Where as we intend to entreat (according to the true sense and meaning of holy word of God) of the verity and excellency of the Sacrifice of the Altar (which commonly is called the Mass) it seems to be as well requisite for the understanding thereof,  as also consonant to good method and order, first to declare and define what thing properly is a Sacrifice.

A Sacrifice therefore properly may be defined, to be an act or operation, by the which some one thing is consecrate and offered up to God, thereby as well to appease his wrath and indignation towards us, as also to give him due reverence and honor in recognizing the supreme dominion of his Divine Majesty: although we offer him nothing else, but the selfsame things which we receive of him.

The en wherefore Sacrifice is done, is (as St. Augustine saith) to make us by a holy and blessed fellowship, to be coupled and joined with God, to whom that our work and operation is referred, as unto such an end of perfection and goodness, by the which we may undoubtedly become blessed and happy.

The substantial and proper parts of Sacrifice are, the Consecration, the Oblation, and the receiving or eating: to these chief parts are consequently also required, both the authority to make it, and also the means necessary and instruments appertaining to the same: as Priesthood, Altar, Chalice, and other the like things, whereof both in the Old Scripture generally, and also particularly in the New, mention is made no less by our Saviour himself (by the mouths of his Evangelists) then by his elect vessel St. Paul, as hereafter we shall more at large declare.

Four things principally are to be considered in every Sacrifice.

1. To whom it is offered (for it is convenient only for God)
2. By whom it is offered, and is, by a man which is institute in holy Orders of Priesthood.
3. What thing is offered.
4. And for the salvation of whom.

Now, since then Sacrifice is an action, which in a most excellent wise is convenient only to God, and to men, neither unto Angels, for as much as God only is a most sufficient means to obtain and give us the graces which we demand of him: it followeth, that by all means the Sacrifice of the Law of the Gospel ought to be a better Sacrifice and in a far more perfect sort, then either that was of the Law of Nature, either of the Law of Moses.

This Sacrifice could be no other (as St. Paul proveth) then that which was after the order of Melchisedech, of which shall no less, saith he, continue ever unto the end of the world, and unto the last coming of our Lord at the day of judgment, then now it doth succeed after that Sacrifice, which was by the order of Aaron.

Wherefore St. Augustine (conformable to the faith of all Christianity) speaking of this, saith: that we do often times sacrifice unto God, only after those rites and ceremonies, with which Christ in the publishing and manifestation of his new Testament commanded us to do: as the which do appertain to that kind of worshipping, which is called Latria, that is to say, such adoration as is due to be given to God only.

And in another place he writeth: For this cause is he both the Priest, saith he, that is, party which doth offer up, and also the oblation and offering itself: the Sacrament whereof he hath ordained to be a daily Sacrifice of the Church.

And again elsewhere he addeth, and saith in these words: Christ of his own body and blood hath instituted the Sacrifice after the order of Melchisedech.

It remaineth therefore, that the truth hereof be set forth and seen more at large, as well by the Figures and Prophecies of the Old Testament. as also by the testimonies of many and sundry places of the New, which by Gods grace we shall do in the Chapters following.

Fr. Antonio Possevino