I’ve never really addressed this before. At least I don’t think I have. Here’s a brief 
glimpse into to how the deranged mass of neurons I call a brain works: Weeks ago I had a very brief (something on the order of three sentences) conversation with a friend along these lines. I finished the conversation today in my head. I do that a lot: I have entire conversations with other people in my head that they didn’t actually participate in. Oh, c’mon, you know you do it too.
If you ask the average atheist why he/she does not believe in God, the 
answer is simple: there’s no proof for god. Basically those of us who label ourselves as skeptics have adopted the scientific method as a way of approaching life in general. It goes something like this:
Fundie: There is a god. He is the one true God and he loves you. Through him only will you find salvation and enter the kingdom of Heaven.
Skeptic: Fine. Where is your proof for said god?
Fundie: Right here! The Holy Bible! This is the sacred word of God and the path to Heaven through Jesus Christ our Lord.
Skeptic: Right. We’ll get back to this Jesus character. So you have a book that you claim was written by a supernatural deity. How do you know that it was actually written by a supernatural being and not written by people?
Fundie: Because it says so right here in the book of I Corinthians.
Skeptic: That’s circular reasoning. The bible was written by a supernatural creator of the universe because it says it was. You have failed the burden of proof. Until you have provided evidence for your claims, the null hypothesis applies, and it is unlikely that there is a supernatural being at all. Your book was most likely written by 3000 year old goat herders with nothing but oral traditions handed down over centuries borrowed from other cultures and no working knowledge of modern science.
Fundie: Infidel! You shall burn in Hell! The Lord thy God shall cast thee into the pits of Hell and watch you burn for eternity!!!
Skeptic: Bring it. By the way, you’re drooling.
The problem though, is that it’s more than this. There’s more to it than just a simple lack of proof. The entire concept of God fails any kind of logical reasoning. For instance, take this example.
Something bad happens. It doesn’t really matter what. Something bad 
happens and it leads to a series of events. The end result of this chain of events is that someone gets hurt, probably me or you. This has happened to all of us, each and every one. The specifics of this particular example don’t really matter, because the same pattern has happened several times in my life, and probably several times in yours. Let’s go through a couple of scenarios now.
Scenario 1: God fucked up.
Let’s start with the following assumptions:
1. God exists.
2. God knows everything that is happening (Omniscient)
3. God does not see the future.
4. God controls everything (Omnipotent)
In this example, God started a chain of events. Possibly God thought that something positive would come of it all down the road (e.g. he meant well). However, things did not turn out the way he intended. Basically, God fucked with my life and screwed everything up. God is incompetent. He fucked up. Everything would have been better if he just stayed the fuck out of everything.
Scenario 2: God is an asshole.
Let’s start with these assumptions now:
1. God exists.
2. God knows everything that is happening (Omniscient)
3. God can see the future (Prescient)
4. God controls everything (Omnipotent)
Let’s forget the logical inconsistencies of God being all of these things at the same time, and suspend disbelief just long enough to finish the example. In this example, God knew full well that the outcome of the events he set into motion would be and the disaster that occurred as a result. He knew full well the pain waiting for me (or you) at the end of these events. Why would he do that? The fundamentalist would say some dumbass thing like “God works in mysterious ways” or “He was teaching you a lesson” or some other completely inane bullshit. If he’s all powerful, couldn’t he just simply pass said knowledge along? The fundie says “but you wouldn’t learn the lesson that way”. Okay, but if he designed and made me, why would he design me that way? Why not “design” me to just simply know? There’s only one inescapable conclusion to made here no matter how many logical rabbit holes the fundie goes down, God is a complete and utter flatulating butthole.
So, we’re left with two choices, 1. God is incompetent, 2. God is an asshole. Using the bible as a guide, I think we can safely say that #2 is a gimme, but the point of the whole exercise is this: If you proved God’s existence tomorrow, I would, of course, accept the existence of God, but I would not convert back to religion even then. There is no escape from the logical conclusion that if God exists, he is not worth my time. On the 
other hand, if we accept the null hypothesis that God does not exist, than all of this is nothing more than random bad luck, the kind that statistically happens to everybody all the time. No supernatural explanation is required for this, and I have no reason to be angry at any supernatural entities who refuse to prove their own existence to anybody. Nice, simple, clean, and so much easier to accept and explain.
And THAT is why I’m an atheist.
