The Eucharist and ecclesial communion
15. The Eucharist is thus constitutive of the Church's being and activity. This is why Christian antiquity used the same words, Corpus Christi, to designate Christ's body born of the Virgin Mary, his eucharistic body and his ecclesial body.(34) This clear datum of the tradition helps us to appreciate the inseparability of Christ and the Church. The Lord Jesus, by offering himself in sacrifice for us, in his gift effectively pointed to the mystery of the Church. It is significant that the Second Eucharistic Prayer, invoking the Paraclete, formulates its prayer for the unity of the Church as follows: "may all of us who share in the body and blood of Christ be brought together in unity by the Holy Spirit." These words help us to see clearly how the res of the sacrament of the Eucharist is the unity of the faithful within ecclesial communion. The Eucharist is thus found at the root of the Church as a mystery of communion (35).
The relationship between Eucharist and communio had already been pointed out by the Servant of God John Paul II in his Encyclical Ecclesia de Eucharistia. He spoke of the memorial of Christ as "the supreme sacramental manifestation of communion in the Church" (36). The unity of ecclesial communion is concretely manifested in the Christian communities and is renewed at the celebration of the Eucharist, which unites them and differentiates them in the particular Churches, "in quibus et ex quibus una et unica Ecclesia catholica exsistit" (37). The fact that the one Eucharist is celebrated in each Diocese around its own Bishop helps us to see how those particular Churches subsist in and ex Ecclesia. Indeed, "the oneness and indivisibility of the eucharistic body of the Lord implies the oneness 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." (38) Consequently, in the celebration of the Eucharist, the individual members of the faithful find themselves in their Church, that is, in the Church of Christ. From this eucharistic perspective, adequately understood, ecclesial communion is seen to be catholic by its very nature (39). An emphasis on this eucharistic basis of ecclesial communion can also contribute greatly to the ecumenical dialogue with the Churches and Ecclesial Communities which are not in full communion with the See of Peter. The Eucharist objectively creates a powerful bond of unity between the Catholic Church and the Orthodox Churches, which have preserved the authentic and integral nature of the eucharistic mystery. At the same time, emphasis on the ecclesial character of the Eucharist can become an important element of the dialogue with the Communities of the Reformed tradition (40).