"Yet holy teaching employs such authorities (e.g. human reason, philosophy) only in order to provide, as it were, extraneous arguments from probability. Its own proper authorities are those of canonical scripture, and these it has applied with convincing force. It has other proper authorities, the doctors of the church, and these it looks to as its own, but for arguments that carry no more than probability. For our faith rests on the revelation made to the prophets and apostles who wrote the canonical books, not on a revelation, if such there be, made to any other teacher." (Italics mine.)
From Thomas Aquinas, Summa Theologiae, Question 1 Article 8.
I urge readers to follow these quotes up for themselves if possible, and read them in context. Many public libraries now carry one of the numerous abridged editions of Aquinas' Summa in English, while decent theological libraries will probably have the excellent English Dominican translation of the complete work.
This is a particularly clear espousal of a position that is basically in accord with the magisterial Reformation's doctrine of the sufficiency of scripture for the establishing all articles of faith necessary to be believed in order to be saved. This position (which, I would contend, is also the position of the early church) stands somewhat in contrast to that set forth by Rome at the Council of Trent in 1546and reiterated in the Vatican II document Dei verbum (1965), which states, "Sacred Scripture is the speech of God as it is put down in writing under the breath of the Holy Spirit. Sacred Tradition transmits in its entirety the Word of God which has been entrusted to the apostles by Christ the Lord and the Holy Spirit. It transmits it to the successors of the apostles so that, enlightened by the Spirit of truth, they may faithfully preserve, expound and spread it abroad by their preaching. Thus it comes about that the Church does not draw her certainty about all revealed truths from the holy Scripture alone. Hence both Scripture and Tradition must be accepted and honoured with equal feelings of devotion and reverence... Sacred tradition and sacred Scripture make up a single sacred deposit, which is entrusted to the Church... the task of giving an authentic interpretation of the Word of God, whether in its written form or in the form of Tradition, has been entrusted to the living teaching office of the Church alone..." (once again, italics are mine).
This position, I'm afraid, seems to subsume scripture entirely under the rubric of "sacred tradition", whose content in practice is determined by the teaching office of the papacy, a fear which is confirmed when one considers the doctrine of papal infallibility (Vatican I, 1870) and the Marian dogmas of the Immaculate Conception (defined as a dogma in 1854) and the Assumption (defined in 1950), through which the papacy attempts to bind consciences on the fear of losing salvation with dogmatic pronouncements which have no scriptural basis (should we perhaps refer to them as "other revelations, if such there be"). This would appear to be a long way from the view of Aquinas as stated above.
Indeed, only a theory of doctrinal development, such as was put forward by John Henry Newman while he was an Anglican on the way to Rome in his Essay on the Development of Christian Doctrine (1845) could provide a semblance (i.e. a superficial or outward appearance) of intellectual respectability for such a position. That such a semblance of intellectual respectability has played the crucial role it has in swaying numerous otherwise intelligent and pious people to convert to Rome from Lutheranism and other branches of the magisterial Reformation must be regarded as one of the great mysteries of modern times.