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There is a reason that was addressed in that Epistle.. do you know what it was?

I don't understand your point. Please make it directly.

Also note that Paul does not call it the "body and blood" of Jesus ..He calls it bread and a cup

He says that the bread and wine is the Body and Blood of Christ. He's predicating the latter of the former, since the latter appears as the former.

"For those who eat and drink without discerning the body of Christ eat and drink judgment on themselves."

The passage has always been understood this way.

Ignatius of Antioch
"I have no taste for corruptible food nor for the pleasures of this life. I desire the bread of God, which is the flesh of Jesus Christ, who was of the seed of David; and for drink I desire his blood, which is love incorruptible" (Letter to the Romans 7:3 [A.D. 110]).
"Take note of those who hold heterodox opinions on the grace of Jesus Christ which has come to us, and see how contrary their opinions are to the mind of God. . . . They abstain from the Eucharist and from prayer because they do not confess that the Eucharist is the flesh of our Savior Jesus Christ, flesh which suffered for our sins and which that Father, in his goodness, raised up again. They who deny the gift of God are perishing in their disputes" (Letter to the Smyrnaeans 6:2–7:1 [A.D. 110]).
Justin Martyr
"We call this food Eucharist, and no one else is permitted to partake of it, except one who believes our teaching to be true and who has been washed in the washing which is for the remission of sins and for regeneration [i.e., has received baptism] and is thereby living as Christ enjoined. For not as common bread nor common drink do we receive these; but since Jesus Christ our Savior was made incarnate by the word of God and had both flesh and blood for our salvation, so too, as we have been taught, the food which has been made into the Eucharist by the Eucharistic prayer set down by him, and by the change of which our blood and flesh is nurtured, is both the flesh and the blood of that incarnated Jesus" (First Apology 66 [A.D. 151]).
Irenaeus
"If the Lord were from other than the Father, how could he rightly take bread, which is of the same creation as our own, and confess it to be his body and affirm that the mixture in the cup is his blood?" (Against Heresies 4:33–32 [A.D. 189]).
"He has declared the cup, a part of creation, to be his own blood, from which he causes our blood to flow; and the bread, a part of creation, he has established as his own body, from which he gives increase unto our bodies. When, therefore, the mixed cup [wine and water] and the baked bread receives the Word of God and becomes the Eucharist, the body of Christ, and from these the substance of our flesh is increased and supported, how can they say that the flesh is not capable of receiving the gift of God, which is eternal life—flesh which is nourished by the body and blood of the Lord, and is in fact a member of him?" (ibid., 5:2).
Clement of Alexandria
"’Eat my flesh,’ [Jesus] says, ‘and drink my blood.’ The Lord supplies us with these intimate nutrients, he delivers over his flesh and pours out his blood, and nothing is lacking for the growth of his children" (The Instructor of Children 1:6:43:3 [A.D. 191]).
Tertullian
"[T]here is not a soul that can at all procure salvation, except it believe whilst it is in the flesh, so true is it that the flesh is the very condition on which salvation hinges. And since the soul is, in consequence of its salvation, chosen to the service of God, it is the flesh which actually renders it capable of such service. The flesh, indeed, is washed [in baptism], in order that the soul may be cleansed . . . the flesh is shadowed with the imposition of hands [in confirmation], that the soul also may be illuminated by the Spirit; the flesh feeds [in the Eucharist] on the body and blood of Christ, that the soul likewise may be filled with God" (The Resurrection of the Dead 8 [A.D. 210]).
Hippolytus
"‘And she [Wisdom] has furnished her table’ [Prov. 9:2] . . . refers to his [Christ’s] honored and undefiled body and blood, which day by day are administered and offered sacrificially at the spiritual divine table, as a memorial of that first and ever-memorable table of the spiritual divine supper [i.e., the Last Supper]" (Fragment from Commentary on Proverbs [A.D. 217]).
Origen
"Formerly there was baptism in an obscure way . . . now, however, in full view, there is regeneration in water and in the Holy Spirit. Formerly, in an obscure way, there was manna for food; now, however, in full view, there is the true food, the flesh of the Word of God, as he himself says: ‘My flesh is true food, and my blood is true drink’ [John 6:55]" (Homilies on Numbers 7:2 [A.D. 248]).
Cyprian of Carthage
"He [Paul] threatens, moreover, the stubborn and forward, and denounces them, saying, ‘Whosoever eats the bread or drinks the cup of the Lord unworthily, is guilty of the body and blood of the Lord’ [1 Cor. 11:27]. All these warnings being scorned and contemned—[lapsed Christians will often take Communion] before their sin is expiated, before confession has been made of their crime, before their conscience has been purged by sacrifice and by the hand of the priest, before the offense of an angry and threatening Lord has been appeased, [and so] violence is done to his body and blood; and they sin now against their Lord more with their hand and mouth than when they denied their Lord" (The Lapsed 15–16 [A.D. 251]).
Council of Nicaea I
"It has come to the knowledge of the holy and great synod that, in some districts and cities, the deacons administer the Eucharist to the presbyters [i.e., priests], whereas neither canon nor custom permits that they who have no right to offer [the Eucharistic sacrifice] should give the Body of Christ to them that do offer [it]" (Canon 18 [A.D. 325]).
Aphraahat the Persian Sage
"After having spoken thus [at the Last Supper], the Lord rose up from the place where he had made the Passover and had given his body as food and his blood as drink, and he went with his disciples to the place where he was to be arrested. But he ate of his own body and drank of his own blood, while he was pondering on the dead. With his own hands the Lord presented his own body to be eaten, and before he was crucified he gave his blood as drink" (Treatises 12:6 [A.D. 340]).
Cyril of Jerusalem
"The bread and the wine of the Eucharist before the holy invocation of the adorable Trinity were simple bread and wine, but the invocation having been made, the bread becomes the body of Christ and the wine the blood of Christ" (Catechetical Lectures 19:7 [A.D. 350]).
"Do not, therefore, regard the bread and wine as simply that; for they are, according to the Master’s declaration, the body and blood of Christ. Even though the senses suggest to you the other, let faith make you firm. Do not judge in this matter by taste, but be fully assured by the faith, not doubting that you have been deemed worthy of the body and blood of Christ. . . . [Since you are] fully convinced that the apparent bread is not bread, even though it is sensible to the taste, but the body of Christ, and that the apparent wine is not wine, even though the taste would have it so, . . . partake of that bread as something spiritual, and put a cheerful face on your soul" (ibid., 22:6, 9).
Ambrose of Milan
"Perhaps you may be saying, ‘I see something else; how can you assure me that I am receiving the body of Christ?’ It but remains for us to prove it. And how many are the examples we might use! . . . Christ is in that sacrament, because it is the body of Christ" (The Mysteries 9:50, 58 [A.D. 390]).
Theodore of Mopsuestia
"When [Christ] gave the bread he did not say, ‘This is the symbol of my body,’ but, ‘This is my body.’ In the same way, when he gave the cup of his blood he did not say, ‘This is the symbol of my blood,’ but, ‘This is my blood’; for he wanted us to look upon the [Eucharistic elements] after their reception of grace and the coming of the Holy Spirit not according to their nature, but receive them as they are, the body and blood of our Lord. We ought . . . not regard [the elements] merely as bread and cup, but as the body and blood of the Lord, into which they were transformed by the descent of the Holy Spirit" (Catechetical Homilies 5:1 [A.D. 405]).
Augustine
"Christ was carried in his own hands when, referring to his own body, he said, ‘This is my body’ [Matt. 26:26]. For he carried that body in his hands" (Explanations of the Psalms 33:1:10 [A.D. 405]).
"I promised you [new Christians], who have now been baptized, a sermon in which I would explain the sacrament of the Lord’s Table. . . . That bread which you see on the altar, having been sanctified by the word of God, is the body of Christ. That chalice, or rather, what is in that chalice, having been sanctified by the word of God, is the blood of Christ" (Sermons 227 [A.D. 411]).
...
"What you see is the bread and the chalice; that is what your own eyes report to you. But what your faith obliges you to accept is that the bread is the body of Christ and the chalice is the blood of Christ. This has been said very briefly, which may perhaps be sufficient for faith; yet faith does not desire instruction" (ibid., 272).
Council of Ephesus
"We will necessarily add this also. Proclaiming the death, according to the flesh, of the only-begotten Son of God, that is Jesus Christ, confessing his resurrection from the dead, and his ascension into heaven, we offer the unbloody sacrifice in the churches, and so go on to the mystical thanksgivings, and are sanctified, having received his holy flesh and the precious blood of Christ the Savior of us all. And not as common flesh do we receive it; God forbid: nor as of a man sanctified and associated with the Word according to the unity of worth, or as having a divine indwelling, but as truly the life-giving and very flesh of the Word himself. For he is the life according to his nature as God, and when he became united to his flesh, he made it also to be life-giving" (Session 1, Letter of Cyril to Nestorius [A.D. 431]).

Just one more thing Thomas Is there a Magisterial, infallible interpretation of that passage somewhere? If so please don't forget to cite the document or statement that contains the interpretation is stated to be infallible.

The writings of the early Christians are an aspect of Sacred Apostolic Tradition --the context within which Scripture is interpreted.

With regard to Church Teaching, below is a portion of the entry on the Eucharist from the Catechism of the Catholic which draws on both Scripture and Apostolic Tradition. Pope John Paul II called the Catechism a "sure norm of the faith."

"Listen to the church... If he refuses to listen to the church, treat him as a pagan or tax collector." --Jesus

ARTICLE 3
THE SACRAMENT OF THE EUCHARIST
1322 The holy Eucharist completes Christian initiation. Those who have been raised to the dignity of the royal priesthood by Baptism and configured more deeply to Christ by Confirmation participate with the whole community in the Lord's own sacrifice by means of the Eucharist.
1323 "At the Last Supper, on the night he was betrayed, our Savior instituted the Eucharistic sacrifice of his Body and Blood. This he did in order to perpetuate the sacrifice of the cross throughout the ages until he should come again, and so to entrust to his beloved Spouse, the Church, a memorial of his death and resurrection: a sacrament of love, a sign of unity, a bond of charity, a Paschal banquet 'in which Christ is consumed, the mind is filled with grace, and a pledge of future glory is given to us.'"135
I. THE EUCHARIST - SOURCE AND SUMMIT OF ECCLESIAL LIFE
1324 The Eucharist is "the source and summit of the Christian life."136 "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."137
1325 "The Eucharist is the efficacious sign and sublime cause of that communion in the divine life and that unity of the People of God by which the Church is kept in being. It is the culmination both of God's action sanctifying the world in Christ and of the worship men offer to Christ and through him to the Father in the Holy Spirit."138
1326 Finally, by the Eucharistic celebration we already unite ourselves with the heavenly liturgy and anticipate eternal life, when God will be all in all.139
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."140
II. WHAT IS THIS SACRAMENT CALLED?
1328 The inexhaustible richness of this sacrament is expressed in the different names we give it. Each name evokes certain aspects of it. It is called:
Eucharist, because it is an action of thanksgiving to God. The Greek words eucharistein141 and eulogein142 recall the Jewish blessings that proclaim - especially during a meal - God's works: creation, redemption, and sanctification.
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.143
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,144 above all at the Last Supper.145 It is by this action that his disciples will recognize him after his Resurrection,146 and it is this expression that the first Christians will use to designate their Eucharistic assemblies;147 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.148
The Eucharistic assembly (synaxis), because the Eucharist is celebrated amid the assembly of the faithful, the visible expression of the Church.149
1330 The memorial of the Lord's Passion and Resurrection.
The Holy Sacrifice, because it makes present the one sacrifice of Christ the Savior and includes the Church's offering. The terms holy sacrifice of the Mass, "sacrifice of praise," spiritual sacrifice, pure and holy sacrifice are also used,150 since it completes and surpasses all the sacrifices of the Old Covenant.
The Holy and Divine Liturgy, because the Church's whole liturgy finds its center and most intense expression in the celebration of this sacrament; in the same sense we also call its celebration the Sacred Mysteries. We speak of the Most Blessed Sacrament because it is the Sacrament of sacraments. The Eucharistic species reserved in the tabernacle are designated by this same name.
1331 Holy Communion, because by this sacrament we unite ourselves to Christ, who makes us sharers in his Body and Blood to form a single body.151 We also call it: the holy things (ta hagia; sancta)152 - the first meaning of the phrase "communion of saints" in the Apostles' Creed - the bread of angels, bread from heaven, medicine of immortality,153 viaticum. . . .
1332 Holy Mass (Missa), because the liturgy in which the mystery of salvation is accomplished concludes with the sending forth (missio) of the faithful, so that they may fulfill God's will in their daily lives.
III. THE EUCHARIST IN THE ECONOMY OF SALVATION
The signs of bread and wine
1333 At the heart of the Eucharistic celebration are the bread and wine that, by the words of Christ and the invocation of the Holy Spirit, become Christ's Body and Blood. Faithful to the Lord's command the Church continues to do, in his memory and until his glorious return, what he did on the eve of his Passion: "He took bread. . . ." "He took the cup filled with wine. . . ." The signs of bread and wine become, in a way surpassing understanding, the Body and Blood of Christ; they continue also to signify the goodness of creation. Thus in the Offertory we give thanks to the Creator for bread and wine,154 fruit of the "work of human hands," but above all as "fruit of the earth" and "of the vine" - gifts of the Creator. The Church sees in the gesture of the king-priest Melchizedek, who "brought out bread and wine," a prefiguring of her own offering.155
1334 In the Old Covenant bread and wine were offered in sacrifice among the first fruits of the earth as a sign of grateful acknowledgment to the Creator. But they also received a new significance in the context of the Exodus: the unleavened bread that Israel eats every year at Passover commemorates the haste of the departure that liberated them from Egypt; the remembrance of the manna in the desert will always recall to Israel that it lives by the bread of the Word of God;156 their daily bread is the fruit of the promised land, the pledge of God's faithfulness to his promises. The "cup of blessing"157 at the end of the Jewish Passover meal adds to the festive joy of wine an eschatological dimension: the messianic expectation of the rebuilding of Jerusalem. When Jesus instituted the Eucharist, he gave a new and definitive meaning to the blessing of the bread and the cup.
1335 The miracles of the multiplication of the loaves, when the Lord says the blessing, breaks and distributes the loaves through his disciples to feed the multitude, prefigure the superabundance of this unique bread of his Eucharist.158 The sign of water turned into wine at Cana already announces the Hour of Jesus' glorification. It makes manifest the fulfillment of the wedding feast in the Father's kingdom, where the faithful will drink the new wine that has become the Blood of Christ.159
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?"160 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?":161 the Lord's question echoes through the ages, as a loving invitation to discover that only he has "the words of eternal life"162 and that to receive in faith the gift of his Eucharist is to receive the Lord himself.
The institution of the Eucharist
1337 The Lord, having loved those who were his own, loved them to the end. Knowing that the hour had come to leave this world and return to the Father, in the course of a meal he washed their feet and gave them the commandment of love.163 In order to leave them a pledge of this love, in order never to depart from his own and to make them sharers in his Passover, he instituted the Eucharist as the memorial of his death and Resurrection, and commanded his apostles to celebrate it until his return; "thereby he constituted them priests of the New Testament."164
1338 The three synoptic Gospels and St. Paul have handed on to us the account of the institution of the Eucharist; St. John, for his part, reports the words of Jesus in the synagogue of Capernaum that prepare for the institution of the Eucharist: Christ calls himself the bread of life, come down from heaven.165
1339 Jesus chose the time of Passover to fulfill what he had announced at Capernaum: giving his disciples his Body and his Blood:
Then came the day of Unleavened Bread, on which the passover lamb had to be sacrificed. So Jesus sent Peter and John, saying, "Go and prepare the passover meal for us, that we may eat it. . . ." They went . . . and prepared the passover. And when the hour came, he sat at table, and the apostles with him. And he said to them, "I have earnestly desired to eat this passover with you before I suffer; for I tell you I shall not eat it again until it is fulfilled in the kingdom of God.". . . . And he took bread, and when he had given thanks he broke it and gave it to them, saying, "This is my body which is given for you. Do this in remembrance of me." And likewise the cup after supper, saying, "This cup which is poured out for you is the New Covenant in my blood."166
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.
"Do this in memory of me"
1341 The command of Jesus to repeat his actions and words "until he comes" does not only ask us to remember Jesus and what he did. It is directed at the liturgical celebration, by the apostles and their successors, of the memorial of Christ, of his life, of his death, of his Resurrection, and of his intercession in the presence of the Father.167
1342 From the beginning the Church has been faithful to the Lord's command. Of the Church of Jerusalem it is written:
They devoted themselves to the apostles' teaching and fellowship, to the breaking of bread and the prayers. . . . Day by day, attending the temple together and breaking bread in their homes, they partook of food with glad and generous hearts.168
1343 It was above all on "the first day of the week," Sunday, the day of Jesus' resurrection, that the Christians met "to break bread."169 From that time on down to our own day the celebration of the Eucharist has been continued so that today we encounter it everywhere in the Church with the same fundamental structure. It remains the center of the Church's life.
1344 Thus from celebration to celebration, as they proclaim the Paschal mystery of Jesus "until he comes," the pilgrim People of God advances, "following the narrow way of the cross,"170 toward the heavenly banquet, when all the elect will be seated at the table of the kingdom.
IV. THE LITURGICAL CELEBRATION OF THE EUCHARIST
The Mass of all ages
1345 As early as the second century we have the witness of St. Justin Martyr for the basic lines of the order of the Eucharistic celebration. They have stayed the same until our own day for all the great liturgical families. St. Justin wrote to the pagan emperor Antoninus Pius (138-161) around the year 155, explaining what Christians did:
On the day we call the day of the sun, all who dwell in the city or country gather in the same place. The memoirs of the apostles and the writings of the prophets are read, as much as time permits.
When the reader has finished, he who presides over those gathered admonishes and challenges them to imitate these beautiful things.
Then we all rise together and offer prayers* for ourselves . . .and for all others, wherever they may be, so that we may be found righteous by our life and actions, and faithful to the commandments, so as to obtain eternal salvation.
When the prayers are concluded we exchange the kiss.
Then someone brings bread and a cup of water and wine mixed together to him who presides over the brethren.
He takes them and offers praise and glory to the Father of the universe, through the name of the Son and of the Holy Spirit and for a considerable time he gives thanks (in Greek: eucharistian) that we have been judged worthy of these gifts.
When he has concluded the prayers and thanksgivings, all present give voice to an acclamation by saying: 'Amen.'
When he who presides has given thanks and the people have responded, those whom we call deacons give to those present the "eucharisted" bread, wine and water and take them to those who are absent.171
1346 The liturgy of the Eucharist unfolds according to a fundamental structure which has been preserved throughout the centuries down to our own day. It displays two great parts that form a fundamental unity:
- the gathering, the liturgy of the Word, with readings, homily and general intercessions;
- the liturgy of the Eucharist, with the presentation of the bread and wine, the consecratory thanksgiving, and communion.
The liturgy of the Word and liturgy of the Eucharist together form "one single act of worship";172 the Eucharistic table set for us is the table both of the Word of God and of the Body of the Lord.173
1347 Is this not the same movement as the Paschal meal of the risen Jesus with his disciples? Walking with them he explained the Scriptures to them; sitting with them at table "he took bread, blessed and broke it, and gave it to them."174
The movement of the celebration
1348 All gather together. Christians come together in one place for the Eucharistic assembly. At its head is Christ himself, the principal agent of the Eucharist. He is high priest of the New Covenant; it is he himself who presides invisibly over every Eucharistic celebration. It is in representing him that the bishop or priest acting in the person of Christ the head (in persona Christi capitis) presides over the assembly, speaks after the readings, receives the offerings, and says the Eucharistic Prayer. All have their own active parts to play in the celebration, each in his own way: readers, those who bring up the offerings, those who give communion, and the whole people whose "Amen" manifests their participation.
1349 The Liturgy of the Word includes "the writings of the prophets," that is, the Old Testament, and "the memoirs of the apostles" (their letters and the Gospels). After the homily, which is an exhortation to accept this Word as what it truly is, the Word of God,175 and to put it into practice, come the intercessions for all men, according to the Apostle's words: "I urge that supplications, prayers, intercessions, and thanksgivings be made for all men, for kings, and all who are in high positions."176
1350 The presentation of the offerings (the Offertory). Then, sometimes in procession, the bread and wine are brought to the altar; they will be offered by the priest in the name of Christ in the Eucharistic sacrifice in which they will become his body and blood. It is the very action of Christ at the Last Supper - "taking the bread and a cup." "The Church alone offers this pure oblation to the Creator, when she offers what comes forth from his creation with thanksgiving."177 The presentation of the offerings at the altar takes up the gesture of Melchizedek and commits the Creator's gifts into the hands of Christ who, in his sacrifice, brings to perfection all human attempts to offer sacrifices.
1351 From the very beginning Christians have brought, along with the bread and wine for the Eucharist, gifts to share with those in need. This custom of the collection, ever appropriate, is inspired by the example of Christ who became poor to make us rich:178
Those who are well off, and who are also willing, give as each chooses. What is gathered is given to him who presides to assist orphans and widows, those whom illness or any other cause has deprived of resources, prisoners, immigrants and, in a word, all who are in need.179
1352 The anaphora: with the Eucharistic Prayer - the prayer of thanksgiving and consecration - we come to the heart and summit of the celebration:
In the preface, the Church gives thanks to the Father, through Christ, in the Holy Spirit, for all his works: creation, redemption, and sanctification. The whole community thus joins in the unending praise that the Church in heaven, the angels and all the saints, sing to the thrice-holy God.
1353 In the epiclesis, the Church asks the Father to send his Holy Spirit (or the power of his blessing180) on the bread and wine, so that by his power they may become the body and blood of Jesus Christ and so that those who take part in the Eucharist may be one body and one spirit (some liturgical traditions put the epiclesis after the anamnesis).
In the institution narrative, the power of the words and the action of Christ, and the power of the Holy Spirit, make sacramentally present under the species of bread and wine Christ's body and blood, his sacrifice offered on the cross once for all.
1354 In the anamnesis that follows, the Church calls to mind the Passion, resurrection, and glorious return of Christ Jesus; she presents to the Father the offering of his Son which reconciles us with him.
In the intercessions, the Church indicates that the Eucharist is celebrated in communion with the whole Church in heaven and on earth, the living and the dead, and in communion with the pastors of the Church, the Pope, the diocesan bishop, his presbyterium and his deacons, and all the bishops of the whole world together with their Churches.
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":181
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."182

I assume that you regard the Eucharist to be merely symbolic.

If that's the case, your position contradict's Luther's doctrine of consubstantiation.

If this is correct, then you must regard Luther's interpretation of Scripture to be erroneous.

If Luther misinterpreted Scripture with regard to something as important as the "Lord's Supper," how can you be sure that he didn't err with respect to his doctrine of Sola Scriptura, which doesn't appear anywhere in the Bible, or in Christian history, until the invention of the printing press?

Finally, St. Thomas' commentary on 1 Corinthians is worth reading, but is very long. Below is a brief exerpt:

688. – First, therefore, he says, Therefore, from the fact that this which is received sacramentally is the body of Christ and what is drunk is the blood of Christ, whoever eats this bread or drinks the cup in an unworthy manner will by guilty of profaning the body and blood of the Lord. In these words must be considered, first, how someone eats or drinks unworthily. According to a Gloss this happens in three ways: first, as to the celebration of this sacrament, namely, because someone celebrates the sacrament in a manner different from that handed down by Christ; for example, if he offers in this sacrament a bread other than wheaten or some liquid other than wine from the grape of the vine. Hence it says in Lev (10:1) that Nadab and Abihu, sons of Aaron, offered before the Lord “unholy fire, such as he had not commanded them. And fire came forth from the presence of the Lord and devoured them.”
689. – Secondly, from the fact that someone approached the Eucharist with a mind not devout. This lack of devotion is sometimes venial, as when someone with his mind distracted by worldly affairs approaches this sacrament habitually retaining due reverence toward it; and such lack of devotion, although it impedes the fruit of this sacrament, which is spiritual refreshment, does not make one guilty of the body and blood of the Lord, as the Apostle says here. But a certain lack of devotion is a mortal sin, i.e., when it involves contempt of this sacrament, as it says in Mal (1:12): “But you profane it when you say that the Lord’s table is polluted and its food may be despised.” It is of such lack of devotion that the Gloss speaks.
690. – In a third way someone is said to be unworthy, because he approaches the Eucharist with the intention of sinning mortally. For it says in Lev (21:23): “He shall not approach the altar, because he has a blemish.” Someone is understood to have a blemish as long as he persists in the intention of sinning, which, however, is taken away through penitence. By contrition, indeed, which takes away the will to sin with the intention of confession and making satisfaction, as to the remission of guilt and eternal punishment; by confession and satisfaction as to the total remission of punishment and reconciliation with the members of the Church. Therefore, in cases of necessity, as when someone does not have an abundance of confessors, contrition is enough for receiving this sacrament. But as a general rule, confession with some satisfaction should precede. Hence in the book on Church Dogmas it says: “One who desires to go to communion should make satisfaction with tears and prayers, and trusting in the Lord approach the Eucharist clean, free from care, and secure. But I say this of the person not burdened with capital and mortal sins. For the one whom mortal sins committed after baptism press down, I advise to make satisfaction with public penance, and so be joined to communion by the judgment of the priest, if he does not wish to receive the condemnation of the Church.” ...