Where is the weakness in the ontological proof for God's existence?

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I read the ontological proof for God's existence. As much as I understood, it says that if you consider that existence is part of essence, then the most complete essence should also exist.

Now, I see that as a perfect, flawless argument, on the condition that we accept the premise that "existence is part of essence". Am I right? Is this proof 100% valid, if we accept that premise?

I know that one can argue on the first place that "essence excludes existence". That's equivalent to not accepting the premise, and is valid enough to be noticed. But my question is that, if we accept the premise, then can we regard this argument as a really complete argument?

6This question falls directly in line with how I imagined the course of this site. Cool. – davidlowryduda – 2011-07-20T17:46:05.950

"Existence is not a predicate" is the usual formulation in modern terms, from Russell. – None – 2011-07-21T12:05:44.790

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No, it is not a flawless argument even if you accept the premise. It simply does not follow that, from the premise that existence is a part of essence, the most complete essence must exist; it is a non sequitur.

Consider Anselm's argument:

Premise: God is that than which nothing greater can be thought.

Argument: The greatest thing must exist, or it is not the greatest thing.

Conclusion: Hence god exists.

Compare this to the following argument:

Premise: The perfect number is the number who has no greater number.

Argument: The perfect number must exist, or it is not the perfect number.

Conclusion: Hence a greatest number exists.

Here it becomes obvious what the error in the argument is: even if we accept that the existence of perfection is necessary for it to be perfect, perfection can still just as well simply not exist.

So if existence is a part of essence, that does not mean that the most complete essence exists. It only says that, if it doesn't exist, it is not the most complete essence. So all you say is that, if the most complete essence doesn't exist, then it doesn't exist, but if it exists, then it exists. Well, we can agree on that. :-)

But that's why God is compared with infinity. – rus9384 – 2018-09-13T07:51:36.990

6+1 for the most excellent analogy (is that original with you?) – Ben Hocking – 2011-07-21T01:27:00.663

@Ben: I don't know. Most things I've come up with is something other people already came up with way before me, so probably not. :-) – Lennart Regebro – 2011-07-21T05:25:37.373

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St. Anselm was faced with essentially this objection from Gaunilo in his own lifetime. Consider Islandia, and Island greater than which none can be conceived. https://secure.wikimedia.org/wikipedia/en/wiki/Gaunilo

– vanden – 2011-07-21T17:47:51.537

1I think your second argument was meant to say: Premise: The perfect number is the number who has no greater number. Argument: The greatest number must exist, or it is not the greatest number. Conclusion: Hence the perfect number exists. Otherwise the analogy between the two arguments is flawed. – Decent Dabbler – 2011-09-18T12:31:35.860

@fireeyedboy: No "great" in when it comes to god should be interpreted not as "big" but as "good", ie perfect. When it comes to numbers "great" suddenly mean "big" instead, which would be confusing – Lennart Regebro – 2011-09-18T15:12:13.260

1Alright, but even so, the analogy is still flawed then. You are flipping the logic in the second example. Taking your second example as a base, by analogy, the first example should then be: Premise: God is that than which nothing greater can be thought. Argument: God must exist, or it is not God. Conclusion: That than which nothing greater can be thought exists.) In other words: in the second example you are circularly arguing for the existence of the term being defined by the premise, not the existence of the premise, from which we can conclude the existence of the term, itself. – Decent Dabbler – 2011-09-18T16:16:49.317

Sorry for not being able to express myself more clearly. English is not my native language, and I'm having a bit of a hard time conveying my exact point at this moment. :-/ Hope it's clear enough nonetheless. – Decent Dabbler – 2011-09-18T16:18:12.260

@fireeyedboy: Yeah, I see what you mean. I don't think this changes the fundamental argument though. – Lennart Regebro – 2011-09-18T17:44:43.653

No, I don't think so either. – Decent Dabbler – 2011-09-18T18:25:33.270

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I was looking for some clues for other reasons, and I think a weakness would be found in article 2 where it seems that the ontological proof is unnecessary if you can see God's effects.

One might ask the question, "Why would a God who manifests Himself in human history need to be merely self-evident?"

Because merely asking this might beg the question of whether or not "We need God" or "God needs us" because it would seem to imply that God needs to manifest himself. St. Thomas also states that we can't have total knowledge of God, by his effects, so it is irrelevant to say God needs us since we can't fully know Him.

If you can see my toe, then you can infer that I exist whether or not my toe is still attached in any meaningful way to my body.

My problem with your question is where the need is. You assume that the need is for god to make himself available to you. When the need is for you to make yourself available to God. You assume that god has a need to prove to you that he exists. This infers the assumpton that you benefit god more in heaven than hell. Our existance, assuming modeled after his, would lead me to believe that he would benefit more from an eternity of labors in hell, rather than a cushy eternity in heaven. – Chad – 2011-07-20T17:43:57.827

1@chad, read Summa, Q1 Article2 Reply to objection 3. Wherein it is written, on whatever it is they write it on up there, that since God is infinite we'll never have full knowledge of His existence based on His effects, glorious as they may be. Since God knows the limit to human imagination and understanding, things that can't be reasoned must be revealed. – Peter Turner – 2011-07-20T17:57:10.630

My last line was my conclusion based on evidence and what is written. Everything else is yours to interpret. – Chad – 2011-07-20T18:06:03.747

I am not sure about ontology or proof, but if we are said to be God's Children, then it seems reasonable that a good parent teaches by example. That would discharge any questions of need or visibility. – None – 2015-09-07T22:49:22.570

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Let us borrow the template of the argument from Internet Encyclopedia of Philosophy for sake of formality:

St. Anselm's argument runs as follows:

1. It is a conceptual truth (or, so to speak, true by definition) that God is a
being than which none greater can be imagined (that is, the greatest possible
being that can be imagined).
2. God exists as an idea in the mind.
3. A being that exists as an idea in the mind and in reality is, other things
being equal, greater than a being that exists only as an idea in the mind.
4. Thus, if God exists only as an idea in the mind, then we can imagine
something that is greater than Ω (that is, a greatest possible being that
does exist).
5. But we cannot imagine something that is greater than God (for it is a
contradiction to suppose that we can imagine a being greater than the
greatest possible being that can be imagined.)
6. Therefore, God exists.


Let us now look at the framework of the argument and for notation we shall use Ω in placee of God.

1. It is a conceptual truth (or, so to speak, true by definition) that Ω is a
being than which none greater can be imagined (that is, the greatest possible
being that can be imagined).
2. Ω exists as an idea in the mind.
3. A being that exists as an idea in the mind and in reality is, other things
being equal, greater than a being that exists only as an idea in the mind.
4. Thus, if Ω exists only as an idea in the mind, then we can imagine
something that is greater than Ω (that is, a greatest possible being that
does exist).
5. But we cannot imagine something that is greater than Ω (for it is a
contradiction to suppose that we can imagine a being greater than the
greatest possible being that can be imagined.)
6. Therefore, Ω exists.


Then a natural question follows, what is Ω? Part of the problem that lies is the semantics in which it is cloaked. Gaunilo the monk argued by same line of reasoning that Lost Island exists substituting that term for Ω:

Gaunilo's argument runs along the same lines:

1. The Lost Island is that than which no greater can be conceived.
2. It is greater to exist in reality than merely as an idea.
3. If the Lost Island does not exist, one can conceive of an even greater
island, *id est* one that does exist.
4. Therefore, the Lost Island exists in reality.


The faulty reasoning becomes apparent when we generalize the argument, substituting either a concept of Non-Being, Non-God, Nothing or Anti-God (if you will). We shall use the notation !Ω. Does the argument still remain valid if we proceed in the opposite direction?

 1. !Ω is that than which no greater can be conceived.
2. It is greater to exist in reality than merely as an idea.
3. If !Ω does not exist, one can conceive of an even greater !Ω,
one that does exist.
4. Therefore, !Ω exists in reality.


But by definition of "Non-Being" !Ω does not exist, yet we are asserting it does hence giving us a contradiction. Non-Being ipso facto does not exist if we take the premise that "existence is part of essence". One could also plug in the abstract concept of Nothing but that runs the danger of solipsism from linguistic abuse (ie bearing in mind when we state "Nothing" is that than which no greater can be conceived we agree that we cannot head in the opposite direction to conceive of, say, Ultra-Nothing or Meta-Nothing). Note: we do not interpret Nothing to be zero,] as one can always consider 0 plus an integer to counter the argument.

We can conclude that the fault lies in the not being able to manufacture a well-defined definition for the term greater or stems from taking Deity of Judeo-Christian background, and, St Anselm being an Archbishop, possibly, did not consider the dual of God (as in the argument above where loosely Zen philosophy was utilized of an idea of Non-Being).

As a side-note, I mention that we discussed it in college and our professor argued against the idea of being able to plug anything for Ω because of the meaning of greater. If we do so we need to come to an agreement of the meaning of greater than and thus the problem does not go away for the notions of Non-Being or Non-Existence.

Roughly, It is akin to visualizing God at top of peak of mountain or "upward light cone" and Nothing can be greater than Him. However, we can always conceive of a valley or "downward light cone" where at the very bottom resides Devil or Anti-Christ or the concept of Non-Existence. If we acknowledge St. Anselm's argument than there is nothing that prevents us from imagining something that is infinitesimal or dual to infinite nature of God.

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The ontological proofs that God exists by Anselm and Descartes use the logical device of contradiction, but their assumptions are indeed questionable. Anselm assumes that the greatest being that can be concieved of must exist outside the mind otherwise it is not the greatest being one can concieve of. So that the concept of such a being implies its existence. Descartes assumes that existence is more perfect than non-existence and so God, being perfect, has the attribute of existing. Both, however, do not jump from the assumption about existence being a part of God's nature to the conclusion that "therefore God exists". If this were so, their arguements would seem blatanly un-logical since they both assumed what they were trying to prove. Instead, both find a contradiction with the statement "God does not exist" (based on their assumption) and thus make the conclusion. Do their argument's seem more logical since they found a contradiction? Is it appropriate to use the law of excluded middle for this subject: if "god does not exist" is false then "god exists" is true?

If we accept that existence is a characteristic of that which we conceptualize as God then yes, God exists by finding a contradiction with "God does not exist" and then using the law of excluded middle to conclude "God exists".