Solemnity of Corpus Christi
In the sacramental theology of the Church, we must recognize a threefold distinction. In Latin: Res, Sacramentum, Res et Sacramentum. In English: Reality, Sacrament, Reality and Sacrament. The reality is that invisible grace given by the sacrament. The sacrament is that visible sign which is used in the rite. And the reality and sacrament is an invisible reality which is yet a sign of something further (like, for example, the way the sacred character of baptism is a reality in the soul of the baptized but is also a sacrament of the individual’s participation in Christ).
To properly understand the manner in which the Mass is a sacrifice, we must understand how each of these elements relates to the Real Presence of Christ in the Eucharist. This will make clear how it is that, even though Jesus does not die upon the altar but remains living and glorified in the Holy Eucharist, the Mass is yet the very self-same sacrifice of the Cross.
Res tantum (The thing or reality alone): The grace of the Sacrament
The res of the Eucharist is twofold: the Real Presence of Christ and the Mystical Body of Christ which is the Church. Further, we may state that the reality of this sacrament is the grace given to the one who receives worthily.
Sacramentum tantum (The sign or sacrament alone): The visible species of bread and wine
The simple sign or outward sacrament, in the case of the Eucharist, is the visible bread and wine. These are a sign insofar as they are food which give nourishment and refreshment to the body. Thus also, the Body and Blood of Christ are spiritual nourishment for the soul.
Further, as those who join in a common meal are made one; so too, the Church is united in this sacred feast.
Res et Sacramentum (The reality or thing which is also a sign or sacrament of a further reality): The glorified Body and Blood of Christ
Now, we had earlier that the Real Presence of Jesus in the Holy Eucharist is one res of this sacrament. However, Christ’s Presence is not merely a res, for it is a sacramental presence. Therefore, it is obvious that the Real Presence is the res et sacramentum (the thing and the sign) of the Eucharist.
We must specify: The Real Presence of Christ in the Eucharist is res et sacramentum insofar as the glorified Body of Christ (under the visible sign of bread) and the glorified Blood of Christ (under the visible sign of wine) are the res et sacramentum of the Eucharist.
Surely, the body and blood, soul and divinity of Jesus are wholly present in each species and under each of their parts. Still, it is not for no reason that we call the one the sacrament of Christ’s body and the other the sacrament of his blood. In her sacred rites, the Church refers to the one as “The Body of Christ” and the other as “The Blood of Christ” (as, for example, in the distribution of Holy Communion).
For more on this, please consider our earlier article [here].
For now, we will focus only on this one point: The glorified and living Body of Christ and the glorified and living Blood of Christ are themselves not mere realities but are also signs and sacraments of another reality.
Upon the altar of the Mass, the glorified and living Body of Christ is sacramentally separated from the glorified and living Blood of Christ (in truth, they are united, as the whole Jesus is wholly present in each). They are sacramentally separated, insofar as the one is the sacrament of his Body and the other the sacrament of his Blood. Thus, under sacramental signification, we see the body and blood of Christ separated upon the altar.
This separation of the two Eucharistic species is the sacrament of the Cross – the only time and place in which the body and blood of Christ were separated as the lance of Longinus pierced the expired Heart of our Savior to allow both blood and water to pour forth.
Thus, as the body and blood of Christ were (in their proper and natural species) separated upon the altar of the Cross, so too they are (in their sacramental species) separated upon the altar of the Mass. This is why the Mass is a sacrifice, because it is a sacramental sacrifice.
Not two sacrifices, but only one sacrifice
The Mass is a sacramental sacrifice, not a physical and bloody sacrifice. Just as there are not two bodies of Christ (one in heaven and one in the sacrament), so too there cannot be two sacrifices (one on Calvary and one in the Mass).
No, precisely because the Eucharist is a sacrament and the sacrifice is a sacramental sacrifice, there is no multiplication of offerings or of deaths. Jesus died once and only once for all people, and this one death is made sacramentally present through the sacramental separation of the body and blood of Christ upon the altar.
Jesus present in the Blessed Sacrament is living, but his Presence is itself a sacrament of when he was dead.
From the Angelic Thomas
When considering whether it would be superfluous for the whole Christ (body and blood, soul and divinity) to be present under each species, the Doctor from Aquino states:
“Although the whole Christ is under each species, yet it is so not without purpose. For in the first place this serves to represent Christ’s Passion, in which the blood was separated from the body; hence in the form for the consecration of the blood mention is made of its shedding.” (ST III, q.76, a.2, ad 1 [here])