I don't know if you've been following the debate between the religion-despising Sam Harris and the religion-defending Andrew Sullivan over here and here. I'm, of course, on Sullivan's side in this debate, but my tack in debating somebody like Harris would be to say that there is no debate if the terms of the debate are defined by an obsolete Enlightenment rationalist narrative that Harris quaintly clings to. Sullivan is too conventional in his thinking to make such a case, but it's the only one I think that works.
I've written a lot on this and you can find relevant posts among the ones found here and here. The fundamental mistake materialists like Harris make lies in a belief they hold, even if they are unconscious of it because it is so deeply woven into the Enlightenment rationalist narrative. They believe that all of reality is potentially knowable by reason, and when it is finally known, science will have proved that reality has no spiritual dimension and therefore no God.
Well, until that happens--and it's not going to--it's a belief that has no more reasonable basis than theism. Harris calls himself an atheist, and atheism is just as much a belief system as theism. Harris can believe whatever he wants, but to think that atheism is more reasonable than theism is preposterous. The only rigorously reason-based thinking about God is agnostic--to say you can't know with one way or the other. Pure reason cannot know anything except what it is able to abstract from sense data. Kant made that point over two hundred years ago. But sense is not the only human cognitive faculty. There is also what the heart knows, a point the great mathematician and scientist Pascal understood at the dawn of the Enlightenment over three hundred years ago. Both Kant and Pascal were prodigies of reason, but they knew its limits and did not make an idol of it.
Perhaps the more interesting point Harris makes lies in his assertion that religion has had more of a negative than a positive effect in influencing human thinking and behavior. He might be right about that if we were to use a purely quantitative measure to settle the issue. But the argument is kind of along the lines of asserting that singing is something that is bad for humanity because most people do it poorly, even those who think they are good at it. If nothing else American Idol proves the point. As some people are deluded about their level of singing talent, there are many people who are deluded in their religious ideas. That doesn't mean that there are no good singers just because most are not good.
As with most things having to do with things that really matter to human beings, there's a wide quality spectrum, and the truth of something cannot be measured by evaluating it on a quantitative basis. You can't measure quality by a quantitative metric. It's evaluating the redness of something by using a green scale. For if anyone is truly religious it has very little to do with the quantity of his or her experiences of transcendence but with the few moments of quality which make all the difference in the way he or she thinks about the world on the quantitative level on which the bulk of experience takes place.
And this quality of spiritual experience, like the quality of art, has very little to do with cultural or educational sophistication. Some people, though, and very often the untutored, are prodigies when it comes to expressing qualitative experiences verbally, visually or musically. As there are artistic prodigies, there are also religious prodigies, people who have had particularly intense experiences of transcendence, and their testimony counts for something. And while it may differ in breadth and intensity from the experience of those of us who are not prodigies, there is enough in our own experience that resonates with it, and while we may not be able to sing as beautifully as the prodigy, our song nevertheless participates in the same melody.
The tone-deaf Harris wants to reduce this song to terms he can understand in his atonal world, and it is impossible to argue with such a person. Either you hear the music or you don't. The best you can do is help him to listen for it, but if he has made up his mind that there is no possibility that music exists, it's not likely he ever will.