5. Didn't the apostles and leaders of the church meet to determine doctrine?
Someone might say, "the church leaders met to decide doctrine in the early church" and may point to events recorded in the book of Acts. These can be understood when we take a look at the development of the early church and how things were being revealed.
Christ told his disciples there were more things that he wanted to tell them but they weren't able to bear them at that time (John 16.12). Christ told them that the Holy Spirit would guide them into all truth (John 16.13). The writer of Hebrews reveals that the spread of the Gospel and fading of the Law of Moses took place slowly (Heb 8.13). We find that during the growth of the church things were being revealed to the apostles first and then passed on to others. As these events took place there was a need to meet and discuss them to understand what was bring revealed.
Peter was sent to the house of Cornelius to preach the Gospel (Acts 1). Prior to leaving for the centurion's house he received a vision and told to rise kill and eat a number of unclean animals. After refusing to do this three times he was told that what God had cleansed should not be considered unclean. At Cornelius house the Holy Spirit fell on the Roman and his household demonstrating that the Gospel was for all nations not just the Jews.
On his return to Jerusalem Peter was called on the carpet so to speak for going to the house of a Gentile (Acts 11.1-4). Afer recounting the episode and the appearance of the Holy Spirit (Acts 11.5-17) the brethren were satisfied that God had offered salvation to the Gentiles as well (Acts 11.18). In this instance the meeting resulted in understanding what God was revealing - not to determine doctrine.
Later as the Gospel spread to more Gentiles there were Jewish converts, Pharisees, who insisted that the Gentiles had to observe certain elements of the Law in order to be acceptable (Acts 151,5). One of the main points of contention was that of circumcision. A meeting was convened in Jerusalem with the apostles and elders to discuss this (Acts 15.4-6). As the conversation developed Peter recounted how he had taken the Gospel to the Gentiles and there was now no difference between them and the Jews explaining what had been revealed through the event (Acts 15.7-11). James, referring to the prophecy of Amos (Amos 9.11) declared that the gentiles were acceptable and not required to observe the Law of Moses (Acts 15.13-2). Letters with this conclusion were then sent to Antioch (Acts 15.23-31). This letter didn't represent a doctrinal determination made by the consensus of the group at Jerusalem. It was a declaration of understanding of what was being revealed by God through these events.
In the same manner today we meet to study the scriptures, not to make changes to doctrine but to understand what has been revealed. No human has the ability to change the message of the scriptures. There are warnings about doing this in places such as Proverbs 30.6 and Revelation 22.18-19. The falling away of the church and growth of denominationalism are examples of what happens when humans take it upon themselves to determine what we believe and practice rather than accepting what's been revealed.