are metaphysical and logical possibility the same?
Posted by tejretics 1 year ago
tejretics
@Philocat, we should discuss if it is *metaphysically* possible, not logically. For something to be "logical", it need merely be non-contradictory and subjectively accurate.

For example:

Water =/= H2O
Water /= H2O is *logically* possible
Water = H2O is also logically possible
Water = H2O is metaphysically possible
Water /= H2O is metaphysically *impossible*
Posted by orangutan 1 year ago
orangutan
A minor error- one sentence should read, "No atheist would agree that it is necessarily true that God exists, since that would mean that it is logically impossible that God does not exist, and the atheist clearly thinks it is logically possible that God does not exist. "
Posted by tejretics 1 year ago
tejretics
Same here, @Chaos!
Posted by Chaosism 1 year ago
Chaosism
~makes popcorn~
Posted by tejretics 1 year ago
tejretics
Wow ... orangutan v. Philo ... should be a great debate. The two debaters with whom I've had the toughest debates of my life! =)
4 votes have been placed for this debate. Showing 1 through 4 records.
Vote Placed by johnlubba 1 year ago
johnlubba
orangutanPhilocat
Who won the debate:-Vote Checkmark
Reasons for voting decision: Con never showed up in the final rounds.
Vote Placed by dsjpk5 1 year ago
dsjpk5
orangutanPhilocat
Who won the debate:-Vote Checkmark
Reasons for voting decision: Ff
Vote Placed by Chaosism 1 year ago
Chaosism
orangutanPhilocat
Who won the debate:-Vote Checkmark
Reasons for voting decision: Forfeiture by Con.
Vote Placed by tejretics 1 year ago
tejretics
orangutanPhilocat
Who won the debate:-Vote Checkmark
Reasons for voting decision: Forfeiture.