Many Christians today believe that they can interpret scripture on their own without any guidance from the Church, priests, bishops, etc. They believe that the Holy Spirit will guide them to truth through themselves. While it is true the Holy Spirit will guide the Church to truth when it comes to Holy Scripture, that does not mean that everyone can come to scripture and let it interpret itself. This false doctrine/belief has led to the splintering and division within the Church.
I want to look at a passages from the Bible that make the point. Acts 8:26-35 tells the story of the Ethiopian eunuch and clearly shows the role of the Holy Spirit in guiding the Church to truth but it also clearly shows the role in the Church and the role of Bishops and priest. Philip was an Apostle and the Apostles had the authority of bishop or overseer. The Ethiopian eunuch clearly indicated that he could not understand what the scripture was saying unless someone instructs him. Now the Holy Spirit did instruct him but it was not through himself, it was through Philip. Many misunderstand how the Holy Spirit accomplishes his task of bringing them to truth. The Holy Spirit works through the Church to bring us to the truth.
2 Peter 3:16-17 shows us why this false doctrine is not the doctrine of the Bible:
Peter follows up with the message of Acts in telling us that the ignorant (or untaught) and unstable will distort the Biblical truth to their own destruction. This clearly shows the need for teaching and guidance when it comes to interpreting scripture on a whole.
The Holy Spirit may work through us directly or he may work through the Pope and the Magisterium to bring us the truth. How can we gauge what we believe the Holy Spirit is saying to us is true? We can be sure by measuring it against what the Church teaches. The Church is the Pillar and Foundation of Truth and is guided by the Holy Spirit. The Church is ,indeed, the measuring rod for truth. Do not be deceived by those who claim that they know the truth because the holy spirit guides them. Measure what they say against what the Church has taught for 2000 years. In this way you will know whether what they say is true or not. You will know if they are guided by the holy spirit as they claim to be.