Wait, so I can't argue that your inference is incorrect because you're only engaging with people who accept that your inference is correct? Okay. Never mind then. Don't know why you bother arguing at all then.

I absolutely am "engaging the argument." Your argument is a worse version of Plantinga's modal argument, and (as Plantinga himself acknowledges) if you reject S5 then his argument is not valid.

Yeah, I think your first premise here is false, as I've said. If you want to assume it is true, fine, but that is not an argument.

Why does a being with existence as, "the attribute or set of attributes that make an entity or substance what it fundamentally is, and which it has by necessity, and without which it loses its identity" lose the ability to be material? If we define a being fundamentally as existence (which, to me, is strange to begin with, since as soon as we conceive of anything it exists in the mind, does it not, so saying it exists doesn't add anything to it) that doesn't mean it becomes "pure existence" does it? What I'm getting at is that even if we picked out or defined some quality as the fundamental one of God, that doesn't mean it's His only quality.

I don't think he's saying that any more than others are saying all reality is God.

Wow. OK.

I keep coming back to a similar question: How is the argument affected by the fact that ten different people can--using the same definition provided by one of the OAs--conceive of ten different God's, some of whom will be mutually exclusive to each other? (For example, with such drastically different conceptions of how this God would balance greatest Justice with greatest Mercy that both could not possibly exist, yet they both must exist according to the OA being used.)

The conceivability of a being whose non-existence is inconceivable.

That’s the cornerstone of the argument, that any candidate for the office of a necessary being must meet. Now I can conceive of a possible world in which the laws of nature in that world preclude the possibility of a “hoofed quadruped with a horn” existing. Closer to home, the state-of-affairs during the very early stages of our universe renders the existence of a unicorn nomologically impossible, at that time. Hence, a “shunicorn” is not a candidate for the office, and that holds equally so for any sort of material being subject to, or contingent upon, the laws of nature.

In the sense you’re saying, 'pure' existence doesn’t mean ‘only’ existence, so yeah, we can. For instance, we can say existence is one, or existence is truth, or existence is good.

It doesn't matter how we define "greatest", it's about conceiving something which nothing greater could be conceived, presumably only one thing can be the "best."
So if different people conceive of different Gods, they should all conclude in the one which no greater could be conceived, regardless of how they think that looks.

I always thought it was strange, personally, to add omni-benevolence to this list. A nihilist would not agree that this concept even exists, let alone be "better" than omni-malevolence, which seems to beg the question a little. But for the sake of the OA, it is implied, so it doesn't matter how we define justice and mercy, but this all-powerful God would posses these attributes, regardless of how we think they might look. In the end it doesn't matter how we personally conceive this being to look like, but that we can't conceive of a greater being.

The truth is we can't conceive of eternity. We can't comprehend what omnipotence truly means. We understand what it implies, but I'm not sure we can really grok these concepts to say with confidence - "I can conceive of that which none greater can be conceived." Does this negate the entire OA? I'm not sure, I think this is what Orp was alluding to earlier. I think just the fact that we can imagine one thing being greater than the others is enough, but I'm not entirely sure.

To be fair (to Everitt) he wasn't the one arguing for a necessary unicorn, that was me, and on reflection it was a bad argument.