St. Paul’s authority was accepted in faith by his followers. He spoke with great authority. He said he was delivering truth and tradition, and he expected his followers to accept it without question. There is no hint that he thought otherwise. No one denies that he had profound apostolic authority. The question is whether Scripture alone was the only infallible authority.
St. Paul explained things, and argued and defended and so forth, but his authority was unquestioned. So was the authority of the Church, which is why it held a council in Jerusalem and then Paul went out proclaiming the infallible (Acts 15:22, 28) decisions of the council (Acts 16:4) in his missionary journeys.
Acts 17:10-11 (RSV) The brethren immediately sent Paul and Silas away by night to Beroea; and when they arrived they went into the Jewish synagogue. Now these Jews were more noble than those in Thessalonica, for they received the word with all eagerness, examining the scriptures daily to see if these things were so.
The example of the Bereans does not disprove Catholic authority or suggest sola Scriptura at all. The word that they received with “all eagerness” was Paul’s oral teaching and preaching, which they confirmed as consistent with Holy Scripture (as Catholics believe all legitimate tradition to be), and an additional revelation. Once they had done that, for them, his teaching was on a par with Scripture and of binding authority.
My friend and fellow apologist Steve Ray exhibited great insight regarding this question in a classic 1997 article:
[The Bereans] were not Christians; they were Hellenistic Jews. There was no doctrine of sola scriptura within Jewish communities, but the Scriptures were held as sacred. Although the Jews are frequently referred to as “the people of the book,” in reality they had a strong oral tradition that accompanied their Scriptures, . . . The Jews had no reason to accept Paul’s teaching as “divinely inspired,” since they had just met him.
. . . they were willing to accept Paul’s new oral teaching as the word of God (as Paul claimed his oral teaching was; see 1 Thess. 2:13). The Bereans, before accepting the oral word of God from Paul, a tradition as even Paul himself refers to it (see 2 Thess. 2:15), examined the Scriptures to see if these things were so. They were noble-minded precisely because they “received the word with all eagerness.” Were the Bereans commended primarily for searching the Scriptures? No. Their open-minded willingness to listen was the primary reason they are referred to as noble-minded—not that they searched the Scriptures.
Searching the Scripture to confirm or defend some doctrine is not the same as sola Scriptura. The latter means making the Bible the only infallible authority. The mainstream tradition of the Jews at that time (in all likelihood including the Bereans) was Pharisaism, and it accepted oral tradition and an oral Torah received by Moses on Mt. Sinai.
The ones who held to a strict Bible-alone view were the Sadducees, who accepted only the written Torah (the first five books of the Bible). But they denied the resurrection of the righteous in the afterlife.
Searching the Scriptures is not opposed to Catholic authority (I do it all the time myself — in the course of my apologetics efforts — in order to defend and “confirm” Catholic teaching). When Jesus explained to the two disciples on the road to Emmaus the doctrine of the suffering Messiah (after His Resurrection), He did so by means of Scripture (Luke 24:25-27).
He authoritatively “interpreted to them in all the scriptures the things concerning himself” (Luke 24:27). This is the role of Church and Tradition. Scripture has to be interpreted by someone with authority. Our Lord did the same when He appeared to the eleven disciples (Luke 24:36-38): “Then he opened their minds to understand the scriptures” (Luke 24:45).
The Holy Spirit and the intervention of Jesus were required in order for them to understand. If we interpret on our own apart from the Holy Spirit and disregard for the apostolic tradition preserved by the Church, we can often be led astray (Acts 8:27-35; 2 Pet. 1:20-21; 3:16).
When certain Jews were opposing Jesus, He took them to task for searching the Scriptures (almost as an end in itself) but not seeing that the same Scripture testified to Him (John 5:39). In other words, they were trying to separate God from His Word, as if God’s Word didn’t direct men toward God Himself. St. Paul used the same method when he went to the Jews and proclaimed the gospel (see, e.g., Acts 17:2).
Now, if both Jesus and Paul argued from the Scriptures, then Jews who were considering whether their claims were true would naturally do the same. So the Bereans did exactly that. It was a both/and methodology. They weren’t opposing one thing to the other. Both were true, and their harmony with each other confirmed that. They didn’t rule out the possibility that the oral proclamation was true (simply because it was oral); they merely confirmed it from existing written, inspired revelation.
If they had been operating with an either/or mentality, on the other hand, they wouldn’t have “received the [oral] word with all eagerness.” They would have been highly skeptical of it and would have checked it against Scripture; and even if it lined up with Scripture, they would have denied that it was infallible unless it eventually made it into Scripture. But exactly what Paul said to them is not recorded in Scripture.
Catholics say that Paul’s word was authoritative and infallible, whether it was “inscripturated” or not. But many Protestants argue (based on the false premise of sola Scriptura) that it only is if it is later recorded in Scripture (a distinction that is itself unbiblical, since Paul’s words are presented as authoritative, when they are spoken). This notion itself is never found in Scripture, which means that it is an arbitrary and unbiblical tradition (how ironic!).