Being Irish, my whole family is Catholic on both sides (even the Ukranian chunk of my dad's family is Catholic). As a kid, when we were closer as a family and more involved in the community, we would go to church more. As the years went on, I went through the rites, not really understanding what was going on or why it was important. I never really doubted God. When we went into philosophy class in high school. I explored intellectually the argumentation of theology. Accepting God as an unconditional in an argument allowed a fairly good basis for argumentation: if I could relate something back to God and have it make sense, and the other person accepted the theistic premise, I could probably win the argument. I didn't understand how or why this worked.
When I started working at the photo lab, I met a girl who was to become a good friend of mine. She claimed to be an athesit. We would have civil philosophical arguments about the nature of the universe and the nature of ethics, the composition of the self and the validity of Christianity. These inquiries allowed me to further explore, but the idea of what God was or how Christianity made sense to me was still a bunch of airy things I didn't have a complete grasp on.
It was out there plugging trees into the Canadian Shield, where you have nothing to do for eleven hours a day but walk, plant, and think, that I realized that God is Truth. And what is the (capital T) Truth? The truth is what we can understand but cannot realize, what we can reason but not know. The Truth is the reality which is skewed by our perception. The Truth is the moral which is skewed by our accustomed or legitimated ethics.
To me, the world then consists of an absolute truth, the actual, and then the billions of individuals who occupy it, attempting to understand it in thier own way, including myself. So how would I come to understand this world? Well, I'm Catholic, so let's see what this Christ guy had to say, I thought. As I read the Gospels, and learned more about the most fundamental aspects of Christ's message, the things he described: reciprocal altruism, unconditional compassion, humility, patience, a desire to become better people, an enjoyment of life and of each other that can exist without worldly things. If I accepted Jesus's teachings as the Truth, then maybe things would begin to make more moral sense, and I could learn to be a better person.
My background in history helped me understand that cultural things like cannibalism, sacrifice, maybe even warfare, are not morally relative in thier context, but then present of the desperation that leads men and societies away from the moral into their most expedient or un-novel solutions to ensure survival and dominance. For me, there's no two ways about it: people killing and then eating other people is bad, and although the extermination of many American indigenous people was a very sorrowful thing, it is a good thing that institutions like sacrifice and cannibalism and self mutilation (all popular in the pre-industrial Pacific Northwest) were brought to an end.
But was I so different? Everyone does bad things. I do really bad things. I'm proud, pretentious, arrogant, vain, I've got the worst of it all. Things began to happen in my life where I could see that I could be a better person, and instilling some of that unconditional compassion and humility that Christ was talking about should be something I try to take to heart everyday.
I began to think of Christianity in new ways. Being a historian, the Bible could only ever be that to me, a history. It could convey a message, but as far as it was directly representative of the Truth was to always be in question, but it may contain within it elements of the Truth, as all things do. What's important then?, I asked myself.
I'd come to try and wrap my head around how to be a Christian, and I thought of a symbolic model that was representative of how I had come to understand things, if I needed to explain it to someone else. God the Father as the metaphysical God, a first cause, the source of The Absolute Truth of the universe, the thing that makes the stuff of the universe work, the most perfect of the Platonic Formes, how I won those arguments in high school (by practicing involuntary exegesis) etc, etc.
Jesus would then be what? The son of God? Well, I can't reason that. What I can reason though, is that Jesus's ethic is something that I accept as true and good. Could Jesus then be the source of all moral truth?, I thought. Well, this is the way I want to try and live my life, this is the ethic by which I have come to understand what is right and wrong, and even though I may never reach it, I can understand how it incorperates into everything.
What about the Holy Spirit? Well, maybe that's just the idea that there is something more to all of us, that we all contain in us some Truth, some bit of us that is more that what we can observe, the Self in each of us, which cannot be reasoned away.
Of course, I would still try to further understand what God is, what the Truth is, and how to live my life in a way that lets me try to be a better person.
In as far as understanding Catholocism, the Church as an institution is something I have been grappling with, being a historical skeptic, and not completely being able to accept the premise of an Abrahamic God, and of course being a little sour at the millenia of hypocrasy, the ritualism, the rites, etc. If I could come to understand how these things fit into what Jesus was talking about and not just being part of the socio-political quasi-monarchical institution that led these things to be, I might be able to eventually become more accepting of Catholicism, and probably start going to church again.
So yeah. The most wholehearted reason why I believe in God today, is because I have chosen to believe in Truth, and I have come to understand that Truth as many things, including the teachings of Jesus. All the while, I've considered the alternatives and have the counteraguments presented to me by my family, friends, classmates, co-workers, internet forum goers, and I've weighed the counter arguments, but the completeness of the theological and theistic model has helped me make sense of the world and understand how I can be a better person in such a complete way that the alternative never look complete.
I have a hard time finding people who think the same way.