The short answer to 'why I'm a Christian' is God's grace. He came looking for me, long before I was looking for Him. I'm sure that God speaks to each person in a unique way, because He knows our hearts. In my life God speaks to me by showing me. When I ask a question in prayer, His answer usually comes in an act, sometimes several days later, that I see as His reply. It has happened to me so many times now that it no longer surprises me. I'll want His guidance, and He provides it, by showing me the answer.
I had been an atheist/agnostic most of my life. I was raised in a functionally atheist home. My mom dragged me to church on occasions, but it was more social than spiritual.
I liked Ayn Rand for a while in college. Rand's atheism made a lot of sense to me. I liked her comparison between totalitarian thugs and mystic thugs. Reason seemed a fine thing to worship. I was a little uncomfortable with the suspicion that Rand's ideology could lead to a particularly ugly form of repression itself, because it was based in no objective moral code except "A is A" and rational self-interest. I wasn't so sure that that code would end well if widely practiced, but my affection for Objectivism remained.
The portrayal of Howard Roark in the Fountainhead fascinated me. Still does, in a way. I never liked Atlas Shrugged (too strident), and I was never an Objectivist in any formal sense. I never wore an dollar-bill-broach and I didn't smoke. But Rand got me thinking, at a young age. My thoughts took me in a different direction, but I have to thank her at least for that.
I had been a faithful atheist for many years. I liked Christians. I respected Christianity. I didn't think it was nuts, just untrue. Too good to be true. I equated Christian belief with televangelists, who I despised. I still don't like them, although I seem them a bit more sympathetically than I did. I believed that Darwin explained life and Hawking explained the universe and that science was the reliable path to knowledge.
But I came across a quote from St. Paul. I don't recall where I saw it, or even exactly when, except that it was years ago. I seem to remember that it was in an essay that wasn't particularly religious. The quote struck me as more philosophical than religious when I heard it, but I couldn't get it out of my mind. The quote was:
"What do you have that you did not receive?"
It haunted me. The context was that Paul was chastising the Corinthian Christians for taking pride in their sectarian faith or in their personal abilities (1Cor 4:7). I think that he also meant it in a much more general sense.
I couldn't stop thinking about it.
What did I have that I did not receive? I had always been an ambitious person. My family was poor. We were on welfare for a while when I was a kid. I became a paratrooper in the Army, went to an Ivy League college, got into an Ivy League medical school, became a neurosurgeon. I married a wonderful woman-- the love of my life-- and I had four great kids I love with all my heart.
I was a self-made man. But that line- "What do you have that you did not receive?"-- dogged me.
I couldn't stop thinking about it. Because when I thought about it, I realized how utterly contingent I was. Where I was born, how I was raised, my health and intellect, nearly all of the chance and purpose in my life, was not from me. My life was largely without my request and without my consent. It could be altered or ended without my consent. Certainly I worked hard, and took opportunities when I found them, but nearly all that I took pride in I received, in a very real sense. My health, my life, my abilities, my circumstances, the good and the bad, were not from me in any essential way.
That is not to say that I didn't take responsibility for myself. I did, and do. But I was overwhelmed with the fact of how little of my life was not received. I was not my own.
I saw that this wasn't a scientific question, in the sense that I could explain things by biology, etc. It was deeper than that. It was a question about ultimate origins, not mechanism. When I thought about mechanism, I saw how shallow that was. Science described things, but didn't explain them, in any ultimate way. The real question was my origin.
I came to see that I was contingent. That just as my life began without my having any say, it could end without my having any say. I came to see that I was not responsible for my existence. My experiences in medicine brought that point home even more intensely: I saw people's lives changed radically in a moment, saved or lost by a power not theirs or ours.
I began to ask the obvious question: if what I have, I received, where did I get it from? What, or Who, gave it to me?
So I began looking.