The Ontological Argument - valid or debunked?

[SteveII]

Then you have simply changed the definition of omnipotent. Equivocating. An omnipotent God could prevent getting eaten. 

My point is that there exists, if we so wish to discuss it, an infinite number of ever increasingly maximally great beings, each one identical to the last, only with the ability to limit the one preceding it. You propose an omnipotent god, and this is your maximally great being, in response I propose a being with an identical power set, plus one more ability which allows it to weaken your god, thus making it the maximally great being, and so on, ad infinitum. Yes, I suppose in some sense I'm simply broadening the definition of omnipotence, but we're not talking about omnipotence, we're talking about maximally great beings within the premises of the ontological argument, and the fact that I can erect an infinite regress around that at all demonstrates my point: the concept of a maximally great being is logically incoherent in that any maximally great being that actually exists serves as little more than a platform from which other, more powerful beings can be posited. The moment you show a demonstrably real maximally great being is the moment that being can be surpassed simply by proposing additional beings capable of negatively influencing the extant one. And you can say that a really omnipotent god could prevent that, but that's the point: that god would no longer be omnipotent because I've built into the power set of my being the ability to take that power away from yours, and it's hardly like we're discussing real things anyway, we're just talking in hypotheticals. You've no reason to dismiss my concept out of hand.

Greatness has no defined criteria, nor an upper bound, and this is the problem here. The first premise of the ontological argument is roughly akin to saying "the greatest possible number exists," and then you, as a numberist, telling me what number you think that is. 64, you say, for the benefit of my analogy. Then I rightly point out that 65 is a higher number than 64: you just telling me that 64 is the highest possible number necessarily, therefore it can prevent 65 from being higher... well, that just doesn't make any sense, does it? 

When Anselm first wrote this argument, he was careful to distinguish between what we could think of as the greatest possible being and God is the greatest being possible, that is to say, it is impossible for there to be any being greater than God. Your infinite regress is a result thinking of God simply as the greatest being there is.