Secondary doctrine is hard to explain.
I guess to start off, it should be noted that the idea of secondary doctrine is not clear in Scripture. This is not because it is anti-biblical, but because there was really no huge secondary issues that the writers had to address. Paul, Peter, John, and the other writers of the New Testament were solidifying the gospel in their writings for the most part. Outside of that, the writers edified believers by affirming aspects of primary doctrine (1 Corinthians would be a good example-- how Paul addresses sexual immorality, lawsuits, marriage, divorce, food offered to idols, head coverings, spiritual gifts, etc.).
It was not until certain councils and synods formed over the centuries following Christ's resurrection that "official" theologies (and consequently, opposing theologies) formed. These theologies include topics such as
- Paterology - The study of God the Father
- Christology - The study of the Person/work of Jesus Christ
- Pneumatology - The study of the Person/work of the Holy Spirit
- Bibliology - The study of the word of God
- Soteriology - The study of salvation through Jesus Christ
- Christian Anthropology - The study of the nature of humanity
- Hamartiology - The study of the nature and effects of sin
- Angelology - The study of angels
- Christian Demonology - The study of demons
- Ecclesiology - The study of the nature and mission of the church
- Eschatology - The study of the end times
Now disagreement in any of these areas creates subdoctrinal theologies. Notice I did not say "rejection" in any of these areas. If there was a complete rejection of any of these topics, it would be considered rejection of primary doctrine.
And why's that?
It's because each one of the listed theologies assumes a doctrine. For instance, Paterology (the study of God the Father) assumes that there is a heavenly Father who is God. Christology assumes that Jesus is the Christ. Eschatology assumes that God does have a plan for the future of humanity that will achieve glory for Himself.
Secondary doctrine is formed when we explain how, not what. "God has provided salvation through His Son"-- that's a what-- soteriology, primary doctrine. "God elects believers in eternity past based on foreseen human decisions/His choice completely separate from Man"-- that's a how-- secondary doctrine.
You see, rejecting the overarching doctrine of soteriology, which is that God has provided salvation through Jesus Christ, is heresy. But disagreeing on the intricate nuts and bolts of how we receive it is secondary.
With all that said, secondary doctrine can be defined as issues on which Scripture allows for interpretive differences that are not heretical, yet result in denominational divides.
Secondary doctrine is "open-hand," meaning that no one is burned at the stake for disagreeing with your position. However, it affects worship and ministry with other believers. It is why there are Bible churches, Baptist churches, and Evangelical Free churches. None of those believe that the other is heretical; but they do have disagreements that led them to be in different places on Sunday mornings.
Perhaps the clearest acting-out of this in Scripture is between Paul and Barnabas concerning John Mark in Acts 15. It says,
And after some days Paul said to Barnabas, “Let us return and visit the brothers in every city where we proclaimed the word of the Lord, and see how they are.” Now Barnabas wanted to take with them John called Mark. But Paul thought best not to take with them one who had withdrawn from them in Pamphylia and had not gone with them to the work. And there arose a sharp disagreement, so that they separated from each other. Barnabas took Mark with him and sailed away to Cyprus, but Paul chose Silas and departed, having been commended by the brothers to the grace of the Lord. And he went through Syria and Cilicia, strengthening the churches.
An important note to make here is that Paul and Barnabas were not arguing over doctrine, but a person. However, the principle is still applicable.
The reason why John Mark had abandoned Paul in Pamphylia is not stated here or in the original account of it (Acts 13:13). It is sure, though, that whatever the reason was, Paul thought it was unjustified. He did not think that John Mark should have left their mission at that time and he disagreed "sharply" with Barnabas over the issue.
Now stepping back for a moment, we can see how this easily translates to secondary doctrine. For example, I am a dispensationalist. Several people think dispensationalism is ridiculous. Do I have sharp opinions concerning the topic of Israel's distinction from the Church? I sure do! When talking about this issue to someone who holds to covenant or replacement theology, the disagreement will arise and we will likely go to different churches.
When a person believes in cessationist theology-- that the sign gifts of the Holy Spirit have ceased-- will he go to a Pentecostal church Sunday mornings? Highly doubtful. Would a charismatic believer attend Presbyterian services? Not likely.
However, when we recognize these issues as secondary doctrine and not primary, we can still have fellowship with those we disagree with through the unity of Christ. And that's the happy ending to the Paul and John Mark story.
When Paul was on his deathbed so-to-speak, he wrote to Timothy and said "Get Mark and bring him with you, for he is very useful to me for ministry," (2 Tim 4:11).
Whatever the issue was at the heart of the sharp disagreement, Paul realized that John Mark was still his brother and their unity in fellowship was more important than their disagreement in personality and other secondary issues.
This is something we must understand.
Our unity in fellowship is more important than our disagreement in personality and other secondary issues. Our unity in fellowship is more important than our disagreement in personality and other secondary issues. Our unity in fellowship is more important than our disagreement in personality and other secondary issues. Our unity in fellowship is more important than our disagreement in personality and other secondary issues.
Is this to say that we should not have an opinion on secondary issues? Not at all! In fact, I would say it is unbiblical to avoid the hard-to-understand topics of Scripture. We are all called to rightly divide the Word of truth. Let us understand the intricacies of the Bible.
But we should not do so at the expense of our brothers and sisters who disagree, yet can teach us so much.