As the Second Vatican Council got underway, it was commonly supposed that the assembled bishops — 2,400 of them filed into St. Peter’s Basilica for the opening session on Oct. 11, 1962 — would meet for a few weeks, ratify some documents written for them in advance, and then go home.

Nothing much would change. The council would be declared a success. That would be that.

When Vatican II came to a close on Dec. 7, 1965, after four momentous sessions, everyone realized that something historic had occurred. Today, 50 years later, the 21st ecumenical council in the history of the Church is widely considered the most important Catholic event in centuries — arguably, the most important since the Council of Trent more than 400 years earlier.

Understanding the Council

The most readily visible answer can be found in the 103,000 Latin words of its 16 documents. Among the topics covered are, to mention only a few, the nature of the Church, understanding the Bible, renewing the liturgy, and the role of the Catholic Church in the modern world. Taken together, the documents of Vatican II offer a sweeping agenda for updating Catholicism (aggiornamento) by means of a return to the sources of Christian faith and practice (ressourcement).

Early in the game, another view emerged as a competitor to the emphasis on the council’s actual decisions. It argued that what really mattered wasn’t what the council said, but the conciliar process itself. This view came to be called “the spirit of Vatican II.” Marking a sharp break with the past, it sought to open the door to ongoing, open-ended change.

That viewpoint was roundly rejected by Pope Benedict XVI. As a young theologian, Father Joseph Ratzinger had an important role at the council. In December 2005, addressing the Roman Curia, Pope Benedict pointed to two different ways of interpreting Vatican II. One he called “a hermeneutic of discontinuity and rupture,” which he accused of causing “confusion” in the years since the council; the other was a “hermeneutic of reform” rooted in tradition and committed to “renewal in the continuity of the one subject-Church.”

This second approach is the correct way of understanding Vatican II, Pope Benedict said. (Pope Francis, the first pope since Vatican II not to have been a council participant, has said he agrees.)

The Major Issues

What, then, was the council all about? In a famous speech opening the council, Pope St. John XXIII, the man who convoked it, said its primary purpose was “that the sacred deposit of Christian doctrine be guarded and taught more effectively.” Speaking at its closing session, Pope Paul VI, Pope John’s successor, said, “His great purpose has now been achieved.”

Along the way, nevertheless, Vatican II did a great deal else besides. Many volumes have been written spelling out — and sometimes arguing over — what that was. What follows here are highlights to just a few major issues.

It is sometimes said the great central theme of the Second Vatican Council was the Church itself. Indeed, Vatican II’s doctrinal centerpiece, the Dogmatic Constitution on the Church (Lumen Gentium is its Latin name), discusses the nature and structure of the Church at length and makes important theological and pastoral points.

The constitution considers the Church in its aspect as a communio, or communion — a community of faith whose members, hierarchically structured and uniquely joined to one another by the action of the Holy Spirit, work together on behalf of the glory of God, the spreading of the Gospel and the salvation of souls.

In speaking of the Church, Vatican II revives the ancient principle of collegiality. This is the doctrine that today’s bishops, like Jesus’ Twelve Apostles, whose successors they are, make up a “college” whose members share in the task of teaching and governing the universal Church in union with the pope. During the council, Pope Paul acted to implement this insight by establishing a new collegial body — the world Synod of Bishops — to advise the Bishop of Rome.

Vatican II also set a new task for itself as an ecumenical council in undertaking to produce another document — the Pastoral Constitution on the Church in the Modern World (Gaudium et Spes — Joy and Hope). This pastoral constitution, at more than 23,000 words the council’s longest document, takes up a broad range of contemporary issues extending from marriage and family life to economic development, modern warfare and nuclear weapons. This marked the first time an ecumenical council had sought to address the secular world of its time regarding a host of social, political and economic problems it faced.

Perhaps because this had never been done before — as well as because of some of its analyses and judgments — Gaudium et Spes was controversial from the start and the final verdict on it was mixed. The consensus view was that it was a good first try. In a newspaper report at the time, later published in a book called “Theological Highlights of Vatican II,” Father Ratzinger wrote the following concerning the pastoral constitution: “What was important … was that it recognized these problems and moved toward solving them. We must go on from there.”

Vatican II also broke new ground in its discussion of the laity and their place in the Church. This was the first time an ecumenical council had devoted so much attention specifically to laypeople, with the laity receiving their own chapter in the Dogmatic Constitution on the Church in addition to being the subject of an entire document — the Decree on the Apostolate of the Laity (Apostolicam Actuositatem).

In view of developments since Vatican II emphasizing ministries performed by laypeople in their parishes and other structures of the Church, it’s noteworthy that the council gives pride of place to the laity’s apostolate in and to the secular world.

Declaring that the call to apostolate comes to laypeople directly through their reception of the Sacraments of Baptism and Confirmation, the Dogmatic Constitution on the Church says this: “The lay apostolate … is a participation in the salvific mission of the Church…. The laity are called in a special way to make the Church present and operative in those places and circumstances where only through them can it become the salt of the earth” (No. 33).

Possibly the most important thing Vatican II said about the laity, however, was to affirm that they, just as much as priests and religious, are called to holiness. The Church had always recognized this fundamental fact, but for a long time, as a practical matter, it was common to propose a legalistic, minimal version of spirituality to laywomen and men. Its principal elements: go to Mass on Sunday; obey the laws of the Church; try to avoid serious sins; be sure to confess sins if you nevertheless fall.

These are all obviously good and necessary things to do. But the council also offered lay members of the Church a loftier vision.

There is “a common dignity as members from their regeneration in Christ, having the same filial grace and the same vocation to perfection; possessing in common one salvation, one hope and one undivided charity” (No. 32). And again, “Thus it is evident to everyone, that all the faithful of Christ of whatever rank or status, are called to the fullness of the Christian life and to the perfection of charity; by this holiness as such a more human manner of living is promoted in this earthly society” (No. 40).

What the council says about the liturgy and about sacred Scripture can best be understood against this background.

For example, the Constitution on the Liturgy, declaring public worship to be the “summit” toward which all the Church’s activity is directed and the “fount” from which all its power comes, instructs pastors to make sure the faithful participate in the liturgy “fully aware of what they are doing, actively engaged in the rite, and enriched by it” (see Sacrosanctum Concilium, Nos. 5-13).

And the Dogmatic Constitution on Divine Revelation, recalling St. Jerome’s saying that “ignorance of the Scriptures is ignorance of Christ,” urges greater efforts to make study and use of the Bible an integral part of the prayer and worship of lay Catholics (see Dei Verbum, No. 25).

In his firsthand account of Vatican II, Father Ratzinger remarked that the decisions of an ecumenical council are “a beginning.” A council’s real importance, he explained, “is only achieved in its translation into the realities of everyday Church life.”

In the last 50 years, much has been done to “translate” Vatican II principles like the ones sketched here into Church life. Conflict and controversy have often accompanied the effort. Much remains to be done.

That’s hardly a surprise. “The century following each council has ever been a time of great trial,” Father John Henry Newman wrote at the time of Vatican Council I (1869-70). At the half century mark since Vatican II, that leaves another half century to go. It should be interesting.

Russell Shaw is a prolific author and is former communications director for the U.S. Conference of Catholic Bishops. He also serves as Our Sunday Visitor’s Washington correspondent.