Q. Please explain why it is that Communion services are not encouraged in place of Mass, especially where shortages of priests occur? Why not schedule Communion services even on Sundays? Couldnt they be conducted by deacons or by ministers of Holy Communion?
A. Questions like these (which are quite common in my own pastoral experience) reflect fundamental gaps in youth or adult faith formation classes, or, occasionally, in homilies and other sermons.
For one thing, the Churchs ancient and perennial Tradition is that the sacrifice of the Mass is the central act of worship. The Blessed Sacrament derives from the Mass. Thus, even when, for an adequate reason, a Liturgy of the Word with Distribution of Holy Communion is permitted, the faithful should remain aware that in the reception of Holy Communion, they are closely united with the Eucharistic Sacrifice that perpetuates the Sacrifice of the Cross. (See, for example, "Holy Communion and Worship of the Eucharist outside Mass," Congregation for Divine Worship, 1973.)
The Mass rehearses the Last Supper, during which Christ our Lord inaugurated the Sacrificial Memorial Banquet of the New Covenant, with the instruction to his first priests, "do this in remembrance of me." (Cf. 1 Cor. 11:24)
For anyone desiring to better understand why it is that the Liturgy of the Word together with the Distribution of Holy Communion does not constitute a substitution for the Mass, the Catechism of the Catholic Church provides a magnificent and most instructive explanation. Basing its synopsis on Biblical texts such as 1 Cor. 11:17-34, Acts 2:42, 46, 30:7, 11; as well as the teachings of the early Church Fathers (e.g., St. Justin), the Catechism demonstrates that the Tradition received from Apostolic times is to gather (the Eucharistic assembly, known in Greek as synaxis, which means "assembly") for the memorial ("anamnesis"), sacrificial banquet of the Lords Passion, Death and Resurrection in response to his invitation to act in "remembrance" of him until he comes again. This gathering must include all of its ancient elements in accordance with the Churchs Tradition; specifically, (1) introductory prayers and (2) a Liturgy of the Word (i.e., Scripture readings); (3) a presentation of offerings (especially, bread and wine, used by the Lord at the Last Supper); (4) the anaphora (Greek for "offering") or Eucharistic Prayer; (5) an epiclesis (invoking God the Father in sending the Holy Spirit upon the offerings of the bread and wine to effect what the Church calls transubstantiation; (6) the priest celebrants rehearsal of Jesus institution narrative ("This is my Body this is the cup of my Blood ) spoken in persona Christi ("in the person of Christ," who is the Eternal, Perfect High Priest); (7) the anamnesis ("memorial" of the Churchs recalling the Passion and Resurrection, together with the Second Coming of Jesus); (8) the intercessions (emphasizing the Communion of Saints); (9) the Communion, preceded by the "breaking of bread" (a New Testament Biblical term) and the Pater Noster.
This Tradition has essentially remained unchanged throughout the Ages, and is known to us today from the Scriptural term, "Eucharist," as well as the Latin derivative, "Mass" (a code word for the Eucharist used during the early Roman persecutions).
All of the above is summarized and elaborated upon in Part Two, Article 3, Numbers 1322 sqq., of the Catechism.
It is possible, for various good reasons, to distribute Communion outside Mass (e.g., illness), and, in unusual circumstances (e.g., inability to schedule a Mass). But these are extraordinary situations. Some Communion services are permitted by the local Bishop, who regulates them. But the Tradition concerning the Mass is so crucial to an authentic understanding of the Eucharist that even when permission is granted to reserve the Blessed Sacrament in a chapel, say, Church law requires that Mass should be offered at that altar at regular intervals. (Canon 934, ¶2)
Deacons may, of course, conduct Communion services, where they are permitted either by liturgical norms or by their Bishop. Very special regulations in extraordinary situations apply to instituted acolytes and to Extraordinary Ministers of Holy Communion.