For me, I think the thing that makes me trust the Scriptures so much is that these are real people who gave their lives for what they KNEW they had seen Christ do and say.
No one would die for a lie; it profits no one. This along with the fulfillment of prophecies, the historical and archeological accuracy of the Bible, the fact that the Bible has remained unaltered for thousands of years, creationism and intelligent design do fit in with what we know of science, and also the fact that there's nothing in the Bible that has or can be falsified and proven to be untrue gives me all the faith I need.
But like I said, what really gets me is that the apostles/disciples actually gave their lives for their testimonies of Christ; they had nothing to gain from lying about Jesus and being killed for it - time and time again they were given the chance to renounce their claims and testimonies of Christ, but they stuck to it and were willing to die because they KNEW what they saw!
I'm not sure an unbeliever would call this "proof" but it's certainly convincing to me.