I was reading through the prolegomena of Aquinas's Summa again this afternoon - if you want to learn to appreciate clarity of thought and expression, Aquinas is a good place to go, even in translation (not that I always agree with his conclusions ;0), but at least it is clear as to why when this is the case) - and I came once again across the following, which forms Aquinas's response to an imagined objection that sacred doctrine is not a matter of argument from authority. I have quoted a shorter extract of this paragraph before, but it is so important that I now post it in its entirety, italicising the crucial passage where Aquinas teaches the same doctrine on the primacy of scripture and its relation to other authorities that would later be explicated by such Lutheran divines as Martin Chemnitz:
"This doctrine is especially based upon arguments from authority, inasmuch as its principles are obtained by revelation: thus we ought to believe on the authority of those to whom the revelation has been made. Nor does this take away from the dignity of this doctrine, for although the argument from authority based on human reason is the weakest, yet the argument from authority based on divine revelation is the strongest. But sacred doctrine makes use even of human reason, not, indeed, to prove faith (for thereby the merit of faith would come to an end), but to make clear other things that are put forward in this doctrine. Since therefore grace does not destroy nature but perfects it, natural reason should minister to faith as the natural bent of the will ministers to charity. Hence the Apostle says: "Bringing into captivity every understanding unto the obedience of Christ" (2 Cor. 10:5). Hence sacred doctrine makes use also of the authority of philosophers in those questions in which they were able to know the truth by natural reason, as Paul quotes a saying of Aratus: "As some also of your own poets said: For we are also His offspring" (Acts 17:28). Nevertheless, sacred doctrine makes use of these authorities as extrinsic and probable arguments; but properly uses the authority of the canonical Scriptures as an incontrovertible proof, and the authority of the doctors of the Church as one that may properly be used, yet merely as probable. For our faith rests upon the revelation made to the apostles and prophets who wrote the canonical books, and not on the revelations (if any such there are) made to other doctors. Hence Augustine says (Epis. ad Hieron. xix, 1): "Only those books of Scripture which are called canonical have I learned to hold in such honor as to believe their authors have not erred in any way in writing them. But other authors I so read as not to deem everything in their works to be true, merely on account of their having so thought and written, whatever may have been their holiness and learning."
Thomas Aquinas, Summa Theologica, The Nature and Extent of Sacred Doctrine, Q8. Whether Sacred Doctrine Is A Matter of Argument?
Aquinas is known mainly as the great synthesiser of Christian theology and Aristotelianism, an innovation which, however necessary at the time, is in some parts highly questionable. Perhaps his greater achievement was in synthesising and presenting in concise dogmatic form the history of Christian thought and doctrine down to the early middle ages. Here he expoounds with great clarity the consensus view of the ancient Fathers on the primacy of the authority of scripture, quoting Augustine as the greatest patristic witness.
An excellent introduction to Aquinas's thought, particularly in relation to his Aristotelianism, can be found in the late Fr Copleston's little paperback volume that was published by Penguin - the American division of Penguin still has it in print.