St. Irenaeus, from Smyrna, became bishop of Lyons in 177, and throughout his life wrote several works to defend and explain the beliefs of the Christian Faith. His work Against Heresies (which he wrote in A.D. 180) was especially instrumental in defending the faith against Gnosticism, and he writes quite explicitly in this work about the need to rely on the Church’s oral tradition in order to interpret Sacred Scripture and combat heresy. Here, and in the circumstances of the time, we can see that the early Christians did not believe in relying on the Bible alone, but respected and in fact needed the authority of the Catholic Church.
Furthermore, it is important to note that we can especially trust the word of Irenaeus because he had close association with those who knew the Apostles. He had been a disciple of Bishop Polycarp of Smyrna, “who had sat at the feet of the apostle John. ‘I remember,’ writes Irenaeus, ‘How he [Polycarp] spoke of his conversion with John and with others who had seen the Lord; how he repeated their words from memory.’” Also, Irenaeus showed his absolute dedication to the Christian faith by giving his life as a martyr in 202 A.D., during the persecution of the Roman Emperor Septimius Severus.
Assembling the Bible
First of all, we know that those of the early church did not—could not—rely on a written Scripture alone because the Bible was not even fully assembled yet. Before the late second century, “the only scriptural norm was the Jewish Scriptures, which Christians called simply ‘the books.’” They weren’t even calling it the “Old Testament” yet. And the first book of the New Testament to be written, the letters of St. Paul, were not written until 65 years after Christ (over thirty years after his death). And that was only the first of the writings that would become the New Testament. Furthermore, it’s important to point out that, as the first writings of the Christians were being written, the Church was the one who determined that (and which of) these writings were inspired by the Holy Spirit in the first place.
Interpreting the Bible
Furthermore, even as they began to organize the writings of this New Testament, Christians had to look to the tradition of the apostles and their successors to understand how to interpret it. We know that the meaning of the Scriptures were already being misinterpreted and twisted into heresies by groups very early on. For example, during this time of the late second century, the sect of the Gnostics formed around the beliefs (among other things) that the material world was evil, created by the evil God of the old covenant, and that only the spiritual world and the God of the new covenant were good. This was not what Christ or His Apostles taught, nor was it what the Bishops of the early Church taught as the Apostles’ successors.
Irenaeus’ Against Heresies
As previously mentioned, Irenaeus wrote against these Gnostics in Against Heresies. He emphasized that Christians must adhere to the Church’s teaching as passed down from the apostles, and explained how the Gnostics refused to do so:
“when we refer them to that tradition which originates from the apostles, [and] which is preserved by means of the succession of presbyters in the Churches, they object to tradition, saying that they themselves are wiser not merely than the presbyters, but even than the apostles, because they have discovered the unadulterated truth.” (Book III, Chapter 2)
Before he starts getting into his arguments against the heresies, he supports his argument’s truth by appealing to the authority of the Church:
He says that they respond to those who “assemble in unauthorized meetings … by indicating that tradition derived from the apostles, of the very great, the very ancient, and universally known Church founded and organized at Rome by the two most glorious apostles, Peter and Paul; as also [by pointing out] the faith preached to men, which comes down to our time by means of the successions of the bishops. For it is a matter of necessity that every Church should agree with this Church, on account of its preeminent authority [potiorem principalitatem].”
Then, he goes on to list each of the bishops in order from the apostles to the present bishops. We can see that this is not some loose idea of tradition; this is the oral teachings passed down through a direct line of bishops who were first appointed by the Apostles (who of course knew Jesus directly and very closely).
In the next chapter, Irenaeus then reiterates why Christians should refer to the Church’s tradition rather than interpreting Scripture on their own. “Suppose there arise a dispute relative to some important question among us,” he says—as evidently has occurred with the Gnostics, and occurred with many other heretical sects during this time as well, such as the Montanists. “Should we not,” he asks, “have recourse to the most ancient Churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings?” Of course, we have the apostles’ writings, but there are also theological and moral matters not directly discussed in the New Testament or that have been misinterpreted as we have seen. In such cases then, he concludes, “Would it not be necessary … to follow the course of the tradition which they handed down to those to whom they did commit the Churches?”
Hence, we can see how “Christianity was not simply an affair of beliefs or ideas drawn from the Scriptures; the apostolic faith was known through the witness of persons and the teaching and practices of a community that extended back in time.”
Irenaeus’ work and the situation of the times unquestioningly shows us what the early church believed about the role of Scripture and oral tradition. And this direct line from bishop to bishop back to the Apostles has remained unbroken up to today; the writings of the early church fathers continue to show us that this tradition of beliefs passed down through the generations is still the same today as it was in the early church. That is why Christians can rely on the Catholic Church’s interpretation of the Bible and its teachings.
 John Laux, Church History (Charlotte, NC: TAN, 2012), 60.
 Robert Louis Wilken, The First Thousand Years (New Haven, CN: Yale University Press, 2012), 42.
 Ibid. 42.
 Ibid. Ch. 4.
 Laux, 60.
 Wilken, 41.
 Laux, 62.
 Ibid. 45.