Compendium Theologiae Dogmaticae Tomus I: De Christo Legato Divino, De Ecclesia Christi, De Fontibus Theologicis

301. We have shown that Christ brought a revealed doctrine which all people are bound to embrace. We have also shown that, to preserve this doctrine and propose and explain it to all people in every age, he instituted an infallible ecclesiastical teaching office. This living teaching office is not itself a motive of faith, but is the rule of faith and the motive of credibility, that is, an objective logical means by which people know that these or those things have been revealed by God. Hence knowledge of revealed things is drawn from the preaching of the Church. This holds for ordinary believers and also for theologians, because the principles of faith are the same for everyone; but theologians proceed from these principles to cultivate theological science.

The means from which the principles for argument in a given science are drawn are called the “sources” or “loci” (τόποι) of that science, especially when it is a positive science, such as history and, in part, theology. Thus, theological sources or loci are the seats of theological arguments, or any instruments that furnish arguments for theological conclusions.

Properly speaking, the only source of faith is: the apostolic preaching, begun by the apostles themselves and continued—and to be continued—through their successors in the apostolic teaching office. For this is the only way Christ indicated: “Go and teach. Whoever believes will be saved. And I am with you until the consummation of the age.” In fact, the apostolic teaching office, which here and now carries out the office received from Christ, is the proximate and universal rule to which all must conform (above, n. 187). This rule and source is available to everyone for believing truths divinely revealed; nothing else is possible for everyone, and nothing else is commanded of everyone (cf. I. V. Bainvel, De magisterio vivo et traditione, Paris 1905, 56 sqq).

It remains, however, to ask how the apostolic teaching office exercises its office, and this question must be answered first of all. This question, in turn, divides into two others: one on the exercise of the ecclesiastical teaching office, and one on the objects around which the ecclesiastical teaching office is exercised.

302. Moreover, the ecclesiastical teaching office teaches not only now but also taught in earlier centuries, and it set down its doctrine not only orally but also in writing. These writings, therefore, are also sources of faith and theology. For what the Church once taught as true is still true now, since truth is immutable. Therefore, as soon as it is established what the Church once taught, it is also established what it teaches now, since the infallible Church that exists now cannot contradict the infallible Church that existed in the past. Indeed, since the Church now receives no new public revelations but must hand on the revelations once made to the apostles, later teachers must necessarily receive these revelations from earlier teachers. This could in itself have occurred through purely oral tradition; even in that way the Holy Spirit could, by his assistance, have ensured that nothing of revealed truth was lost and nothing false was mixed in. Nevertheless, it accords better with human nature for important matters also to be committed to writing so that they may be preserved more easily. Accordingly, divine providence, accommodating itself in this matter too to human nature, ensured that not only the divine revelations themselves but also the explanations of them given in each age would be written down, so that later generations might thus inherit a sacred treasury, which they too would enlarge and pass on in turn to those who came after them under similar conditions. Thus, the writings of earlier centuries—that is, the acts of councils and pontiffs, the works of the holy Fathers, and the works of theologians—are also theological sources. These writings of our forebears constitute a mediate rule of faith, insofar as the teaching office of our own times draws from them the doctrine it proposes to the faithful. Theologians too must have recourse to these sources, both to show that our faith is the same as the faith of our fathers and to draw arguments from these sources for resolving theological questions on matters not yet defined by the ecclesiastical teaching office.

303. Finally, God deigned to become the author of the sacred books through human beings as his instruments. These books contain divine revelations and are called Sacred Scripture. He did not give them to individual believers as an immediate rule of faith, but entrusted them to the ecclesiastical teaching office so that it might explain them to the people. Theologians too receive Sacred Scripture from the ecclesiastical teaching office, so that, according to the mind of the Church, they may draw out, explain, prove, and defend the revealed doctrine from it. For theologians, insofar as they have a canonical mission, are assistants to those who, by virtue of their ordinary office, are authentic teachers in the Church, that is, the Supreme Pontiff and the bishops. It is the task of theologians to develop scientifically what the teaching office proposes with authority.

All theological sources, then, contain the word of God; but Sacred Scripture, because it was written principally by God, is also formally the Word of God, whereas the other instruments through which the word of God is handed on are materially the word of God only, but formally the sayings or writings of human beings. In this sense, the treatise on theological sources comprises two parts, one On Tradition, the other On Scripture. Scripture indeed surpasses tradition insofar as it is the word of God in a more perfect way, while tradition is more necessary because we receive Scripture from it and because it is more universal (cf. Denz. n. 783 1781).

Both Scripture and tradition can be taken actively, as the instrument by which revealed doctrine is proposed, and passively, as the doctrine proposed. In the passive sense, tradition can in turn be understood either strictly, as doctrine proposed through oral tradition alone and not in Scripture, or broadly, insofar as it comprises the whole doctrine proposed by the ecclesiastical teaching office, including what is read in Scripture and Scripture itself as an object of tradition (cf. 2 Thess 2, 14), “the revelation handed on through the apostles, or the deposit of faith,” in its entirety (Denz. n. 1836). In the strict sense, we speak in the plural of sacred traditions, that is, doctrines and institutions not mentioned in Scripture (cf. Conc. trid. sess. 4; Denz. n. 783). These, when divine-apostolic traditions are at issue, are relatively few, such as the doctrine of the canon of Scripture and certain others, which will be discussed in their proper place. For now, we insist not so much that the apostles proposed certain other things in addition to Scripture, but rather—and this is much more important—that the whole revealed doctrine was and still is proposed otherwise, or in another way than through Scripture alone, by virtue of the institution established by Christ, namely, through the living teaching office. Hence we must treat first of all the exercise of this teaching office.