A Christian friend of mine once asked me, and I'm paraphrasing, "As an atheist, what is the most knock down drag out argument against God you can think of?"
I initially answered, "Theological noncognitivism."
My Christian friend was a little put off by the big words, and demanded "I try to keep things simple, for the sake of the argument."
So I explained that it is the technical term for Ignosticism, which basically states that the definition of God that Christians derive from their faith is so convoluted, and so divergent, from every other possible definition, of every single denomination, regarding that very same God, it's impossible to actually determine what God is as a concept.
In other words, if you can't explain what God is, and nobody can agree as to what constitutes that specific God, then chances are you don't actually have enough information to determine if the definition you are giving refers to the God you profess to believe in. The problem has to do with a lack of a referent, where no actual experiential knowledge can support your definition, mainly because your definition has nothing tangible to reference.
Likewise, if you can't explain what it is you are talking about, then that means you have a problem. How can you pretend to believe in something if you can't even determine what it is. If you can explain what you are talking about, clearly and lucidly--and have a solid notion of what it is, but eighty thousand different people each claim eighty thousand different things about the same thing you supposedly believe in, with only but a few of those things overlapping, then you have a freakin' huge problem. What it means is your certainty is erroneous. But worse, it means your definition is unsound, and so too your convictions.
He seemed to not even give it a second thought (we're talking the most bad-ass knock down argument I have ever come across--and he didn't even bat an eye--what faith!) and he quickly changed the topic to the Holy Spirit and how God speaks to him... you know... in his imagination.
Remember, he still doesn't even know what it is he is supposedly talking with, because he can't even find a definition to adequately describe whatever it might be--but whatever it is--he's certain it's God. Convenient as it is for him to "feel" God working in his life, it still doesn't solve the problem. At any rate, I digress.
After a few minutes of listening to him prattle on, I was beginning to wear thin on patience. After all, if you let a theist start professing their convictions, they often times just keep going and going, like the freakin' Energizer Bunny. Usually this tells me they aren't even interested in learning about other perspectives, beliefs, or ideologies. They just want to assert theirs. Personally, I think it's rude, and so, I had to interrupt.
So I walked over to the window, opened the curtains, and pointed outside and said, "You want a knock down drag out argument for the non-existence of God? There it is! You're looking at it."
He automatically assumed I was pointing at the big airy scenery, and the emptiness between the earth and sky, and scoffed, "Typical thing for a materialist to say. Demanding to see material proof of God."
I said, "Well, seeing God would help prove his existence quite nicely. In fact, seeing any evidence of his affect on the world, that would be almost as good, but that's not what I'm pointing at."
"What are you pointing at then?" he asked.
"I'm pointing at the affect God should have on the world, you know, if he existed, but apparently doesn't. I'm pointing at the suffering of the world--which wouldn't be there at all if an all loving all powerful God existed and could do anything about it. I'm pointing at nature, which runs her course uninterrupted by supernatural events, and which can be explained almost entirely by science, and that which cannot yet be explained via science probably will be very soon. I'm pointing at the world as it looks--with no God in it. I'm pointing at what makes every concept of God I've ever heard about completely irrelevant--I'm pointing at reality."
At that point, he didn't feel like carrying the conversation on any further, and quietly composed himself and walked out of the room, with his faith rattled but still intact.
A week after that, I recieved a long miandering email, referencing Answers in Genesis dot org for all it's knock down drag out apologetics which refute everything--apparently--and which allowed him to claim I hadn't come up with a good enough argument because I couldn't address any of the additional objections he raised--such as proving that evolution is true, or explaining what caused the universe, he brought up fine tuning and intelligent design, and finally the last defense, he asked, "If God doesn't exist, then where does morality comes from?"
*Sigh. At this point I really desperately wanted to share a Robert G. Ingersoll quote, in which Ingersoll states:
"No one infers a god from the simple, from the known, from what is understood, but from the complex, from the unknown, and incomprehensible. Our ignorance is God; what we know is science."
Although his apologetic tap dancing let me know that he was desperately grasping at straws, throwing every argument he could at me, I still knew he wasn't actually trying to seriously consider the gravity of the situation. How could he? Even as he was throwing lame arguments against me, to defend his own faith from uncertainty, he neglected to understand the devastating blow I had dealt him earlier.
I'm not looking for professions of faith. If you can find things to justify your faith, then fine, so be it. But whenever you happen to realize the conversation isn't about what you feel is true, or what you "know" is true in your heart, but what you can demonstrate, then get back to me. I'm looking for facts--because facts typically deal with reality--and if you aren't talking about things which deal with reality--then chances are--all you have is faith. Not facts.
What he failed to see was, faith isn't an argument. It's a position of certitude based off of poor reasons to believe. Poor reasons because the evidence which could justify the reasoning is all but non-existent. As Burtrand Russell once stated, "Where there is evidence, no one speaks of 'faith'. We do not speak of faith that two and two are four or that the earth is round. We only speak of faith when we wish to substitute emotion for evidence."