But it gets worse. Sola Scriptura, which literally means "Scripture alone", is itself not scriptural.
sola scriptura is taught by Scripture:
"16 All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, 17 so that the man of God may be thoroughly equipped for every good work."
It should be noted that much of the New Testament has not been written at the time of this letter. Paul is then referring to the Old Testament Scriptures and possibly a few apostolic writings regarded as Scripture that would later be compiled into the New Testament. Thus, if one takes the word "thoroughly" to mean that Scripture is the only thing that one needs for "teaching, rebuking, correcting and training in righteousness", then most of the New Testament becomes unnecessary. Paul here is saying here that Scripture is useful for a person to become thoroughly equipped, but is not saying that Scripture is the only thing that is useful. For isn't preaching useful? Aren't spiritual disciplines useful? Isn't discipleship useful? Isn't confession useful? Isn't even personal experience sometimes useful? Of course, all of these things are useful. The Scripture, already in existence as Paul is writing this letter, as well as the Scripture that was later written, is a very important part of a person following Christ.
Suffice it to say, it's difficult to prove this negative except to say that the doctrine of sola scriptura is simply nowhere to be found in Scripture.
But I can show you where the opposite is found in Scripture:
"So then, brothers, stand firm and hold to the teachings we passed on to you, whether by word of mouth or by letter." (2 Thessalonians 2.15)
Paul is saying that those at the church in Thessalonica should "stand firm and hold to" all of his teachings, whether communicated to them orally or in a written form. Clearly, Paul is affirming the authority of his teachings even if they are not written down. His apostolic authority was not only effective when he wrote something down. It was also effective when he spoke to them. Paul does not say, 'Test everything I say by what I write, because only my writing is inspired by God and is authoritative.' No, he tells them to follow his teachings transmitted in both forms.
Also, remember that Jesus himself, the full manifestation of God's revelation to humans, didn't actually write anything down. Everything we know about Jesus has been passed on to us in some way.
Catholics refer to what has been passed on orally from the apostles as Tradition (not to be confused with a tradition, which is a man-made custom that develops over time; see end of post for more). Some try to place Tradition in opposition to Scripture, often wondering which one supersedes the other. Catholics, it is claimed by Protestants, place Tradition above Scripture, while Protestants supposedly place Scripture ahead of Tradition - if they recognize Tradition to have any place at all in theology. The issue of whether Tradition is above Scripture or vice versa is only a question if one assumes that they ever contradict.
The true Catholic teaching sees no opposition here because Catholics view Tradition and Scripture as simply two different means by which the whole Word of God has been passed down.
Here is part of the Church's teaching on this issue in her own words:
"In keeping with the Lord's command [to preach the Gospel], the Gospel was handed on in two ways:
—orally 'by the apostles who handed on, by the spoken word of their preaching, by the example they gave, by the institutions they established, what they themselves had received—whether from the lips of Christ, from his way of life and his works, or whether they had learned it at the prompting of the Holy Spirit' (DV [Dei Verbum], 7);
— in writing 'by those apostles and other men associated with the apostles who, under the inspiration of the same Holy Spirit, committed the message of salvation to writing.' (DV, 7)" (CCC [Catechism of the Catholic Church], paragraph 76)
The equality of Scripture and Tradition is also clearly affirmed by the Catholic Church:
"Sacred Tradition and Sacred Scripture, then, are bound closely together and communicate one with the other. For both of them, flowing out from the same divine well-spring, come together in some fashion to form one thing and move towards the same goal"
"Both Scripture and Tradition must be accepted and honored with equal sentiments of devotion and reverence."
(CCC 80, 82; DV 9)
The Church recognizes the importance of believing in Tradition in order to make sense of early Christianity:
"The Tradition here in question comes from the apostles and hands on what they received from Jesus' teaching and example and what they learned from the Holy Spirit. The first generation of Christians did not yet have a written New Testament, and the New Testament itself demonstrates the process of living Tradition." (CCC 83a)
Included in Tradition are not new revelations, but only that which has been passed on from the Apostles:
"Throughout the ages, there have been so-called 'private' revelations, some of which have been recognized by the authority of the Church. They do not belong, however, to the deposit of faith. It is not their role to improve or complete Christ's definitive Revelation, but to help live more fully by it in a certain period of history. Guided by the magisterium of the Church, the sensus fidelium knows how to discern and welcome in these revelations whatever constitutes an authentic call of Christ or his saints to the Church.
Christian faith cannot accept 'revelations' that claim to surpass or correct the Revelation of which Christ is the fulfillment, as is the case in certain non-Christian religions and also in certain recent sects which base themselves on such 'revelations.' " (CCC 67)
Lastly, in the comment section of a previous post, I accused a commenter of confusing the Tradition with traditions. This is what I meant:
"Tradition is to be distinguished from the various theological, disciplinary, liturgical, or devotional traditions, born in the local churches over time. These are the particular forms, adapted to different places and times, in which the great Tradition is expressed. In the light of Tradition, these traditions can be retained, modified or even abandoned under the guidance of the Church's magisterium." (83b)
Sola scriptura is simply nowhere to be found in Scripture. It is a man-made tradition invented in the Reformation. In fact, Scripture itself explicitly teaches against sola scriptura. The Church's understanding of Tradition is not that Scripture is ever superceded or corrected by Tradition, but that they both form the one, authoritative, infallible Word of God.