When it’s asked where in the Bible does it teach that the Bible alone is the sole authoritative rule of faith and practice, the verse most commonly cited is 2 Timothy 3:16,17:
All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work.
But do these verses teach that the Bible alone is sufficient? Sometimes we see or hear in a statement something that isn’t actually being said, because we are expecting to see or hear it. These verses say that the Bible was given so that we may be “equipped for every good work.” But they do not actually say that with the Bible alone we are equipped (thoroughly equipped in the NKJV). “Alone” is not in these verses in word or concept; we mentally insert it because we have been told the idea is there.
Consider as an analogy an auto mechanic. He has all the tools of that trade except for a set of wrenches. So you give him a set of wrenches. Now you can say that he is thoroughly equipped for every job. But you would not say that with a set of wrenches alone he is thoroughly equipped; far from it.
Also, citing this passage to prove “the Bible alone” assumes that the phrase “the man of God” refers to each and every Christian, and is not a more technical term denoting those in leadership positions in the Church. It’s far from evident from the context that it does. If it’s not evident in the context, then we are interpreting the phrase in light of our tradition, which is incompatible with “Bible alone.”
Well then; it’s one thing to point out that the word “alone” does not appear in the above verses. It’s another thing to show that the Bible teaches that other things are necessary and authoritative. But that’s easy to do.
First let’s look a this one:
The gifts he gave were that some would be apostles, some prophets, some evangelists, some pastors and teachers, to equip the saints for the work of ministry, for building up the body of Christ, until all of us come to the unity of the faith and of the knowledge of the Son of God, to maturity, to the measure of the full stature of Christ. Ephesians 4:11–13 (NRSVCE)
Perhaps the most relevant point here is that it states the purpose of these gifts of leadership as equipping God’s people: that’s the same word used in 2 Tim. 3:17. So if the Bible being given to equip us means that the Bible alone is sufficient to equip us, then St. Paul is contradicting himself, because here he says other things –these gifts, these leadership positions– are also given to equip us. Either it’s a contradiction or else St. Paul never meant in 2 Tim. 3:17 what Protestants have taken him to mean.
While I was a Protestant I wrestled with the problem of competing doctrines ostensibly based on the “Bible alone.” All sides assumed that they were the ones whose understanding of the Bible’s real meaning was illumined by the Holy Spirit. But how could you tell? So I asked how the Holy Spirit operates among Christians. The Bible has the answer and says it in a number of places like Eph. 4:11-13. It also answers the question in places like Romans 12:6-8.
The whole of 1 Corinthians 12 makes the case that all Christians are members together of the one Body of Christ, the Church. It is within this context that we are equipped to live the life we are called to. That’s how the Holy Spirit illumines our minds “until all of us come to the unity of the faith and of the knowledge of the Son of God, to maturity, to the measure of the full stature of Christ.” Not each of us individually, having varying levels of affinity to one another based on how closely our doctrines or focuses agree, but all of us doing our part together because each of us has need of the others (1 Cor. 12:19-21) in order to reach unity in the faith and fulfill the roles God has given us. Once I had truly come to grips with what 1 Corinthians 12 was saying, that more than any other passage led me to the Catholic Church, because that is what catholic means: universal, as in all of us together.
Here are a couple of verses that I never saw pointed out as a Protestant:
So then, brothers and sisters, stand firm and hold fast to the traditions that you were taught by us, either by word of mouth or by our letter. 2 Thessalonians 2:15 (NRSVCE)
and
…if I am delayed, you may know how one ought to behave in the household of God, which is the church of the living God, the pillar and bulwark of the truth. 1 Timothy 3:15 (NRSVCE)
The Bible is authoritative not because it is written but because it is apostolic teaching in written form. This verse specifically rules out the idea that only apostolic teaching that is written is authoritative. Justin Martyr, writing around AD 150, repeatedly refers to the New Testament as “the memoirs of the apostles” (e.g. 1 Apology 67).
The Bible doesn’t teach “Bible alone.” It teaches the Bible as illumined through the Holy Spirit and the Church (led by the successors of the apostles, the bishops) as the normative means through which the Holy Spirit does so. That has been the Catholic position for 2000 years.