The transcendental argument for God (TAG) seems to be very popular with Christian apologists these days, mostly as a tactic of just baffling with bullshit, I suspect. I've heard it myself, from people who apparently don't understand it themselves, but are just parroting what they've heard elsewhere.
This video clip is a compilation of four different videos debunking the TAG argument. (There are links to the individual videos on YouTube here.) I thought it was excellent.
At that same link, in the description of the video, there is also a brief summary of two variations of the TAG argument, as well as a link to the Iron Chariots page which goes into the same thing in more detail.
But my fundamental problem with the TAG argument - and similar arguments for the existence of 'God' - is that these aren't the reasons why proponents of such arguments believe in God themselves. No, they already believed in God - almost always because they were raised in a particular religious tradition - and the TAG argument is just an attempt to convince other people.
Hey, why not tell me what convinced you to believe in your 'God'? If you actually had a good reason to believe, why not tell me what that reason was? Is it because you didn't have a good reason? Is it because you only believe because you want to believe what you were raised to believe? (And no, a "good reason" needs to be something you can clearly distinguish from delusion and wishful-thinking.)
As I noted, I've heard people using the TAG argument who don't understand it themselves. Ask them a question and they can't answer it, because they're just parroting back what someone else told them. It's something they wanted to believe, because they already believed in their god, already believed in the religion they were (almost always) raised to believe.
But that's why the TAG argument is so popular with believers. It really is baffling with bullshit, and they're eager to be baffled. Furthermore, it's easy to baffle other people with the same bullshit, if they haven't encountered this stuff before.
Now, I'm not a philosopher. I'm not an expert in any of this. I'm just trying to understand it myself, by writing about my understanding here. (Note that the following quotes are taken from the summary of the video.) I could easily be wrong, but that's the whole point. If I am wrong, I want to be corrected.
There are several versions of TAG. For example:
There are some objective logical absolutes.
We can have concepts of these logical absolutes.
These logical absolutes are not physical (you can't find them within the natural world).
These logical absolutes are therefore conceptual.
Concepts require a mind.
Since the logical absolutes are true everywhere they must exist within an infinite mind.
That mind is God.
Frankly, I have no idea if "objective logical absolutes" exist at all. (If I understand correctly, that terminology is only used in Christian apologetics, not in philosophy.) But we do have "concepts" of them. And it's those concepts which are conceptual and require a mind (ours).
Philosophy is a human concept. Logic is a human concept. Mathematics is a human concept. Those concepts attempt to describe and model what exists in the real universe, but that existence is not dependent on our understanding of it. A rock would still be what it is, even if we weren't around to label it "rock."
So the fact that we can conceive of a rock, that we have a mental construct of what "rock" means, does indeed require a mind, but only ours. The rock itself does not. At least, there's no good evidence that it does. And this is the same way with other concepts. Our concepts require our mind to exist, but what those concepts refer to might not.
Logic is rational, but atheism presupposes that everything comes from material sources.
Logic isn't material, so atheism lacks any objective source for logic.
Without an objective source for logic, atheism cannot employ logic.
Therefore atheism is self refuting.
Since atheism is refuted, theism must be true.
I think I'd disagree that atheism presupposes anything, since atheism is just the disbelief in god claims. I don't have to know, myself, in order to say that you haven't made your case for a god (let alone for 'God'). I don't believe any of the claims I've heard, though I certainly haven't heard them all. But I don't believe that I "presuppose" anything, really.
Sure, I have certain beliefs of my own. I believe that I exist, for example. I believe that the universe exists, even though my understanding of it might be imperfect. And in order to have a useful debate, we both have to agree on certain basics (like the fact that we both exist). But I would be willing to change my mind if there were good evidence that I don't exist. :)
I mean, let's not confuse what we might both accept in order to have a practical discussion with what we're dogmatically demanding. I don't believe that a god exists, even a very simple, undemanding kind of deistic god, because I haven't been shown any good evidence of that. But if you've got the evidence, I'm always open to changing my mind.
Still, the main reason that "Version 2" fails is this: Logic isn't material, because it's a human concept from human minds. We've created logic. We've tried to make our rules of logic conform, as closely as possible, to what we see in the real world. That's the whole point of logic, right? But the world is there, whether we understand logic, and whether we use logic to try to make sense of it, or not.
Logic wouldn't exist independently of our minds - independently of any minds, at least. But the universe which we try to understand with logic would still exist. Or, at least, we have no evidence otherwise. (You can argue that it wouldn't, but you can't expect us to just accept what you're claiming without evidence.)
This video's summary concludes with just that point:
The video points out some of the main problems with the different versions of TAG. All versions equivocate between the consistent behavior of nature (facts of reality), and the language that humans have developed to describe it (laws of logic). The language of logic simply represents and points to what exists objectively, in the same way a map represents a real location in space without actually being a location itself.
TAG proponents are essentially trying to claim that the symbolic representation of reality (logical statements made with language, math, etc) are "things" that exist in their own right and must be accounted for, but this is simply false. All that actually exists is matter, energy, and forces that interact in consistent ways. Human logic is merely a verbal DESCRIPTION of what nature is doing, and does not need to exist for nature to behave the way it behaves.
Iron Chariots goes into this in much more detail, and discusses Matt Slick's particular version of TAG, too. (Here's another detailed refutation of Matt Slick's version of the argument.) Note this brief summary of the basic problem:
To summarize, a simple analogy to the logical absolutes would be abstract mathematics. The number 4 is “transcendent” by the TAG definition. It isn't a 'thing' that 'exists'. It cannot be photographed, frozen, weighed, or measured. It is always the number 4. It always remains the same. It always remains true.
However, if there were no minds in existence to conceive of the number 4, the shape we currently call a square would still have the same number of sides it has now. It would not physically gain or lose any sides. The abstraction of the number 4 is conceptual, but the concept isn't dependent on a transcendent mind for the real world underpinning of the concept to remain true.
Here is another critically important point (note that I cleaned it up, slightly, and added paragraphs to make it easier to read):
It should always be remembered that theists are in the same position as non-theists once enough layers are peeled back. The goal of TAG and other presuppositionalist arguments is to stay on the offensive and keep asking "why" and "how do you account for" questions until you hit bedrock at "The universe just exists and behaves consistently".
This is a brute fact and it makes no sense to ask for "why" beyond this point, however the TAG proponent will declare victory if you don't have an answer, then baldly assert that they do (God did it). This usually trips up atheists because they don't realize that they are being asked an impossible question that equally applies to ANY worldview, including the theistic one. Your goal should be to mirror the questions they ask you and go on the offensive yourself until you expose that they also don't have answers to the "why" question at the bottom of their worldview.
You will find that TAG proponents are trying to account for the consistent behavior of nature by appealing to the consistent mind of a god that can't be accounted for! They can't account for why god exists instead of not existing. He "just exists" for no reason and no cause, and just has the properties he has for no reason and no cause. His will is effective rather than ineffective, for no reason and no cause. In other words they cannot account for the existence or capabilities of the being they are appealing to as the foundation of logic! So they have actually accounted for nothing. They've just pushed the question back a level.
If 'God' just is, then why couldn't that apply to the universe itself - or to some multiverse, perhaps? 'God' as an explanation simply doesn't solve anything.
But there's one more thing to take away from this. If you don't understand an argument, then don't accept it. If you don't understand something, ask questions. And if you still don't understand it, don't let it convince you just because it sounds impressive. Many people baffle with bullshit for the same reason that scam-artists confuse their victims. If you don't understand it, don't believe it - and that includes what you read here, too.
Don't accept an argument you don't understand even if you really want to believe it - maybe even especially if you want to believe it. If a person can't be clear about what he's claiming, either he doesn't understand it himself or he's just trying to convince you of something that isn't so. Unfortunately, we tend to be very, very gullible when it's something we really want to believe.