Communionis Notio

The concept of communion (koinonRa), which appears with a certain prominence in the texts of the Second Vatican Council^{1Cf. Const. Lumen gentium, nn. 4, 8, 13-15, 18, 21, 24-25; Const. Dei Verbum, n. 10; Const. Gaudium et spes, n. 32; Decr. Unitatis redintegratio, nn. 2-4, 14-15, 17-19, 22.}, is very suitable for expressing the core of the Mystery of the Church, and can certainly be a key for the renewal of Catholic ecclesiology^{2Cf. SYNOD OF BISHOPS, Second Extraordinary Assembly (1985), Relatio finalis, II, C), 1.}. A deeper appreciation of the fact that the Church is a Communion is, indeed, a task of special importance, which provides ample latitude for theological reflection on the mystery of the Church, "whose nature is such that it always admits new and deeper exploring"^{3PAUL VI, Opening address for the second period of the Second Vatican Council, 29-IX-1963: AAS 55 (1963) p. 848. Cf., for example, the perspectives for further reflection indicated by the INTERNATIONAL THEOLOGICAL COMMISSION, in its Themata selecta de ecclesiologia: "Documenta (1969-1985)", Lib. Ed. Vaticana 1988, pp. 462-559.}. However, some approaches to ecclesiology suffer from a clearly inadequate awareness of the Church as a mystery of communion, especially insofar as they have not sufficiently integrated the concept of communion with the concepts of People of God and of the Body of Christ, and have not given due importance to the relationship between the Church as communion and the Church as sacrament.

Bearing in mind the doctrinal, pastoral and ecumenical importance of the different aspects regarding the Church understood as Communion, the Congregation for the Doctrine of the Faith has considered it opportune, by means of this Letter, to recall briefly and to clarify, where necessary, some of the fundamental elements that are to be considered already settled also by those who undertake the hoped-for theological investigation.

The concept of communion lies "at the heart of the Church's selfunderstanding"^{4JOHN PAUL II, Address to the Bishops of the United Sates of America, 16-IX-1987, n. 1: "Insegnamenti di Giovanni Paolo II" X, 3 (1987) p. 553.}, insofar as it is the Mystery of the personal union of each human being with the divine Trinity and with the rest of mankind, initiated with the faith^{51 Jn 1, 3: "that which we have seen and heard, we proclaim also to you, so that you may have fellowship with us; and our fellowship is with the Father and with his Son Jesus Christ". Cf. also 1 Cor 1, 9; JOHN PAUL II, Ap. Exh. Christifideles laici, 30-XII-1988, n. 19; SYNOD OF BISHOPS (1985), Relatio finalis, II,}, and, having begun as a reality in the Church on earth, is directed towards its eschatological fulfilment in the heavenly Church^{6Cf. Phil 3, 20-21; Col 3, 1-4; Const. Lumen gentium, n. 48.}. If the concept of communion, which is not a univocal concept, is to serve as a key to ecclesiology, it has to be understood within the teaching of the Bible and the patristic tradition, in which communion always involves a double dimension: the vertical (communion with God) and the horizontal (communion among men). It is essential to the Christian understanding of communion that it be recognised above all as a gift from God, as a fruit of God's initiative carried out in the paschal mystery. The new relationship between man and God, that has been established in Christ and is communicated through the sacraments, also extends to a new relationship among human beings. As a result, the concept of communion should be such as to express both the sacramental nature of the Church while "we are away from the Lord"^{72 Cor 5, 6. Cf. Const. Lumen gentium, n. 1.}, and also the particular unity which makes the faithful into members of one and the same Body, the Mystical Body of Christ^{8Cf. ibidem, no. 7; PIUS XII, Enc. Mystici Corporis, 29-VI-1943: AAS 35 (1943) pp. 200ff.}, an organically structured community^{9Cf. Const. Lumen gentium, n. 11/a.}, "a people brought into one by the unity of the Father and of the Son and of the Holy Spirit"^{10ST. CYPRIAN, De Oratione Dominica, 23: PL 4, 553; cf. Const. Lumen gentium, n. 4/b.}, and endowed with suitable means for its visible and social union^{11Cf. Const. Lumen gentium, n. 9/c.}.

Ecclesial communion is at the same time both invisible and visible. As an invisible reality, it is the communion of each human being with the Father through Christ in the Holy Spirit, and with the others who are fellow sharers in the divine nature^{12Cf. 2 Pet 1, 4.}, in the passion of Christ^{13Cf. 2 Cor 1, 7.}, in the same faith^{14Cf. Eph 4, 13; Philem 6.}, in the same spirit^{15Cf. Phil 2, 1.}. In the Church on earth, there is an intimate relationship between this invisible communion and the visible communion in the teaching of the Apostles, in the sacraments and in the hierarchical order. By means of these divine gifts, which are very visible realities, Christ carries out in different ways in history his prophetical, priestly and kingly function for the salvation of mankind^{16Cf. Const. Lumen gentium, nos. 25-27.}. This link between the invisible and visible elements of ecclesial communion constitutes the Church as the Sacrament of salvation. From this sacramentality it follows that the Church is not a reality closed in on herself; rather, she is permanently open to missionary and ecumenical endeavour, for she is sent to the world to announce and witness, to make present and spread the mystery of communion which is essential to her: to gather together all people and all things into Christ^{17Cf. Mt 28, 19-20; Jn 17, 21-23; Eph 1, 10; Const. Lumen gentium, nn. 9/b, 13 and 17; Decr. Ad gentes, nn. 1 and 5; ST. IRENAEUS, Adversus haereses, III, 16, 6 and 22, 1-3: PG 7, 925-926 and 955-958.}; so as to be for all an "inseparable sacrament of unity"^{18ST. CYPRIAN, Epist. ad Magnum, 6: PL 3, 1142.}.

Ecclesial communion, into which each individual is introduced by faith and by Baptism^{19Eph 4, 4-5: "There is one body and one Spirit, just as you were called to the one hope that belongs to your call, one Lord, one faith, one baptism". Cf. also Mk 16, 16.}, has its root and centre in the Blessed Eucharist. Indeed, Baptism is an incorporation into a body that the risen Lord builds up and keeps alive through the Eucharist, so that this body can truly be called the Body of Christ. The Eucharist is the creative force and source of communion among the members of the Church, precisely because it unites each one of them with Christ himself: "Really sharing in the body of the Lord in the breaking of the eucharistic bread, we are taken up into communion with him and with one another. 'Because the bread is one, we, though many, are one body, all of us who partake of the one bread' (1 Cor 10, 17)"^{20Const. Lumen gentium, n. 7/b. The Eucharist is the sacrament "through which in the present age the Church is made" (ST. AUGUSTINE, Contra Faustum, 12, 20: PL 42, 265). "Our sharing in the body and blood of Christ leads to no other end than that of transforming us into that which we receive" (ST. LEO THE GREAT, Sermo 63, 7: PL 54, 357).}. Hence, the pauline expression the Church is the Body of Christ means that the Eucharist, in which the Lord gives us his Body and transforms us into one Body^{21Cf. Const. Lumen gentium, nn. 3 and 11/a; ST. JOHN CHRYSOSTOM, In 1 Cor. hom., 24, 2: PG 61, 200.}, is where the Church expresses herself permanently in most essential form. While present everywhere, she is yet only one, just as Christ is one.

The Church is a Communion of the saints, to use a traditional expression that is found in the Latin versions of the Apostles' Creed from the end of the fourth century^{22Cf. Denz.-Sch`n. 19, 26-30.}. The common visible sharing in the goods of salvation (the holy things), and especially in the Eucharist, is the source of the invisible communion among the sharers (the saints). This communion brings with it a spiritual solidarity among the members of the Church, insofar as they are members of one same Body^{23Cf. 1 Cor 12, 25-27; Eph 1, 22-23; 3, 3-6.}, and it fosters their effective union in charity by constituting "one heart and soul"^{24Acts 4, 32.}. Communion tends also towards union in prayer^{25Cf. Acts 2, 42.}, inspired in all by one and the same Spirit^{26Cf. Rom 8, 15-16.26; Gal 4, 6; Const. Lumen gentium, n. 4.}, the Holy Spirit "who fills and unites the whole Church"^{27ST. THOMAS AQUINAS, De Veritate, q. 29, a. 4 c. Indeed, "lifted up on the cross and glorified, the Lord Jesus poured forth the Spirit whom he had promised, and through whom he has called and gathered together the people of the New Covenant, which is the Church, into a unity of faith, hope and charity" (Decr. Unitatis redintegratio, n. 2/b).}. In its invisible elements, this communion exists not only among the members of the pilgrim Church on earth, but also between these and all who, having passed from this world in the grace of the Lord, belong to the heavenly Church or will be incorporated into it after having been fully purified^{28Cf. Const. Lumen gentium, n. 49.}. This means, among other things, that there is a mutual relationship between the pilgrim Church on earth and the heavenly Church in the historical-redemptive mission. Hence the ecclesiological importance not only of Christ's intercession on behalf of his members^{29Cf. Heb 7, 25.}, but also of that of the saints and, in an eminent fashion, of the Blessed Virgin Mary's^{30Cf. Const. Lumen gentium, nn. 50 and 66.}. Devotion to the saints, which is such a strong feature of the piety of the christian people, can thus be seen to correspond in its very essence to the profound reality of the Church as a mystery of communion.

The Church of Christ, which we profess in the Creed to be one, holy, catholic and apostolic, is the universal Church, that is, the worldwide community of the disciples of the Lord^{31Cf. Mt 16, 18; 1 Cor 12, 28; etc.}, which is present and active amid the particular characteristics and the diversity of persons, groups, times and places. Among these manifold particular expressions of the saving presence of the one Church of Christ, there are to be found, from the times of the Apostles on, those entities which are in themselves Churches^{32Cf. Acts 8, 1; 11, 22; 1 Cor 1, 2; 16, 19; Gal 1, 22; Rev 2, 1.8; etc.}, because, although they are particular, the universal Church becomes present in them with all its essential elements^{33Cf. PONTIFICAL BIBLICAL COMMISSION, UnitJ et diversitJ dans l'Eglise, Lib. Ed. Vaticana 1989, especially, pp. 14-28.}. They are therefore constituted "after the model of the universal Church"^{34Const. Lumen gentium, n. 23/a; cf. Decr. Ad gentes, n. 20/a.}, and each of them is "a portion of the People of God entrusted to a bishop to be guided by him with the assistance of his clergy"^{35Decr. Christus Dominus, n. 11/a.}.

The universal Church is therefore the Body of the Churches^{36Const. Lumen gentium, n. 23/b. Cf. ST. HILARY OF POITIERS, In Psalm., 14, 3: PL 9, 301; ST. GREGORY THE GREAT, Moralia, IV, 7, 12: PL 75, 643.}. Hence it is possible to apply the concept of communion in analogous fashion to the union existing among particular Churches, and to see the universal Church as a Communion of Churches. Sometimes, however, the idea of a "communion of particular Churches" is presented in such a way as to weaken the concept of the unity of the Church at the visible and institutional level. Thus it is asserted that every particular Church is a subject complete in itself, and that the universal Church is the result of a reciprocal recognition on the part of the particular Churches. This ecclesiological unilateralism, which impoverishes not only the concept of the universal Church but also that of the particular Church, betrays an insufficient understanding of the concept of communion. As history shows, when a particular Church has sought to become self-sufficient, and has weakened its real communion with the universal Church and with its living and visible centre, its internal unity suffers too, and it finds itself in danger of losing its own freedom in the face of the various forces of slavery and exploitation^{37Cf. PAUL VI, Ap. Exh. Evangelii nuntiandi, 8-XII-1975, n. 64/b.}.

In order to grasp the true meaning of the analogical application of the term communion to the particular Churches taken as a whole, one must bear in mind above all that the particular Churches, insofar as they are "part of the one Church of Christ"^{38Decr. Christus Dominus, n. 6/c.}, have a special relationship of "mutual interiority"^{39JOHN PAUL II, Address to the Roman Curia, 20-XII-1990, n. 9: "L'Osservatore Romano", 21-XII-1990, p. 5.} with the whole, that is, with the universal Church, because in every particular Church "the one, holy, catholic and apostolic Church of Christ is truly present and active"^{40Decr. Christus Dominus, n. 11/a.}. For this reason, "the universal Church cannot be conceived as the sum of the particular Churches, or as a federation of particular Churches"^{41JOHN PAUL II, Address to the Bishops of the United States of America, 16-IX-1987, n. 3: as quoted, p. 555.}. It is not the result of the communion of the Churches, but, in its essential mystery, it is a reality ontologically and temporally prior to every individual particular Church. Indeed, according to the Fathers, ontologically, the Church-mystery, the Church that is one and unique, precedes creation^{42Cf. SHEPHERD OF HERMAS, Vis. 2, 4: PG 2, 897-900; ST. CLEMENT OF ROME, Epist. II ad Cor., 14, 2: Funck, 1, 200.}, and gives birth to the particular Churches as her daughters. She expresses herself in them; she is the mother and not the product of the particular Churches. Furthermore, the Church is manifested, temporally, on the day of Pentecost in the community of the one hundred and twenty gathered around Mary and the twelve Apostles, the representatives of the one unique Church and the founders-to-be of the local Churches, who have a mission directed to the world: from the first the Church speaks all languages^{43Cf. Acts 2, 1ff. ST IRENAEUS, Adversus haereses, III, 17, 2 (PG 7, 929-930): "at Pentecost (...) all nations (...) had become a marvellous choir to intone a hymn of praise to God in perfect harmony, because the Holy Spirit had brought distances to nought, eliminated discordant notes and transformed the varieties of the peoples into the first-fruits to be offered to the Father". Cf. also ST. FULGENTIUS OF RUSPE, Sermo 8 in Pentecoste, 2-3: PL 65, 743-744.}. From the Church, which in its origins and its first manifestation is universal, have arisen the different local Churches, as particular expressions of the one unique Church of Jesus Christ. Arising within and out of the universal Church, they have their ecclesiality in it and from it. Hence the formula of the Second Vatican Council: The Church in and formed out of the Churches (Ecclesiae in et ex Ecclesia)^{44Const. Lumen gentium, n. 23/a: "it is in these and formed out of them that the one and unique Catholic Church exists". This doctrine develops in the same line of continuity what had been stated previously, for example by PIUS X, Enc. Mystici Corporis, as quoted, p. 211: "out of which the one Catholic Church exists and is composed".}, is inseparable from this other formula: The Churches in and formed out of the Church (Ecclesiae in et ex Ecclesia)^{45Cf. JOHN PAUL II, Address to the Roman Curia, 20-XII-1990, n. 9: as quoted, p. 5.}. Clearly the relationship between the universal Church and the particular Churches is a mystery, and cannot be compared to that which exists between the whole and the parts in a purely human group or society.

Every member of the faithful, through faith and Baptism, is inserted into the one, holy, catholic and apostolic Church. He or she does not belong to the universal Church in a mediate way, through belonging to a particular Church, but in an immediate way, even though entry into and life within the universal Church are necessarily brought about in a particular Church. From the point of view of the Church understood as communion, this means therefore that the universal communion of the faithful and the communion of the Churches are not consequences of one another, but constitute the same reality seen from different viewpoints. Moreover, one's belonging to a particular Church never conflicts with the reality that in the Church no-one is a stranger^{46Cf. Gal. 3, 28.}: each member of the faithful, especially in the celebration of the Eucharist, is in his or her Church, in the Church of Christ, regardless of whether or not he or she belongs, according to canon law, to the diocese, parish or other particular community where the celebration takes place. In this sense, without impinging on the necessary regulations regarding juridical dependence^{47Cf., for example, C.I.C., can. 107.}, whoever belongs to one particular Church belongs to all the Churches; since belonging to the Communion, like belonging to the Church, is never simply particular, but by its very nature is always universal^{48ST. JOHN CHRYSOSTOM, In Ioann. hom., 65, 1 (PG 59, 361): "whoever is in Rome knows that the Indians are his members". Cf. Const. Lumen gentium, n. 13/b.}.

Unity, or communion, between the particular Churches in the universal Church, is rooted not only in the same faith and in the common Baptism, but above all in the Eucharist and in the Episcopate. It is rooted in the Eucharist because the eucharistic Sacrifice, while always performed in a particular community, is never a celebration of that community alone. In fact, the community, in receiving the eucharistic presence of the Lord, receives the entire gift of salvation and shows, even in its lasting visible particular form, that it is the image and true presence of the one, holy, catholic and apostolic Church^{49Cf. Const. Lumen gentium, n. 26/a; ST. AUGUSTINE, In Ioann. Ev. Tract., 26, 13: PL 35, 1612-1613.}. The rediscovery of a eucharistic ecclesiology, though being of undoubted value, has however sometimes placed unilateral emphasis on the principle of the local Church. It is claimed that, where the Eucharist is celebrated, the totality of the mystery of the Church would be made present in such a way as to render any other principle of unity or universality non-essential. Other conceptions, under different theological influences, present this particular view of the Church in an even more radical form, going as far as to hold that gathering together in the name of Jesus (cf. Mt 18, 20) is the same as generating the Church: the assembly which in the name of Christ becomes a community, would hold within itself the powers of the Church, including power as regards the Eucharist. The Church, some say, would arise "from base level". These and other similar errors do not take sufficiently into account that it is precisely the Eucharist that renders all self-sufficiency on the part of the particular Churches impossible. Indeed, the unicity and indivisibility of the eucharistic Body of the Lord implies the unicity of his mystical Body, which is the one and indivisible Church. From the eucharistic centre arises the necessary openness of every celebrating community, of every particular Church; by allowing itself to be drawn into the open arms of the Lord, it achieves insertion into his one and undivided Body. For this reason too, the existence of the Petrine ministry, which is a foundation of the unity of the Episcopate and of the universal Church, bears a profound correspondence to the eucharistic character of the Church.

In fact, the unity of the Church is also rooted in the unity of the Episcopate^{50Cf. Const. Lumen gentium, nn. 18/b, 21/b. 22/a. Cf. also ST. CYPRIAN, De unitate Ecclesiae, 5: PL 4, 516-517; ST. AUGUSTINE, In Ioann. Ev. Tract., 46, 5: PL 35, 1730.}. As the very idea of the Body of the Churches calls for the existence of a Church that is Head of the Churches, which is precisely the Church of Rome, "foremost in the universal communion of charity"^{51ST. IGNATIUS OF ANTIOCH, Epist. ad Rom., prol.: PG 5, 685; cf. Const. Lumen gentium, n. 13/c.}, so too the unity of the Episcopate involves the existence of a Bishop who is Head of the Body or College of Bishops, namely the Roman Pontiff^{52Cf. Const. Lumen gentium, n. 22/b.}. Of the unity of the Episcopate, as also of the unity of the entire Church, "the Roman Pontiff, as the successor of Peter, is a perpetual and visible source and foundation"^{53Ibidem, n. 23/a. Cf. Const. Pastor aeternus: Denz.-Sch`n. 3051-3057; ST. CYPRIAN, De unitate Ecclesiae, 4: PL 4, 512-515.}. This unity of the Episcopate is perpetuated through the centuries by means of the apostolic succession, and is also the foundation of the identity of the Church of every age with the Church built by Christ upon Peter and upon the other Apostles^{54Cf. Const. Lumen gentium, n. 20; ST. IRENAEUS, Adversus haereses, III, 3, 1-3: PG 7, 848-849; ST. CYPRIAN, Epist. 27, 1: PL 4, 305-306; ST. AUGUSTINE, Contra advers. legis et prophet., 1, 20, 39: PL 42, 626.}.

The Bishop is a visible source and foundation of the unity of the particular Church entrusted to his pastoral ministry^{55Cf. Const. Lumen gentium, n. 23/a.}. But for each particular Church to be fully Church, that is, the particular presence of the universal Church with all its essential elements, and hence constituted after the model of the universal Church, there must be present in it, as a proper element, the supreme authority of the Church: the Episcopal College "together with their head, the Supreme Pontiff, and never apart from him"^{56Ibidem, n. 22/b; cf also n. 19.}. The Primacy of the Bishop of Rome and the episcopal College are proper elements of the universal Church that are "not derived from the particularity of the Churches"^{57JOHN PAUL II, Address to the Roman Curia, 20-XII-1990, n. 9: as quoted, p. 5.}, but are nevertheless interior to each particular Church. Consequently "we must see the ministry of the Successor of Peter, not only as a 'global' service, reaching each particular Church from 'outside', as it were, but as belonging already to the essence of each particular Church from 'within'"^{58JOHN PAUL II, Address to the Bishops of the United States of America, 16-IX-1987, n. 4: as quoted, p. 556.}. Indeed, the ministry of the Primacy involves, in essence, a truly episcopal power, which is not only supreme, full and universal, but also immediate, over everybody, whether Pastors or other faithful^{59Cf. Const. Pastor aeternus, chap. 3: Denz.-Sch`n 3064; Const. Lumen gentium, n. 22/b.}. The ministry of the Successor of Peter as something interior to each particular Church is a necessary expression of that fundamental mutual interiority between universal Church and particular Church^{60Cf. supra, n. 9.}.

The unity of the Eucharist and the unity of the Episcopate with Peter and under Peter are not independent roots of the unity of the Church, since Christ instituted the Eucharist and the Episcopate as essentially interlinked realities^{61Cf. Const. Lumen gentium, n. 26; ST. IGNATIUS OF ANTIOCH, Epist. ad Philadel., 4: PG 5, 700; Epist. ad Smyrn., 8: PG 5, 713.}. The Episcopate is one, just as the Eucharist is one: the one Sacrifice of the one Christ, dead and risen. The liturgy expresses this reality in various ways, showing, for example, that every celebration of the Eucharist is performed in union not only with the proper Bishop, but also with the Pope, with the episcopal order, with all the clergy, and with the entire people^{62Cf. ROMAN MISSAL, Eucharistic Prayer III.}. Every valid celebration of the Eucharist expresses this universal communion with Peter and with the whole Church, or objectively calls for it, as in the case of the Christian Churches separated from Rome^{63Cf. Const. Lumen gentium, n. 8/b.}.

"The universality of the Church involves, on the one hand, a most solid unity, and on the other, a plurality and a diversification, which do not obstruct unity, but rather confer upon it the character of 'communion'"^{64JOHN PAUL II, Address, General Audience, 27-IX-1989, n. 2: "Insegnamenti di Giovanni Paolo II" XII,2 (1989) p. 679.}. This plurality refers both to the diversity of ministries, charisms, and forms of life and apostolate within each particular Church, and to the diversity of traditions in liturgy and culture among the various particular Churches^{65Cf. Const. Lumen gentium, n. 23/d.}. Fostering a unity that does not obstruct diversity, and acknowledging and fostering a diversification that does not obstruct unity but rather enriches it, is a fundamental task of the Roman Pontiff for the whole Church^{66Cf. ibidem, n. 13/c.}, and without prejudice to the general law of the Church itself, of each Bishop in the particular Church entrusted to his pastoral ministry^{67Cf. Decr. Christus Dominus, n. 8/a.}. But the building up and safeguarding of this unity, on which diversification confers the character of communion, is also a task of everyone in the Church, because all are called to build it up and preserve it each day, above all by means of that charity which is "the bond of perfection"^{68Col 3, 14. ST. THOMAS AQUINAS, Exposit. in Symbol. Apost., a. 9: "The Church is one (...) through the unity of charity, because all are joined in the love of God, and among themselves in mutual love".}.

For a more complete vision of this aspect of ecclesial communion -unity in diversity- one needs to bear in mind that there are institutions and communities established by the Apostolic Authority for specific pastoral tasks. They belong as such to the universal Church, though their members are also members of the particular Churches where they live and work. The manner of belonging to the particular Churches, with its own particular flexibility^{69Cf. supra, n. 10.}, takes different juridical forms. But it does not erode the unity of the particular Church founded on the Bishop; rather, it helps endow this unity with the interior diversification which is a feature of communion^{70Cf. supra, n. 15.}. In the context of the Church understood as communion, consideration should also be given to the many institutes and societies that express the charisms of consecrated life and apostolic life, with which the Holy Spirit enriches the Mystical Body of Christ. Although these do not belong to the hierarchical structure of the Church, they belong to its life and holiness^{71Cf. Const. Lumen gentium, n. 44/d.}. Given their supradiocesan character, rooted in the Petrine ministry, all these ecclesial realities are also elements at the service of communion among the various particular Churches.

"The Church knows that she is joined in many ways to the baptized who are honoured by the name of Christian, but who do not however profess the Catholic faith in its entirety or have not preserved unity or communion under the successor of Peter"^{72Const. Lumen gentium, n. 15.}. Among the non-Catholic Churches and Christian communities, there are indeed to be found many elements of the Church of Christ, which allow us, amid joy and hope, to acknowledge the existence of a certain communion, albeit imperfect^{73Cf. Decr. Unitatis redintegratio, nn. 3/a and 22; see also Const. Lumen gentium, n. 13/d.}. This communion exists especially with the Eastern orthodox Churches, which, though separated from the See of Peter, remain united to the Catholic Church by means of very close bonds, such as the apostolic succession and a valid Eucharist, and therefore merit the title of particular Churches^{74Cf. Decr. Unitatis redintegratio, nn. 14 and 15/c.}. Indeed, "through the celebration of the Eucharist of the Lord in each of these Churches, the Church of God is built up and grows in stature"^{75Ibidem, n. 15/a.}, for in every valid celebration of the Eucharist the one, holy, catholic and apostolic Church becomes truly present^{76Cf. supra, nn. 5 and 14.}. Since, however, communion with the universal Church, represented by Peter's Successor, is not an external complement to the particular Church, but one of its internal constituents, the situation of those venerable Christian communities also means that their existence as particular Churches is wounded. The wound is even deeper in those ecclesial communities which have not retained the apostolic succession and a valid Eucharist. This in turn also injures the Catholic Church, called by the Lord to become for all "one flock" with "one shepherd"^{77Jn 10, 16.}, in that it hinders the complete fulfilment of its universality in history.

This situation seriously calls for ecumenical commitment on the part of everyone, with a view to achieving full communion in the unity of the Church; that unity "which Christ bestowed on his Church from the beginning. This unity, we believe, subsists in the Catholic Church as something she can never lose, and we hope that it will continue to increase until the end of time"^{78Decr. Unitatis redintegratio, n. 4/c.}. In this ecumenical commitment, important priorities are prayer, penance, study, dialogue and collaboration, so that, through a new conversion to the Lord, all may be enabled to recognise the continuity of the Primacy of Peter in his successors, the Bishops of Rome, and to see the Petrine ministry fulfilled, in the manner intended by the Lord, as a worldwide apostolic service, which is present in all the Churches from within, and which, while preserving its substance as a divine institution, can find expression in various ways according to the different circumstances of time and place, as history has shown.

The Blessed Virgin Mary is the model of ecclesial communion in faith, in charity and in union with Christ^{79Cf. Const. Lumen gentium, nn. 63 and 68; ST. AMBROSE, Exposit. in Luc., 2, 7: PL 15, 1555; ST ISAAC OF STELLA, Sermo 27: PL 194, 1778-1779; RUPERT OF DEUTZ, De Vict. Verbi Dei, 12, 1: PL 169, 1464-1465.}. "Eternally present in the mystery of Christ"^{80JOHN PAUL II, Enc. Redemptoris Mater, 25-III-1987, n. 19.}, She is, in the midst of the Apostles, at the very heart of the Church at its birth^{81Cf. Acts 1, 14; JOHN PAUL II, Enc. Redemptoris Mater: as quoted, n. 26.} and of the Church of all ages. Indeed, "the Church was congregated in the upper part (of the Cenacle) with Mary, who was the Mother of Jesus, and with his brethren. We cannot therefore speak of the Church unless Mary, the mother of the Lord, is present there, with the Lord's brethren"^{82ST. CROMATIUS OF AQUILEIA, Sermo 30, 1: "Sources ChrJtiennes" 164, p. 134. Cf. PAUL VI, Ap. Exh. Marialis cultus, 2-II-1974, n. 28.}. In bringing this Letter to a close, the Congregation for the Doctrine of the Faith, echoing the final words of the Constitution Lumen gentium^{83Cf. Const. Lumen gentium, n. 69.}, invites all the Bishops and, through them, all the faithful, especially the theologians, to entrust to the intercession of the Blessed Virgin their commitment to communion and to theological reflection upon communion. The Sovereign Pontiff John Paul II, at the Audience granted to the undersigned Cardinal Prefect, approved this Letter, agreed upon in the ordinary meeting of this Congregation, and ordered its publication. Rome, at the Congregation for the Doctrine of the Faith, 28th may 1992.