The Catechism of St. Thomas Aquinas



The third Sacrament is the Holy Eucharist. Its matter is wheaten bread and wine from the grape mixed with a little water so that the water becomes part of the wine. The water signifies the faithful who are incorporated into Christ. Other than wheaten bread and wine from the grape cannot be the matter for this Sacrament. The form of this Sacrament is the very words of Christ, “This is My Body,” and “This is the chalice of My Blood of the new and eternal testament; the mystery of faith; which shall be shed for you and for many, to the remission of sins.” These words spoken by the priest in the person of Christ brings into being this Sacrament. The minister of this Sacrament is the priest; and no one else can consecrate this matter into the Body of Christ.


The effect of this Sacrament is twofold: first, in the very consecration of the Sacrament, since in virtue of the above words bread is changed into the Body of Christ, and wine into His Blood; so that Christ is entirely contained under the appearances of bread which remain without a subject; and Christ is entirely contained under the appearances of wine. And, moreover, under each part of the consecrated Host and of the consecrated wine, Christ is totally present even after the separation is made.[21] The second effect of this Sacrament brought about in the soul of one who worthily receives is the union of man with Christ, as He himself says: “He that eateth My Flesh, and drinketh My Blood, abideth in Me, and I in him.”[22] And since man is incorporated with Christ and united to His members through grace, it follows that through this Sacrament grace is increased in those who receive it worthily. Thus, therefore, in this Sacrament there is that which is the Sacrament alone (“sacramentum tantum”), that is, the species of bread and wine; and that which is known as the “res et sacramentum,” that is, the true Body of Christ; and that which is the “res tantum,” that is the unity of the Mystical Body, that is, the Church which this Sacrament both signifies and causes.[23]


There have been many errors regarding this Sacrament. The first error is of those who say that in this Sacrament is not the true Body of Christ but only a sign of it. The author of this error is said to be Berengarius against whom it is written: “For My Flesh is meat indeed; and My Blood is drink indeed.”[24] The second is the error of the Arrodinici, who offer in their sacrament bread and cheese because they say men at first made offerings of the fruits of the earth and of their flocks. Against this, however, stands the fact that the Lord who is the institutor of this Sacrament gave to His disciples bread and wine. The third is the error of the Cataphrygae and the Praeputiati, who drew the blood of an infant from tiny punctures in its body, and mixing this with flour made a bread of it; and

thus asserted that they consecrated the sacrament. This is more like the sacrifices of demons than that of Christ: “And they shed innocent blood . . . which they sacrificed to the idols of Chanaan.”[25] The fourth is the error of the Aquarii, who offer water only in their sacrifices. But against this are the words from the mouth of Wisdom, which is Christ: “Drink the wine which I have mingled for you.”[26] Another error is that of the Poor People of Lyons who hold that any just man can consecrate this Sacrament. Against such errors is the fact that the Lord gave to the Apostles the power to celebrate this Sacrament; and hence only those who receive this power in a certain succession from the Apostles can consecrate this Sacrament.

(For “Questions for Discussion” see Chapter 6.)


21. “Hence it also follows that Christ is so contained, whole and entire, under either species that, as under the species of bread are contained not only the body but also the blood and Christ entire, so in like manner under the species of wine are truly contained not only the blood, but also the body and Christ entire. These are matters on which the faithful cannot entertain a doubt. Wisely, however, was it ordained that two distinct consecrations should take place. They represent in a more lively manner the Passion of Our Lord, in which His blood was separated from His body; and hence in the form of consecration we commemorate the shedding of His blood. Again, since the Sacrament is to be used by us as the food and nourishment of our souls, it was most appropriate that it should be instituted as food and drink, two things which obviously constitute the complete sustenance of man.

“Nor should it be forgotten that Christ is, whole and entire. contained not only under either species, but also in each particle of either species. ‘Each,’ says St. Augustine, ‘receives Christ the Lord, and He is entire in each portion. He is not diminished by being given to many, but gives Himself whole and entire to each’ (cited in Gratian, ‘De consecratione,’ dist. 2). This is also an obvious inference from the narrative of the Evangelists. It is not to be supposed that Our Lord consecrated the bread used at the Last Supper in separate parts, applying the form particularly to each, but that all the bread then used for the sacred mysteries was consecrated at the same time and with the same form, and in a quantity sufficient for all the Apostles. That the consecration of the chalice was performed in this manner, is clear from these words of the Saviour: ‘Take and divide it among you’ (Luke, xxii, 17)” (“Roman Catechism,” “The Eucharist,” 35-36).

22. John. vi. 57.

23. “Those who receive this Sacrament piously and fervently must, without any doubt, so receive the Son of God into their souls as to be united as living members to His Body. For it is written, ‘He that eateth Me, the same also shall live by Me.’ And again: ‘The bread which I will give is My flesh for the life of the world’ (John, vi. 58). . . . For the Eucharist is the end of all the Sacraments, and the symbol of unity and brotherhood in the Church” (“Roman Catechism,” “loc. cit.,” 49).

24. John, vi. 56.

25. Ps. cv. 39.

26. Prov., ix. 5.

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