Erik Thoennes, Life’s Biggest Questions: What the Bible Says About the Things That Matter Most, (Wheaton: Crossway, 2011), 35–37 (formatting added):

Essential vs. Peripheral Doctrine

The ability to discern the relative importance of theological beliefs is vital for effective Christian life and ministry. Both the purity and unity of the church are at stake in this matter. The relative importance of theological issues can fall within four categories:

1. absolutes define the core beliefs of the Christian faith;
2. convictions, while not core beliefs, may have significant impact on the health and effectiveness of the church;
3. opinions are views or personal judgments that generally are not worth dividing over; and
4. questions are currently unsettled issues.

These categories can be best visualized as concentric circles, similar to those on a dart board, with the absolutes as the “bull’s eye” (see fig. 3.4).

Into which category an issue falls should be determined by the cumulative force of at least eight considerations:

1. biblical clarity;
2. relevance to the character of God;
3. relevance to the essence of the gospel;
4. biblical frequency and significance (how often in Scripture it is taught, and what weight Scripture places upon it);
5. effect on other doctrines;
6. consensus among Christians (past and present);
7. effect on personal and church life; and
8. current cultural pressure to deny a teaching of Scripture.

We should consider the cumulative weight of these criteria when determining the relative importance of particular beliefs.

For instance, just the fact that a doctrine may go against the general consensus among believers (see item 6) does not necessarily mean it is wrong, although that might add some weight to the argument against it.

All the categories should be considered collectively in determining how important an issue is to the Christian faith. The ability to rightly discern the difference between core doctrines and legitimately disputable matters will keep the church from either compromising important truth or needlessly dividing over peripheral issues.