Nevertheless, sacred doctrine makes use of these authorities [i.e., philosophers who are able to know the truth by natural reason] 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.)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 (c. 1225-1274), Summa Theologica, First Part, Treatise on God, Question 1, “The Nature and Extent of Sacred Doctrine,” Article 8, “Whether Sacred Doctrine is a Matter of Argument?”, Reply to Objection 2, in Robert Maynard Hutchins, ed., Great Books of the Western World, Volume 19, (Chicago, IL, USA: Encyclopædia Britannica, Inc., 1988), 8.]

ˆ ¹There is a discrepancy in my sources for the precise reference of Epis. ad Hieron. (abbreviated Latin for “Epistle to Jerome”). The texts provided by both the Encylopædia Britannica and the Christian Classics Ethereal Library (to which the above bibliographic reference is linked) are based on the translation of the Summa by the Fathers of the English Dominican Province. Britannica’s revision (by Daniel J. Sullivan), however, has properly corrected the reference from Augustine’s 19th (xix) letter (which was not written to Jerome but to Gaius) to his 82nd (lxxxii). Cf. “Letters of St. Augustin,” translated by J.G. Cunningham, in Philip Schaff, ed., Nicene and Post-Nicene Fathers, First Series, Volume 1, (Peabody, MA, USA: Hendrickson Publishers, Inc., reprinted 2004), 350. ˆ