There are also signs of a resurgence of fideism, which fails to recognize the importance of rational knowledge and philosophical discourse for the understanding of faith, indeed for the very possibility of belief in God. One currently widespread symptom of this fideistic tendency is a "biblicism" which tends to make the reading and exegesis of Sacred Scripture the sole criterion of truth. In consequence, the word of God is identified with Sacred Scripture alone, thus eliminating the doctrine of the Church which the Second Vatican Council stressed quite specifically. Having recalled that the word of God is present in both Scripture and Tradition, the Constitution Dei Verbum continues emphatically: "Sacred Tradition and Sacred Scripture comprise a single sacred deposit of the word of God entrusted to the Church. Embracing this deposit and united with their pastors, the People of God remain always faithful to the teaching of the Apostles". Scripture, therefore, is not the Church's sole point of reference. The "supreme rule of her faith" derives from the unity which the Spirit has created between Sacred Tradition, Sacred Scripture and the Magisterium of the Church in a reciprocity which means that none of the three can survive without the others.I'm reminded of the following section from Scott Hahn's description of his coming into the Catholic Church:
One professor whom I greatly respect, an Oxford theologian, said to me, "Scott, you don't expect to find the Bible proving sola Scriptura because it isn't something the Bible demonstrates. It is our assumption; it is our presupposition when we approach the Bible." That struck me as odd; I said, "But professor, that seems strange because what we are saying then is that we should only believe what the Bible teaches, but the Bible doesn't teach us to only believe what the Bible teaches. Our assumption isn't taught by the Bible." I said, "That feels like we're cutting off the branch that we're sitting on." Then he said, "Well what other options do we have?"
What is right about sola scriptura is its recognition that there is no authority higher than that of the word of God. But the first problem with sola scriptura is that it assumes that the word of God is wholly contained in the books of the Bible. It thereby assumes that nothing else that the Apostles said to the early Church, and that was passed down by the Church and later written by the Church fathers, is part of the word of God to the Church. But that assumption cannot itself be found in Scripture or grounded by Scripture. Those teachings of the Apostles that were not included in the books of the New Testament, but were passed down orally (especially in the prayers and liturgical practices of the Church) and in the writings of the Fathers, are what Pope John Paul II refers to in the quotation above as Tradition. (See Carl Olson's comments here.)
The second problem with sola scriptura is that it implicitly denies [sacramental] magisterial authority. Here's John Frame's definition of sola scriptura, found in his article, "In Defense of Something Close to Biblicism":
Sola Scriptura is the doctrine that Scripture, and only Scripture, has the final word on everything, all our doctrine, and all our life. Thus it has the final word even on our interpretation of Scripture, even in our theological method.Implicit in this definition of sola scriptura is the notion that each man is under no higher ecclesial authority than his own determination of Scripture's interpretation of Scripture. In its rejection of the authority of the magisterium to provide the authoritative interpretation of Scripture, sola scriptura is an endorsement of individualism and the rule of private judgment. (See here for my response to Keith Mathison on the individualism of sola scriptura.)
By rejecting those two other loci of ecclesial authority, sola scriptura turns into each man doing what is right in his own eyes. As Pope John Paul II said, "[N]one of the three can survive without the others."