God and theists.

[Mister Agenda]

1. There are no natural explanations.

Here's one: Quantum foam can't not exist and produces minuscule bubbles of space-time that occasionally experience runway expansion and become universes. Absolute nothingness is impossible and quantum foam has always (for any meaningful sense of 'always') existed.

That's the point, we are beyond that. I can, with logical arguments (which is the only option since we are on to metaphysics and not something that can be deduced from science), deduct what sort of properties an explanation of the physical world would have. The best you can say is the universe or the multiverse is a brute fact despite the logical problems that come with that.

Maybe you should take a class on the theoretical physics of cosmology before boldly declaring the origin of the universe is something science isn't qualified to speak on. Within the constraints of not violating what we know of physics and having math that works, there are multiple explanations for the origin of the universe.

 
2. Why would you insert the word 'philosophical' in front of 'nothingness'? Are there different definitions of nothing? Nothing is quite easy--it is not anything.

The closest science can get to 'not anything' is still full of quantum foam. Philosophical nothingness is what you're talking about: not the hardest vacuum possible, but literally not anything. No space, no time, no properties other than nothingness. This presents immediate problems. When would there have been absolute nothingness without time? How long can a state without time last? It's often referred to as a void, but you can't have a void without space. Not being able to stop being nothing is a property besides nothingness, so what is to stop nothing from becoming something? And in your own religion, if God was eternal, there never was absolute nothingness, and the question applies to God: why is there God instead of nothing? God can't be an answer to the question of why is there something instead of nothing because if God exists, God is the prime example of there being something instead of nothing. But you don't require an explanation for that question, do you? And it's the exact same question you say must have an explanation, Steve, only with the word 'God' in it.

3. The anthropic principle in no way changes anything. We can all readily admit that we should not be surprised that we are not observing features of the universe which are incompatible with our existence. But it does not follow from that that we shouldn't be surprised to observe features of the universe compatible with our own existence. 

That is precisely what follows from the Anthropic Principle. The only thing that should surprise you about the universe is if you find out it's not possible for us to exist in it. THAT would be evidence of omnipotent intervention.

Fine tuning is a fact because it is true that the physical constants must be in a narrow range for a variety of things ranging from the universe holding together, not collapse on itself or burn out too quickly all the way to forming the necessary heavy elements needed for more complex things (like life). Even if I granted you that the universe had to have these values because of some prior condition, that simply pushes the fine tuning back one level: why is the thing that produces only finely tuned universes finely tuned to do so? 

But it is not a fact that the universe having the properties it does is improbable. It's speculation. If anything, given a sample size of one, we should suspect that our universe is exactly what ought to be expected from universes, but that's probably a step too far as well. We just don't know. That's the problem with small sample sizes.

If there is something producing only fine-tuned universes, the most logical explanation is that universes like ours are the way they are by necessity. Since most the universe-production mechanisms proposed that I'm familiar with don't have a feature that would limit them to one universe, a mechanism that produced universes with completely random physical constants would eventually produce one like ours by chance, so I don't know where you're getting the idea that whatever spawns universes would have to be fine-tuned to produce a universe like ours.

All of these are thought experiments (which is just another way of describing attempts to answer metaphysical questions) and are the appropriate form in which to tackle these questions.

Theoretical physics has not gotten the memo that it isn't qualified to tackle the origins of our cosmos and has been blithely following the evidence.

 Like I have been saying for quite some time, this in only one component in a list of reasons that become a cumulative case for God.

A cumulative case is only as strong as it's weakest component.