In the first chapter of their confession of faith, on Holy Scripture, the Westminster Divines say (among other things):

VI. The whole counsel of God concerning all things necessary for His own glory, man’s salvation, faith and life, is either expressly set down in Scripture, or by good and necessary consequence may be deduced from Scripture: unto which nothing at any time is to be added, whether by new revelations of the Spirit, or traditions of men. Nevertheless, we acknowledge the inward illumination of the Spirit of God to be necessary for the saving understanding of such things as are revealed in the Word: and that there are some circumstances concerning the worship of God, and government of the Church, common to human actions and societies, which are to be ordered by the light of nature, and Christian prudence, according to the general rules of the Word, which are always to be observed. VII. All things in Scripture are not alike plain in themselves, nor alike clear unto all: yet those things which are necessary to be known, believed, and observed for salvation are so clearly propounded, and opened in some place of Scripture or other, that not only the learned, but the unlearned, in a due use of the ordinary means, may attain unto a sufficient understanding of them. X. The supreme judge by which all controversies of religion are to be determined, and all decrees of councils, opinions of ancient writers, doctrines of men, and private spirits, are to be examined, and in whose sentence we are to rest, can be no other but the Holy Spirit speaking in the Scripture.

What’s weird is that Augustine basically says this. No, I’m serious, though. At the end of Book 2 of On Merit and the Forgiveness of Sins, and the Baptism of Infants, he writes:

The question also arises, how God (even if He does not create souls by natural propagation) can yet not be the Author of that very guilt, on account of which redemption by the sacrament is necessary to the infant’s soul. The subject is a wide and important one, and requires another treatise. The discussion, however, so far as I can judge, ought to be conducted with temper and moderation, so as to deserve the praise of cautious inquiry, rather than the censure of headstrong assertion. For whenever a question arises on an unusually obscure subject, on which no assistance can be rendered by clear and certain proofs of the Holy Scriptures, the presumption of man ought to restrain itself; nor should it attempt anything definite by leaning to either side. But if I must indeed be ignorant concerning any points of this sort, as to how they can be explained and proved, this much I should still believe, that from this very circumstance the Holy Scriptures would possess a most clear authority, whenever a point arose which no man could be ignorant of, without imperilling the salvation which has been promised him. (2.59)

Notice what he says here. When there is a doctrinal question that cannot be answered with “clear and certain proofs” from Scripture, we must not be dogmatic about it. In other words, assent cannot be required to any such answer that is proffered. To do so would be “presumption.” Such cases are cases for “restraint” (for that reason, Augustine would not insist dogmatically on, e.g., purgatory; of course, he could have insisted dogmatically against it, but we’ll take what we can get). Man’s presumption should not “attempt anything definite”–i.e., it should not define any dogmas in such cases. Pious speculation? Yeah, ok, sure, Augustine was pretty chill with a lot of that. But the logic of this passage rules out dogmatic definition from such speculations.

Notice, too, that such questions will never strike at the heart of faith. On any doctrinal point on which the salvation of man would be “imperiled” due to ignorance of it, “the Holy Scriptures…possess a most clear authority.” This is what the Divines mean in WCF 1.6-7 above. They admit that some things are clearer, some less clear in Scripture–but whatever must be known an believed for salvation are clearly set out in its pages.

Contrast Augustine’s position with some other possibilities. E.g.:

Furthermore, we declare, we proclaim, we define that it is absolutely necessary for salvation that every human creature be subject to the Roman Pontiff.

(This follows the assertion–which is not just a pious suggestion–that “one sword ought to be subordinated to the other and temporal authority, subjected to spiritual power.”)

Or, say:

We teach and define that it is a divinely-revealed dogma: that the Roman Pontiff, when he speaks ex Cathedra, that is, when in discharge of the office of Pastor and Teacher of all Christians, by virtue of his supreme Apostolic authority, he defines a doctrine regarding faith or morals to be held by the Universal Church, by the divine assistance promised to him in blessed Peter, is possessed of that infallibility with which the divine Redeemer willed that His Church should be endowed for defining doctrine regarding faith or morals: and that therefore such definitions of the Roman Pontiff are irreformable of themselves, and not from the consent of the Church.

Or maybe:

We declare, pronounce, and define that the doctrine which holds that the most Blessed Virgin Mary, in the first instance of her conception, by a singular grace and privilege granted by Almighty God, in view of the merits of Jesus Christ, the Savior of the human race, was preserved free from all stain of original sin, is a doctrine revealed by God and therefore to be believed firmly and constantly by all the faithful. […] Hence, if anyone shall dare — which God forbid! — to think otherwise than as has been defined by us, let him know and understand that he is condemned by his own judgment; that he has suffered shipwreck in the faith; that he has separated from the unity of the Church; and that, furthermore, by his own action he incurs the penalties established by law if he should dare to express in words or writing or by any other outward means the errors he thinks in his heart.

Mark that: refusing assent to something which all sides must agree is not clearly propounded in Scripture entails the loss of salvation. Let it sink in: the forgiveness of sins and salvation from everlasting torment in hell depends on believing that Mary was preserved from original sin.

Or this:

[B]y the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, we pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory. 45. Hence if anyone, which God forbid, should dare willfully to deny or to call into doubt that which we have defined, let him know that he has fallen away completely from the divine and Catholic Faith.

Again, observe what this means. If one should express agnosticism about this point (let alone deny), which–again–all sides must agree is not clearly propounded in Scripture, he gets straight on the highway to hell, AC/DC-style. Munificentissimus Deus proclaims that this doctrine is part of the “deposit of faith” and is “a truth that has been revealed by God”; but it immediately bifurcates revelation into “the written Word of God” and “Tradition,” which is not what Augustine says above.

To conclude: Yes, I am aware of other remarks of Augustine on Scripture and tradition. But the point here is to think through the logic of what he says in the passage quoted above and to show its harmony and adaptability to Reformational conceptions of Scripture and authority. In other words, they weren’t making this stuff up. They were pulling on threads that were already there, drawing out trajectories that were implicit in what was said before, and recovering what might be called “suppressed traditions.” In this instance, the point is that one ought not to be threatened with damnation over things that have not clearly been revealed. In addition, the position sketched above preserves the truth that what one has needed to believe to be saved has always been the same–in AD 33, 1302, 1854, 1870, and 1950–and has always been publicly accessible in Scripture, as Augustine says.

It is no surprise, then, that this passage of Augustine appears in Calvin’s preface to the Institutes of the Christian Religion, where, claiming a greater faithfulness to antiquity than his opponents, he writes:

It was a Father who pronounced it rashness, in an obscure question, to decide in either way without clear and evident authority from Scripture. They forgot this landmark when they enacted so many constitutions, so many canons, and so many dogmatical decisions, without sanction from the word of God.

500 years after the Reformation, and nearly 2000 years after the Resurrection, we ought still to heed Solomon: “Remove not the ancient landmarks which thy fathers have set.”