Doubt of Scriptural validity is a human issue.

One way is to "test" the Bible. The Bible gives promises. It basicly says if you do certian things God promises certian results. To those who have "tested" this there is no doubt as to validity of the Word. They've lived it. Theyve seen it with their own eyes. Also it can be "tested" by seeing the things around us that have come about exactly like the Bible said they would.

Yet in part, Christianity and Bible believing will always require a measure of faith. Its ordained to be that way. The reason - God wants humans to believe Him, just on his word alone, and He wants to preserve/save only those that have that kind of faith in order to make an utter end of sin/evil.

As I have said before, if you believe in a God that can create the worlds with only his spoken word how can you not believe this same God has the power to preserve His Book and the integrity of it? But if you want to be sure just "test" it.