Catholic theology states that the sacrifice of the Mass is the same (numerical) sacrifice of the cross (i.e., it is a propitiatory sacrifice that is re-presented by Christ through the instrumentlity if the priest acting in persona Christi). While arguing for such, Joseph Pohle wrote the following about some of the important differences between the sacrifice of the cross and the so-called "sacrifice of the altar":
How the Two Sacrifices Differ.—The main difference between the Sacrifice of the Cross and the Mass lies, as we have seen, in the manner of offering. But there are other differences, though of minor importance.
a) In the first place, the Sacrifice of the Cross was an absolute, while the Mass is a relative sacrifice.
Another difference is that the Sacrifice of the Cross was offered but once, whereas the Mass is repeated indefinitely until the coming of the Lord.
A third difference lies in this, that the Sacrifice of the Cross completed the redemption of the human race, while the Mass conveys the fruits of that Sacrifice to the faithful.
A fourth difference is that on the Cross Christ was the sole Priest, whereas in the Mass He employs human minsters, Himself merely acting as Sacerdos principalis.
The manner of offering entails a fifth difference, viz.: that whereas the Cross our Lord was immolated as a passible and mortal man, in the Moss He offers Himself in the immortal state of glorification.
b) Regarding the relation between the Mass and the Last Supper, we may add that both sacrifices are identical in object and subject (Christ) as well as in the manner of offering. It is perfectly correct, therefore, to say that the Last Supper was the first Mass, though there are a few non-essential distinctions between the two.
(1) The Last Supper, like the Mass was a relative sacrifice, but it was its very nature an anticipatory commemoration of the Sacrifice of the Cross, whereas the Mass is retrospective. (2) At the Last Supper Christ celebrated in His own person, whereas in the Mass He is represented by the priest. (3) Regarded in its origin, the Last Supper appears as the institution, and consequently as the pattern exemplar, of the Mass, which in its part only imitates what Christ has done and commanded His Church to repeat. (Joseph Pohle, The Sacraments: A Dogmatic Treatise, Volume 2: The Holy Eucharist [London: B. Herder Book Co., 1917], 338-40)
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