BEHOLD CHRIST. The Eucharistic miracle in Lanciano, Italy, is preserved from the eighth century. (photo: Wikipedia/Public domain)
Catechism of the Catholic Church
1400 - Ecclesial communities derived from the Reformation and separated from the Catholic Church, "have not preserved the proper reality of the Eucharistic mystery in its fullness, especially because of the absence of the sacrament of Holy Orders." It is for this reason that Eucharistic intercommunion with these communities is not possible for the Catholic Church.
39 Articles of the Anglican Church
XXVIII - Of the Lord's Supper.
Transubstantiation (or the change of the substance of Bread and Wine) in the Supper of the Lord, cannot be proved by Holy Writ; but is repugnant to the plain words of Scripture, overthroweth the nature of a Sacrament, and hath given occasion to many superstitions.
48 I am the bread of life. 49 Your fathers ate the manna in the wilderness, and they died. 50 This is the bread that comes down from heaven, so that one may eat of it and not die. 51 I am the living bread that came down from heaven. If anyone eats of this bread, he will live forever. And the bread that I will give for the life of the world is my flesh.”
52 The Jews then disputed among themselves, saying, “How can this man give us his flesh to eat?” 53 So Jesus said to them, “Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you. 54 Whoever feeds on my flesh and drinks my blood has eternal life, and I will raise him up on the last day. 55 For my flesh is true food, and my blood is true drink. 56 Whoever feeds on my flesh and drinks my blood abides in me, and I in him. 57 As the living Father sent me, and I live because of the Father, so whoever feeds on me, he also will live because of me. 58 This is the bread that came down from heaven, not like the bread the fathers ate and died. Whoever feeds on this bread will live forever.” 59 Jesus said these things in the synagogue, as he taught at Capernaum.
Catechism of the Catholic Church
1374 - The mode of Christ's presence under the Eucharistic species is unique. It raises the Eucharist above all the sacraments as "the perfection of the spiritual life and the end to which all the sacraments tend."201 In the most blessed sacrament of the Eucharist "the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained."202 "This presence is called 'real' - by which is not intended to exclude the other types of presence as if they could not be 'real' too, but because it is presence in the fullest sense: that is to say, it is a substantial presence by which Christ, God and man, makes himself wholly and entirely present."203
1375 - It is by the conversion of the bread and wine into Christ's body and blood that Christ becomes present in this sacrament. The Church Fathers strongly affirmed the faith of the Church in the efficacy of the Word of Christ and of the action of the Holy Spirit to bring about this conversion. Thus St. John Chrysostom declares:
It is not man that causes the things offered to become the Body and Blood of Christ, but he who was crucified for us, Christ himself. The priest, in the role of Christ, pronounces these words, but their power and grace are God's. This is my body, he says. This word transforms the things offered.204
And St. Ambrose says about this conversion:
Be convinced that this is not what nature has formed, but what the blessing has consecrated. The power of the blessing prevails over that of nature, because by the blessing nature itself is changed. . . . Could not Christ's word, which can make from nothing what did not exist, change existing things into what they were not before? It is no less a feat to give things their original nature than to change their nature.205
201 - St. Thomas Aquinas, STh III,73,3c.
202 - Council of Trent (1551): DS 1651.
203 - Paul VI, MF 39.
204 - St. John Chrysostom, prod. Jud. 1:6:PG 49,380.
205 - St. Ambrose, De myst. 9,50; 52:PL 16,405-407.