What the Catechism of the Catholic Church says on the "Eucharist:"
1106. "Together with the anamnesis, the epiclesis is at the heart of each sacramental celebration, most especially of the
Eucharist: You ask how the bread becomes the Body of Christ, and the wine . . . the Blood of Christ I shall tell you: the
Holy Spirit comes upon them and accomplishes what surpasses every word and thought . . . Let it be enough for you to understand
that it is by the Holy Spirit, just as it was of the Holy Virgin and by the Holy Spirit that the Lord, through and in himself,
took flesh. [St. John Damascene, De fide orth 4, 13: PG 94, 1145A.]"
1324. "The Eucharist is 'the source and summit of the Christian life.' [LG 11.] 'The other sacraments, and indeed all ecclesiastical
ministries and works of the apostolate, are bound up with the Eucharist and are oriented toward it. For in the blessed Eucharist
is contained the whole spiritual good of the Church, namely Christ himself, our Pasch.' [PO 5.]"
1327. "In brief, the Eucharist is the sum and summary of our faith: 'Our way of thinking is attuned to the Eucharist, and
the Eucharist in turn confirms our way of thinking.' [St. Irenaeus, Adv. haeres. 4, 18, 5: PG 7/l, 1028.]"
1329. "The Lord's Supper, because of its connection with the supper which the Lord took with his disciples on the eve of
his Passion and because it anticipates the wedding feast of the Lamb in the heavenly Jerusalem. [Cf. 1 Cor 11:20; Rev 19:9.]
The Breaking of Bread, because Jesus used this rite, part of a Jewish meat when as master of the table he blessed and distributed
the bread, [Gal 3:27 .] above all at the Last Supper. [Cf. Mt 26:26 ; 1 Cor 11:24 .] It is by this action that his disciples
will recognize him after his Resurrection, [Cf. Lk 24:13-35.] and it is this _expression that the first Christians will use
to designate their Eucharistic assemblies; [Cf. Acts 2:42, 46 ; Acts 20:7, 11.] by doing so they signified that all who eat
the one broken bread, Christ, enter into communion with him and form but one body in him. [Cf. 1 Cor 10:16-17.] The Eucharistic
assembly (synaxis), because the Eucharist is celebrated amid the assembly of the faithful, the visible _expression of the
Church. [Cf. 1 Cor 11:17-34 .]"
1336. "The first announcement of the Eucharist divided the disciples, just as the announcement of the Passion scandalized
them: 'This is a hard saying; who can listen to it?' [Jn 6:60 .] The Eucharist and the Cross are stumbling blocks. It is the
same mystery and it never ceases to be an occasion of division. 'Will you also go away?': [Jn 6:67 .] the Lord's question
echoes through the ages, as a loving invitation to discover that only he has 'the words of eternal life' [In 6:68.] and that
to receive in faith the gift of his Eucharist is to receive the Lord himself."
1340. "By celebrating the Last Supper with his apostles in the course of the Passover meal, Jesus gave the Jewish Passover
its definitive meaning. Jesus' passing over to his father by his death and Resurrection, the new Passover, is anticipated
in the Supper and celebrated in the Eucharist, which fulfills the Jewish Passover and anticipates the final Passover of the
Church in the glory of the kingdom."
1355. "In the communion, preceded by the Lord's prayer and the breaking of the bread, the faithful receive 'the bread of
heaven' and 'the cup of salvation,' the body and blood of Christ who offered himself 'for the life of the world': [Jn 6:51.]
Because this bread and wine have been made Eucharist ('eucharisted,' according to an ancient _expression), 'we call this food
Eucharist, and no one may take part in it unless he believes that what we teach is true, has received baptism for the forgiveness
of sins and new birth, and lives in keeping with what Christ taught.' [St. Justin, Apol. 1, 66,1-2: PG 6, 428.]"
1356. "If from the beginning Christians have celebrated the Eucharist and in a form whose substance has not changed despite
the great diversity of times and liturgies, it is because we know ourselves to be bound by the command the Lord gave on the
eve of his Passion: 'Do this in remembrance of me.' [1 Cor 11:24-25 .]"
1359. "The Eucharist, the sacrament of our salvation accomplished by Christ on the cross, is also a sacrifice of praise
in thanksgiving for the work of creation. In the Eucharistic sacrifice the whole of creation loved by God is presented to
the Father through the death and the Resurrection of Christ. Through Christ the Church can offer the sacrifice of praise in
thanksgiving for all that God has made good, beautiful, and just in creation and in humanity."
1360. "The Eucharist is a sacrifice of thanksgiving to the Father, a blessing by which the Church expresses her gratitude
to God for all his benefits, for all that he has accomplished through creation, redemption, and sanctification. Eucharist
means first of all 'thanksgiving.'"
1365. "Because it is the memorial of Christ's Passover, the Eucharist is also a sacrifice. The sacrificial character of
the Eucharist is manifested in the very words of institution: 'This is my body which is given for you' and 'This cup which
is poured out for you is the New Covenant in my blood.' [Lk 22:19-20.] In the Eucharist Christ gives us the very body which
he gave up for us on the cross, the very blood which he 'poured out for many for the forgiveness of sins.' [Mt 26:28 .]"
1367. "The sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice: 'The victim is one and the
same: the same now offers through the ministry of priests, who then offered himself on the cross; only the manner of offering
is different.' 'In this divine sacrifice which is celebrated in the Mass, the same Christ who offered himself once in a bloody
manner on the altar of the cross is contained and is offered in an unbloody manner.' [Council of Trent (1562): DS 1743; cf.
Heb 9:14, 27.]"
1368. "The Eucharist is also the sacrifice of the Church. The Church which is the Body of Christ participates in the offering
of her Head. With him, she herself is offered whole and entire. She unites herself to his intercession with the Father for
all men. In the Eucharist the sacrifice of Christ becomes also the sacrifice of the members of his Body. The lives of the
faithful, their praise, sufferings, prayer, and work, are united with those of Christ and with his total offering, and so
acquire a new value. Christ's sacrifice present on the altar makes it possible for all generations of Christians to be united
with his offering. In the catacombs the Church is often represented as a woman in prayer, arms outstretched in the praying
position. Like Christ who stretched out his arms on the cross, through him, with him, and in him, she offers herself and intercedes
for all men."
1369. "The whole Church is united with the offering and intercession of Christ. Since he has the ministry of Peter in the
Church, the Pope is associated with every celebration of the Eucharist, wherein he is named as the sign and servant of the
unity of the universal Church. The bishop of the place is always responsible for the Eucharist, even when a priest presides;
the bishop's name is mentioned to signify his presidency over the particular Church, in the midst of his presbyterium and
with the assistance of deacons. The community intercedes also for all ministers who, for it and with it, offer the Eucharistic
sacrifice: Let only that Eucharist be regarded as legitimate, which is celebrated under (the presidency of) the bishop or
him to whom he has entrusted it. [St. Ignatius of Antioch, Ad Smyrn. 8:1; SCh 10, 138.] Through the ministry of priests the
spiritual sacrifice of the faithful is completed in union with the sacrifice of Christ the only Mediator, which in the Eucharist
is offered through the priests' hands in the name of the whole Church in an unbloody and sacramental manner until the Lord
Himself comes. [PO 2 # 4.]"
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.' [St. Thomas Aquinas, STh III, 73,
3c.] 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.' [Council of Trent (1551): DS
1651.] '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.' [Paul VI, MF 39.]"
1378. "Worship of the Eucharist. In the liturgy of the Mass we express our faith in the real presence of Christ under the
species of bread and wine by, among other ways, genuflecting or bowing deeply as a sign of adoration of the Lord. 'The Catholic
Church has always offered and still offers to the sacrament of the Eucharist the cult of adoration, not only during Mass,
but also outside of it, reserving the consecrated hosts with the utmost care, exposing them to the solemn veneration of the
faithful, and carrying them in procession.'[Paul VI, MF 56.]"
1384. "The Lord addresses an invitation to us, urging us to receive him in the sacrament of the Eucharist: '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.' [Jn 6:53 .]"
1396. "The unity of the Mystical Body: the Eucharist makes the Church. Those who receive the Eucharist are united more
closely to Christ. Through it Christ unites them to all the faithful in one body - the Church. Communion renews, strengthens,
and deepens this incorporation into the Church, already achieved by Baptism. In Baptism we have been called to form but one
body. [Cf. 1 Cor 12:13 .] The Eucharist fulfills this call: 'The cup of blessing which we bless, is it not a participation
in the blood of Christ? The bread which we break, is it not a participation in the body of Christ? Because there is one bread,
we who are many are one body, for we all partake of the one bread:' [1 Cor 10:16-17.] If you are the body and members of Christ,
then it is your sacrament that is placed on the table of the Lord; it is your sacrament that you receive. To that which you
are you respond 'Amen' ('yes, it is true!') and by responding to it you assent to it. For you hear the words, 'the Body of
Christ' and respond 'Amen.' Be then a member of the Body of Christ that your Amen may be true. [St. Augustine, Sermon 272:
PL 38, 1247.]"