[RC¶88] The Prex Eucharistica (“Thanksgiving Request”) is our plea to the Father that he accept the gift which he has already and eternally blessed, acknowledged and approved. It is a little like going to a café and thanking the waiter for a cup of coffee as a means of asking him for a cup of coffee. In the Holy Mass, we offer God our thanks by offering him the Divine Lamb he has already accepted as the means of saving us from our sins, for which we thank God by offering him the Divine Lamb. But while our sacrifice does not follow a historical orientation, it is certainly not circular. Rather, the key to full, conscious and active participation in the sacrifice is to understand that the Mass flows backwards to us from the future. It is only because the Father already accepts our gift of his Lamb that we can offer him the Lamb from our bread and wine today, not as a second or third offering, but as Christ’s original offering of himself to the Father from the Cross.
Let me use another example. The Church prefers that for the processional parts of the Mass, namely the procession of the Priest at the beginning of Mass, the procession of the faithful at the offering of your sacrifice of bread and wine, and at the procession of the Bride of Christ to receive the Body of the Groom at Holy Communion, we sing a psalm or other text of Sacred Scripture, rather than a hymn of human origin. The idea is that God reveals the truth of our future salvation to us by means of the Scriptures he gives us from our future, which we then turn into song, and offer back to him. The further back you go in the Sacred Scriptures, the more you see that the texts prefigure the end of time, so that the Scriptures are more intelligible the more we move into the future. When we take these gifts from the future, and add our voices to them, singing into the future to our Heavenly home, we are offering sacrifice. The Church tolerates hymns when necessary, but hymns at the processional parts of Mass begin in history with a merely human author, and so lack the liturgical dance with time that is liturgical sacrifice. (I should also add that the Church is a pilgrim in procession to our future, and never processes back in time. So there is no procession at the end of Mass, and, therefore, no chant at the end of Mass. We can sing a song at the end of Mass, or recite a devotional prayer, but these are not liturgical; they are not part of the Mass.)
When we understand that the Holy Mass comes to us from our future, we begin to understand that there are no separate Masses: Thursday Mass, Sunday Mass, Requiem Mass, etc. Neither is the Mass weighted in the past, as is the Passover observance of the Jews, in which they truly step back into the past event of their salvation from slavery to man. Ours is a salvation from ourselves, and so finds its final effect only in the future, when we leave the world of time as we know it, passing through death and purgation, perhaps, into the Promised Land.
When we realize that this is all a little beyond our comprehension, and certainly beyond our usual experience of reality, we begin the procession into the mystery of the Mass, and start to participate fully, consciously, and actively in the mystery. And we can understand that the priest can pray, in thanksgiving for a prayer that’s already been answered, that the Father bless, acknowledge, and approve our offering bread and wine in every respect, only because the Father already accepts the Lamb in our future.