I've been asked by many people over the years, most recently by commenter Edward what proof would I need to accept that the Christian god, or any god actually exists.
Well, I'll tell you, kind of.
Back in collage I took a class where religion and atheism were compared. We discussed this question frequently amongst ourselves. Everyone pretty much agreed that if Jesus descended from the skies on a beam of light for all the world to see that would be enough proof. But we are taught that the lord does not work in such garish ways. He's not going to show himself in public. We just have to have faith.
So I thought, If god won't show himself to the masses anymore (he was constantly showing up unannounced in the OT), would he give me a "personal" sign of his existence? If so, I'm sure he would allow me to pick my proof because I would have to know the sign beforehand so that I knew it was God contacting me.
So I set out to create a set of rules.
1) I had to rule out mental illness as a possibility so it would have to be verifiable by others. Others would have to be able to see the sign but not need know what it meant.
2) It would have to be something very personal. Something only I would understand as a sign.
3) It would have to be something that occurred in the the natural world. The sun couldn't "dance in the sky", the trees couldn't start talking and the stars in the night sky could spell out BRUCE IS AWESOME (although that would be nice, and true).
4) I can't tell anyone what that sign would be to rule out the possibility that someone would try to trick me into believing.
I have my sign and have been waiting almost 25 years for a higher power to show it to me.
If/When I see it I will spend the rest of my life trying to convince the rest of the world that they need to praise this god as well.
Atheists, what proof do you require? Did you believe and now you don't? Do you have a plan? Is mine sound?
Believers, What made you believers? Did you have an experience that changed you? Could you apply the above rules to your experience? Are those rules even relevant to your faith?