What Apostles had WRITTEN and SPOKE are the same. The problem is that no Roman Catholic can prove that any oral tradition they have came from the original apostles, especially things said by a Pope who was not quoting any apostle but brought it extemporaneously (ex cathedra). Can they show the original apostle the pope is quoting from? They can't; therefore they have a flawed unthought through argument they are parroting from their church. There is no mention that the church was to hold unwritten traditions from the apostles. It is convenient to say something that is not at all mentioned that becomes a proof unto itself simply because a church says it is so.

The fact that Peter quotes Paul’s letters in 2 Peter 3:15-16 “Paul, according to the wisdom given to him, has written to you, as also in all his epistles, speaking in them of these things, in which are some things hard to understand, which untaught and unstable people twist to their own destruction, as they do also the rest of the Scriptures.”

Notice he spoke of the Old Testament along with the new as Scripture.

That Paul is constantly quoting the Old Testament (that was not approved by any council) saying it is written, (just as Jesus did) Galatians 3:10 “For as many as are of the works of the law are under the curse; for it is written”

John states the same, 1 John 1:1-4 “That which was from the beginning, V.4 And these things we write to you that your joy may be full.” Not that he speaks but writes, and not only him but the others.

1 John 2:21-22 “I have not written to you because you do not know the truth, but because you know it, and that no lie is of the truth.’ They learned the truth from him teaching them, the same truth we learn when we read, otherwise we have lost truth from the beginning.

Clearly if what was written was incomplete John could not say in Revelation 22:18 “For I testify to everyone who hears the words of the prophecy of this book: If anyone adds to these things, God will add to him the plagues that are written in this book.”

2 Thessalonians 2:15 finding the word “tradition” does not prove a oral method is equal to what was inspirationally written from the Holy Spirit through the apostles to be our Bible.

It means anything delivered in the way of teaching; the doctrines delivered by the apostle to the Thessalonians; by his preaching, or by letters; and particularly the first letter, as the apostle here states. Whatever these traditions were, they were already made known.

Prior to this in v.5 “Do you not remember that when I was still with you I told you these things?” these “things” are what we are reading in his epistle. So in v.15 when he says “whether by word or our epistle’ he means that it was the same that he wrote.

[Our letter]-as distinguished from the "letter AS from us," (2 Thessalonians 2:2). He means his first letter to the Thessalonians. (from Jamieson, Fausset, and Brown Commentary)

V.15 Therefore, brethren, stand fast and hold the traditions which you were taught, whether by word or our epistle.” When he states [or our epistle] He is then referring to the former letter which he had written to them.

He speaks only of what had been delivered to them by himself when he was with them teaching or by letter.

[Whether by word or by letter] By preaching, when we were with you. It is not endorsing an oral message to them by a third person. But referring back to the first letter he wrote to them.

2 Thessalonians 2:15 the tradition of speaking, and writing continued until, John, the last apostle died in the first century. Then the speaking was no longer conducted. Scripture is what Paul himself said, that "the man of God perfect, thoroughly furnished unto all good works" (2 Timothy 3:16-17). Paul also said “that you may learn in us not to think beyond what is written” (1 Cor. 4:6)This could not be a honest command if oral tradition was accepted, again it is plural, not just of himself.

The apostles' oral word was as trustworthy as their written word at the time the Bible was being formed, it by no means follows that the oral word of those not apostles is as trustworthy as the written word of those who were apostles or inspired evangelists. There is no oral tradition of the apostles; they cannot show the original apostle they are quoting from. Only the written word can be proved genuine by evidence.