1. What is Sola Scriptura?
Sola scriptura is the Latin phrase that means ‘Scripture alone’ and it was coined as one of the legendary slogans of the sixteenth-century Reformation movement against the false teachings of the Roman Catholic church.
Chapter 1 Point 6 of the Westminster Confession of Faith summarises this doctrine nicely:
The whole counsel of God concerning all things necessary for His own glory, man’s salvation, faith and life, is either expressly set down in Scripture, or by good and necessary consequence may be deduced from Scripture: unto which nothing at any time is to be added, whether by new revelations of the Spirit, or traditions of men. Nevertheless, we acknowledge the inward illumination of the Spirit of God to be necessary for the saving understanding of such things as are revealed in the Word: and that there are some circumstances concerning the worship of God, and government of the Church, common to human actions and societies, which are to be ordered by the light of nature, and Christian prudence, according to the general rules of the Word, which are always to be observed. 
We will explore this doctrine in greater detail. In summary it teaches that the Bible is the final authority for all matters that pertain to salvation and godly conduct.
2. Why is Sola Scriptura so important?
Martin Luther brought massive attention to the Roman Catholic church on the issue of the sufficiency of Scripture through his posting of the Ninety-five Theses. The recovery of this one particular doctrine has led to the recovery of other biblical doctrines that are foundational for Christian belief: justification by faith alone, the sufficiency of Christ’s atonement, the doctrines of grace and many more. Three essential aspects of this doctrine stand to enable believers to have confidence to know what God has declared to mankind:
a) Sufficiency of Scripture
Believers can be confident that the Scriptures, as they are right now, are all that believers need to have a sufficient knowledge of God’s glory, to know the way of salvation and to equip them for godly Christian living. They do not have to disperse their efforts to find truth from various teachings that come from all sorts of different authorities. They are given liberty and freedom to discover what God requires of them solely from His Word.
The apostle John wrote in his gospel concerning the miraculous works of Jesus:
Jesus performed many other signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Messiah, the Son of God, and that by believing you may have life in his name.
(John 20:30–31 NIV)
No doubt Jesus has performed many miraculous signs that were not recorded in Scripture (John 21:25). However, John by the conviction of God’s Spirit saw it fit to include in his gospel account what he believed would be necessary and sufficient for his readers to know and believe that Jesus is really the Messiah who has come to bring eternal life.
Dr James White wisely says, “It is not necessary that the Bible contain every single possible detail about the life and ministry of Jesus for it to function just as God intended.” 
b) Authority of Scripture
Believers can be confident that the words from Scripture are true in what it teaches about because these words come from the very mouth of God Himself.
When the apostle Paul was living his final days in prison alone and was no longer able to give his spiritual son Timothy any more guidance, he directs him to the Scriptures as the all-sufficient source of truth to guard against popular heresies that threatened his ministry:
But as for you, continue in what you have learned and have become convinced of, because you know those from whom you learned it, and how from infancy you have known the Holy Scriptures, which are able to make you wise for salvation through faith in Christ Jesus. All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the servant of God may be thoroughly equipped for every good work. (2 Timothy 3:14-17 NIV)
Paul does not direct Timothy to continue seeking spiritual wisdom from the sages of his time, from various popular philosophies, or from his own experiential insights. None of these authorities are equal to the authority of Scripture, for only the Scriptures is able to lay claims that it has originated from the very mouth of God Himself.
c) Clarity of Scripture
Believers can be confident that the Scriptures are clear and comprehensive for those who seek the way of salvation and to know what God desires for them to do. Moses told the people of Israel, regarding God’s commandment to them:
These commandments that I give you today are to be on your hearts. Impress them on your children. Talk about them when you sit at home and when you walk along the road, when you lie down and when you get up. (Deuteronomy 6:6-7 NIV)
Wayne Grudem explains this passage that “if all of the parents in Israel were expected to teach the words of Scripture to their children, this implies that ordinary people were able to understand the words rightly, at least for the most part. And it even implies that children were able to understand them and learn from them, at least to some extent.” 
It is notable that most of the Israelites, whom Moses was speaking to, were not well-educated and wouldn’t have been able to read the Scriptures very well. Yet, the Scriptures are clear enough that despite their literacy deficiencies, they would have been able to understand them and teach them to their children.
When God intends to communicate with a human being, He will be able to do it efficaciously. This means His word is always clear and it is demonstrated by the fact that Scripture was written to the masses of ordinary people who need to live on God’s Word (Deut 8:3; Ps 19:7; Matt 4:4).
3. What happens when we reject Sola Scriptura?
If the doctrine of Scripture alone is thrown out of our doctrinal confessions, then a good way to picture its catastrophic implications is to follow this analogy:
As of 2018, the Human Immunodefiency Virus (HIV) has claimed over 35 million lives around the world so far . The virus boasts of a 100% fatality rate due to its incurability. However, despite the staggering number of lives it has statistically claimed, it could also be argued that HIV has a 0% fatality rate. What do I mean? HIV hasn’t and doesn’t actually kill you. What HIV does is that it targets your immune system and destroys the function of your immune cells, which results in increased vulnerability to a wide range of different infections, cancers and diseases that would in effect be the true killers that claim their victims’ lives.
Now imagine this: the doctrine of sola scriptura is the ‘immune system’ for your Christian faith and spiritual life. The doctrine functions as a defence wall that helps you guard against viral heresies from infiltrating your mind and into your theological bloodstream as you study the Scriptures. If you demolish the defence wall that sola scriptura has built, the Christian faith is open to being attacked on all fronts. This is what it means to be swayed by every wind of doctrine (Eph 4:14).
Similarly to the effects of HIV, denying sola scriptura won’t directly place you outside the Kingdom. However, breaking the wall invites heresies that slip through the cracks, which often lead to placing you outside God’s Kingdom. If you reject sola scriptura, you fall into the possibility of rejecting the orthodox doctrines of justification by faith alone, the deity of Christ – fundamentals of the faith that, if rejected, are significant enough to place you in condemnation.
The scriptural sufficiency-deficiency virus (I’ve coined the term) has claimed more spiritual lives in this present age than God’s people could ever have imagined. Once the foundation of the absolute authority of God’s Word is gone, the certainty of any biblical truth is gone, which marks the eradication of any assurance we can have of knowing what the God of the universe has to say to mankind like us.
4. What does Sola Scriptura NOT mean?
a) Scripture alone does not mean ‘Scripture only’
WCF 1.6 takes into account this consideration:
...there are some circumstances concerning the worship of God, and government of the Church, common to human actions and societies, which are to be ordered by the light of nature, and Christian prudence, according to the general rules of the Word, which are always to be observed.
This doctrine is often misunderstood by many to mean that Scripture is the ‘only’ authority that we can appeal to in order to understand the matters of salvation and faith-living. But the doctrine of Scripture alone recognizes the existence of other authorities that teach other areas of knowledge that are beyond the scopes of Scripture’s intention. Scripture will not teach you algebra, how to change your tire, or even how to fry up some good, tasty chicken!
The doctrine of Scripture alone even affirms the role of other authorities, such as the writings of past Christian thinkers (tradition), as well as our reasoning faculties (logic) and personal reflections (experience) to comprehend the divine truths of God. However, since they are not God-breathed (and hence fallible), these authorities are to be tested by the higher authority of Scripture.
b) Scripture alone does not nullify the Spirit’s role in helping us understand Scripture
WCF 1.6 affirms this following statement:
Nevertheless, we acknowledge the inward illumination of the Spirit of God to be necessary for the saving understanding of such things as are revealed in the Word:
Though the doctrine of Scripture alone teaches that Scripture is all that is necessary for our salvation from sin and to know God’s standards for righteous living, it does not deny the Spirit’s active participation in teaching the believer spiritual truths that come through reading the Scriptures. Unless the Spirit is present at working in the person’s heart to bring about faith and obedience, there can never be any understanding of the spiritual truths from what God has freely given to them (1 Cor 2:12, 14).
c) Scripture alone does not mean you read your Bible all alone!
This doctrine does not hand out permits for individuals to interpret Scripture in solitude and to reject the collective wisdom of the many faithful Christian thinkers of the past, or to block their ears to the insights of our wiser spiritual peers and mentors. As stated previously, Scripture makes use of other authorities to assist us in understanding spiritual truths with greater depth. Don’t deprive yourself of these God-given resources, lest you fall into misinterpreting Scripture and finding contentment in your own false interpretations. The Spirit often uses the cumulative wealth of wisdom of our church community and the written works of many deep-thinking historical Christian men and women of the past to reveal falsehoods in our interpretations. Therefore, you should humbly allow your brothers and sisters to challenge your understanding of Scripture!
5. What does sola scriptura mean for us?
a) Sola Scriptura places obligations on Christians to live by God’s commands
The clarity of Scripture gives no believer the excuse to say that they cannot find what God demands of them in how they ought to live their life. If God has spoken so clearly in His Word that even children to some degree are able to comprehend its truths, then we are especially held accountable to search for God’s will in Scripture in order to live a righteous and godly life that pleases God.
b) Sola Scriptura gives Christians profound confidence that they can know the truths of God
The cultural mantra of postmodernism has annihilated any certainty of knowing what we can know. Secular humanism has trusted in fallacious human reason as its source of authority. The ever-changing whims of our culture has produced a wide range of different popularised beliefs that has brought no end to the challenges of defending the sufficiency of Scripture.
Yet, our everlasting and unchangeable God has spoken and He speaks with authority, sufficiency and with clarity. Out of His graciousness, He has preserved His Word for His people so that they may depend on it to know who God truly is, in order that they may have an intimate relationship with the Author of Scripture Himself. Believers can anchor faithfully in the Word as they navigate through the Christian life, knowing it is sufficient for their spiritual needs.
 – WCF 1.6
 – White, J 2004, Scripture Alone: Exploring the Bible’s Accuracy, Authority, and Authenticity, Bethany House Publishers, pg 33
 – Grudem, W 2018, Christian Ethics: An Introduction to Biblical Moral Reasoning, Crossway, pg 90-91
 – World Health Organisation. (2019, 19 July). HIV/AIDS. Accessed at <https://www.who.int/news-room/fact-sheets/detail/hiv-aids>
James R. White, Scripture Alone: Exploring the Bible’s Accuracy, Authority, and Authenticity (Bethany House Publishers 2004)
J.I Packer, Fundamentalism and the Word of God (Eerdmans 1958)