Over the years, I have been in various conversations with non-believers. Whether they identify themselves as atheist, agnostic, secular-humanist or some other category title, every conversation eventually comes to a screeching halt. No explanation I can offer to a person who doesn't believe in God will suffice, because their parameters of acceptance are simply too narrow. It's the irony of enlightenment: you're only enlightened if you accept a worldview that fits into very specific, very narrow parameters.
OK, Christian readers. Here's a scenario for you:
You and a young man, perhaps in his early 20's, step into an elevator at the same time. You're both going to the tenth floor. He notices something that indicates that you're a Christian (maybe you're wearing a cross necklace, or he saw a bumper sticker for your church on your car outside, etc.)"
I don't believe in God or anything like that, but you seem like a reasonable enough person," he says as the doors close. "I'd be interested to know: why are you a Christian?"
You have about 40 seconds to answer. What do you say?
How do you explain to a person (who states outright that he doesn't believe in God) that not only do you believe in God, but that you believe He is a being beyond your comprehension who created all things in existence and that you have a relationship with this being in all three of His persons?
I don't think I would answer his question directly.
Instead, I would give him a little food for thought. I would hand him a little piece of paper--a receipt, a note, a business card, a voided check (tear off the routing numbers at the bottom. No sense in being careless.)--through which I've poked a hole with a pen or pencil. I'd ask him to close one eye and look through the hole with the other eye. I'd then stand behind him, and ask him the following question: "Without turning your head or using any other evidence besides what you can see with your eye through that little hole, why do you believe I'm standing behind you?"
Allow the message to sink in for a couple of seconds before saying, "It's hard to explain? You just know what you know?" I suppose I could hit the guy with some Justin Martyr, Augustine or Tertullian, or offer him a personal witness, but ultimately I think keeping it simple, non-defensive and sincere would be the way to go.
"You ask why am I a Christian? It's hard to explain. I just know what I know. Soooo, why do you ask, my friend?"