The first chapter of Dei Verbum (DV)—which I wrote about here and here—is about revelation and faith. The second chapter is about Tradition, a topic that has been controversial since the Protestant Reformation and the Council of Trent in the sixteenth century. DV teaches that, far from being rivals, Scripture and Tradition are united.
To understand what DV says about Tradition, it is helpful to go back to Trent. To free themselves from the decrees of popes and councils, the Reformers made the Bible the sole rule of faith, absolutely superior to Tradition, canon law, and ecclesiastical judgments. This is called sola scriptura (Latin for “Scripture alone”). In response, the Ecumenical Council of Trent had to formulate a decree that would accept both Scripture and Tradition as authoritative.
Just as at Vatican II, not every bishop and theologian at Trent had the same opinion on the matter. One popular idea was to say that the teachings of the Catholic faith (often called “truths necessary for salvation”) were found “partly” in the Bible but also “partly” in Tradition. Some, however, found this problematic because it meant that some truths must be absent from the Bible. Although they fully maintained the importance of Tradition, they believed the Bible was “sufficient” for salvation. God made sure that everything a person needed to be saved was included in the Bible. Probably because of this objection, the two instances of the word partly (“partim” in Latin) were removed from the final decree, which says that “[saving] truth and [moral] discipline are contained in the written books and unwritten traditions.”
This formulation accommodated both positions: it could mean that some truths are in the books of Scripture and others in Tradition; or it could mean that they are all found in both Scripture and Tradition (or that all are found in Tradition, but only some in Scripture, as some later theologians held). After the Council, however, theologians tended to assume the partim-partim theory, almost as if Trent had rejected the “sufficiency” of Scripture rather than avoiding the question. I think that is how most Catholics think of it to this day: there are a handful of doctrines not in the Bible, which are known only from Tradition, such as the Assumption of Mary or purgatory. This common view is called two-source theology, meaning there are two sources of revelation: Scripture and Tradition.
On the eve of Vatican II, two-source theology was challenged by Joseph Geiselmann. He argued that, since Trent dropped the “partly” language, two-source theology was not official Church teaching, as commonly assumed. Instead, he argued, there is only one source of revelation: the Gospel. He even argued that this better reflects the final teaching of Trent, since it calls the Gospel “the font of all saving truth and moral teaching.” This may sound like an overly-fine distinction (typical of theologians), but the point is that Scripture and Tradition are not two distinct, let alone separable, “sources.” Divine revelation is singular, not bifurcated. There is only “one sacred deposit of the word of God” (as DV 10 would later put it), though it is handed down through two modes. Giselmann’s viewpoint was quickly adopted by the “New Theologians,” notably Yves Congar, who became the intellectual drivers of the Second Vatican Council.
Which brings us to Dei Verbum. In the first paragraph of chapter two, it quotes that phrase of Trent: “font of all saving truth and moral teaching” (DV 7). Like Trent, it passes by the question of whether Scripture is “sufficient.” Instead it strongly emphasizes the unity of Scripture and Tradition:
“Sacred Scripture and Sacred Tradition are closely connected and share with each other. For both, flowing from the same divine spring, in a certain manner coalesce into one thing and travel toward the same goal” (DV 9).
They have one origin, unite as “one thing” (unum), and have one goal. Although the language of sharing could still be interpreted as meaning partly in Scripture, partly in Tradition, the obvious sense is that they share the same revelation: it is all in Scripture, and it is all in Tradition. This is the one-source view, as held by those who actually wrote Dei Verbum.
The one Gospel is accessed in multiple ways: through the Old Testament, in which it is “promised beforehand” (DV 7), the four gospels, the other writings of the New Testament, and the various elements of Tradition. The authors of the New Testament “committed the message of salvation to writing” (ibid.). Not part of the message, but simply the message. Although we venerate Scripture and Tradition equally (DV 9), Scripture is singled out as of special importance: “the apostolic preaching … is expressed in a special way in the inspired books” (DV 8). Scripture will always be preeminent in the Church because it has a fixed form: the words cannot be altered, and their recitation and study is the backbone of the Church’s spiritual life and of Tradition itself.
Thus there is no doctrine or element of Tradition that does not take its essential foundation from words or principles contained in Scripture. This is what we mean when we say that all, not merely part, of revelation is found in Scripture. The strongest proof of this is the Church’s actual practice. If you search the decrees of popes and councils, as well as the writings of the Fathers and Doctors of the Church, you find that they always ground their teachings in Scripture, even when discussing things that may seem extra-biblical. Likewise the liturgy. On the feasts of the Immaculate Conception and the Assumption, the scriptural readings are not replaced with papal decrees! The foundational biblical passage of the event being celebrated is proclaimed, the same as on any feast day.
Discussions of Mary’s sanctity can be found in the writings of such saints as Ambrose, Ephrem, Augustine, Thomas Aquinas, and many others, prior to being settled by Pius IX with an extraordinary dogmatic definition in 1854. But the foundation of the entire discussion has always been Mary’s special status as the Mother of God, which is principally narrated in Luke 1 when the Angel Gabriel tells her, “Hail, full of grace, the Lord is with thee!” (v. 28). As such, on the feast of the Immaculate Conception, Luke 1:26-38 is read. Her bodily Assumption into heaven was a well-established tradition by the fourth century. It has long been seen as reflected in the image of the woman clothed with the sun in Rev 12:1-6, which is thus one of the readings at Mass that day.
My point is not that these dogmas are explicitly taught in Scripture, as if one could derive them through careful exegesis. One cannot. This is why most Catholic-Protestant debates on the subject are fruitless exercises in talking past each other. It is impossible to prove the dogmas using just the scriptural passages. It is equally impossible to disprove them. The whole argument proceeds from a misunderstanding of the relationship between Scripture and Tradition, as if they were rivals.
The correct understanding, as taught by Dei Verbum, is that everything in Tradition is rooted in Scripture, because the two are one. Tradition is not a corpus of extra-biblical content, as if the authors of the New Testament forgot to write down some of the key points. Rather, Tradition is the matrix in which the Scriptures are handed over and interpreted, from generation to generation. How this process takes place will be the subject of my next article.
 Council of Trent, Session IV: contineri in libris scriptis et sine scripto traditionibus (DS 1501).
 Josef Geiselmann, “Scripture and Tradition in Catholic Theology,” Theology Digest 6 (1958): 73-78.
 Council of Trent, Session IV: fontem omnis et salutaris veritatis et morum disciplinae (DS 1501).
 Chapter six explores the myriad ways in which Scripture is used in the Church’s life.
Image: Fr. Josef Ratzinger and Yves Congar, OP. Source: https://www.flickr.com/photos/levanrami/43923263275. Public Domain.