Second Vatican Council



…if they really want to sell the product, in this secular age, what they ought to do is to redo some of the liturgical music in popular song forms. The Second Vatican Council (Concilium Oecumenicum Vaticanum Secundum, or Vatican II : Papal Boogaloo to the rest of us) was a 1962-1965 ecumenical council (that is, a big gathering of bishops) of the Roman Catholic Church which was convened by Pope John XXIII (and later continued by Pope Paul VI) in order to determine the direction of the Church in an increasingly modern world. In this regard, it finished what Vatican I (nearly a century earlier) had been unable to get around to due to the Italian conquest of Rome. While its reforms are accepted within mainstream Catholicism, both traditionalists and sedevacantists hate it with a burning passion.

Reforms
The assembled bishops approved (and the Pope promulgated) several dogmatic constitutions and other declarations. Some of the most notable are below.

Lumen gentium – Dogmatic Constitution on the Church
Lumen gentium (titled, as with most church documents, for its incipit) is considered to be the main dogmatic statement of Vatican II. It declares, among other things, the following:


 * that " [the church] constituted and organized as a society in the present world, subsists in the Catholic Church, which is governed by the successor of Peter and by the bishops in communion with him, although many elements of sanctification and of truth are found outside its visible confines." This either differs from the historical Catholic understanding that the Church is the Catholic Church or elaborates upon it, depending upon who you ask. Mainstream Catholicism holds that subsistit in is simply a more specific statement than the traditional est, while many traditionalists, especially sedevacantists, think that this is outright heresy.
 * that "the Church recognizes that in many ways she is linked with those who, being baptized, are honored with the name of Christian, though they do not profess the faith in its entirety or do not preserve unity of communion with the successor of Peter", or, in layman's terms, that those silly Protestants are Christians too.
 * that laypeople should strive for holiness just as the clergy ought.
 * that Mary is the mother of the Church and the mediator of salvation. Some at the Council additionally wished to describe her as co-redeemer with Jesus, but this was not written in. Some bishops wished to deal with Mary in an altogether separate document so that Lumen gentium would be more acceptable to non-Catholics, but those leading the council, including the Pope, urged against this, saying that a discussion of Mary's role with regard to the Church belonged in the document on, well, the Church, and so the proposed separation did not occur.

Dignitatis humanae – Declaration on Religious Freedom
This document declares support for freedom of religion, stating that nobody should be forced to profess a given faith, that in particular man's response to (the Christian) God must be free and willing, and also sets forth some principles on dealing with secular states. While it does not exactly mirror the idea of total separation of church and state, it is roughly analogous to the free exercise clause of the United States Constitution's First Amendment.

Nostra aetate – Declaration on the Relation of the Church with Non-Christian Religions
Much to some people's chagrin, this one makes no mention of burning at the stake. Rather, it states the willingness of the Catholic Church to accept certain teachings of other religions when they are consistent with Catholic teachings and can lead people to Christ. It also points out the many things that Muslims and Christians hold in common, and then takes time to say that we can't blame Jesus's death on all the Jews then alive, and we certainly cannot lay the blame at the feet of today's Jews.

Sacrosanctum concilium – Constitution on the Sacred Liturgy
If your grandmother is rambling on about the altar being backwards, the priest being turned around, or something similar, this is why. This document declares that the Mass is to be revised so that "the intrinsic nature and purpose of its several parts, as also the connection between them, may be more clearly manifested." It also encourages greater use of vernacular languages, centuries too late, as well as more Scripture readings during the Mass. Basically, it tried to cut back on the silly ritual aspects of the Mass and replace them with things that would make sense to the folks in the nave.

Gaudium et spes – Pastoral Constitution on the Church in the Modern World
This one declares that "every type of discrimination, whether social or cultural, whether based on sex, race, color, social condition, language or religion, is to be overcome and eradicated as contrary to God's intent..." immediately after going on a rant about how atheists are evil. To the Vatican's credit, it realizes that the term "atheist" can indicate several different things, an idea most Americans still haven't figured out. Would be great for smacking anti-Semitic traditionalists over the head with if they didn't really hate everything to do with Vatican II.

Dei Verbum – Dogmatic Constitution on Divine Revelation
Though often overlooked by non-Catholics, Dei Verbum is actually a fairly substantial and influential document. Literally titled "the Word of God," it details all kinds of information about the nature of God's teachings, including both the Bible and the so-called Sacred Tradition or Magisterium. Some high points:


 * "...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." There is still presumably a traditionalist somewhere decrying this as modernist heresy. Evangelical Protestants presumably also disagree, though they tend not to share the same fascination with all things papal.
 * a nice rebuke to biblical literalists.
 * An insistence that the Gospels were written by the four apostles for whom they are named and present merely different aspects of the same events, contradictions be damned.

It also started a small controversy/debate between the supporters of biblical inerrancy and those of biblical infallibility. Apparently those are different things.

Objections
Disagreement with some or all of Vatican II's reforms is a defining characteristic of traditionalist Catholics. Common objections include the following:


 * You're being just too nice to those derned heretics!
 * You changed my mass! That's heresy!
 * You can't give the infidels *gasp* freedom of religion!
 * General desire to continue blaming the Jews for everything. See Mel Gibson.

In the various sedevacantist churches, these objections are followed up with the claim that the Pope and some variable number of his predecessors are/were heretics and therefore not popes at all. Conclavists take this a step further and "elect" their own pope.