Plantinga's ontological argument

[bob135]

http://en.wikipedia.org/wiki/Ontological_argument#Plantinga.27s_modal_form_and_contemporary_discussion

"
Alvin Plantinga has given us another version of the argument, one where the conclusion follows from the premises, assuming axiom S5 of modal logic. A version of his argument is as follows:

1. By definition a maximally great being is one that exists necessarily and necessarily is omniscient, omnipotent and perfectly good. (Premise)
2. Possibly a maximally great being exists. (Premise)
3. Therefore, possibly it is necessarily true that an omniscient, omnipotent and perfectly good being exists (By 1 and 2)
4. Therefore, it is necessarily true that an omniscient, omnipotent and perfectly good being exists. (By 3 and S5)
5. Therefore, an omniscient, omnipotent and perfectly good being exists. (By 4 and since necessarily true propositions are true.)
6. The axiom S5 says that if a proposition is possibly necessarily true, then it is necessarily true."

I'm just looking for someone to explain this proof in more detail, especially the premises. With P1, how do we know that existence is greater than nonexistence? Is that another premise that should be part of the argument? Why is perfect good greater than perfect evil? With P2, how can we come to the conclusion that it is possible that such a being exists? Of course, we can say we are uncertain, but this tells us nothing about the possibility. My biggest problem in understanding is with Axiom S5. Wikipedia's short article didn't help much, but it does claim that S5 is accepted by many contemporary philosophers. Can anyone tell me how the proof works? Here's the article:

http://en.wikipedia.org/wiki/Axiom_S5
"Axiom S5 is the distinctive axiom of the S5 system of modal logic and says that if possibly necessarily p, then necessarily p. If the modality here is what Alvin Plantinga calls "broadly logical" necessity and possibility, then an argument for the axiom can be given as follows. If possibly necessarily p, then there is a possible world w at which p necessarily holds. Then, it is true at w that p is a broadly logically necessary truth, something whose negation would in a broadly logical sense be self-contradictory. But if something is self-contradictory at some possible world, then it is self-contradictory at all worlds, and Plantinga holds that this is true even in the case of broadly logical self-contradictions as well."

 

[simpleton]

I wasn't able to make the jump from 3 to 4 or understand how "possibly" equates to "necessarily".

I'm at work... but there's possibly a minature pink buffalo in my closet at home.

 

[fuzzyh]

I wasn't able to make the jump from 3 to 4 or understand how "possibly" equates to "necessarily".

It has to do with an understanding of modal logic. I still don't understand modal logic completely, so I wish I could give you more. It basically means that if something is possible, then it can be possible in all possible world. If something was necessary it is necessary in all possible worlds. If something was possibly necessary, it would be necessary in all possible world.

I hope that helps with out confusing to much.

 

[psychedelicist]

I suppose one could argue that in an eternally existing and everchanging universe such as the one we live in, any logical possibility can, and will, occur an infinite amount of times. That's the beauty of infinite-ness.

This is what the major premises of his arguement is lacking- any LOGICAL possibility can and will occur, but it has yet to prove that an omnipotent, omniscient creator is a logical being. It certainly seems paradoxical enough. On top of that, I wonder ig an omnimax being could simply come into existence from the universe. Perhaps if, in the same way humans are self aware of their selves, the universe was to instantly become an entity aware of it's own existence this would be a possibility, but once again we can't (at least not with our present knowledge) say this is at all logical either.

 

[fuzzyh]

The universe it seems is not finite though. This is not dealing with an infinite universe, but rather an infinite amount of universes. Why wouldn't a omnipotent, omniscient creator be logical? Also, an omnimax being could not come into existence from the universe. The universe would be greater than it. Furthermore, the omnimax being that sprang from the universe would not be infinite. To be infinite means that it must have never have had a beginning.

 

[psychedelicist]

The universe it seems is not finite though. This is not dealing with an infinite universe, but rather an infinite amount of universes. Why wouldn't a omnipotent, omniscient creator be logical? Also, an omnimax being could not come into existence from the universe. The universe would be greater than it. Furthermore, the omnimax being that sprang from the universe would not be infinite. To be infinite means that it must have never have had a beginning.

By infinite I meant in a temporal manner, I guess I should have made that clear in my first post. Like the old arguement about monkeys and typewriters, if one monkey had one typewriter and an infinite amount of time he would produce not only all the works of shakespeare but all the books ever written an infinite amount of times.

As for an omnipotent being being illogical, it seems more the fact that he could be omnipotent and create anything. An omnimax being would have to be objective, unbiased, all that. But if it was a truly objective being he would also be without goals, desires, or anything that would prompt him to create anything at all.

 

[fuzzyh]

However, the best theories of our universe start with a beginning and wind down, much like a clock. So really, the argument about monkeys and typewriters is only potential and speculative at best.

I don't you have provided much evidence as to how an omnimax being could be illogical. I don't see how a being truly objective could be without goals desires, etc. Of course, I hold to a God of love (the Christian God), so my worldview has no problem with creation. In fact, I would say that the Christian God is the only God that avoids logical contradictions. Although, there have been some arguments against the Christian God, I haven't found any to be all that strong.

 

[Species8472]

1. Possibly a maximally great being exists. (Premise)
2. Therefore, possibly it is necessarily true that an omniscient, omnipotent and perfectly good being exists (By 1 and 2)
3. Therefore, it is necessarily true that an omniscient, omnipotent and perfectly good being exists. (By 3 and S5)
4. Therefore, an omniscient, omnipotent and perfectly good being exists. (By 4 and since necessarily true propositions are true.)
5. The axiom S5 says that if a proposition is possibly necessarily true, then it is necessarily true."

It must also necessarily be True that if a being that is omnipotent, omniscient and omnibenevolent exists then there must be a hierarchy of consciousness that spans all creation.
Therefore, an antediluvian must exist that consists of the nature of Satan, who is omnimalevolent; since all beings have free will and therefore free choice, then it is in necessary agreement (if we are to look at logic) that a being consisting of an (evil) or imperfect will; that exceeds natural power and knowing, must, necessarily exist.

 

[Species8472]

I wasn't able to make the jump from 3 to 4 or understand how "possibly" equates to "necessarily".

I'm at work... but there's possibly a minature pink buffalo in my closet at home.

3 is talking about the possibility that such a being exists, according to the first two premise. 4 is talking about the necessity of such a being existing because of the possibility that such a being exists. Through logical deduction: If it is possible, by definition, that such a being exists then possibility relates to necessity. In logical argument, that which is possible, is necessarily True.

 

[bob135]

Hmm...I was really looking for someone to just explain the argument. If anyone wants to try to answer my original questions that would be helpful.

My understanding of S5 is that since a maximally great being is possibly necessary, it exists in at least one of an infinite number of hypothetical universes. However, for it to exist in just one universe, that would mean that this maximally great beings existence in that universe was a result of a property of that universe. This is the only way to explain why the being would exist in one universe, but not the other. However, this would mean that the beings existence is contingent, not necessary, resulting in a contradiction. Therefore, to avoid this contradiction, the maximally great being must exist in all universes.

If that explanation of S5 is correct, than the conclusions clearly follow from the premises, so the only remaining questions would be about the soundness of the premises.

 

[Species8472]

Hmm...I was really looking for someone to just explain the argument. If anyone wants to try to answer my original questions that would be helpful.

My understanding of S5 is that since a maximally great being is possibly necessary, it exists in at least one of an infinite number of hypothetical universes. However, for it to exist in just one universe, that would mean that this maximally great beings existence in that universe was a result of a property of that universe. This is the only way to explain why the being would exist in one universe, but not the other. However, this would mean that the beings existence is contingent, not necessary, resulting in a contradiction. Therefore, to avoid this contradiction, the maximally great being must exist in all universes.

If that explanation of S5 is correct, than the conclusions clearly follow from the premises, so the only remaining questions would be about the soundness of the premises.

I am trying to explain the argument by shedding some light onto it. First, you have to understand logical argument:

3 is talking about the possibility that such a being exists, according to the first two premise. 4 is talking about the necessity of such a being existing because of the possibility that such a being exists. Through logical deduction: If it is possible, by definition, that such a being exists then possibility relates to necessity. In logical argument, that which is possible, is necessarily True.(that is the summation of the axiom).

By definition, if such a being is omnipotent then its power exceeds that of the physical (or one possible) universe. If such a being is omniscient then its knowing exceeds that of one possible universe.
If such a being is omnibenevolent then its goodness must exceed that of one possible universe.
You are correct in your assumption that if such a being exists then it is necessarily contingent to all possible worlds, since by definition, such a being must be infinitesimal in nature; according to power, knowledge and goodness.
If you really want to shed some light upon this argument then I would recommend Baruch Spinoza and his work, The Ethic.

 

[StrugglingSceptic]

Hmm...I was really looking for someone to just explain the argument. If anyone wants to try to answer my original questions that would be helpful.

My understanding of S5 is that since a maximally great being is possibly necessary, it exists in at least one of an infinite number of hypothetical universes. However, for it to exist in just one universe, that would mean that this maximally great beings existence in that universe was a result of a property of that universe. This is the only way to explain why the being would exist in one universe, but not the other. However, this would mean that the beings existence is contingent, not necessary, resulting in a contradiction. Therefore, to avoid this contradiction, the maximally great being must exist in all universes.

If that explanation of S5 is correct, than the conclusions clearly follow from the premises, so the only remaining questions would be about the soundness of the premises.

That's a decent explanation of S5. Platinga is using the possible worlds semantics of modal logic, so try to recast *every* statement he makes in terms of possible worlds. According to this semantics, we have a set of possible or hypothetical worlds (not necessarily infinitely many, we could well only have 1 for instance), and we can interpret statements of the form

"Possibly, P is necessarily true"

as saying that in at least one of these worlds, it is true to assert that P is true in every possible world. But this just means that P is true in every possible world. Hence, S5 is true and can be taken as an axiom under this semantics.

You can attack the argument in a few ways. You have suggested questioning the soundness of the premises. My first question would be how to interpret P1. Perhaps something like this:

If x is a maximally great being, then x exists, is omniscient, omnipotent and perfectly good in all possible worlds.

I'm not sure that "omniscient", "omnipotent" and "perfectly good" are coherent properties, but I think we can let that slide for now, and accept the axiom as sound.

Premise 2 is now

In some possible world, there exists an x which is a maximally great being.

And from this, we can validly deduce that x exists in all possible worlds, and therefore exists.

I would not accept premise 2, and I think you would have to be a fool to do so (Hartsthorne pulls this stunt, also). More importantly, I don't accept a theory of possible universes in the first place, rendering the whole strategy a waste of time in my eyes from the start.

 

[fuzzyh]

The axion S5 is still debated among many people today. Those that hold to it say that Plantinga's argument is valid. Those that do not hold to it say that his argument is invalid.

As to opinions on it, my opinion is that it is a valid argument for the existence of God. Although, I'd probably never use it in a debate. I know that Norman Geisler, Christian Philosopher, says that it's valid and his philosophy is extremely Thomistic. Based upon my own reasoning and Geisler's, I have a pretty high view of it.

I haven't heard much about what the universities think about this argument. Perhaps I should run down to the local college and talk with them about it.