The Kalam Cosmological Argument

[The Grand Nudger]

I don't think it even gets you there, lol.

[Thumpalumpacus]

There are a few problems with Plantinga's MOA. The argument is logically valid but not necessarily sound. The conclusions follow from the premises but the initial premise can't be demonstrated. It's troublesome to demonstrate that a "maximally great being" is possible, or even conceivable. That's further confounded if you view "greatness" as a value judgment. At the end of the day, that leaves us at "If god exists then god exists."

I also take exception to Plantinga's use of the term "God". Christianity is the only religion that refers to their deity in this way, so it's pretty clear that is Who is being discussed, whereas the MOA only gets you as far as a deistic god.

Right, the unquestioned premises are exactly why I pointed out GIGO. What is moral perfection? Omnipotence is reduced to "able to do anything 'possible'", which is an unspoken limitation on what is doable -- which limitation Christians won't admit for their god.

The limitations bump up against our definitions of "omnipotence" and "omniscience". That prefix, "omni-", has a specific meaning, and that meaning is that the suffix is unlimited.

It follows that this argument is semantical and not realistic. If something is "omni-" anything, then inserting "what he i]can[/i]" do or know is a sly admission that it is not actually "omni-", because with an omnipotent god, there really isn't a "can" -- or "cannot" -- there is only a will.

An omnipotent god who cannot do anything is not omnipotent. An omniscient god who cannot know everything is not omniscient. Sliding in the "can do" or "can know" is acknowledging that the "omni-" isn't "omni-".

That's not even to address whether an omnipotent god can act in a way that he might surprise himself. If he can surprise himself by a whimsical decision, he isn't omniscient; surprise means he did not foresee his own behavior. If he cannot surprise himself, because he knows everything, then he isn't omnipotent, because he can't break his vision.

Thus this omnigod collapses under contradiction, fancy logickifying notwithstanding. Godel in a roundabout way addresses this, no?

[Belacqua]

changed my mind

[Sheldon]

What is moral perfection? 

Subjective obviously, it even has apologists like Lane Craig claiming genocide is moral perfection.

 Omnipotence is reduced to "able to do anything 'possible'", which is an unspoken limitation on what is doable -- which limitation Christians won't admit for their god.

The limitations bump up against our definitions of "omnipotence" and "omniscience". That prefix, "omni-", has a specific meaning, and that meaning is that the suffix is unlimited.

Agreed, the word inevitably leads to contradictions, and post ad hoc rationalisations from apologists.

That's not even to address whether an omnipotent god can act in a way that he might surprise himself. If he can surprise himself by a whimsical decision, he isn't omniscient; 

Well the notion has larger problems than that, several posters myself included have mentioned the problems omniscience presents for any notion of free will or autonomy of choice for humans. However this must logically apply to the deity as well, if it is omniscient it must know what it will do, before it does it, thus it cannot have any autonomy itself. 
Parenthetically, since any notion of morality must involve autonomous choice, it also contradicts the idea that we or the deity could be moral at all, let alone that it could be perfectly moral, and of course if it has no autonomy of choice, that is the very antithesis of omnipotent. I have seen the kind of mental gymnastics and special pleading required to square this circle, in any number of debates.

[Pat Mustard]

Omnipotence, to plantinga, is the ability to do anything that is possible.  Similarly, his definition of omniscience is knowing everything that can be known.  Thus, in plantingas view, there are things that gods cant do or know.

It's not clear why being able to do any possible thing would make it impossible to know any thing that could be known, or vv.

Because knowing everything would mean knowing every future event, thus reducing that beings choice down to one single action for every event in the future. Therefore that being cannot be all powerful because it doesn't have the power to change its actions in the face of its future knowledge. In a similar way being all powerful will constrain knowledge of the future because the being possessing all power cannot be constrained into one choice of action.

[Mister Agenda]

In plantingas formulation there are, conceivably, all sorts of things a god can't do or can't know.  I understand that in your (broadly..our) conception of omniscience and omnipotence any failure in any of these things would seem disqualifying - but that is a disagreement over definitions and not a logical fallacy - as you seem to have hit on.

Woudn't an argument have to be both valid and sound to be successful?

All cats are green, Smoky is a cat, therefore Smoky is green. Perfectly valid. I imagine the problem with Plantinga's argument is in the premises, like whether a possible world argument can get you to a real thing in the first place. I mean there are possible worlds where cucumbers taste like chocolate, or John Kerry became president in 2004, but I don't think there're any real world implications from that.

[The Grand Nudger]

@Pat Mustard
You're insisting that a god must be able to do a thing you've deemed impossible for it to be called omnipotent..but, again, plantingas omnipotence does not make such a demand or claim.

[The Grand Nudger]

Woudn't an argument have to be both valid and sound to be successful?

All cats are green, Smoky is a cat, therefore Smoky is green. Perfectly valid. I imagine the problem with Plantinga's argument is in the premises, like whether a possible world argument can get you to a real thing in the first place. I mean there are possible worlds where cucumbers that taste like chocolate, or John Kerry became president in 2004, but I don't think there're any real world implications from that.

Yeah, maybe, but a whole lot of other things we might think are un-controversially true and can be expressed in modal terms or possible world semantics are also implicated in that.  Modal logic is..ironically, used in formal verification.  To test the safety and reliability of systems or software. Let that sink in. We may have good reason to doubt a system of logic we use to test the reliability of other logical systems, lol.

OTOH, maybe the world really is stranger than we normally suppose - and a things possibility is the chief determinant of it's existence and/or central to necessity.

[Mister Agenda]

It may just be my mental limitations, I just can't make the connection between something being possible, therefore true. I think perhaps there may be a big difference between something being conceivable and something being possible.

[The Grand Nudger]

Couple more steps, not much - but..yeah. There are lots of systems that yield unintuitive results. The arguments form was chosen by plantinga for exactly that operation. It's not like he stumbled across it. What if I'd introduced it to you another way, though?

What if I'd said that it was possible that there are two possible worlds that share no elements. That if a maximally great being exists it would have to exist in all possible worlds. That there was at least one possible world that did not contain a maximally great being. Thus maximally great beings cannot exist.

Would it seem counterintuitive then - or does it just look fact-check true....?