I heard an interesting thing on NPR the other day concerning muslims. A summary of the quote: "It doesn't matter so much what the Koran says, it only matters what the particular muslim thinks it means and how they understand it and apply it."
Is this same thing true with Scripture? At some level, I think it is... which is why we must have names for things, creeds, and confessions of faith. Most people say they believe the bible, but by names and terms, we help define what we believe the bible to teach.
When our terms, definitions etc. conflict with what they Bible actually says, we are in trouble. Which is why we need to prove ourselves from the true teaching of Scripture.