The term “Magisterium” is not commonly used in parish life and preaching. The word derives from the Latin magister or “teacher,” but in Catholic theological usage the term goes much further in meaning than, say, the term "catechist." Wikipedia, a secular source, actually has it right: “In Catholicism, the magisterium is the authority that lays down what is the authentic teaching of the Church. For the Catholic Church, that authority is vested uniquely in the pope and the bishops who are in communion with him.”
The issue of the Magisterium will probably come up this year in catechetical aids and discussions in the observance of the 500th anniversary of the Reformation, since this teaching authority of the Catholic Church has been and remains a source of contention between Roman Catholicism and Protestantism (as well as between the Roman Catholic Church and the Orthodox Church.) While the Reformation is quite complicated in its issues, one of the constants of Protestant reformers was a return to reliance upon the Scriptures alone as the source of divine authority; hence the Latin battle cry sola scriptura!
The purists who advocate Scripture alone as the source of all religious teachings charge bravely onto a field studded with landmines. Most tellingly, history itself narrates a different story. The first-generation Church existed without any written texts discovered to date. The dating of the first known written text, Paul’s letter to Thessalonica, has been estimated at 50 A.D., give or take. The formal establishment of a canon of revealed books, what we call today the New Testament, was a lengthy process debated by the Church as recently as the Council of Trent (1545-1563). Purists or literalists cannot claim history as a source for the direct and solely divine authority of the Bible, as the Church itself recorded the texts and vouched for their authenticity and inspiration.
It is probably the Church’s role in the development of the New Testament that has led to the recognition of the Church’s authority as based in the New Testament but in some way distinct from it, particularly in matters of interpreting and applying scriptural teaching. The collected body of Church authoritative teaching is known as Tradition; the formal exercise of this authority is described as the Magisterium or act of teaching. Magisterium is the exercise of Church teaching; Tradition is the content of Church teaching.
Paragraph 88 defines both the nature of the Magisterium and its extent. The Church enjoys Christ’s authority to the fullest when it defines dogmas, truths contained in divine Revelation. It goes on to include under this umbrella “truths having a necessary connection with these.” Luther and other Protestant reformers would probably have had little argument with the first half of para. 88, since they never rejected the Nicene Creed. It is the final clause, “truths having a connection with these,” where Protestants take issue. In Luther’s time, the Church’s assurance of salvation through indulgences was the issue, viewed by many as a Magisterial overreach.
However, even within Roman Catholicism, there is theological debate about the legitimate extent of defining doctrinal truths. Yesterday, while I waited for my carpets to dry, I was able to finish John W. O’Malley’s What Happened at Vatican II? (2010), a work which throws considerable light on the nature and extent of Tradition and Magisterium, since both were exhaustively debated at the Council. Vatican II, it may be recalled, produced the Dogmatic Constitution Dei Verbum [Word of God] in 1965. Although the final vote was 2344 in favor to 6 against, the public and private debate over the wording of the document was intense, specifically on the matter of Magisterium, Tradition, and the “necessary connection” dogmas.
Conservatives at the Council fought to retain the “Two Source” principle of divine Revelation, i.e., Scripture and Tradition. Progressives fought to avoid the definition of Tradition in the document as a source independent of and equal to Scripture. Many scholars were uncomfortable defining the Church as a separate font of Revelation and fought to bring the Bible into greater visibility in the development of the ongoing exercise of the Magisterium. Conservatives fought to preserve the “Two Source” wording; their concerns were fueled by the fact that two dogmatic statements involving the Virgin Mary rested very heavily upon Tradition and not Scripture, specifically the Doctrine of the Immaculate Conception defined in 1854 by Pope Pius IX, and the Doctrine of the Assumption of Mary defined in 1950 by Pope Pius XII. (see O’Malley, pp. 277-280) Neither doctrine is found directly in the Scriptures.
[For the record, the approved formula defined by the Council in Dei Verbum, section 9: “Hence there exists a close connection and communication between sacred tradition and Sacred Scripture. For both of them, flowing from the same divine wellspring, in a certain way merge into a unity and tend toward the same end. For Sacred Scripture is the word of God inasmuch as it is consigned to writing under the inspiration of the divine Spirit, while sacred tradition takes the word of God entrusted by Christ the Lord and the Holy Spirit to the Apostles, and hands it on to their successors in its full purity, so that led by the light of the Spirit of truth, they may in proclaiming it preserve this word of God faithfully, explain it, and make it more widely known. Consequently, it is not from Sacred Scripture alone that the Church draws her certainty about everything which has been revealed. Therefore, both sacred tradition and Sacred Scripture are to be accepted and venerated with the same sense of loyalty and reverence.] How would you like to serve on that drafting committee???
In my lifetime, the Church has not come close to making another definition of dogma. There was some talk that Pope John Paul II considered defining Mary The Mediatrix of All Graces, but the title was seen as detracting from the unique role of Christ. The more common discussion in the Church today is the binding of the ordinary [non-doctrinal] Magisterial teaching on the faithful in matters of morals. For example, some theologians in the late 1960’s argued that Humanae Vitae in 1968 was infallible in its teaching on artificial birth control, but wisely the teaching was not held infallible to a level of the Creed. The constant challenges of new circumstances require that the Magisterium have a certain freedom of movement, which Pope Francis enjoyed in his recent encyclicals Laudato Si and Amoris Laetitia.