In a discussion with Protestant to Roman Catholic convert Kentucky Gent, he made a typical appeal to sacred tradition. Catholics argue that “sacred tradition” is not merely written, but also included spoken instruction. Thus he cited:
2 Thessalonians 2:15
So then, brothers, stand firm and hold to the traditions that you were taught by us, either by our spoken word or by our letter.
“In other words, scripture commands us to keep Holy Tradition, so I cannot discard it and yet remain true to His Word.”
But this reflects a lack of knowledge of the deep history of the church.
During the apostolic era, churches only had a few written letters. Apostles would travel around, visiting churches, and giving them oral teachings in addition to those that were written down. Certainly some of the Apostle’s letters would themselves have been committed to memory and transmitted that way. And so the earliest Christians had the Apostles, the words of the Apostles, the letters of the Apostles, and the Jewish Scriptures (in the form of the Septuagint). That first generation of Christians did exactly what they were instructed to do, believing both the spoken and written instructions that they received.
In the generations that followed, the words of the Apostles would be distributed—notably including the gospels—as copies of the writings were made and distributed. No longer were any apostles or those who witnessed their words alive to attest to them. The writings became the church’s scripture and oral tradition was no longer required. So it was that church tradition became scripture and scripture alone.
In the late second century, Victor, Bishop of Rome, declared that everyone must celebrate the feast of the Passover in the same way. Victor was attempting to impose on all congregations something that wasn’t contained in scripture. He proceeded to excommunicate any who disagreed with him.
If there was ever a time for the Bishops of the church to cite the oral tradition of the church handed down by Peter and through his successors in Rome, now would have been the time to point it out. But, this did not go well with the Bishops of the church. Instead, Irenaeus and other Bishops rebuked Victor sharply, stating that he must accept different customs and that he could not cut off whole churches because they decide to emulate an ancient observances. Eusebius wrote that there was no single tradition commanded by one voice, because there were many apostles who had different ideas of how to celebrate. Indeed, he argued that the disagreements confirmed the overall agreement in the faith! Irenaeus similarly noted that the church had long lived in peace (unity) without needing or requiring uniformity of the practice.
On matters that were not stated explicitly by scripture, the Bishops held that congregations could setup their own non-authoritative practices and customs. There was no authoritative tradition outside of scripture itself. Let’s read the words of Irenaeus, writing against the Gnostics in Against Heresies:
“Such, then, is their system, which neither the prophets announced, nor the Lord taught, nor the apostles delivered, but of which they boast that beyond all others they have a perfect knowledge. They gather their views from other sources than the Scriptures; and, to use a common proverb, they strive to weave ropes of sand, while they endeavour to adapt with an air of probability to their own peculiar assertions the parables of the Lord, the sayings of the prophets, and the words of the apostles, in order that their scheme may not seem altogether without support. In doing so, however, they disregard the order and the connection of the Scriptures, and so far as in them lies, dismember and destroy the truth.” — Book I, Chapter 8
What did they heretics do? They gathered their views from other sources than the Scriptures. They didn’t use the prophets, nor the words of Christ, nor what the Apostles delivered, but they claimed to have knowledge outside of these, a separate authoritative tradition.
“The method which these men employ to deceive themselves, while they abuse the Scriptures by endeavouring to support their own system out of them. […specific refutations of Gnosticism…] their whole system sinks into ruin — a system which they falsely dream into existence, and thus inflict injury on the Scriptures, while they build up their own hypothesis.” — Book I, Chapter 9
Again, the heretics looked outside scripture, falsely dreaming into existence invalid arguments which could only fall to ruin upon exposure to scripture. Indeed, by appealing to something other than scripture, they inflicted injury up it.
“As I have already observed, the Church, having received this preaching and this faith, although scattered throughout the whole world, yet, as if occupying but one house, carefully preserves it. She also believes these points [of doctrine] just as if she had but one soul, and one and the same heart, and she proclaims them, and teaches them, and hands them down, with perfect harmony, as if she possessed only one mouth. For, although the languages of the world are dissimilar, yet the import of the tradition is one and the same. For the Churches which have been planted in Germany do not believe or hand down anything different, nor do those in Spain, nor those in Gaul, nor those in the East, nor those in Egypt, nor those in Libya, nor those which have been established in the central regions of the world. But as the sun, that creature of God, is one and the same throughout the whole world, so also the preaching of the truth shines everywhere, and enlightens all men that are willing to come to a knowledge of the truth. Nor will any one of the rulers in the Churches, however highly gifted he may be in point of eloquence, teach doctrines different from these (for no one is greater than the Master); nor, on the other hand, will he who is deficient in power of expression inflict injury on the tradition. For the faith being ever one and the same, neither does one who is able at great length to discourse regarding it, make any addition to it, nor does one, who can say but little diminish it.” — Book I, Chapter 10
Here Irenaeus states that the tradition of the church was scripture, and that this scripture has been fully received by the church, scattered throughout the world, but carefully preserved, so that the whole church was as one. The tradition is the same because the scripture is the same, one scripture handed to all the churches. Moreover, no Bishop of the church, no matter how gifted in speech, may teach doctrines contrary to the scriptures. One can neither add to nor remove from scripture anything by their words.
“Since, therefore, the tradition from the apostles does thus exist in the Church, and is permanent among us, let us revert to the Scriptural proof furnished by those apostles who did also write the Gospel, in which they recorded the doctrine regarding God, pointing out that our Lord Jesus Christ is the truth, and that no lie is in Him.” — Book III, Chapter 5
Because the tradition of the apostles existed in the church and was completed, one need only look at the scriptural recording of doctrine.
The early church did not teach there there was an oral tradition of the Apostles. It taught that Holy Tradition was contained in the Scriptures, which all the churches had, and that no doctrine could be based on anything outside those scriptures. The early church was not Roman Catholic.