I was confused because I couldn't grok why believing that there is no god required more confidence than believing that there is one.
But some recent hearsay has clarified it a little for me - people are wondering how you can be so sure because the stakes are so much higher if you don't believe than if you do. If you don't believe and the religious text in question is correct, you go to hell. If you do and it's wrong, no harm/no foul.
When the lightbulb went on about this (arguably, a whole lot later than it should have) it reminded me of a Bible verse from Revelation (note: Revelation. There is no book in the Bible called Revelations. I know a lady who is routinely driven bonkers by that common mistake):
Because you are lukewarm and neither hot not cold, I will vomit you out of my mouth
I remember that verse from my Christian schooling (which was ample, you guys). Maybe I remember it because it's so gross, or maybe because it's very evocative. As I interpret the verse (and I'm no scholar), I'm pretty sure it implies that god doesn't care to be treated like a safety school. God doesn't want to enter into an agreement with you that if neither of you have found someone by 40, you'll just marry each other.
If you're going to believe in god, I think you ought to believe in God. Not believe in "well, I might as well just in case."
My atheism is a life choice. I can't know for sure if there's a god or not. You can't really prove a negative. I really don't think so, especially not in the way god has been explained to me for my whole life. But it doesn't matter: I choose to operate under the assumption that all we have is us, so we'd better be good to each other. Ain't no one coming in to rescue us. We're on our own.
And I also don't want to live my life lukewarm. I'm not going to believe in something because I'm scared I might be wrong. Such weak tea! The very thought makes me want to vomit myself out of my mouth (not really - but that is an excellent descriptor, right? Even if the logistics are a little hard to conceive).
I love, by the way, to talk religion. I'm neither scornful nor precious about it. If you want to discuss this, tell me I'm wrong, ask me questions, go for it. I probably won't offend you, unless you're one of those people who are super quick to offense. If you are, stop being like that; life is short with or without god, don't waste it with your dander up. There's probably a Bible verse to that effect.