The modal ontological argument for God

[Sheldon]

You not accepting a premise doesn't make the next premise a fallacy.  

Without P1, P2 has all the appearances of being circular, since stating "a deity exists in all possible worlds" would be an assumption of the conclusion it exists in this one, yes it follows, but then it would since the first part assumes the second. 

However since (P2) says IF at the start, then my assertion goes too far. 

Though before I accept a deity exists in all possible worlds or anywhere, I would need to see this demonstrated in some objective way, I don't think the argument establishes a deity is possible. 

Parenthetically the conclusion in the argument only follows IF a deity is possible. (Which is of course what it says) However I am also dubious that IF a deity is possible, it follows (in P1) that it exists in every possible world?

Ultimately one would need to demonstrate a deity is possible, or the argument does not seem like a  compelling reason to believe a deity exists anywhere. 

I don't think it's accurate to say that any arbitrary definition would work - because it's really just the one thing or quality or attribute or x that the argument works -on-. Necessity.

My apologies if I misunderstand here, but are you saying that one would have to accept a priori, that a deity is necessary, in order for the argument to work? Since the argument seems to argue existence based on whether a deity is possible. So is possibility that one attribute you're referring to?

As I said if we replace god with unicorn, then the argument doesn't appear to lose anything, not to me anyway?