I tend to be fairly pragmatic when it comes to decision making. At their core, the answers to your questions are binary. You either do something, or you don't do it. You either believe it, or you don't. The outcome is irrelevant, as is any reasoning behind the decision. There is typically a yes or no, on or off option at the bottom of any choice. How you interpret your decision, and the "why" of your decision, is what makes you who you are. Religion is a prime example of this.
The question of "do you believe in a higher power?" has little to do with your specific belief system. You either do, or you don't. If you ascribe to any number mono or polythiestic belief systems, than you quite obviously belive in a higher power. If you believe in fate, then yes, you believe in a higher power. A seemingly infinite number of beliefs, with one common answer. "No" means that you believe there is no higher power, no external, willful force capable. The only other answer is "yes". Even if your answer is "maybe," you likely have your answer. Every agnostic I've met had a leaning, an inclination. Some thought that the existence of a higher power was likely impossible, or that there was something but they just couldn't know what.
I have read articles and essays in which the authors describes the basis of their belief in atheism. Many attributed their belief to the absolutes of science, to the fact that science seems to follow its own laws where religion has none. Or that there is no God, because before the Big Bang there was nothing, including a god (I think that last one was Stephen Hawking). I found my answer to the question of a god for much more emotional reasons. For me, the question was never "is there a higher power?", it was "if there is a god, how does he account for the suffering in the world?"
I think my faith in God as an all powerful deity started to fall apart when I read the early testament. Laws about the correct way to deal with slavery, rules allowing slavery, and how if an virgin is raped, her rapist either has to pay her father money, or marry her; it's up to the father. It was the idea that was just as sinful for me to think about sex as it was for man who on his wife. That Hitler could have begged forgiveness and gone to paradise. It was the idea that I was a bad person for thinking bad things, even if I didn't do them. There first time I read all of this, I just felt angry at how unfair it all was. And then I felt terrible. Because I would never be good, and each natural thought and desire I had as a prepubescent teen made my inadequate. For a socially anxious teen with self-esteem issues, those notions weighed me down.
These doubts were never far from my mind. Whenever I discuss the issue of suffering in general terms with someone of faith, their answers tend to fall into one of three basic categories: "it's God will", "it's the outcome of human free will, given to us by God," or "God's reasons are not for us to know." I say bullshit. I was raised to believe that God so loved the world, he gave his only son for the sake of humanity. But that same God, only a few millenia before (and in the second book of Peter, they say that "With the Lord... a thousand years are like a day"), God felt that we were all too wicked, so he decided "fuck 'em all, they can go drown."
All of my life, I couldn't stop thinking about the cruelty of man. In college, I did a bible study with an older couple I'd known for years. I asked them some of the questions that had been building in the back of my mind. Like the Holocaust; seriously, 6 million Jews, and 5 million others of "undesirable" status were killed in the concentration camps, to say nothing of the others killed in the crossfire. How could a loving god let that happen?
My surrogate grandfather answered yes, it was cruel, that it was sad, but that Jews were a "hard-hearted people." I can't really recall what he said after that in any details, that's the phrase that sticks out. The remainder of his words were just hollow reiterations of what I'd always heard. It was God's will, and that we can't know why it happened, but God does allow us the free will to make our own decisions. I would take two ideas away from this conversation, ideas I couldn't believe, but that I was starting to understand were the rote actions of many religious people: victim blaming the those that have suffered, and the glossing over of the serious questions with difficult actions. But that was when I was presented with my first question: was the bible the word of God, or was is it just the word of man?
I wanted to believe that there was someone out there, someone powerful who loved me, who cared for me. The cruelty shown in the bible by God and those who followed him seemed unfathomable. Yet it was nothing when compared with the suffering since. So, I made my first decision: the bible was just words, nothing more than a historical text. I still believed that there was a God, and the ideas in the bible, the tenants espoused by Jesus, that was what mattered. It was the love in those words, not in the ugly parts written in an attempt to control other men. The question of whether or not God existed wasn't even on the table. That question didn't start lurking in my mind until I was in my 20's.
As I grew older, I declared myself agnostic. But at that time, I was really just a confused christian. I still believed, still wanted to believe in God. But that faith, my ability to blindly believe, was slipping. Of course, this was when my depression started to worsen, and I was frantically seeking any lifeline, any way to make myself feel loved. At this time, I became incapable of truly seeing the cruelty and capricious nature of life. I knew it existed, but I could barely fathom the numb chaos in my own mind; I couldn't handle facing the sorrows of the world.
It was in my mid 20's that the tide truly began to turn. I was somewhat balanced and I forced myself to see the things that were happening in the world. I forced myself to look at worldwide human rights abuses, the terrible abuses seen in followers of all faiths, the greed of all mankind, and the widespread poverty that crosses all borders. If there was a God, he allowed a lot of suffering. So it was at this time I needed to answer another question: was God good?
This was the question that led me to atheism. Because suffering exists, it is a basic truth. So God either allowed it because he would not intercede on our free will, or he had his own reasons, a plan. Neither notion sat well with me. I didn't care if he was all powerful, he was all seeing. I couldn't understand how he could see all the suffering in the world, listen to parents cry over the bodies of murdered children, watch as humans starved, allowed mass killings, all while not sending down a lightning bolt or two. Because I sure as hell wouldn't allow it. If I was omnipotent, rapists, child molesters, and unflinchingly greedy would get fried, with nothing left except a scorched message on the ground reading "Big God AG hates rapists/child molesters/ greed." I would stop it and people would know why.
I realized that I didn't care why God allowed suffering; what mattered was that he did allow it. This epiphany shook my faith that a god, any god existed. If a God did exist, he didn't care. We were as important to him as ants to a toddler. In fact, the only reasonable religion to my mind was the Greek Pantheon. Yeah, there was suffering, and yeah, the gods caused it. But they were spoiled, self centered deities, hardly capable of thinking beyond themselves. Their cruelty made sense.
I found myself faced with a choice: did I believe, did I want to believe, in an uncaring higher power. The notion of a cruel, capricious higher power made me feel ill. And it made me mad. As long as there was a god, there was someone we could blame, someone we could point to as we shirked our responsibilities to our fellow humans. Thus, I came to my last questions: is there even a god?
My answer was a resounding no that echoed in my heart and my mind. I decided that all we had, all we had ever had was, at best, a shared belief to encourage good behavior that at its worst gave us the ammunition to forsake each other. But after I made this decision, I was just happy, because it made things seem easier. I wasn't a bad person for my thoughts; I was a bad person if I did bad. Thoughts and beliefs meant nothing; it was what I did, what anyone did, that mattered. It meant that we have to fight for this life, because it's the only one we have. Because life isn't a trial to decide your fate in heaven or hell. Life is the entirety of our existance, and our actions are what define us.