Why Don't Catholics Believe in the Bible Only?
The Bible plays a central and primary role in Christian faith, but it is not sufficient as the sole authoritative source of belief. If it were, the more than thirty thousand "Bible-based" Protestant denominations in the world would not have such fundamental disagreements over what the biblical text really means. Clearly, Scripture needs both a wider context of Tradition and a living, authoritative interpreter if it is to be rightly understood.
The fact that Baruch and certain other books don't even appear in the Protestant Bible places the problem in even sharper focus: Many ancient books claimed to speak for God. How can we even know which ones belong in the Bible unless we have an authority outside Scripture itself to tell us?
From the beginning, the magisterium of the Catholic Church has exercised the God-given authority to discern which books belong in the Bible and how they are correctly interpreted in the light of sacred Tradition .
Catholics thus view the Bible, the Church, and Tradition as harmonious pieces of a whole. In fact, the Bible itself points to Tradition and the Church as authoritative; it doesn't teach that Scripture is the Christian's sole ultimate authority.
St. Paul, for example, commands Christians to "hold fast" to the traditions he has passed on to them, both those that were written down (and were later recognized as Scripture) and those that were not written down (see 2 Thes 2:15). He writes to St. Timothy that the Church (not Scripture) is "the pillar and foundation of truth" (1Tm 3:15).
Nor is Scripture, as some Christians claim, fully self-interpreting. As 2 Peter notes, for example, in St. Paul's letters "there are some things hard to under- stand that the ignorant and unstable distort to their own destruction, just as they do the other scriptures" (3:16).The Catholic Church avoids such dangers by relying on the authoritative interpretation of the magisterium in the light of Tradition.