Generally speaking, an atheist arguing with a Christian is like this guy:
doing battle against this guy:
The atheist is simply better armed. And why is that? Because logic.
It’s logic that wins arguments. Nothing else. And a Christian employing logic to win the argument that God exists—let alone that the Christian one is the only god that exists—tends to be like a hang glider employing buckets of cement to help him fly. Not so much with the helpful.
That is not to say that there is no logically sound argument for Christianity to be made. I daresay that I have made such an argument myself, both here on my blog (see, for instance, my The Rational Genius of Christianity) and via my book Penguins, Pain and the Whole Shebang: Why I Do the Things I Do, by God.
As a response to the human experience, Christianity isn’t one iota less logical than atheism. But the fact remains that the locus of the religious sentiment lies beyond the purview of the logical mind. In the final analysis, the phenomenon of the human spirit communing with the eternal divine is not a thing which can be discussed. It it something that begins right about where language leaves off.
As intense and radical as it is, the religious experience necessarily and inviolately remains an entirely subjective experience. As such its essence cannot be captured, communicated, delineated, or explicated. It is not transferrable. It is what it is. To attempt to make more of it by universalizing it is to degrade it. To argue for its preeminence is to render it fodder for the arguments of rational humanists, who have every right to drag kicking and screaming into the ring of rational discourse any bumptious Christian he chooses, and to there soundly thrash him or her before sending them off with their vestigial tail tucked between their legs.
As a Christian, I get to feel as Christian and God-centered as I want to or can. What I don’t get to do–or what I should steadfastly resist the (egotistical—always egotistical) temptation to do, because it’s not only a fool’s errand but an offensive fool’s errand–is try to insist or prove that what is real and true for me must also be real and true for everyone else. That category mistake—that effort to make something that is subjective objective—is how wars are begun.
As Christians we must hold God in our hearts, minds, and souls. And then we must do what all good people do: go out into the world, and be loving and respectful toward all—especially, and even particularly, to those who do not share our religious views. Let people argue, if they must—and certainly if we give them reason to—that we are illogical beings. In the end we are, and can good-naturedly resign ourselves to being, vulnerable to that charge. But let us never give anyone sound reason to argue that we are unkind, or anything less than entirely thoughtful.