Most of us, I think, are familiar with the famous (infamous?) Bahnsen/Stein debate where Bahnsen broadsided Stein out of left field with his transcendental argument, the impossibility of the contrary. Unfortunately, I have heard of Reformed folks using this as something of a "silver bullet" argument, that "you can't account for logic" is a sufficient show-stopper for any debate with an atheist. But I think I'd like to understand the argument a bit better. What if an atheist or agnostic were to counter that there doesn't really need to be something transcendental that grounds logic? That is to say, that I can observe an apple and I can observe an orange, and I can see that they have different qualities. I can observe that one is not like the other in the same way, the same time, and the same sense, thus establishing the law of non-contradiction. I can observe that they have qualities unique to themselves as well as having qualities that are universal, such as redness or "orangeness". So why do I need to bring God into the picture? If one were to ask why things are that way, maybe they would assert that these differences emerge simply because we have these discreet and universal entities in the world, and not because anything divine underlies them. That's kind of brief, but I think it would be my first step to understanding the presuppositional view a bit better.