God is so quiet

[SteveII]

You can definitely have a possible world where there is nothing concrete. One such possible world is where only God exists--or beings like him.

Your examples of abstract objects are all over the place. "Round" and "beauty" are contingent (and are therefore not necessary) properties. "Space-time" is not an abstract object at all. Only "numbers" are examples of necessary abstract objects.

Either God is a concrete being or he is abstract. I don't think you want to go with the latter option. Just because God is spirit (in your view) doesn't mean he is not concrete.

If God exists, he would be a unique entity and I don't think there is any reason to insist he has to be either category. 'Concrete' carries connotations of existing in time and space that don't apply. 

And I don't agree that your God is even possible. After all, we're dealing with a being who supposedly created things from "nothingness" (no material cause) and can timelessly act (can act without time, even though acts imply time) and that makes me have doubts about even its possibility. Since they imply logical contradictions (which I got into in other threads), then God as the Creator is not logical.

There is nothing illogical about God existing timelessly (in a changeless state) prior to creation and upon the instant of creation exists in a temporal one. 

There is also nothing logically wrong with God being the efficient cause and having the power to create matter. You are using our laws of physics to apply to a state prior to our universe. You can't show why that is even remotely appropriate. Logically, all questions/answers prior to our universe are metaphysical in nature. Science simply does not apply. 

I'm not sure I agree with you that space-time is not abstract, but I'll set that aside either way and focus on the important point being made here.

Now, numbers. I think even those which we deem necessary abstract objects require concrete entities to refer to. Without such references, it is meaningless to talk about such abstract objects existing. What do numbers mean without the existence of something that they can refer to? How does "two" exist in the absence of concrete entities that have the potential to add up to "two entities"? Again, we may as well talk about true "nothingness".

I have already conceded that there is not a possible world where nothing (in its most basic sense) exists. As such, we only have words that have something for numbers to apply. You don't need a possible world to have physical objects in it. For example, one possible world is one in which only God (or something like him) exists with no physical objects. Numbers would still exist since they are key to rational thought. 

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And maybe reality doesn’t need a cause.  Maybe reality is necessarily real by definition.  What’s the logical alternative?  Non-reality?

Yes, and if theists like Steve want to keep God and "our" reality separate from each other, then this means God coexisted with "non-reality" before creating reality out of "it"? So many wrongs with the notion of a Creator God, and this is just the tip of the iceberg.

That's just silly reasoning. Reality prior to the universe would just contain God. You are conflating 'reality' with something physical. That is wrong.

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I agree with your analysis about abstract objects. I for one do not believe they are real objects because I think all those things can be grounded in the mind of God. However, atheists have to wrestle with the question and the consequences of either decision. 

I think you're not working in the right direction...
When trying to establish that a god exists, one can't posit that it already does so and has a mind.

Whether I am a realist or and anti-realist when it comes to abstract objects does not matter to any argument. It is an a posteriori conclusion after belief in God had been established.  

However, why do you say our space-time contains within it an explanation of its existence (the definition of necessary)? Most philosophers consider all concrete objects as contingent.

Space-time is not exactly a "concrete object" is it?
I'd describe it more as a framework upon which concrete objects exist.... a framework that can bring forth concrete objects, it seems.

I don't think so. Cosmologist do not consider space-time to have existed prior to the big bang. So the singularity (all matter in one spot) existed prior to our space-time.