Sola Scriptura is true only in the sense that it is only the Bible that has God as its primary author, but is in error with the concept of the Bible being the sole authority and source of God’s truth. The books and the letters contained in the New Testament are some of the documents in the Church’s deposit of faith—commonly known as the Tradition. Due to circumstances, a canon was defined to distinguish among the writings what are inspired—that is those that has God’s authorship—and what are not. It does not mean that those “uninspired” rest do not hold God’s truth. There are millions of books today that explain God’s will and teaching, yet they don’t have God as their author. It is the same with the Church Tradition. These texts, although not part of the Bible, came from the apostles and passed down to their disciples, whom the Church called the Apostolic Fathers. These fathers in turn have their own followers, whom we call now as the Early Church Fathers. The church preserved this Tradition (handed teachings) from the beginning (cf. 1 Co 11:1) until today. Just as the Lord has promised, not in the 21-century history of the Church did it become unfaithful in keeping God’s revelation intact. The impossibility of that event to occur does not depend on human effort but rather on the continuous fulfillment of Christ’s word that not even the corruption of Satan may destroy the purity of the deposit of Faith (Mt 16:18).
Another error of the Protestant’s “Bible alone” is the idea that the issue of Scriptural interpretation is a matter to be left between the Bible and the reader. There is only one truth, so if thousands of groups claimed to hold thousands of different “one truth”, then it is certain that those who hold on to their own individual understanding do not actually hold the truth. God’s revelation is not a matter of private interpretation as the Scripture itself says (2 P 1:20); neither is it accurate that “Scripture interprets Scripture”. It is true that a part of the Scripture is being supported by another part, but it is also true that wrong interpretation of one part will be aggravated by the other part that supports it.
The Scripture (the New Testament documents and the canon of both testaments) was drawn from the Church and it is the Church alone who has the authority and protection to teach it free from error. Just as Paul proclaims, the Church is the one that upholds the truth and keeps it safe (1 Tm 3:15).