The theist side of most of these debates usually consists of three main angles of attack:
- God's existence can be logically proved via a number of different arguments, such as the Cosmological Argument, the Argument from Design or the Argument from Contingency (which is really just a subset of the Cosmological Argument).
- Science (usually equated with atheism for some reason) can't explain everything (or anything, with 100% certainty), but the "God" hypothesis can, so therefore it is more reasonable to believe that God exists.
- Faith, personal revelation, etc., "prove" that the theist's accepted version of God is the right one (which is why Muslims use the same exact arguments as Christians to "prove" wildly different versions of God).
And so, most of these debates tend to revolve around the first angle of attack. The theist runs through the same tired arguments that have been refuted time and time again, and the atheist goes through the motions of pointing out how they have been refuted time and time again. And nothing ever gets resolved! Even if the atheist refutes every single point made by the theist, even if he explains in careful detail the unwarranted assumptions, begged questions, leaps of logic and major fallacies employed while making the arguments, the theist just continues blithely on to the second and third angles of attack as if nothing happened.
And this is when I had my revelation. Theists who make these arguments purporting to prove the existence of God aren't actually trying to convince atheists that God exists. Instead, they are simply trying to offer logical-sounding justifications for what they believe so as to not appear illogical, foolish, gullible, stupid, idiotic, or what have you. They know that their belief in God is based on a wholly irrational foundation of faith (not to mention cultural inertia, family experience, etc.), and they trot out these arguments to make themselves feel better.
Again, this becomes extremely apparent after a theist runs through all the "logical" arguments as to why a God (of some sort) must necessarily exist, but then has to resort to an appeal to faith or personal revelation or an appeal to emotion to bridge the gap between the supposedly proven "first cause" God and the God that they personally believe in and worship.
All of which is to say that debating theists over the existence of God is probably a useless exercise. People don't tend to believe in God for logical reasons in the first place, so refuting the logic of their proposed arguments isn't likely to change their opinions. The arguments are nothing but smokescreens to hide the fact that their beliefs are not based on logic or evidence, since appeals to faith typically don't carry too much weight with the faithless.