What do you think of this argument for God?

[Nonpareil]

NonPareil,

Perhaps it is a result of when I grew up, and some of the changes I have seen and always hearing quotes like those below, but from my view of the semantics in modal logic, I think that possible is the more neutral and default term.   It is possible, if and only if; it is not necessarily false.  This is independant of whether it is actually true or false.   It is saying, that the claimant doesn't find any reason to find it logically impossible.  How would you go about showing that something is possible in this sense?

By showing that it is a logically coherent definition with parameters that can actually be fulfilled.

It is quite possible, for example, to challenge the coherence (and, therefore, possibility) of a definition that is "omniscient, omnipotent, and 'wholly good'", as none of these concepts are particularly well-defined and the latter is completely nonsensical, as "goodness" is a value judgment and has no objective standard.

Even if you could demonstrate this, though, you would still have to demonstrate that it is possible for an entity with these characteristics to exist. You would, in fact, have to be able to show that the universe is logically compatible with the existence of a maximally excellent entity - but you don't know enough about the universe's characteristics to be able to argue that.
 

Now you main objection as I see it, is that you consider the definition of maximally great in the premise to be incoherent.  I am assuming (from what you have stated thus far) that you mean incoherent in an ambiguous sense, and not that it is logically incoherent.

No. I mean logically incoherent - or, at least, semantically incoherent, which is essentially the same thing, as incoherent definitions necessarily lead to incoherent propositions. See above.

"Omniscient", "omnipotent", and "wholly good" have never been particularly well-defined terms.

From this, at best, I think that the best that you can say is that you cannot comment on it, because you do not know what it means.

Even if that were the case, it wouldn't actually help the ontological argument. It would just mean that we don't know enough to know if its definition is any good - which is precisely the issue that we have anyway.

In one view, this may make it a bad argument because people may come at it with different views.  Christians certainly have a longstanding view of what constitutes greatness concerning God, and I don't think that most of it would be considered controversial.  However; I don't think that most would argue that nothing is greater in an objective sense.  Is Love and self sacrifice greater than hate  and self serving?  Is greater potential in power greater than weakness?  Even if different people disagree on what is considered greatness.  They can be incorrect, and it doesn't make it subjective.

No. The fact that a measure of "greatness" is a judgment of value, and therefore by definition subjective, makes it subjective.

Would you agree, that apart from simply not taking a view on the argument (which is equivalent to pleading ignorance on the topic); that the argument makes the concept of God either impossible or necessary?

That is how the argument defines "God", so yes. If it weren't necessary, the argument would not recognize it as God.

That God is either possible, or logically incoherent.

No. Again, even if the definition of "God" can be shown to be logically incoherent, it can only be shown to be so with respect to itself. It is not a matter of whether or not the definition is coherent; it is a matter of whether or not it is compatible with the definition of "universe".

This is where we get into the issue of S5 not necessarily being the appropriate set of axioms for Plantinga to use. It is the only axiom set which allows him to move from "possibly necessary" to "necessary", but the specific axiom set that you use is dependent on exactly what sense in which you mean "possible" or "necessary".

The two ways in which these can be used, for purposes of this argument are the epistemic and the metaphysical. Epistemic possibility has to do with whether the thing is actually possible in our world, while metaphysical possibility only cares about whether or not there is a logically coherent abstract world in which it could be true. S5 is a set of axioms specifically designed for use with epistemic statements, but Plantinga is asserting the metaphysical possibility of his necessary entity. Again, modal logic is not my particular area of expertise, but it is entirely possible that S5 does not apply, and that Plantinga should instead be working under, say, S4, which does not allow for the leap from "possibly necessary" to "necessary" - and if he is working under S5, then he still needs to establish that it is actually epistemically possible for this being to exist.