Subsistit in (subsists in) is a Latin phrase which appears in Lumen gentium, the fundamental document on the church from the Second Vatican Council of the Catholic Church. Since the Council the reason for use of the term "subsists in" rather than simply “is” has been disputed. Generally, those who see little or no change in church teaching in Vatican II insist on the equivalence of subsistit in and “is”. Those who point to a new, ecumenical thrust in Vatican II insist that the term was introduced as a compromise after much discussion, and acknowledges new elements in the Council's teaching.
The context of the statement is:
This Church constituted and organized in the world as a society, 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 of its visible structure. These elements, as gifts belonging to the Church of Christ, are forces impelling toward catholic unity. (Lumen Gentium, 8)
This is a debate about externals, the institutional integrity of a church, the fullness of the means of salvation. "There is no question of denying that a non-Catholic community, perhaps lacking much in the order of means, can achieve a higher degree of communion in the life of Christ in faith, hope and love than many a Catholic community."
The Catholic Church used both the "subsists in" and "is" formula in the Second Vatican Council, stating in the Decree on the Eastern Churches: "The Holy Catholic Church, which is the Mystical Body of Christ, is made up of the faithful who are organically united in the Holy Spirit by the same faith, the same sacraments and the same government." Thus the Council itself saw no essential difference between the terms "subsists in" and "is" regarding the identity of the Catholic Church as the one Church of Christ.
The correct meaning of "subsists in" has important implications for how the Catholic Church views itself and its relations with other Christian communities and other religions. Questions have been raised about whether Lumen gentium altered the longstanding phrase according to which the Church of Christ is (Latin est) the Catholic Church, as expressed for example in Mystici corporis Christi which namely states: "this true Church of Jesus Christ - which is the One, Holy, Catholic, Apostolic and Roman Church". Lumen gentium does recognize that other Christian ecclesial communities have elements of sanctification and of truth. And the Council used the traditional term "Church"— in the sense of "particular Church", and not "universal Church"— to refer to the Eastern Churches not in full communion with the Catholic Church. "These Churches," it said, "although separated from us, yet possess true sacraments and above all, by apostolic succession, the priesthood and the Eucharist, whereby they are linked with us in closest intimacy."
After the 16th century Reformation, Catholic theology identified the Church of Christ with the Catholic Church. This continued through the teaching of popes Pius XI and Pius XII. At the Second Vatican Council, the preparatory draft for the Decree on the Church contained this long-held understanding, following Pius XII in identifying the Mystical Body of Christ with the Catholic Church.
The American ecclesiologist Joseph A. Komonchak chronicles the breakdown of this long-held understanding at the Council. The Council's Doctrinal Commission explained the change in the final draft of Lumen gentium from "is" to "subsists in", "so that the expression may better accord with the affirmation about ecclesial elements which are present elsewhere." Komonchak points out that since "some wanted to strengthen the statement, others to weaken it" the Doctrinal Commission decided to stay with the change of verb. He suggests that following "the first rule of conciliar hermeneutics" we should examine statements of Vatican II about these "ecclesial elements" found outside the Catholic Church. He mentions that the same document, Lumen gentium, preferred to speak of those "fully incorporated" into the church and avoided the term "membership". It mentioned that "several elements of sanctification and of truth are found outside its visible structure." Elements mentioned as a part of the church's visible structure that are "present elsewhere" include the Spirit of Christ, the means of salvation, the profession of faith, and sacraments.
This is reinforced in the decree on ecumenism (Unitatis redintegratio) which says: "Very many, of the most significant elements and endowments that together go to build up and to give life to the Church itself can exist outside the visible boundaries of the Catholic Church: the written Word of God, the life of grace, faith, hope, and charity, with other interior gifts of the Holy Spirit, as well as visible elements ... (and) not a few of the sacred actions of the Christian religion." The decree then says that only the Catholic Church has the "fullness of the means of salvation".
Cardinal Walter Kasper has pointed out that, as to this claim that the fullness of the Church of Christ resides in the Catholic Church, this "does not refer to subjective holiness but to the sacramental and institutional means of salvation, the sacraments and the ministries."
Sebastian Tromp, a Dutch Jesuit, a Scholastic theologian and close to Pope Pius XII, is considered to have been the main though unacknowledged author of Mystici corporis Christi. As advisor to Cardinal Alfredo Ottaviani during Vatican II, Tromp was also, according to existing tape recordings and diaries, the father of "subsistit", which to his understanding of Latin did not mean anything new but indicated completeness. But Francis A. Sullivan pointed out:
If one considers the fact that the draft in which "est" had been changed to "subsistit in" was the first one that spoke of “Churches” and “ecclesiastical communities” that are found outside the Catholic Church, one can hardly escape the conclusion that the doctrinal commission did not agree with Tromp, who had forcefully insisted that "subsistit in" must be understood to be exclusivum, with the consequence that outside the Catholic Church there could be nothing but elements.
When in 2007 a statement from the Congregation for the Doctrine of the Faith called into question the contemporary consensus on the import of the use of "subsistit", some identified what they considered to be inconsistencies in the Congregation's own statement, and pointed out that it was at variance with several prominent theologians who took a more liberal interpretation, such as Christopher Butler, Yves Congar, George Tavard, Joseph A. Komonchak, and Francis A. Sullivan.
However, the Catholic Church used both the "subsists in" and "is" formula in the Second Vatican Council, stating in the Decree on the Eastern Churches: "The Holy Catholic Church, which is the Mystical Body of Christ, is made up of the faithful who are organically united in the Holy Spirit by the same faith, the same sacraments and the same government." Thus the Council itself saw no essential difference between the terms "subsists in" and "is", regarding the identity of the Catholic Church as the one Church of Christ, or at least viewed them as complimentary terms.
Some Traditional Catholic groups consider Lumen gentium one of several demarcations of when the post-conciliar Church has issued problematic statements, pointing to the use of "subsistit in" rather than "est" as an abdication of the Church's historic (and to them compulsory) identification of itself alone as God's church.
In an interview with Frankfurter Allgemeine Zeitung, then-Cardinal Ratzinger (later elected Pope Benedict XVI) responded to this criticism as follows: