The beautiful sections of Pope Paul VI’s encylical Mysterium Fidei (1965), are the ones dealing with the manner in which Our Lord is present in the Church today. Christmastide is nothing if not about the Presence of Someone who makes a difference in our lives, who redeems us from sin, who gives Himself completely, par excellence, to us in the Eucharist. The Presence is not about the doing of nice things, but offering us concretely eternal life. As Saint Ignatius of Antioch famously said of the Eucharist, the Presence of the Lord in the Eucharist is given to us as the “medicine of immortality.”
The full text of Mysterium Fidei is obligatory reading for those who want to be well-educated in the Faith. Emphasis added.
Glory of the New Born Christ Child in presence of God Father and the Holy Spirit (Annakirche, Vienna) Adam and Eve are represented bellow Jesus Christ Ceiling painted by Daniel Gran (1694-1757).
35. All of us realize that there is more than one way
in which Christ is present in His Church. We want to go into this very joyful
subject, which the Constitution on the Sacred Liturgy presented briefly, at
somewhat greater length. Christ is present in His Church when she prays, since
He is the one who “prays for us and prays in us and to whom we pray: He
prays for us as our priest, He prays in us as our head, He is prayed to by us
as our God”; and He is the one who has promised, “Where two or three
are gathered together in my name, I am there in the midst of them.” He is
present in the Church as she performs her works of mercy, not just because
whatever good we do to one of His least brethren we do to Christ Himself, but
also because Christ is the one who performs these works through the Church and
who continually helps men with His divine love. He is present in the Church as
she moves along on her pilgrimage with a longing to reach the portals of
eternal life, for He is the one who dwells in our hearts through faith, and who
instills charity in them through the Holy Spirit whom He gives to us.
36. In still another very genuine way, He is present in the Church as she preaches, since the Gospel which she proclaims is the word of God, and it is only in the name of Christ, the Incarnate Word of God, and by His authority and with His help that it is preached, so that there might be “one flock resting secure in one shepherd.”
37. He is present in His Church as she rules and governs the People of God, since her sacred power comes from Christ and since Christ, the “Shepherd of Shepherds,” is present in the bishops who exercise that power, in keeping with the promise He made to the Apostles.
38. Moreover, Christ is present in His Church in a still more sublime manner as she offers the Sacrifice of the Mass in His name; He is present in her as she administers the sacraments. On the matter of Christ’s presence in the offering of the Sacrifice of the Mass, We would like very much to call what St. John Chrysostom, overcome with awe, had to say in such accurate and eloquent words: “I wish to add something that is clearly awe-inspiring, but do not be surprised or upset. What is this? It is the same offering, no matter who offers it, be it Peter or Paul. It is the same one that Christ gave to His disciples and the same one that priests now perform: the latter is in no way inferior to the former, for it is not men who sanctify the latter, but He who sanctified the former. For just as the words which God spoke are the same as those that the priest now pronounces, so too the offering is the same.” No one is unaware that the sacraments are the actions of Christ who administers them through men. And so the sacraments are holy in themselves and they pour grace into the soul by the power of Christ, when they touch the body. The Highest Kind of Presence.
These various ways in which Christ is present fill the mind with astonishment and offer the Church a mystery for her contemplation. But there is another way in which Christ is present in His Church, a way that surpasses all the others. It is His presence in the Sacrament of the Eucharist, which is, for this reason, “a more consoling source of devotion, a lovelier object of contemplation and holier in what it contains” than all the other sacraments; for it contains Christ Himself and it is “a kind of consummation of the spiritual life, and in a sense the goal of all the sacraments.”
39. This presence is called “real” not to exclude the idea that the others are “real” too, but rather to indicate presence par excellence, because it is substantial and through it Christ becomes present whole and entire, God and man. And so it would be wrong for anyone to try to explain this manner of presence by dreaming up a so-called “pneumatic” nature of the glorious body of Christ that would be present everywhere; or for anyone to limit it to symbolism, as if this most sacred Sacrament were to consist in nothing more than an efficacious sign “of the spiritual presence of Christ and of His intimate union with the faithful, the members of His Mystical Body.”