- 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.
- Haec Ecclesia, in hoc mundo ut societas constituta et ordinata, subsistit in Ecclesia catholica, a successore Petri et Episcopis in eius communione gubernata, licet extra eius compaginem elementa plura sanctificationis et veritatis inveniantur, quae ut dona Ecclesiae Christi propria, ad unitatem catholicam impellunt.
This sentence and the correct meaning of "subsists in" affects the definition of the Church with important implications for how the Catholic Church views itself, its relations with other Christian communities and other religions. Questions have been raised, if Lumen Gentium reworded the longstanding phrase, which stated that the Church of Christ is (Latin est) the Catholic Church. Lumen Gentium does recognize that other Christian ecclesial communities have elements of sanctification and of truth.
Church of Christ is the Catholic Church 
According to some, to say the Church of Christ "subsists in" the Catholic Church introduces a distinction between the Church of Christ and the Catholic Church. Catholic teaching had traditionally, until then, stated unequivocally that "the Mystical Body of Christ and the Roman Catholic Church are one and the same thing", as Pope Pius XII expressed it in his 1950 encyclical Humani generis, 27). The teaching of Pope Pius XII on the identity of the Mystical Body and the Catholic Church in Mystici Corporis was solemn, theologically integrated, but not new.
Paul VI quotes Pius XII 
A supposed reversal of Mystici Corporis by the Ecumenical Council - which incorporated virtually all teachings of Pius XII in over 250 references without caveats, would have not only been a rejection of a major teaching of the late Pontiff. It would have raised serious questions regarding the reliability and nature of Papal teachings on such essential topics like the Church. And, it would have constituted a major attack on the most recent encyclical teachings of the then reigning Pope Paul VI, who had just issued his inaugural encyclical Ecclesiam Suam, on "The Church". Paul VI quoted Mystici Corporis from Pius XII verbatim:
- "Consider, then, this splendid utterance of Our predecessor:
- "The doctrine of the Mystical Body of Christ, which is the Church, a doctrine revealed originally from the lips of the Redeemer Himself, and making manifest the inestimable boon of our most intimate union with so august a Head, has a surpassing splendor which commends it to the meditation of all who are moved by the divine Spirit, and with the light which it sheds on their minds, is a powerful stimulus to the salutary conduct which it enjoins."
Pope Paul VI continues: We wish to take up this invitation and to repeat it in this encyclical, for We consider it timely and urgent and relevant to the needs of the Church in our day.
If such a reversal really occurred, of a highlighted teaching of a reigning Pope "revealed originally from the lips of the Redeemer Himself", it would have surely been noted inside and outside the Church at the time.
Therefore, the Church states that the phrase "subsists in" of Vatican II does not undermine the preceding manner of expressing the identity of the "Church of Christ" and the "Catholic Church", since, as John XXIII said when he opened Vatican II, "The Council … wishes to transmit Catholic doctrine, whole and entire, without alteration or deviation" (speech of 11 October 1962).
Paul VI confirms continuity 
Pope Paul VI when promulgating the Constitution, said the same. The Council teaches that Christ "established… here on earth" a single Church "as an entity with visible delineation… constituted and organized in the world as a society", a Church that has "a social structure" that "serves the spirit of Christ" in a way somewhat similar to how "the assumed nature, inseparably united to him, serves the divine Word as a living organ of salvation". It is this concrete visible organized Church, endowed with a social structure, that the Council says "subsists in the Catholic Church, which is governed by the successor of Peter and by the Bishops in communion with him."
In another document promulgated on the same day (21 November 1964) as Lumen gentium, the Council did in fact refer to "the Holy Catholic Church, which is the Mystical Body of Christ" (Decree Orientalium ecclesiarum, 2). Here the traditional conventional expression "is" is used, whose clarity can be used to interpret the potential ambiguity of the other phrase.
It is also to the Catholic Church, not to some supposed distinct "Church of Christ", that has been entrusted "the fullness of grace and of truth" that gives value to the other Churches and communities that the Holy Spirit uses as instruments of salvation, though the Church of Christ is not said to subsist in any of them.
In fact, the Council combined the two terms "Church of Christ" and "Catholic Church" into a single term, "Christ's Catholic Church" in its Decree on Ecumenism, promulgated at the same time as its Constitution on the Church.
Sebastian Tromp, a Dutch Jesuit, a solid Thomist theologian and close to Pope Pius XII, is considered to have been the main though unacknowledged author of Mystici Corporis. 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.
Elements of sanctification in other Churches and communities 
The Council used the traditional term "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."
However, "the followers of Christ are not permitted to imagine that Christ's Church is nothing more than a collection (divided, but still possessing a certain unity) of Churches and ecclesial communities. Nor are they free to hold that Christ's Church nowhere really exists today and that it is to be considered only as an end which all Churches and ecclesial communities must strive to reach."
Sedevacantist reaction 
Sedevacantist groups consider Lumen Gentium one of several demarcations of when the post-conciliar Church fell into heresy, 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 (now Pope Benedict XVI) responded to this criticism as follows:
- "The concept expressed by 'is' (to be) is far broader than that expressed by 'to subsist'. 'To subsist' is a very precise way of being, that is, to be as a subject, which exists in itself. Thus the Council Fathers meant to say that the being of the Church as such is a broader entity than the Roman Catholic Church, but within the latter it acquires, in an incomparable way, the character of a true and proper subject."
Vatican interpretation 
On June 29, 2007 the Congregation for the Doctrine of the Faith, under the presidency of William Cardinal Levada signed an official document called "Responses to Some Questions Regarding Certain Aspects of the Doctrine on the Church". It was published July 10, 2007.
Benedict XVI, at an audience granted to the Cardinal Prefect of the Congregation for the Doctrine of the Faith, ratified and confirmed these responses, adopted in the Plenary Session of the Congregation, and ordered their publication.
This document closes the argument about the heterodoxical interpretations of subsistit in by making authoritative a definite interpretation of the phrase. Five questions were posed and answered on the subject:
- Did the Second Vatican Council change the Catholic doctrine on the Church?
- The Vatican: The Second Vatican Council neither changed nor intended to change this doctrine, rather it developed, deepened and more fully explained it. This was exactly what John XXIII said at the beginning of the Council. Paul VI affirmed it and commented in the act of promulgating the Constitution Lumen gentium: "There is no better comment to make than to say that this promulgation really changes nothing of the traditional doctrine. What Christ willed, we also will. What was, still is. What the Church has taught down through the centuries, we also teach. In simple terms that which was assumed, is now explicit; that which was uncertain, is now clarified; that which was meditated upon, discussed and sometimes argued over, is now put together in one clear formulation". The Bishops repeatedly expressed and fulfilled this intention.
- What is the meaning of the affirmation that the Church of Christ subsists in the Catholic Church?
- The Vatican: Christ "established here on earth" only one Church and instituted it as a "visible and spiritual community", 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. "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". In number 8 of the Constitution Lumen gentium "subsistence" means this perduring, historical continuity and the permanence of all the elements instituted by Christ in the Catholic Church, 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. 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.
- Why was the expression "subsists in" adopted instead of the simple word "is"?
- The Vatican: 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". "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".
- Why does the Second Vatican Council use the term "Church" in reference to the oriental Churches separated from full communion with the Catholic Church?
- The Vatican: The Council wanted to adopt the traditional use of the term. "Because these Churches, although separated, have true sacraments and above all – because of the apostolic succession – the priesthood and the Eucharist, by means of which they remain linked to us by very close bonds", they merit the title of "particular or local Churches", and are called sister Churches of the particular Catholic Churches. "It is through the celebration of the Eucharist of the Lord in each of these Churches that the Church of God is built up and grows in stature". However, since communion with the Catholic Church, the visible head of which is the Bishop of Rome and the Successor of Peter, is not some external complement to a particular Church but rather one of its internal constitutive principles, these venerable Christian communities lack something in their condition as particular churches. On the other hand, because of the division between Christians, the fullness of universality, which is proper to the Church governed by the Successor of Peter and the Bishops in communion with him, is not fully realised in history.
- 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?
- The Vatican: 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 Mystery cannot, according to Catholic doctrine, be called "Churches" in the proper sense.
The full text of the section that contains this phrase is, in English translation, as follows:
8. Christ, the one Mediator, established and continually sustains here on earth His holy Church, the community of faith, hope and charity, as an entity with visible delineation through which He communicated truth and grace to all. But, the society structured with hierarchical organs and the Mystical Body of Christ, are not to be considered as two realities, nor are the visible assembly and the spiritual community, nor the earthly Church and the Church enriched with heavenly things; rather they form one complex reality which coalesces from a divine and a human element. For this reason, by no weak analogy, it is compared to the mystery of the incarnate Word. As the assumed nature inseparably united to Him, serves the divine Word as a living organ of salvation, so, in a similar way, does the visible social structure of the Church serve the Spirit of Christ, who vivifies it, in the building up of the body. This is the one Church of Christ which in the Creed is professed as one, holy, catholic and apostolic, which our Saviour, after His Resurrection, commissioned Peter to shepherd, and him and the other apostles to extend and direct with authority, which He erected for all ages as "the pillar and mainstay of the truth". 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. Just as Christ carried out the work of redemption in poverty and persecution, so the Church is called to follow the same route that it might communicate the fruits of salvation to men. Christ Jesus, "though He was by nature God . . . emptied Himself, taking the nature of a slave", and "being rich, became poor" for our sakes. Thus, the Church, although it needs human resources to carry out its mission, is not set up to seek earthly glory, but to proclaim, even by its own example, humility and self-sacrifice. Christ was sent by the Father "to bring good news to the poor, to heal the contrite of heart", "to seek and to save what was lost". Similarly, the Church encompasses with love all who are afflicted with human suffering and in the poor and afflicted sees the image of its poor and suffering Founder. It does all it can to relieve their need and in them it strives to serve Christ. While Christ, holy, innocent and undefiled knew nothing of sin, but came to expiate only the sins of the people, the Church, embracing in its bosom sinners, at the same time holy and always in need of being purified, always follows the way of penance and renewal. The Church, "like a stranger in a foreign land, presses forward amid the persecutions of the world and the consolations of God", announcing the cross and death of the Lord until He comes." By the power of the risen Lord it is given strength that it might, in patience and in love, overcome its sorrows and its challenges, both within itself and from without, and that it might reveal to the world, faithfully though darkly, the mystery of its Lord until, in the end, it will be manifested in full light.
- Lumen gentium, 8 (latin). Accessed 2009-06-13. Lumen gentium, 8 (english) Accessed 2011-10-25.
- Peter Hebblethwaite, Pope Paul VI,Paulist Press 1993
- Ecclesiam Suam 31
- "There is no better comment to make than to say that this promulgation really changes nothing of the traditional doctrine. What Christ willed, we also will. What was, still is. What the Church has taught down through the centuries, we also teach." (Speech at the promulgation of the Constitution on the Church and the Decrees on the Eastern Churches and Ecumenism)
- (English) Lumen gentium, 8
- Unitatis redintegratio, 3
- Alexandra von Teuffenbach Die Bedeutung des subsistit in (LG8). Zum Selbstverständnis der katholischen Kirche, Herbert Utz Verlag, München 2002 ISBN ISBN 3-8316-0187-9 and Alexandra von Teuffenbach Konzilstagebuch Sebastian Tromp SJ mit Erläuterungen and Akten aus der Arbeit der Theologischen Kommission, 2006, Editrice Pontificia Università Gregoriana ISBN 978-88-7839-057-7
- Also claiming credit for this phrase in Lumen Gentium is Wilhelm Schmidt, then Pastor of the Protestant Church of the Holy Cross at Bremen-Horn, who states that "At the time I was pastor ... and during the third and fourth sessions, an observer at the Council as the representative of the Evangelical Fraternity Michael, at Cardinal Bea’s invitation. I submitted in writing the formulation “Subsistit in” to the man who was then the theological adviser of Cardinal Frings: Joseph Ratzinger, who relayed it to the Cardinal. ("Catechism Of the Crisis In the Church, Pt. 6, Angelus Online) This is however most unlikely, since Protestant observers did not have an active role in the proceedings. Wilhelm Schmidt is not mentioned in Bea's diary nor does his name come up in the relevant sections of the authoritative autobiography of Cardinal Augustin Bea by St. Schmidt, the autobiographies of Joseph Ratzinger, Karl Rahner, Küng or in any other historical treatease of Vatican II.
- Unitatis redintegratio, 15. It called them "particular or local Churches".
- Unitatis redintegratio, 14; and these particular or local Churches are referred to as "Sister Churches".
- Ut unum sint, 56.
- Mysterium Ecclesiae, 1
- Talk by Fr. Franz Schmidberger, First Assistant to the Superior General of the SSPX (February 22, 2001).
- "ANSWERS TO MAIN OBJECTIONS AGAINST DOMINUS IESUS" by then-Cardinal Joseph Ratzinger (now Pope Benedict XVI)
- Responses to Some Questions Regarding Certain Aspects of the Doctrine on the Church
Further reading 
- Congregation for the Doctrine of the Faith: Declaration Dominus Iesus on the unicity and salvific universality of Jesus Christ and the Church
- An Examination of Subsistit in: A Profound Theological Perspective, by Fr. Karl Josef Becker, S.J.
- "A Response to Karl Becker, S.J., on the Meaning of Subsistit In", Francis A. Sullivan, S.J., Theological Studies, v. 67 (2006), pp. 395–409.
- Definition of the Latin verb subsistere from Perseus