Question related to the Ontological Argument

[CatholicSoxFan]

I was talking to someone else on the Ontological Argument, and rather than denying the first premise or denying Modal Logic, as I expected they would, they instead said that the idea that it is a great-making property to be omnipotent, omniscient, necessary, etc. is nothing but an a priori assumption, and that the whole argument is basically just begging the question, because the only way someone would only accept the argument if they also accepted the a priori assumptions like the aforementioned claim that omnipotence, omniscience, necessity, etc. are great-making properties. He particularly argued like this in respect to necessity, and contended that to claim that to be necessary is greater than to be contingent is nothing but an a priori assumption. To those who use this argument, how would you answer this objection?

 

[glendab]

Just ask them to define “perfect” and watch the wheels turn.

Glenda

 

[CatholicSoxFan]

I already ended the discussion, and if it’s lawful over here, I’ll post the whole thread for reference. Thus is how the discussion effectively ended:
Him:
“The fact that one can think of a being that is maximally great and, therefore necessary, does not make the existence of that being therefore necessary. It just means that such a being can be imagined within a particular set of consistent and coherent logical axioms and proofs. It says nothing about actual reality.”

Me:
“So, in other words, it is possible for an MGB to exist. You’ve basically defined what a “possible world” is in the context of this argument.”

 

[polytropos]

You seem to be defending Plantinga’s version. I do not think Plantinga’s ontological argument is a very good argument. Given the nature of iterated modalities (ie. possibly necessary), it will be epistemically circular for anyone who is familiar with modal logic. (If you know that something that is possibly necessary exists in all possible worlds, then you will know that admitting the possibly of something defined to be necessary is tantamount to admitting its necessity.)

One could appeal to the consistent conceivability of such a being, but I don’t think doing so is quite adequate, for reasons touched upon here. It seems like one would need to develop some sort of classical theistic framework (which Plantinga does not have) to justify the mutual entailment of the divine attributes. Since Plantinga doesn’t do so, his argument does seem vulnerable to parody objections, as Feser notes.

James Ross defends a somewhat similar modal argument in his book Philosophical Theology. It has certain advantages however. It does not make use of iterated modalities, so it does not face circularity issues. Ross also uses I think a more plausible starting point; his argument shows that a “uncausable and unpreventable” being exists, which seems to be sufficient to work out the other divine attributes. He also handles, in great deal, Kantian (that existence statements are always contingent) and Humean (that it can always be maintained that an empty world is possible) objections. The book is very technical, but worth reading, if you can find a cheap copy (it’s out of print).

 

[DanAl]

I already ended the discussion, and if it’s lawful over here, I’ll post the whole thread for reference. Thus is how the discussion effectively ended:
Him:
“The fact that one can think of a being that is maximally great and, therefore necessary, does not make the existence of that being therefore necessary. It just means that such a being can be imagined within a particular set of consistent and coherent logical axioms and proofs. It says nothing about actual reality.”

Me:
“So, in other words, it is possible for an MGB to exist. You’ve basically defined what a “possible world” is in the context of this argument.”

Why couldn’t conceivability make God necessary? He is just begging the question and asserting that of the notion maximal greatness does not say anything about actual existence…Why is that? I would press him on the point and hound him every time that he makes an assertion.