Like many atheists I know, I was raised Catholic. Unlike some of them, the Catholic Church didn't turn me away from god. What turned me away from god was, interestingly enough, a personal encounter with the Big Guy himself.
In 1983, I attended a Revelation seminar and became a Seventh-day Adventist. I loved the church, it was good to me and for me, and though I hold some things against it, I was happy and pious in a genuine way while I was an Adventist.
In 1990 (wow, twelve years ago), I was working two jobs. Temp secretary by day, convenience-store clerk by night. I wasn't all that happy about working alone on the graveyard shift, but I was a block from my house, and I thought I needed the money. My brothers would come in and keep me company while they played video games, so I really didn't mind it much. I've always been a night person.
On March 21, my brother left around 2 am. My life changed a half hour later.
We weren't supposed to come out from behind the counter while working alone, but then again, there were things we were supposed to do in the store before the boss got in at 6 am. I was filling the coffee machine at around 2:30. Alone in the store, I was facing the street door, with my back to the dairy case. A customer came in. I must have said hello to him, but I don't remember it. I really didn't give him another thought as I filled the coffee filters and he went over to the dairy case. The next thing I knew, he grabbed me from behind. I was so confused and startled. I looked down and saw that he had stabbed me in the abdomen from behind with a hunting knife.
He told me to take my clothes off and lie down. I did. He raped me while I bled all over him.
I was compliant. Let him kiss me. Tried to lie still. Stared at him the whole time, trying to memorize his face. He seemed almost catatonic, like he wasn't really there.
All this time, I was scared but calm in a weird way. I was certain I would be dead within fifteen minutes (don't know why fifteen minutes was what I thought, but there you have it), but I just told god that I hoped he would take care of me and that I was ready to be with him. Over the guy's shoulder, I saw a vision -- it was as real as anything I've ever seen. It was a cliché all the way through, but it comforted me. A being in a white gown hovered a few inches off the floor. I assumed it was god. Later I thought it might be an angel, before I decided it was senseless to give a name to it. Anyway, I felt protected by it, and I felt warm and calm even as I was staring into the attacker's eyes and readying myself to die.
Of course, I didn't die. The details of that night will stay with me forever, but you don't need to hear them now. What I learned will stay with me, too.
I learned a couple of things that night. First, that when we die, no matter who's with us or not with us, we die alone. We get to face that on our own. Second, it's possible to calmly face death. I had been terrified of dying until that night. Now I know I can manage it when it comes. And last (maybe most practical), I learned that there are *very* few life-or-death situations in life (at least for people in my current socioeconomic position), and that gave me a decent sense of perspective, I think.
In subsequent months, but beginning the very next day, I decided that no one who isn't going to die my death is going to live my life. I decided to start trusting myself and stop letting others decide what was right, and what was right for *me*. I stopped going to church and started reading everything I could get on spirituality, religion, philosophy, and non-theistic systems. I was an agnostic for a long time. It was (and is) my position that it would be impossible for me to prove a non-being, and that I hadn't enough evidence to prove the being in question in any affirmative way.
What made me stop calling myself an agnostic was the realization I had one day that I was requiring more certainty of godlessness than I required of anything else in my life. God had not chosen to reveal itself to me unambiguously (some would say the 'angel' was unambiguous, but I'm sorry, something that comes when one is bleeding to death and then disappears doesn't count), yet I was making all these life decisions based on it.
Do I have "faith" in my car because I believe it will work? I turn the key in the ignition a thousand times and something happens, I'm going to believe something will happen the next time. God fails to reveal itself today, and a thousand other days, I think I'm safe acting upon a reasonable belief that it doesn't exist. Kind of like my faith in electricity -- I have none. Just a reasonable expectation that it will work. Certainly I have a reasonable expectation that there is no god, so I call myself an atheist, though it is still my belief that I don't know "for sure" about the existence of a deity. I'm pretty damn sure it's not the gods of modern-day christians/jews/muslims, if it exists, but if it exists, it is its job to reveal itself to me. If it wants blind faith, tough. I don't want a deity on those terms, and I see no clear evidence that I should. After all, what use is my intellect, if not to hold ideas in my mind, examine them, find them whole or lacking?
And if it came down personally to prove its existence and is disappointed in me, well, I'm disappointed in it, too, so we're even.