I. The origin and development of the expression

2. The expression sister Churches does not appear as such in the New Testament; however, there are numerous indications of the sisterly relations which existed among the local Churches of Christian antiquity. The New Testament passage which most explicitly reflects this awareness is the final sentence of the Second Letter of John: «The sons of your elect sister send you their greetings» (2 Jn 13). These are greetings sent by one ecclesial community to another; the community which sends the greetings calls itself the sister of the other.

3. In Christian literature, the expression begins to be used in the East when, from the fifth century, the idea of the Pentarchy gained ground, according to which there are five Patriarchs at the head of the Church, with the Church of Rome having the first place among these patriarchal sister Churches. In this connection, however, it needs to be noted that no Roman Pontiff ever recognized this equalization of the sees or accepted that only a primacy of honour be accorded to the See of Rome. It should be noted too that this patriarchal structure typical of the East never developed in the West.

As is well known, the divergences between Rome and Constantinople led, in later centuries, to mutual excommunications with «consequences which, as far as we can judge, went beyond what was intended and foreseen by their authors, whose censures concerned the persons mentioned and not the Churches, and who did not intend to break the ecclesial communion between the sees of Rome and Constantinople.»¹

4. The expression appears again in two letters of the Metropolitan Nicetas of Nicodemia (in the year 1136) and the Patriarch John X Camaterus (in office from 1198 to 1206), in which they protested that Rome, by presenting herself as mother and teacher, would annul their authority. In their view, Rome is only the first among sisters of equal dignity.

5. In recent times, the Orthodox Patriarch of Constantinople, Athenagoras I, was the first to once again use the expression sister Churches. In welcoming the fraternal gestures and the call to unity addressed to him by John XXIII, he often expressed in his letters the hope of seeing the unity between the sister Churches re-established in the near future.

6. The Second Vatican Council adopted the expression sister Churches to describe the relationship between particular Churches: «in the East there flourish many particular local Churches; among them the Patriarchal Churches hold first place, and of these, many glory in taking their origins from the apostles themselves. Therefore, there prevailed and still prevails among Eastern Christians an eager desire to perpetuate in a communion of faith and charity those family ties which ought to exist between local Churches, as between sisters.» ²

7. The first papal document in which the term sisters is applied to the Churches is the Apostolic Brief Anno ineunte of Paul VI to the Patriarch Athenagoras I. After having indicated his willingness to do everything possible to «re-establish full communion between the Church of the West and that of the East,» the Pope asked: «Since this mystery of divine love is at work in every local Church, is not this the reason for the traditional expression “sister Churches,” which the Churches of various places used for one another? For centuries our Churches lived in this way like sisters, celebrating together the ecumenical councils which defended the deposit of faith against all corruption. Now, after a long period of division and mutual misunderstanding, the Lord, in spite of the obstacles which arose between us in the past, gives us the possibility of rediscovering ourselves as sister Churches.» ³

8. The expression has been used often by John Paul II in numerous addresses and documents; the principal ones, in chronological order, are the following.

In the Encyclical Slavorum Apostoli: «For us they [Cyril and Methodius] are the champions and also the patrons of the ecumenical endeavour of the sister Churches of East and West, for the rediscovery through prayer and dialogue of visible unity in perfect and total communion.» ⁴

In a Letter from 1991 to the Bishops of Europe: «Hence, with these Churches [the Orthodox Churches] relations are to be fostered as between sister Churches, to use the expression of Pope Paul VI in his Brief to the Patriarch of Constantinople, Athenagoras I.» ⁵

In the Encyclical Ut unum sint, the theme is developed above all in number 56 which begins in this way: «Following the Second Vatican Council and in the light of earlier tradition, it has again become usual to refer to the particular or local Churches gathered around their Bishop as “sister Churches.” In addition, the lifting of the mutual excommunications, by eliminating a painful canonical and psychological obstacle, was a very significant step on the way toward full communion.» This section concludes by expressing the wish that the «traditional designation of “sister Churches” should ever accompany us along this path.» The topic is taken up again in number 60 of the Encyclical: «More recently, the joint international commission took a significant step forward with regard to the very sensitive question of the method to be followed in re-establishing full communion between the Catholic Church and the Orthodox Church, an issue which has frequently embittered relations between Catholics and Orthodox. The commission has laid the doctrinal foundations for a positive solution to this problem on the basis of the doctrine of sister Churches.» ⁶