This is a conversation from discord with some added comments.
1. TAG is just a deist argument
First notice that TAG is a deist argument. If it convinced you, you’d be a deist, not a Christian. The apologist would be obliged to use different arguments to show that the deity was the Christian god, not some other god.
Reworded, this sentence is, “Notice that the transcendental argument for Christianity is a deist argument.” This demonstrates ignorance what a transcendental argument is, what the conclusion of TAG is, or both.
It is hard to believe the ‘Absolute Personality’, the ‘Conditioner of all facts’, and etc hardly sound like deism. In fact, many of Van Til’s points are about a personal God. That rationality is personal and hardly could come from a deist being.
Secondly, is the atheist admitting that his worldview doesn’t account for rationality but the deist worldview does? If not, then how can the deist ground these things and not necessarily be correct?
2. We don’t get physics from Christianity
Next, notice that we’ve never gotten physics from Christianity before. Why go to Christianity now to find the fundamental basis for physics? Yes, the Bible tells us how everything got started, but science gives the evidence to make clear that the Bible is wrong.
Nothing useful has ever come from resolving a science question by concluding that God did it. No honest seeker of the truth says, “I don’t know what causes this thing … so therefore I do know! It must’ve been God.”
Galileo, Newton, Watts, and others disagree with you. This is just historic ignorance. Furthermore, it is an oversimplification of the issue in terms of model building, when in fact, Christianity’s primary provision for science is in its philosophy. The Archimedean point of all scientific investigation is a thoroughly Christian view of the universe.
Well, I’ve written something in regards to the relationship between science and Christianity:
3. Avoiding logical puzzles invalidates TAG
Many apologists dodge the “Can God make a rock so heavy he can’t lift it?” puzzle by saying that God can’t do anything illogical (here and here)—he can’t make an impossibly heavy rock, a square circle, a married bachelor, and so on. The question is ill-formed.
But by dodging this pitfall, they land in another as God’s actions become constrained by an external logic. If God is bound by logic, logic isn’t arbitrary. God can’t change it. He acts logically because he must, just like the rest of us.
This creates a Euthyphro-like dilemma: either God is bound by an external logic (and God answers to a fixed logic that he can’t change) or he’s not (and logic becomes arbitrary—it is what it is simply because God said so, and he could change it if he wanted to).
The apologist will try to propose a third option (again, as with Euthyphro): logic is simply a consequence of God’s nature. It’s neither external nor arbitrary. But this simply rephrases the problem. Is this nature changeable? Then logic is arbitrary. Is it fixed? Then God is again bound by logic.
Can God be the origin of logic if he’s bound by it?
4. Could God create logic and mathematics? Or is he bound by them?
Let’s think about God creating arithmetic for a moment. “Creation” seems to mean more than simply “bring into existence.” Were God’s hands tied in creating arithmetic, or did he have some creative control? For example, 2 + 2 = 4 in our universe. Could God have made 2 + 2 = 9? If so, prove it. And if not, God was obliged to make arithmetic the way it is and unable to create any other kind. Here again, he answered to an external reality.
It is unintelligible to ask whether God is bound by His deity, as if someone can be an external law unto themselves, separate from themselves.
5. Consequences of a godless universe
But let’s assume the apologist’s argument and see what happens. God created logic, and logic is the way it is because God made it so. If God’s role here is important, a godless universe must be dramatically different. A godless universe could then have no logic or different logical rules.
In our universe, X can’t be the same thing as not-X (the Law of Identity). Something can’t simultaneously be a rock and not-a-rock. The apologist’s argument tells us that logic is up for grabs. In a godless universe, something might be a rock and not-a-rock. But this is an incredible claim that needs justification. TAG gives none.
This shifts the burden of proof. It is an incredible claim that objects can be logically classified in a consistent fashion by the human mind without any Creator ordering them. Why should anyone believe that?
Now, sure, the apologist can raise the stakes by showing inconsistencies between an unbeliever’s metaphysics and their beliefs, like in the law of noncontradiction. However, if the unbeliever has no default reason for his beliefs in the first place, then his position can be dismissed as arbitrary at the outset.