How can a Christian determine which doctrines are essential and which are not?

To begin with, the strongest words of condemnation in all the New Testament are aimed at false teachers who corrupt the Gospel. Therefore the Gospel message itself must be acknowledged as a primary point of fundamental doctrine.

But what message will determine the content of our gospel testimony? Let's turn to Scripture itself and attempt to lay out some biblical principles for determining which articles of faith are truly essential to authentic Christianity. 

I. All Fundamental Articles of Faith Must Be Drawn from the Scriptures

First, if a doctrine is truly fundamental, it must have its origin in Scripture, not tradition, papal decrees, or some other source of authority. Paul reminded Timothy that the Scriptures are "able to make thee wise unto salvation" (2 Timothy 3:15, KJV). In other words, if a doctrine is essential for salvation, we can learn it from the Bible. The written Word of God therefore must contain all doctrine that is truly fundamental. It is able to make us "adequate, equipped for every good work" (2 Timothy 3:17). If there were necessary doctrines not revealed in Scripture, those promises would ring empty.

The psalmist wrote, "The law of the Lord is perfect, restoring the soul" (Psalm 19:7). That means Scripture is sufficient. Apart from the truths revealed to us in Scripture, there is no essential spiritual truth, no fundamental doctrine, nothing essential to soul-restoration. We do not need to look beyond the written Word of God for any essential doctrines. There is nothing necessary beyond what is recorded in God's Word.

This, of course, is the Reformation principle of sola Scriptura -- Scripture alone. According to the Bible itself, no supposed spiritual authority outside "the sacred writings" of Scripture can give us wisdom that leads to salvation. No papal decrees, no oral tradition, no latter-day prophecy can contain truth apart from Scripture that is genuinely fundamental.

II. The Fundamentals Are Clear in Scripture

Second, if an article of faith is to be regarded as fundamental, it must be clearly set forth in Scripture. No "secret knowledge" or hidden truth-formula could ever qualify as a fundamental article of faith. No cryptic key is necessary to unlock the teaching of the Bible.

The truth of God is not aimed at learned intellectuals; it is simple enough for a child. "Thou didst hide these things from the wise and intelligent and didst reveal them to babes" (Matthew 11:25, KJV). The Word of God is not a puzzle. It does not speak in riddles. It is not cryptic or mysterious. It is plain and obvious to those who have spiritual ears to hear. "The testimony of the Lord is sure, making wise the simple" (Psalm 19:7).

The point is not that every fundamental article of faith must be supported with an explicit proof text. The doctrine of the Trinity, for example, is certainly essential to true Christianity-and it is very clear in Scripture-but you will find no comprehensive statement of the Trinity from any single passage of Scripture.

This does not mean that a doctrine must be non-controversial in order to be considered a fundamental article. Some would argue that the only test of whether something is essential to true Christianity is whether it is affirmed by all the major Christian traditions. By that rule, hardly anything of any substance would remain to distinguish the Christian Gospel from the "salvation" offered by pagan morality or Islamic theology. "There is much truth in the remark of Clement of Alexandria; 'No Scripture, I apprehend, is so favourably treated, as to be contradicted by no one.'" (Herman Witsius, Sacred Dissertations on the Apostles' Creed [Phillipsburg, NJ: Presbyterian & Reformed, 1993 reprint], 1:21)