Suppose an atheist is confronted with a theory of existence which runs contrary to the one he currently holds, and is therefore summarily rejected. The question no one ever seems to ask is: "On what basis did he reject the competing theory?" Think about this. Is it because it failed to square with his current theory of existence? That is, did he enter into the evaluation already assuming the truth of his theory, using it as the criteria by which the competing theory was evaluated? That is a textbook case of question-begging (where theories of existence are the very issue, such as here), a particularly dangerous fallacy in this case because it leaves him incapable of determining whether his theory or the competing one is faulty. What if his theory were faulty but the competing one wasn't? How could he know? Well, he can't, when he dismisses all contrary theories with a question-begging wave of his hand.
Quite frankly, it's pointless to talk about the existence of this or that thing if the very criteria which govern the atheist's ontological conclusions are themselves faulty. Ergo, before there is any argument on the existence of 'X' the atheist needs to adequately defend or show how he has established that his theory of 'existence' is not itself faulty. The Christian apologist must not concede at the outset that atheist metaphysics are correct and that Christian arguments must conform themselves to it, if for nor other reason than the fact that atheist metaphysics may very well be faulty (and they certainly are). As noted by Michael R. Butler (Professor of Philosophy and Dean of Faculty at Christ College, Lynchburg, VA) (blog):
"The reason for this failure [of the traditional arguments for the existence of God] is precisely because they do not presuppose the Christian worldview. Rather, the traditional arguments [concede] the concepts of being, causation, purpose, etc., to the non-Christian; they assume that all of these are intelligible on the unbeliever's worldview. This being the case, the apologist has already conceded to the non-Christian that the world is intelligible without reference to God."
