9. The unerring rule of interpretation of Scripture is the Scripture itself. Therefore, when there is a question about the true and full sense of any Scripture (which is not multiple, but one), it must be searched and known by other places that speak more clearly.
10. The supreme judge by which all controversies of religion are to be determined, and by which all decrees of councils, opinions of ancient writers, doctrines of men, and private spirits are to be examined, and in whose judgment we are to rest, can be nothing other than the Holy Spirit speaking in Scripture. (WCF 1.9-10)
Have you ever been in a conversation with another believer and had two differing opinions on a theological subject? Have you ever heard the phrase, “well, that’s just your opinion”? On the one hand, it is a great thing to have deep and robust conversations on theology, yet on the other, we must be careful that our opinions and doctrine aren’t formed from our opinions alone, but from God’s revelation. Why? Well as we have seen through the weeks, the bible is God’s preserved word to us (Matt 5:18, 2 Tim 3:16-17, 2 Pet 1:20-21), and because it is God’s Word, it is truth (objectively) and without error (Ps 119:89, Jn 17:17). Therefore when it comes to matters about life and doctrine, we are to dig deep and think hard on the things God presents to us - that’s our responsibility as God fearing people - it is our responsibility to search the scriptures and come to conclusions based off what God has revealed, so that we might worship Him in spirit and in truth (Jn 4:23-24, Acts 17:11-12).
However that’s not to say that we just completely cast off the opinion of bible teachers and church doctrine that has come down to us through the years, no not at all, as it has been the good pleasure of Christ through the Holy Spirit to have been building the church for thousands of years (Matt 16:18a). And over those years God has raised up incredible teachers and theologians to bring the wonderful truths of scripture into a more approachable light for His people to comprehend (Jn 16:13, Eph 4:4-13). And indeed, if we look back into the history of the church, we will find that there were many many times when different people in the church had differing opinions on God - yet God raised up various people at various times so that the truth of scripture would win the day and set people free, as He promised He would do (Matt 16:18b c.f. Acts 15:1-29).
For example in the 4th century, there was something called the Arian controversy. Some taught that Jesus was a created being and that “there was a time when the Son was NOT”. Yet faithful bible teachers (mainly a guy named Athanasius) defended the truth (from the whole council of scripture) that “there was NEVER a time when the Son was NOT”. The day was won by good biblical teaching and cemented in something we call the Nicene Creed. Again the Pelagian controversy rose up in the 5th century, in which a British monk named Pelagius taught that humanity didn’t inherit sin from Adam and thus spiritually die in him, meaning he taught that we are born sinless and can - by nature - work jointly with the grace of God to bring ourselves into final justification (something called synergism). Yet again God raised a faithful bible teacher (this time a guy named Augustine) to defend the truth against grave error. He showed (again from the whole council of scripture) that no, we are not just born spiritually sick, but absolutely dead because of Adam’s sin, and therefore God’s grace isn’t something we can cooperate with because spiritual corpses can’t reach up and take hold of Christ, and thus, God’s grace is more than an “influencer” but the very thing that reaches into spiritual death and brings life (something called monogism; Jn 1:4-5, Rom 5:12-21). The day was again won by good biblical teaching and cemented in something we call the the Council of Ephesus.
All this to say, whenever the universal visible church has started to err, whenever there has been a threat to the people of God, God has raised people up to defend and define His truth to guide the church. The creeds and councils and teachers that have stood the test of time haven’t been ones build on the sand of human opinion, philosophy or blind tradition, but on the ROCK of Jesus Christ and the teaching of His Prophets and Apostles (Eph 2:20, 3:5).