The first of the five Solas of the reformation is Sola Scriptura, which means Scripture (the Bible) alone. This is one of the main things that set Protestants apart from Catholics: We recognize only the authority of Scripture and not the authority of a Church leader in terms of doctrine. Our pastors do not determine Church doctorine: Only Scripture does.
One might ask, then, why there is so much division among protestants when it comes to doctrine? Why don’t we all agree?
There are two things to mention in answer to this question:
1) First of all, we do agree on the crucial things, the things that are non-negotiable. That’s important to understand. I remember when I was taking my fourth semester of Greek in college and we were studying textual criticism (the process of figuring out the wording of an original text). The problem is that there are no surviving originals, so we are left only with copies (hand copied, obviously, not photocopied) — and people make mistakes when hand copying, or choose to change something slightly to fit their own desired interpretation. It was disconcerting, sometimes, to realize that we have no way of knowing which manuscript is closest to the original in many of the discrepancies. Then our professor had us step back and look at the big picture. The things we were unable to know for certain were unimportant details. They were not doctrinal issues. The doctrinal issues are intact and clear.
2) The reason various protestants disagree on some of the more minor points of Scripture is because, even if we know what Scripture says, we sometimes disagree on what Scripture means. Again, this is a problem only with minor points, not the ultimately important things — though sometimes we forget that and battle over those minor points as if they are major. (Hey, we’re human!)
The bottom line is that we believe that Scripture (in its original form) is the final authority for doctrine, morality, ethics, etc. We try to follow what the Bible says … and again, we are mere humans, often failing. (Sooooo often failing!) But the more we study Scripture and read it, the more we “hide it in our heart” — which means simply that it becomes planted deep inside us where it can inform our decisions and our day to day lives.
I mentioned studying and reading … and those are two different things, both important. Study involves getting down to the nitty-gritty, pulling it apart, looking at context, trying to mine out all the deeper lessons God has hidden for us there.