Focusing in on the Eucharist, Pope Pius XII notes that “the nature of men requires” a “visible sacrifice.” This sacrifice is “no mere empty commemoration of the passion and death of Jesus Christ, but a true and proper act of sacrifice.” Each celebration of the Mass is the same sacrifice offered by the same person: the once-for-all sacrifice of Christ who offers himself on the Cross. The manner of the offering is different in that the Mass is the unbloody re-presentation (making present again) of the bloody offering on the Cross. Transubstantiation means the bread and wine are truly his body, blood, soul, and divinity.
The pope then makes a complicated point about the Eucharistic “species.” “Species” is the word we use to refer to the bread and wine after consecration. It has always been the Church’s teaching that receiving a single crumb or a single drop is enough to receive all of Christ; body, blood, soul, and divinity.. We do not believe that the wine is only the blood or that the host is only the body. At the same time, the bread and wine do look different. By looking different, they symbolize the fact that Jesus’ body and blood were separated (i.e. Jesus’ blood poured out of his body during his passion). This helps to symbolize the fact of Jesus being a victim even in the unbloody, mystical offering of the Mass.
The reasons (or “ends”) for Christ’s death on the Cross and for the Mass are identical because they are the same offering. Those reasons are fourfold: To give glory to the Heavenly Father, to give thanks to God, to bring about reconciliation and forgiveness of sins, and to make us holy and full of “every blessing and grace.” All of this is accomplished by the one sacrifice of Christ on the cross, but it does not immediately have full effect. This is the reason for the Mass, so that men can come into “vital contact with the sacrifice of the cross” so that these effects can take hold more and more in their lives as time passes.
Because of this wonderful reality, Pope Pius XI writes, it is important for all the faithful to become truly “aware” of the fact that participating in the eucharistic sacrifice is their “chief duty and supreme dignity.” He warns against being distracted and urges the laity to “undergo with Christ a mystical death on the cross.” This thread of thought eventually gets taken up by Vatican II to become “active participation” in the document on the liturgy produced by the council, but we’ll get to that when the time comes. For now, the pope wants to also caution people to realize that lay participation does not make them identical to ministerial priests who act in persona Christi at Mass. It is true that both priest and laity “offer the diving Victim” at Mass, but each in a different sense. It is the priest who truly offers the Eucharist and the laity only do so by participating spiritually in the sacred action of the priest.
The pope then touches on the question of a priest celebrating Mass privately. He strongly emphasizes that, even when a priest celebrates Mass by himself, it benefits the whole Church because he always acts as a minister of the mystical body. Nonetheless, because the Church wants to emphasize that connection to the whole Church, the canon law of that time forbid priests from celebrating Mass alone. This was a matter of discipline and emphasis, not doctrine. In fact, since that time, the Church has changed the policy. Priests are now allowed to celebrate Mass privately so long as they have a just reason. A “just reason” is a relatively low bar, canonically speaking, and it’s generally agreed that a priest being on a day off and that wanting to remain faithful to saying Mass every day has a good enough reason. Still, the point must not be lost that every Mass is for the whole Church and it is preferred that at least one other person be present for each Mass to represent that fact.
Pius XII then stresses the fact that simply participating in Mass (as priest or as layperson) is not enough. The goal of this participation is to become more like Christ, to increase faith and become more fervent in Charity. He quotes the rite of Ordination when priests are told to “imitate what you handle” (since changed to “imitate what you celebrate”). He points out that it is the goal of “readings, homilies and other sermons” to do this and that “the whole cycle of mysteries” also aim at “raising the minds of the faithful… to the contemplation of the sublime truths contained in this sacrifice.” In other words, we should recognize Christ in the Mass and strive to become like him, to be a victim of love along with him