Eucharisticum Mysterium gives a definition of the local Church, with encouragement for communities “frequently small and poor or living in isolation.”
7. Through the eucharist “the Church continually lives and grows. This Church of Christ is truly present in all lawful, local congregations of the faithful, which, united with their bishops, are themselves called Churches in the New Testament. For in their own locality these Churches are the new people called by God in the Holy Spirit and in great fullness (see 1 Thes 1:5). In them the faithful are gathered together through the preaching of Christ’s Gospel and the mystery of the Lord’s Supper is celebrated, so that ‘through the meal of the body and blood of the Lord the whole brotherhood is joined together.’ [Prayer from the Mozarabic Rite: Patrologiae cursus completus: Series latina 96, 759 B.] Any community of the altar, under the sacred ministry of the bishop,” [Lumen gentium no. 26.] or of a priest who takes his place, [See Sacrosanctum Concilium art. 42.] “stands out clearly as a symbol of that charity and ‘unity of the Mystical Body without which there can be no salvation.’ [See Summa theologiae 3a, 73.3.] In these communities, though frequently small and poor or living in isolation, Christ is present and the power of his presence gathers together the one, holy, catholic, and apostolic Church. For ‘the sharing of the body and blood of Christ does nothing less than transform us into what we receive.” [Leo the Great, Serm. 63, 7: Patrologiae cursus completus: Series latina 54, 357 C.], [Lumen gentium no. 26.]
I wonder, though, about the gap for countless communities who, through no fault of their own, lack a physical presence of the bishop’s ministry through a priest. Without doubting the power of the Mass, and the need for an ordained cleric to lead it, does the Eucharist define a Church? We might say the Eucharist makes the Church. But does it define it?