Many non-Catholic Christians believe that praying to the Holy Spirit for guidance will lead them into the correct interpretation of the Bible. While this is a nice thought; reality shows pretty quickly that it doesn't work. The Holy Spirit may be guiding me; but I also am influenced by my education level, my preconceived notions, my biases, and, most importantly, my desire to be right.
The historical and cultural heritage of the Bible makes it quite difficult for a reader in the third millennium to understand the metaphors, the connotations, and subtle word play that would have been obvious to those alive when it was written. What is "so clear" to us is our own, modern understanding of the English translation. It can be hard for us to get a proper context.
For example, the word "works" is used by St. Paul in his letter to the Romans and by St. James. They are speaking, however, about two completely different things. St. Paul speaks about "works of the law" which are those actions required by Jews while St. James speaks of works like loving and charity. This is why St. Paul can say we are saved by faith and not works (of the law) and St. James can say we are saved by works and not faith alone yet there is not contradiction. This context isn't obvious from the text.
If that weren't enough, the Bible itself condemns personal interpretation. Let's take a look:
"And consider the patience of our Lord as salvation, as our beloved brother Paul, according to the wisdom given to him, also wrote to you, speaking of these things as he does in all his letters. In them there are some things hard to understand that the ignorant and unstable distort to their own destruction, just as they do the other scriptures. (2 Pt 3:15-16)
"Philip ran up and heard him reading Isaiah the prophet and said, "Do you understand what you are reading?" He replied, "How can I, unless someone instructs me?" So he invited Philip to get in and sit with him. This was the scripture passage he was reading: "Like a sheep he was led to the slaughter, and as a lamb before its shearer is silent, so he opened not his mouth. In (his) humiliation justice was denied him. Who will tell of his posterity? For his life is taken from the earth." (Acts 8:30-33
"Know this first of all, that there is no prophecy of scripture that is a matter of personal interpretation" (2 Pt 1:20)
Well, if the Bible says we shouldn't interpret it on our own; where should we find the truth?
"the church of the living God, the pillar and foundation of truth" (1 Tim 3:15)