As I said in my last post I will be posting sections from the commentary the CDF released on its document on the Church. I found the commentary an enlightening read. Let me quote some sections for you that I particularly enjoyed. I've may add the occasional comment in parenthesis to make things clearer and use bold emphasis.
"This publication (referring to the document), based on the conciliar and postconciliar texts which it cites, reflects the concern of the Congregation to safeguard the unity and unicity of the Church, which would be compromised by the proposal that the Church founded by Christ could have more than one subsistence. If this were the case we would be forced, as the Declaration Mysterium Ecclesiae puts it, to imagine "the Church of Christ as the sum total of the Churches or the ecclesial Communities – which are simultaneously differentiated and yet united", or "to think that the Church of Christ no longer exists today concretely and therefore can only be the object of research for the Churches and the communities." If this were the case, the Church of Christ would not any longer exist in history, or would exist only in some ideal form emerging either through some future convergence or through the reunification of the diverse sister Churches, to be hoped for and achieved through dialogue."
Reference is made here to the document Mysterium Ecclesiae. This was issued by the CDF back in the early seventies for the same reason the current document has been issued and for the same reason Dominus Jesus was issued. It is a relatively short document, only taking up a few pages in my copy of Flannery's postconcilar documents. If readers have the time and resources I recommend becoming familiar with it.
"The Notification of the Congregation for the Doctrine of the Faith concerning a book of Leonardo Boff is even more explicit. In response to Boff's assertion that the one Church of Christ "is able to subsist in other Christian Churches", the Notification states that "the Council chose the word "subsistit" specifically to clarify that the true Church has only one "subsistence", while outside her visible boundaries there are only "elementa Ecclesiae" which – being elements of the same Church – tend and lead to the Catholic Church." "
Here we see another reference to "visible boundaries." When attention is focused solely on the visible boundaries it becomes quite correct to say as Pius XII did in Humani Generis that "the .. Catholic Church and the Mystical Body of Christ are one and the same thing." Here Pius was reaffirming his teaching in Mystici Corporis Christi.
"In reality, all the Council Fathers simply intended to do was to recognise the presence of ecclesial elements proper to the Church of Christ in the non-Catholic Christian communities. It does not follow that the identification of the Church of Christ with the Catholic Church no longer holds, nor that outside the Catholic Church there is a complete absence of ecclesial elements, a 'churchless void'. "
It gets better:
"In fact, precisely because the Church willed by Christ actually continues to exist (subsistit in) in the Catholic Church, this continuity of subsistence implies an essential identity between the Church of Christ and the Catholic Church. The Council wished to teach that we encounter the Church of Jesus Christ as a concrete historical subject in the Catholic Church. The idea, therefore, that subsistence can somehow be multiplied does not express what was intended by the choice of the term "subsistit". In choosing the word "subsistit" the Council intended to express the singularity and non "multipliability" of the Church of Christ: the Church exists as a unique historical reality."
And the last section I want to quote:
"Contrary to many unfounded interpretations, therefore, the change from "est" to "subsistit" does not signify that the Catholic Church has ceased to regard herself as the one true Church of Christ. Rather it simply signifies a greater openness to the ecumenical desire to recognise truly ecclesial characteristics and dimensions in the Christian communities not in full communion with the Catholic Church, on account of the "plura elementa sanctificationis et veritatis" present in them. Consequently, although there is only one Church which "subsists" in one unique historical subject there are true ecclesial realities which exist beyond its visible boundaries. "