2 Timothy 3:16-17: "All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work."
Our doctrine concerning God’s Word is foundational to all other doctrinal beliefs, for all doctrine must be built upon God’s Word. Essential to our doctrine of God’s Word is the notion of sola Scriptura.
The “Cambridge Declaration” provides a helpful affirmation of what the doctrine of sola Scriptura states.
"We reaffirm the inerrant Scripture to be the sole source of written divine revelation, which alone can bind the conscience. The Bible alone teaches all that is necessary for our salvation from sin and is the standard by which all Christian behavior must be measured. We deny that any creed, council or individual may bind a Christian's conscience, that the Holy Spirit speaks independently of or contrary to what is set forth in the Bible, or that personal spiritual experience can ever be a vehicle of revelation." 
Sola Scriptura was one of the most critical doctrines fleshed out during the Reformation. Michael Kruger states, “This conviction of sola Scriptura—the Scriptures alone are the Word of God and, therefore, the only infallible rule for life and doctrine—provided the fuel needed to ignite the Reformation. Indeed, it was regarded as the ‘formal cause’ of the Reformation.”
The 2LBCF  begins with a statement concerning this all-important doctrine.
“The Holy Scripture is the only sufficient, certain, and infallible rule of all saving knowledge, faith, and obedience, although the light of nature, and the works of creation and providence do so far manifest the goodness, wisdom, and power of God, as to leave men inexcusable; yet they are not sufficient to give that knowledge of God and His will which is necessary unto salvation. Therefore it pleased the Lord at sundry times and in diversified manners to reveal Himself, and to declare (that) His will unto His church; and afterward for the better preserving and propagating of the truth, and for the more sure establishment and comfort of the church against the corruption of the flesh, and the malice of Satan, and of the world, to commit the same wholly unto writing; which makes the Holy Scriptures to be most necessary, those former ways of God's revealing His will unto His people being now completed.”
Though much could be said about this well-written statement, for the sake of this article, we will focus on two statements concerning the doctrine of sola Scriptura. First, Scripture is “… the only sufficient, certain, and infallible rule of all saving knowledge, faith, and obedience….”
Scripture is sufficient in telling a person what they should believe and what they should do.  Scripture’s sufficiency means that we do not need additional special revelation to know what to believe and do.  This truth is clarified further in the concluding sentence:
“Therefore it pleased the Lord at sundry times and in diversified manners to reveal Himself, and to declare (that) His will unto His church; and afterward for the better preserving and propagating of the truth, and for the more sure establishment and comfort of the church against the corruption of the flesh, and the malice of Satan, and of the world, to commit the same wholly unto writing; which makes the Holy Scriptures to be most necessary, those former ways of God's revealing His will unto His people being now completed.”
In this statement, we see that God used to reveal himself and declare his will in various ways, but now that Scripture is complete, God reveals and declares his will to the church in Scripture alone. Hebrews 1:1-2 helps us understand why this is the case:
“In the past God spoke to our ancestors through the prophets at many times and in various ways, but in these last days he has spoken to us by his Son, whom he appointed heir of all things, and through whom also he made the universe.”
In the past, God used to speak at different times and in different ways but now that the Son has come, those ways of speaking have ceased. Why? Because the content of God’s special revelation is always redemptive in scope (Luke 24:27; Acts 10:43; Matthew 5:17). Now that Christ has come and the full intended revelation of him has been put down in writing, God no longer speaks outside of Scripture (Rev 22:18-19). Scripture is sufficient and complete to reveal the Savior and our need for him.
Scripture’s sufficiency and completeness strongly connect with the cessation of new special revelation. Because God’s special revelation in Scripture is sufficient and complete, he does not speak outside of Scripture any longer.
Sola Scriptura not only means that Scripture is the ultimate authority for faith and practice and that it is sufficient for faith and practice, but also that God no longer speaks outside of Scripture concerning faith and practice. Scripture alone is God’s Word to us now.
The doctrine of sola Scriptura was particularly important during the Reformation. Sola Scriptura was a protective shield against the errors of both the Roman Catholics on one side and the radical reformers on the other. Although Roman Catholics and the radical reformers looked quite different, when it came to the doctrine of Scripture, their errors were equally pernicious.
Though Roman Catholics wholeheartedly affirm the authority and sufficiency of Scripture, they deny both these ideas in practice by their views on the authority of tradition.
What do Roman Catholics believe concerning sola Scriptura? The Roman Catholic view of Scripture as enshrined in the Council of Trent states: “Furthermore, in order to restrain petulant spirits, It decrees, that no one, relying on his own skill, shall,–in matters of faith, and of morals pertaining to the edification of Christian doctrine, –wresting the sacred Scripture to his own senses, presume to interpret the said sacred Scripture contrary to that sense which holy mother Church,–whose it is to judge of the true sense and interpretation of the holy Scriptures,–hath held and doth hold.” Here we see that the Council of Trent stated that Scripture must be interpreted according to what Church tradition teaches. Though Roman Catholics, in theory, affirm that Scripture is the ultimate authority, in practice, they put Scripture on equal footing with tradition. If Church tradition alone has the power to interpret Scripture rightly, then Church tradition is, at the very least, an equal authority with Scripture. Tradition, to be sure, has a place in interpreting Scripture. It would be foolish to ignore the Spirit’s work in Christians from the past; however, Scripture ultimately has the final say. This truth is why we affirm:
"The supreme judge, by which all controversies of religion are to be determined, and all decrees of councils, opinions of ancient writers, doctrines of men, and private spirits, are to be examined, and in whose sentence we are to rest, can be no other but the Holy Scripture delivered by the Spirit, into which Scripture so delivered, our faith is finally resolved." 
Sola Scriptura states that Scripture alone is authoritative, certain, and sufficient. The Council of Trent inadvertently denied this. But are there other ways to deny sola Scriptura? Radical Reformers
The radical reformation is a catch-all phrase of a range of groups that wanted more change than men like Luther, Zwingli, and Calvin. In their overreaction to Roman Catholicism, many fell into equal and opposite errors. One of these errors pertained to the notion of sola Scriptura. It is important to note that the radical reformers included a variety of groups with varying beliefs on Scripture. However, for this article, it is helpful to examine the views of one group in particular, the Quakers.
If you were to compare the Roman Catholic church with the Quakers they would look as different as night and day. However, concerning the sufficiency of Scripture, they both make errors that deny sola Scriptura. According to the Friends World Committee for Consultation, “Friends refuse to make the Bible the final test of right conduct and true doctrine. Divine revelation is not confined to the past. The same Holy Spirit which has inspired the scriptures in the past can inspire living believers centuries later. Indeed, for the right understanding of the past, the present insight from the same Spirit is essential. Friends believe that, by the Inner Light, God provides everyone with access to spiritual truth for today.”  
The Quakers believe that the Spirit speaks inwardly in a person's heart to give new revelation. According to the Quakers, believers can expect that the Holy Spirit provides new revelation to them today because they have the same Holy Spirit that “inspired the scriptures.”
The Quakers believe that when it comes to knowing what to believe and do, the Christian can and should listen to an inward voice of the Spirit.
By arguing that the Spirit speaks to Christians inwardly, the Quakers deny both the sufficiency and completeness of God’s revelation in Scripture. If we need the Spirit to guide us through new revelation delivered inwardly, then the Spirit speaking through Scripture is necessarily not complete nor sufficient for the Christian. Some brought this thinking to its logical conclusion. If we have the Holy Spirit speaking to us in our hearts today, giving us new revelation, why do we need the Bible? They argued, quoting Paul out of context, that “the letter killeth, but the Spirit giveth life.” Scripture is dry, old, irrelevant revelation; the inward speaking of the Spirit is fresh, new, and relevant for today.
Their belief in new inward revelation led them to deny not only the sufficiency of Scripture, but also the necessity of Scripture. If “God provides everyone with access to spiritual truth for today,” what need have we for Scripture? Why spend money on Bible translations and missionary endeavors when God has determined to speak in the human heart?
The Apostle Paul may have some thoughts on this. “How then will they call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching?” (Rom 10:14).
Evidently, if the Quakers are right, there is no need for someone to preach the Gospel to the lost because everyone has access to God’s voice today in their hearts from the Holy Spirit.
A Myriad of Voices
Whereas the Roman Catholics proclaimed a doctrine of Scripture plus tradition, many radical reformers held to a doctrine of Scripture (if that!) plus new inward revelation. Though very different in appearance, both deny sola Scriptura.
It is important that we not only affirm the authority of Scripture but that we also affirm the sufficiency of Scripture. For if we affirm the former without the latter, we will likely look to authorities other than Scripture to know what to believe and do. Whether we look externally to tradition or inwardly to our hearts, we will likely be led astray, for neither is infallible and certain since neither is the voice of God. To be sure, history’s voice and our heart’s voice have their proper role and place, but we must remember they are not God’s voice. The Holy Spirit operates and works in the believer’s heart and in church history, but he does not speak there. We must not confuse the Spirit’s work of sanctification (changing his people’s desires to be more Christ-like) and providential direction (guiding and purposing everything including his people’s desires) with him speaking new revelation in their desires.
What Now? What does this all mean for the believer in day-to-day life? When the believer is faced with a decision, how is he to know what to believe and do? Ultimately, does he look to tradition? Or does he look within his heart for a special divine impression? Does he need to read Lombard’s Four Books of Sentences or attempt to read the tea leaves of his heart? No, the believer can look to Scripture and believe it is sufficient to guide them in their decision-making. Counsel from the past is helpful, and our heart’s desires are relevant, but neither is ultimately authoritative, sufficient, and infallible. The Christian is free to follow (or not follow) their heart’s desire and the counsel of others as long as it does not go against God’s revealed will in Scripture. There is much freedom when we understand that we are only accountable to what God has revealed in Scripture. The Christian need not worry about disobeying the voice of God in tradition or the voice of God in their heart because God does not speak in either place. Today, he speaks sola Scriptura, in Scripture alone.
For decision-making, the Christian is only responsible for listening to the voice of God in Scripture. For decision-making, Scripture alone is authoritative, infallible, certain, and sufficient, for in Scripture alone God speaks.
 https://www.alliancenet.org/cambridge-declaration  https://www.ligonier.org/learn/articles/understanding-sola-scriptura  Second London Baptist Confession of Faith  2LBCF 1:1, https://www.the1689confession.com/1689/chapter-1  As a side note, it is important to understand that this truth does not deny the role of natural revelation (the things God has revealed in creation).  Special revelation is revelation that comes directly from God, as opposed to natural revelation which is mediated through creation.  https://www.papalencyclicals.net/councils/trent/fourth-session.htm  2LBCF 1:10, https://www.the1689confession.com/1689/chapter-1  Quakers refer to themselves as “Friends”  https://fwccemes.org/quakers/meeting-the-spirit?pg=2
Stephen Duarte (ME, National University; working on MTS, Reformed Baptist Seminary) is a pastor at Parkside Bible Fellowship in Fallon, NV. He is husband to Debbie and father of three.
Note: The views expressed in this article are that of the author and do not necessarily reflect the views of other contributors on this site.