I first came across the ontological argument (in the form of Anselm) in Religious Studies class when I was 16, and my immediate reaction was, "that's a load of bollocks". However, I was assured repeatedly that all sorts of clever people were impressed by it - even when I went on to study philosophy at university, lecturers were informing me there's more to the argument if you don't look at it superficially. Theists loved trotting out that old story about David Hume walking down the street and proclaiming in shock that the ontological argument is sound!
So, with all this encouragement, I read more, and thought about the arguments for several years. Eventually, I came to the realisation that I had nailed it as a 16-year-old, and for exactly the same reasons.
The Googlesplat is defined as a giant, pink fire-breathing unicorn that necessarily exists.
The Googlesplat exists by definition.
Nevertheless, the Googlesplat does not, in fact, exist.
This is all that's necessary to see why ontological arguments are steaming piles of horseshit, and all the reams of text written to justify them is simply empty hand-waving. Don't be too hard on philosophers in general though - ever since Anselm's day plenty of professional philosophers have laughed derisively at such nonsense.
Perhaps you need to widen your experience and to consider other applications. According to the Free Online Dictionary, it can apply to other things such as theory.
quote: 1. (Philosophy) Philosophy the branch of metaphysics that deals with the nature of being 2. (Philosophy / Logic) Logic the set of entities presupposed by a theory
The definition you're pointing to does not say that ontological arguments 'apply to a theory', however you want to interpret this. It's saying that, in addition to being used to describe a branch of philosophy, the word 'ontology' is also used as a way of saying the sum total of things and the way those things are, in a particular world view.
So, the ontology of your world-view would include a creator God, and a heaven, and whatnot. An atheist wouldn't share that ontology.
None of this has anything to do with the matter under discussion.