For me - I'd need to see something "Godly", you know, things like he was supposedly showing people 2000 years ago.
A bush popping into fire, rotting dead men coming back to life, a man turning to salt, a world where nothing died, a sea parting, an angel - that kind of thing.
Something "impossible".
Like an amputee growing new legs after being prayed on or after having hands layed on.
Or an airplane set gently down on a runway after it's wings fell off.
Or a world with no war, death and disease.
You know - something BIG.
Until then I remain a skeptic's skeptic - on all manner of things. I'm a "show me the money" kind of guy. A "prove it" person.
Like I said before, so far, there is as much proof there is a tooth fairy as there is proof there is a God.
One man's religion - is another man's myth.
Very unlikely as many watched Jesus preach, heal the sick, make the invalids walk, and raise the dead and walked away unbelieving. In fact the Pharisees-perhaps the most religious of all-schemed to kill Lazerus also after Jesus raised him from the dead just to get rid of the evidence. And these were the people who knew the traditions of the OT which prophsied the coming of the Messiah. Those who reject God will not be convinced by any measure of miraculous signs and will rationalize them away.
