After reading everybody's responses in Katzpurs thread. I thought this would be a natural follow up.
1. So how about it, what would suffice as proof of God?
2. Would any of the bilbical miracles convince you if you witnessed them?
I think it a better thing to do is to ask question # 1 to the christians. I know that they act on faith instead of proof, but they also believe Christ will retun. So, you can ask " what would suffice you as proof that God has returned (whenever he does)?