The doctrine of Communitas Perfecta or Societas Perfecta teaches that the Church is a self-sufficient or independent society which already has all the necessary resources and conditions to achieve its overall goal of the universal salvation of all peoples. It has historically been used in order to best define Church-State relations. Its origins are in Aristotelian political philosophy, although its adaptation to ecclesiology was done by the Scholastics. The doctrine was widely used in Neoscholastic circles before the Second Vatican Council. After the Council, the doctrine all but vanished from ecclesiological discourse.
This approach of Pius XII moved beyond the "perfect society" model to the "Mystical Body of Christ", but still identified the Body of Christ with the Catholic Church in a way that would be transcended by Vatican II. Lumen gentium, after mentioning "Christ, present to us in His Body, which is the Church", goes on to speak of those who are fully incorporated, conjoined, and related to the Church. This more expansive idea of the Church is developed in the second chapter of Lumen Gentium on the "People of God". And the Council's decree on ecumenism, Unitatis redintegratio, declares that “The Spirit of Christ has not refrained from using as a means of salvation”. This goes beyond the statement in Mystici corporis Christi that says of non-Catholics that “by an unconscious desire and longing they have a certain relationship with the Mystical Body of the Redeemer”. Pius XII can be said to have popularized the notion of the Church as the Body of Christ, while Vatican II went on to "broaden" this notion.
The second chapter of Lumen Gentium is entitled "On the People of God". “People” avoids membership disputes: there are various ways of association; see "Body of Christ" above, which comes from this chapter. Since this chapter of Lumen Gentium comes before Chapter 3 "On the Hierarchical Structure of the Church and in particular on the Episcopate", commentators note that it turns the focus from the hierarchy to the laity, declaring that the Holy Spirit "distributes special graces among the faithful of every rank. By these gifts He makes them fit and ready to undertake the various tasks and offices which contribute toward the renewal and building up of the Church". This is described as a "welcoming judgment on a great mass of theoretical and practical experimentation clamoring for recognition…. The Church´s life does not flow down from Pope thru BB and clergy to a passive laity. It springs up from the grass-roots of the People of God, and the function of authority is co-ordination, authentication and, in exceptional cases, control.”
Subsistence
Subsistence is the doctrine that the Church of Christ "subsists in" the Catholic Church. Subsistit in is a term taken from Lumen Gentium paragraph 8, and is intended to acknowledge that ecclesial elements of the Catholic Church can also be found elsewhere: The theological commission has stated that "the elements which are mentioned concern not only individuals but their communities as well; in this fact precisely is located the foundation of the ecumenical movement." Those who insist that this is a development in the doctrine of the Church often remark that the Second Vatican Council did not say that the Church of Christ "is" the Catholic Church. However, in another document promulgated on the same day as Lumen gentium, the Council did in fact refer to "the Holy Catholic Church, which is the Mystical Body of Christ". Here the traditional conventional expression "is" is used, whose clarity can be used to interpret the potential ambiguity of the phrase "subsists in". Then again, the Council's decree on Ecumenism stated that "all who have been justified by faith in Baptism are members of Christ's body." Claiming the identity of the Catholic Church with the body of Christ goes against four decades of teaching by such eminent ecclesiologists as Yves Congar, George Tavard, Joseph A. Komonchak, and Francis A. Sullivan.
These terms were not used to describe the Church either in the Baltimore Catechism of 1885 or in the Catechism of the Catholic Church of 1992. But the latter describes what is meant here when it says: "At the present time some of his disciples are pilgrims on earth. Others have died and are being purified, while still others are in glory." The latter two are commemorated on All Souls' Day and All Saints' Day..
Roger Haight characterizes the difference in ecclesiologies as "the contrast between a pope with universal jurisdiction and a combination of patriarchal superstructure with an episcopal and synodal communion ecclesiology analogous to that found in Cyprian."
Many Christian churches have nothing approximating the Catholic Sunday celebration of the Mass as sacrifice. This leads to a different understanding of the role of the minister within these churches. At the same time, the notion of the priesthood is evolving within the Catholic church, even as the understanding of sacrifice faces development.
