So, the Church doesn't change. Surprised yet?
First Question: Did the Second Vatican Council change the Catholic doctrine on the Church?
Response: The Second Vatican Council neither changed nor intended to change this doctrine, rather it developed, deepened and more fully explained it.
So, other Christians are okay, but not as cool as us.
Second Question: What is the meaning of the affirmation that the Church of Christ subsists in the Catholic Church?
Response: Christ "established here on earth" only one Church and instituted it as a "visible and spiritual community"5, that from its beginning and throughout the centuries has always existed and will always exist, and in which alone are found all the elements that Christ himself instituted.6 "This one Church of Christ, which we confess in the Creed as one, holy, catholic and apostolic […]. This Church, constituted and organised in this world as a society, subsists in the Catholic Church, governed by the successor of Peter and the Bishops in communion with him"7.
In number 8 of the Dogmatic Constitution Lumen Gentium ‘subsistence’ means this perduring, historical continuity and the permanence of all the elements instituted by Christ in the Catholic Church8, in which the Church of Christ is concretely found on this earth.
It is possible, according to Catholic doctrine, to affirm correctly that the Church of Christ is present and operative in the churches and ecclesial Communities not yet fully in communion with the Catholic Church, on account of the elements of sanctification and truth that are present in them.9 Nevertheless, the word "subsists" can only be attributed to the Catholic Church alone precisely because it refers to the mark of unity that we profess in the symbols of the faith (I believe... in the "one" Church); and this "one" Church subsists in the Catholic Church.10
Defective Church? They don't make them like they used to!
Third Question: Why was the expression "subsists in" adopted instead of the simple word "is"?
Response: The use of this expression, which indicates the full identity of the Church of Christ with the Catholic Church, does not change the doctrine on the Church. Rather, it comes from and brings out more clearly the fact that there are "numerous elements of sanctification and of truth" which are found outside her structure, but which "as gifts properly belonging to the Church of Christ, impel towards Catholic Unity"11.
"It follows that these separated churches and Communities, though we believe they suffer from defects, are deprived neither of significance nor importance in the mystery of salvation. In fact the Spirit of Christ has not refrained from using them as instruments of salvation, whose value derives from that fullness of grace and of truth which has been entrusted to the Catholic Church"12.
We'll see how this one goes over.
Fifth Question: Why do the texts of the Council and those of the Magisterium since the Council not use the title of "Church" with regard to those Christian Communities born out of the Reformation of the sixteenth century?
Response: According to Catholic doctrine, these Communities do not enjoy apostolic succession in the sacrament of Orders, and are, therefore, deprived of a constitutive element of the Church. These ecclesial Communities which, specifically because of the absence of the sacramental priesthood, have not preserved the genuine and integral substance of the Eucharistic Mystery19 cannot, according to Catholic doctrine, be called "Churches" in the proper sense20.