You don’t seem to have understood the argument yet, Rey. Notice that Lewis does not, as you say, claim that thought comes from God. He doesn’t presuppose God’s existence at all. Rather, the form of his argument is more like:
“Suppose the atheistic/naturalistic picture of the universe is the correct one. If that were true, for [some reason or reasons], I wouldn’t be rational in trusting my own reasoning, including any reasoning process that would lead me to atheism. So if atheism were true, I couldn’t rationally accept it.”
I’m not going to repeat my argument against his quote as it seems you didn’t read a word of it. At the base, he’s presupposing atheism to disprove atheism. However, his predilections can’t be suddenly swept under a rug. This is getting redundant, but I trust my reasoning because it is self-evident and because it is repeatedly effective in the natural world. I don’t need a god, especially not Lewis’ god (starting to seem like your god also), to trust my reasoning. The sooner you understand that, the sooner you’ll get off the topic.
Admittedly, Lewis’s formulation, first delivered as a radio address, seems geared more for the popular level. If you’re interested in seeing the merits of an argument along these lines, you’ll have to do some reading. Try seeing what an analytic philosopher has to say on the subject. I’d recommend you look into Alvin Plantinga’s work on what he calls the evolutionary argument against naturalism.
Plantinga’s evolutionary argument against naturalism is apologetic bunk. It’s been refuted a few times by people far more capable than myself; Stephen Law, for example, has refuted Plantinga’s argument. Thus, I’ve already done the reading and I find it to be utterly unconvincing. When I first saw his argument, I was unconvinced due to his ignorance of evolution. It is not true that cognitive faculties evolved to have survival value; such a notion comes from a poor understanding of natural selection or what is popularly called “survival of the fittest.” Also, he completely ignores the other mechanisms of evolution: genetic drift, mutation, gene flow and non-random mating. Each mechanism played a role in the evolution of h.sapien. Therefore, his misrepresentation of evolution defeats the argument; that was enough for me, but apparently Law, and Fitelson and Sober have other issues with the argument. Obdurate Christians see it as a “knock down” argument. It isn’t even close. Any argument founded on blatant ignorance has failed from the onset; in other words, Plantinga intentionally misrepresents evolution in order for his argument to work and that is precisely one of the reasons why, if not the biggest reason why, his argument fails. Therefore, I still find them both wrong. You aren’t convinced, Lewis wasn’t convinced and Plantinga isn’t convinced, but that’s exactly the problem: most of today’s Christians are an obdurate bunch. There are no corrections, there’s no redux and there sure as hell isn’t any concession. From the point of view of most Christians, they are never wrong and they could never be wrong, and this is the type of obduracy I’m against and it’s the kind of arrogance I’ll continue to humiliate.