A great post, Luke. I have a bone to pick, but first agreement. It's true and often frustrating, in scientific and philosophical endeavors alike, that the efforts to find ultimate explanations turn up all manner of primitives, brutes, givens, and postulates that defy further analysis. In some cases, these may be considered stop signs, in others, merely a yield. But, it cannot be elephants all the way down. Or, as Lewis pointed out, seeing through every veil is equivalent to seeing nothing. So, it is right, in principle, to allow ultimate explanations, though we should not be too hasty in conferring that status.

That being said, I think your shorthand use of "God did it" as the supposed conclusion of the arguments of natural theology is an unfortunate mischaracterization, especially considering the question at hand of appropriate explanation. These arguments, when carefully articulated, are indeed closely analogous to the forms of reasoning in theoretical physics: because of e, some entity x must exist with property p; we'll give it the name y. The unseen postulate in such an argument is ascribed only the property or properties implicated by e, say a charge of -1. Likewise, as far as the argument goes, the careful theist will be content with stipulating only the properties that follow. That is why we have all those terms of art like "an uncaused cause", "an unmoved mover", "a designer", "a necessary being", etc.

If the theist has been appropriately modest in their conclusion, the question that you suggest should be asked instead — "Why is God the best explanation for that?" — will be answered by a return to the argument to see if it is valid sound. For, in that case, "God" is just y, the name he gave for x with property p, and the argument is supposed to have shown that such an entity must exist to explain e. "God" is a freighted term, and I don't mean to deny that calling y "God" is bound to conjure up more than the argument is purported to demonstrate. But at least in academic philosophy of religion, I find that as a rule, care is taken to proscribe the entailments of a given argument. (Of course, if it needs to be said, if x is taken to be the God of Abraham, additional legwork will be required.)

By the way, if the slaughterhouse is still open, it may be time to give your tagline from Roberts another look (bit.ly/aIAtRG). Luke, you are a much appreciated voice in the conversation about ultimate reality from both sides of the aisle. No small feat. Thanks, and keep up the good work. 

Luke responds ...

The question “Why is God the best explanation for that” comes in at one or another premise of the argument. For example, Craig’s version of the teleological argument:

1. The fine-tuning of the universe to support life is either due to law, chance or design.
2. It is not due to law or chance.
3. Therefore, the fine-tuning is due to design.

Here, the “Why is design the best explanation?” comes in to cast doubt on premise #2.

In the Kalam argument, this question comes into play on premise 4, which seeks to establish that God is the cause of the universe. Or, here is Craig’s moral argument:

1. If God does not exist, objective moral values do not exist.
2. Objective moral values do exist.
3. Therefore, God exists.

Here, our best explanation question comes into play on premise 1.

(I use Craig’s versions because they are short and syllogistic.)

Also, re: [Roberts'] quote at the top of my page, see here

A Further Comment

Luke, you're quite right that in the abbreviated form of Craig's moral argument, the move to "God" begs questions. In Craig's case, unless he's debating Shelly Kagan, he will be ready to provide the supplementary premises. For many others, including myself (who concedes the force of Euthyphro), it will be a struggle. Nonetheless, I think the arguments of natural theology more often conform to the outline I suggested above. For example, Craig's version of the Kalam leads to some entity x with the property of personhood or agency.

Thanks for the link to your take on the Stephen Henry Roberts' quote. Your principled objection to epistemic double standards is a bracing and worthy challenge. And, I might add (as you do), that no view is immune, as when belief in God is psychologized or located in the brain without noting the self-referential implications for not believing. I'll be adding some engagement with your thoughts in my own essay on the "one less god" idea. Regards.