I was just watching a Simon and Garfunkle concernt, when I started looking at the guitar and thinking how strange it is that plucking metal strings can produce such emotions in people listening. Steven Den Beste wrote an essay trying to explain, from a materialist perspective, why human beings find music to be beautiful. It's not an easy problem, since enjoying music has no obvious (or even concievable) evolutionary advantage. My recollection is that Den Beste concluded it was a by-product of the way our intelligence organized, and left it at that.
This is something of an encapsulation of the problem that modern american christians face when trying to do apologetics. Materialism, which is something of the default belief in much of America, while technically a positive belief, is really a negative belief. If materialism is true, then nothing in the universe needs to make sense, first because there was noone to make the sense, and secondly because there's no one for it to make sense to. Materialism denies not only God, but also man. For if your brain is just deterministically firing off, there's not the least reason to believe that anything that you think corresponds to reality. That doesn't make what you believe false, as C.S. Lewis sometimes tried to maintain, but it does make it completely unreliable. It's true that this brings you to the very weird circle that if you believe, upon the evidence, that materialism is true, you then have no reason to believe the evidence that you used. This isn't a logical contradiction, so it doesn't make materialism false. It's only a practical problem — if Steven Den Beste tried to convince someone of materialism (which to his credit, I believe that he never tried), the person that he's conversing with might reasonably ask him, "if any of what you said is true, why should I believe you?" And all that he could truthfully answer is, "it doesn't matter if you do."
Because if materialism slits its own throat, it's only after slitting the throat of every other belief first. Materialism is one of those final question — if you answer it in the positive, you can't honestly ask any other questions. You can ask them for fun, of course, which is why materialists don't literally slit their throats. But it's a bizarre sort of game that they play, because they're asking and answering other questions all the while believing that their answers are completely unreliable. But this is a digression.
What's relevant to christian apologetics is that materialism thus has the same sort of imperviousness to objections that Budhism does. When your theory is that nothing makes any sense, no one can object to it by pointing out how it doesn't make any sense. There's nothing in this world that either a Materialist or a Budhist needs to explain. Perhaps a materialist would have to explain it if everything in the universe made sense, but the human intellect is far too limited for any materialist to have to worry about that possibility — even if the universe did all make sense, there's no reason to suppose that any human being could understand it. It's not that materialism can't be disproved theoretically, it's just that it can't be disproven practically.
So that means that an apologist can never argue a materialist into that state of agnosticism where he can give Christianity a fair hearing. What, then are we to do? The answer, I think, lies in awakening the senses which are dulled in the modern world. I don't think that one can argue a materialist out of materialism by pointing to what's wrong with materialism. I do hope that we can argue materialists into Christianity by showing them what's right in Christianity. (Chesterton is right that the way to deal with a skeptic is to lead him to doubt greater and greater things until one day he doubts himself, but materialists are not skeptics.) How to do this is, I think, the great question of our age.
(Incidentally, it never fails to amuse me that Descartes' proof of God was merely a corollary in his attempt to prove his neighbor; I can't help but notice that those who disagree with his proof of God never replace Descartes' argument for the existence of his neighbor with anything. They attack him for his credulity and then assume what he was trying to prove.)