Our comments on Sacred Tradition by no means imply that scripture is unimportant. “Sacred [T]radition and Sacred Scripture are to be accepted and venerated with the same sense of loyalty and reverence” (Dei Verbum 9). The Bible is a Catholic book, and Catholics have a right and a duty to read the scriptures with love and reverence on a regular basis. Sacred Scripture depends on Sacred Tradition, but scripture is still invaluable because it contains the written word of God. While we may have difficulty capturing what someone merely said or even did, we can be sure of it if it is written down. Thus, the scriptures serve as a checkpoint for Sacred Tradition. If someone begins to claim that the apostles said or did certain things which seem contrary to the Faith, we can consult Sacred Scripture for the answer. “All scripture is inspired by God and profitable for teaching, for reproof, for correction, and for training in righteousness” (2 Tim 3:16). This does not mean, however, that scripture contains every truth, even every theological truth.
Scripture is not meant to teach every fact (empirical scientific, mathematic, etc.), nor is it meant to teach us everything that God revealed. “But there are also many other things which Jesus did; were every one of them to be written, I suppose that the world itself could not contain the books that would be written” (Jn 21:25). Instead, God teaches us through scripture about those truths which He has deigned to reveal in writing. So, God works through Sacred Tradition and Sacred Scripture, in tandem, to communicate Divine Revelation to us.
However, even though scripture does not intend to teach us about geography, science, mathematics, etc., it still cannot err in anything, including those topics which it does not primarily intend to teach us about. So it would be problematic to claim that scripture is only true insofar as it concerns our salvation. Scripture is true insofar as it concerns our salvation, as well as regarding everything else it says.
God inspired all the human authors of the books of the Bible to write what they did, while protecting them from error. This truth does not mean that God merely placed the idea of writing scripture in the human authors’ heads (as we might say someone is inspired to do something), but that He protected these human authors from all error when they wrote scripture. God did not put them in a trance and then make them write what He wanted them to say. Rather, He acted as the bank of a river, hemming the river in, until it was guided “into all the truth” (Jn 16:13). Thus, we say that God is 100% the author of scripture and the people who physically wrote the books are 100% the authors of scripture.
Inspiration also means more than merely “without error.” Many writings have no errors, but are not inspired by God. It is commonly believed that the Letter of Saint Clement to the Corinthians is infallible. However, God did not inspire it. The Lord gave St. Clement the grace to write the letter and perhaps He even gave special understanding of certain things to Clement. But God did not will for this letter to be included in the scripture of Divine Revelation.