Question: Why do you Protestants fail to see that without the tradition and pronouncements of an authoritative Church, you wouldn't know what was Scripture? The New Testament was certainly not available for many years. Without the oral teachings of the Apostles, how could people know what was truth?
Response: Catholicism would dearly love to claim the mantle of being the "authoritative" church, but all she has been able to produce through threat of force is a surface conformity riddled by internal dissension and corruption. In contrast, believers are truly given an unfailing authority.
Second Timothy 3:16 is rightly cited as evidence for sola scriptura [by Scripture alone]. Verse 15 says: "From a child thou hast known the holy scriptures...." The "scriptures" here must refer to the Old Testament because Timothy did not have the New Testament in its entirety. Nevertheless, he had at least the two epistles written to him. Furthermore, this verse tells us that "from a child" he had known the Holy Scriptures, undoubtedly taught to him by a godly mother and grandmother. The Apostle Paul is declaring that the Scriptures available were sufficient to lead one to a saving knowledge of Jesus Christ. The book of Acts is filled with examples of the apostles expounding the Scriptures, but we will consider just a few.
In Acts 8, Philip was led of the Lord to where a certain Ethiopian eunuch was passing by. As Philip approached, he heard him reading from the book of Isaiah. Apparently, the Scriptures weren't so scarce that a courtier in Ethiopia couldn't obtain a copy. Philip and the man had an exchange, and the Ethiopian invited him to ride along in the chariot. Then "Philip opened his mouth, and began at the same scripture, and preached unto him Jesus" (Acts:8:35). The book of Isaiah, used at the direction and empowerment of the Holy Spirit, was sufficient to lead this man to a saving knowledge of the Lord Jesus Christ. The Old Testament Scriptures were also sufficient for the Lord Jesus Christ when He confronted the two disciples who were on the road to Emmaus (Luke:24:13-27). Imagine what a Bible study that must have been! Consider the case of Apollos (who was "mighty in the scriptures") in Acts 18. He was preaching the "things of the Lord," but he knew only the baptism of John (v. 25). He did not know that the Messiah had come, lived, bled and died on the Cross, been buried, and then raised again, in power. Two disciples, Aquila and Priscilla, took him aside and "...expounded unto him the way of God more perfectly" (v. 26). At that point, he did not begin teaching a tradition solely on the basis of something orally communicated to him; rather, he continued to preach and exhort, "showing by the scriptures that Jesus was Christ" (Acts:18:28).