We can do even better than that.

A necessary God is true in any case.

Existing things only.obtain when they exist.

A necessary God must obtain, it cannot be dependent on whether it exists or not.

A necessary God, therefore, cannot exist. It cannot be determined by existence, as it must be true in all possible cases.

Not only does atheism obtain (God doesn't exist), but does so necessarily by the necessity of God

A simplification of your post.

I can't follow that.

A necessary God is true in any case. — TheWillowOfDarkness

Do you mean that a necessary god is one that exist in every possible world?

Existing things only obtain when they exist. — TheWillowOfDarkness

Not sure what to make of "obtain" here,

I can't follow that. — Banno

Phew... I thought it was just me.

I tried to pars it in terms of possible worlds, but became stuck at "obtain"; is that just "is true"? Or is it "Exists? Or something else?

The thread is here because I have the gut feeling that there must be something wrong with the argument in the OP; it's just too obvious. But I don't see what the eror is.

I suppose a believer would retort that God exists in all possible worlds (an advocate of the ontological argument/ modal ontological argument for example).

And that would be a mere retort, not an argument.

No, they would have to argue that there cannot be a possible world in which god does not exist; that there is an inherent contradiction in that very notion. And to do that they would have to deny the very logic of possible world semantics. It's part of that semantics that one can construct a possible world in which any given individual is absent, and god is such an individual.

I suppose arguably, pantheism would survive, since it does not suppose god to be an individual.

There is a possible world in which god does not exist. — Banno

Is this supposed to be a true statement?

Well, take the modal ontological argument for instance, they argue: “if God exists necessarily in some possible world, then God exists necessarily in all possible worlds”.

This may seem odd at first, but in some systems of modal logic, inferences with the logical structure: “If it's possible that it is necessary that X is the case, then it is necessary that X is the case, therefore X is the case in the actual world” are valid (replace X with God exists).

This is a matter of controversy in fact, related to the choice between systems S4 and S5 in modal logic.

Yep.

God is supposed to be a necessary being. — Banno

God is the only necessary thing. (cut out being)

Why the only one? How is God being defined here?

How to parse

God exists necessarily in some possible world — Amalac

God exists in every possible world, in some possible world?

But that's 's just "god exists in every possible world" and the argument becomes "if god exists in every possible world, then god exists in every possible world" - not exactly enlightening.

I think that a “necessary” designation doesnt necessarily entail all possible worlds. Why would it? A being can be necessary for one possible world or many or all of them, so by formulating your question like you did you have forced the answer
to be unsatisfying.

Does this curious and venerable argument only apply to monotheism? Why not gods as necessary beings?

God is the only necessary thing — frank

Well, no. See

God and Other Necessary Beings

There are various entities which, if they exist, would be candidates for necessary beings: God, propositions, relations, properties, states of affairs, possible worlds, and numbers, among others. Note that the first entity in this list is a concrete entity, while the rest are abstract entities.

There is a possible world in which god does not exist. — Banno

Why is it (supposed to be) a true statement?

Aquinas said God is the only necessary thing. If you include "being" it's just going to make it harder to understand the medieval mumbo jumbo because of God's status as existence itself.

I think that snippet shouldn't be read as:. "all these things could be necessary at the same time". but just "at one time or another these things have been considered for necessity-hood."

I think that a “necessary” designation doesnt necessarily entail all possible worlds. — DingoJones

I don't know what to make of that. The advantage of possible world semantics is that it gives us a grammar in which we can make sense of modal arguments. If you are going to say necessity does not entail all possible worlds, you are rejecting our best understanding of modal logic.

Not going there with you.

Why not gods as necessary beings? — Tom Storm

Indeed; if one, why not many.

Why is it a true statement? — Daniel

Because I say.

Would you prefer imagine a possible world without god? Same as.

I don't see your point.

"if god exists in every possible world, then god exists in every possible world" - not exactly enlightening. — Banno

The actual world is one among the possible worlds (this again follows in some systems of modal logic). So if one admits that god exists in all possible worlds, that would imply that god exists in the actual world.

So, in those systems, if one accepts that it is possible that it is necessary that god exists in all possible worlds, then it follows that in all possible worlds, god exists in all possible worlds, and therefore “god exists in all possible worlds” is true in the actual world, which is one of the possible worlds in which that statement is true, and therefore god exists in the actual world.

All this follows if one accepts system B of modal logic, from the corollary of axiom B (if the modal ontological argument is valid):

◇□X → X (If it is possible that it is necessary that X, then X is the case).

Likewise in system S5, the corollary of axiom 5:

◇□X → □X

if one accepts that it is possible that it is necessary that god exists in all possible worlds, then it follows that in all possible worlds, god exists in all possible worlds, — Amalac

Interesting. So from the OP, there is a possible world in which god does not exist. Hence, it is not true that it is possible that it is necessary that god exists in all possible worlds, by modus tollens.

That is, since there is a possible world in which god does not exist, god does not exist in every possible world.

Damn it took me a long time to get that; I must be tired.

I dont think modal logic requires “all possible worlds” in order to make sense of possibility (which is what modal logic is about). It can, but modal logic can also be just about single world possibility, or any other framing of possibility.
So I am not abandoning modal logic I just think when you posit god as necessary across all possible worlds you run into problems in the answer, and like an argument that is logically valid but not sound then the answer to your syllogism isn’t satisfying.
What if instead of all possible worlds you just considered god as necessary to this one? My thought was that you would find a more satisfying answer than when you consider all possible worlds.

What if instead of all possible worlds you just considered god as necessary to this one? — DingoJones

Again, there is no clear notion of what necessary might mean, if not "true in all possible worlds". Giving us a clear notion of necessity is the point of possible world semantics.

So, first you have to explain what it might mean for something to be necessary only in the actual world.

Just getting back to first principles - why is god or gods presumed to be necessary? Is the argument essentially:

A being that necessarily exists cannot coherently be thought not to exist. And so God, as the unsurpassably perfect being, must have necessary existence—and therefore must exist.

Word play or a thing?

what about the law of the excluded middle, or the law of identity? Must they not be 'true in all possible worlds'? Put another way how could a world form if those laws did not obtain.

There are various entities which, if they exist, would be candidates for necessary beings: God, propositions, relations, properties, states of affairs, possible worlds, and numbers, among others. Note that the first entity in this list is a concrete entity, while the rest are abstract entities.

so you reckon God is 'a concrete entity'?