To set the stage, it's during this period that we get the Council of Nicea (and thus, the Nicene Creed), the Council of Carthage (a local North African Council which reaffirms in clear terms the Catholic canon of Scripture, which Pope Damasus readily agrees with), and some of the best Christian writers of all time are on the scene. Greats like St. Athanasius, who nearly single-handedly saved the Church from heresy, and St. Augustine, the most important Church Father in the West, close out this century. And throughout it all, from the pre-Nicene period to the age of Augustine, we see a constant reaffirmation of the Real Presence of Christ in the Eucharist, and an affirmation that the words of consecration change bread and wine into His Body and Blood. Here's a sample:
I. Eusebius of Caesarea (c. 310 A.D.)
Eusebius is generally remembered as the first Church historian, and he was that. But he also wrote in defense of the faith in places like Demonstratio Evangelica, which means "The Proof of the Gospel." I should note at the outset that this is a poor translation, but it's the only one I could find in full. In any case, in Book 1, he writes that all of the sacrifices of the Old Testament prefigure Christ's perfect Sacrifice, and that this Sacrifice does away with all the forerunners, explaining:
While then the better, the great and worthy and divine sacrifice was not yet available for men, it was necessary for them by the offering of animals to pay a ransom for their own life, and this was fitly a life that represented their own nature. Thus did the holy men of old, anticipating by the Holy Spirit that a holy victim, dear to God and great, would one day come for men, as the offering for the sins of the world, believing that as prophets they must perform in symbol his sacrifice, and shew forth in type what was yet to be. But when that which was perfect was come, in accordance with the predictions of the prophets, the former sacrifices ceased at once because of the better and true Sacrifice.
Since then according to the witness of the prophets the great and precious ransom has been found for Jews and Greeks alike, the propitiation for the whole world, the life given for the life of all men, the pure offering for every stain and sin, the Lamb of God, the holy sheep dear to God, the Lamb that was foretold, by Whose inspired and mystic teaching all we Gentiles have procured the forgiveness of our former sins, and such Jews as hope in Him are freed from the curse of Moses, daily celebrating His memorial, the remembrance of His Body and Blood, and are admitted to a greater sacrifice than that of the ancient law, we do not reckon it right to fall back upon the first beggarly elements, which are symbols and likenesses but do not contain the truth itself.So the daily Eucharist is a participation in Christ's perfect Sacrifice (but not a re-Sacrifice of Christ, as he makes clear, but a Memorial). And he notes that we Christians don't need to fall back upon "the first beggarly elements" which are mere symbols. Clearly, then, his understanding of the Eucharist wasn't that it was a mere symbol. The view of the Lord's Supper that some Protestants take (that It's simply symbolic, a reminder of the true Sacrifice) is a mirror image of what Eusebius describes as now-worthless in the first paragraph.
Later, Eusebius explains the two sacrifices we offer to God: His Son (in the Eucharist; see 1 John 2:2) and a broken and contrite heart (cf. Psalm 51:17; see 1 Peter 2:5):
So, then, we sacrifice and offer incense: On the one hand when we celebrate the Memorial of His great Sacrifice according to the Mysteries He delivered to us, and bring to God the Eucharist for our salvation with holy hymns and prayers; while on the other we consecrate ourselves to Him alone and to the Word His High Priest, devoted to Him in body and soul.Nota bene: the Eucharist is offered "for our salvation."
II. St. Cyril of Jerusalem (350 A.D.)
Cyril has a lot of great stuff on the Eucharist, but nothing is as clear as Catechetical Lecture XXII. You can find one good translation here, and another here. The entire lecture is about 1 Corinthians 11:23, so it's heavily Eucharistic. In it, he says:
On the night he was betrayed our Lord Jesus Christ took bread, and when he had given thanks, he broke it and gave it to his disciples and said: “Take, eat: this is my body”. He took the cup, gave thanks and said: “Take, drink: this is my blood”. Since Christ himself has declared the bread to be his body, who can have any further doubt? Since he himself has said quite categorically, This is my blood, who would dare to question it and say that it is not his blood?
Therefore, it is with complete assurance that we receive the bread and wine as the body and blood of Christ. His body is given to us under the symbol of bread, and his blood is given to us under the symbol of wine, in order to make us by receiving them one body and blood with him. Having his body and blood in our members, we become bearers of Christ and sharers, as Saint Peter says, in the divine nature.The part I bold is a perfect summary of the Catholic view in a nutshell. Bread looks vaguely like flesh, and wine vaguely like blood. In eating the bread, it becomes part of our flesh, and in drinking the wine, it becomes part of our flesh. These are no mere coincidences. Christ uses these visible elements so that we can begin to grasp the profound invisible reality occurring at the Eucharist. But Cyril couldn't be clearer that it's only a "symbol of bread" and a "symbol of wine," and that it's not actually bread or wine, but the Body and Blood of Christ. He proceeds to explain how this fulfills the Old Testament "showbread," and then repeats:
Do not, then, regard the eucharistic elements as ordinary bread and wine: they are in fact the body and blood of the Lord, as he himself has declared. Whatever your senses may tell you, be strong in faith.
You have been taught and you are firmly convinced that what looks and tastes like bread and wine is not bread and wine but the body and the blood of Christ. You know also how David referred to this long ago when he sang: Bread gives strength to man’s heart and makes his face shine with the oil of gladness. Strengthen your heart, then, by receiving this bread as spiritual bread, and bring joy to the face of your soul.Could Cyril be any clearer?
III. St. Optatus of Milevis (c. 365 A.D.)
I've written about Optatus of Milevis before, because he's a largely-forgotten gem in the Church. Suffice to say that he was a Church Father from a generation before St. Augustine, who Augustine looked up to (listing him as one of the men whose conversion was "a quantity of gold and silver and garments" for the North African church). In Book VI of Against the Donatists, he unleashes on the Donatists for destroying Catholic altars. Now mind you, even the heretical Donatists believed in the Real Presence (Optatus notes that they even have valid sacraments). The Donatist's heresy was that sinful Catholic priests weren't able to validly confer the sacraments. This entire historical controversy, which the greats (like Augustine) get involved in, makes sense only if you believe in the Catholic sacraments. A Protestant time-traveller would find himself completely outside the argument, disagreeing vehemently with everyone. In any case, Optatus says this to the Donatists:
Basil, the founder of Eastern monasticism, had this to say of the Eucharist in his Letter XCIII to a certain Patrician named Coesaria:
Your wicked actions with regard to the Divine Sacraments have----so it seems to me----been clearly shown up. I now have to describe things done by you, as you yourselves will not be able to deny, with cruelty and folly. For what so sacrilegious as to break, to scrape, to take away altars of God, upon which you too once offered sacrifice, upon which were laid both the prayers of the people, and the Members of Christ, where Almighty God was called upon, where the Holy Spirit descended in answer to prayer, from which many have received the pledge of everlasting salvation, and the safeguard of faith, and the hope of resurrection?That's a clear statement that the Eucharist is a Sacrifice offered to God on the altar, and that it's actually His Body - both our prayers, and the "Members" of Christ Himself, are offered. And there's even a reference to the consecration prayer actually calling down the Holy Spirit. And Optatus makes a point that Protestants who speak about "altar calls" would do well to remember: "For what is an altar excepting the seat of both the Body and the Blood of Christ?" To have an altar, you have to have the Real Presence.
IV. St. Basil the Great (c. 372 A.D.)
Basil, the founder of Eastern monasticism, had this to say of the Eucharist in his Letter XCIII to a certain Patrician named Coesaria:
It is good and beneficial to communicate every day, and to partake of the Holy Body and Blood of Christ. For He distinctly says, "He that eateth my flesh and drinketh my blood hath eternal life." And who doubts that to share frequently in life, is the same thing as to have manifold life. I, indeed, communicate four times a week, on the Lord's day, on Wednesday, on Friday, and on the Sabbath, and on the other days if there is a commemoration of any Saint. It is needless to point out that for anyone in times of persecution to be compelled to take the Communion in his own hand without the presence of a priest or minister is not a serious offence, as long custom sanctions this practice from the facts themselves. All the solitaries in the desert, where there is no priest, take the communion themselves, keeping communion at home. And at Alexandria and in Egypt, each one of the laity, for the most part, keeps the Communion, at his own house, and participates in it when he lilies. For when once the priest has completed the offering, and given it, the recipient, participating in it each time as entire, is bound to believe that he properly takes and receives it from the giver. And even in the church, when the priest gives the portion, the recipient takes it with complete power over it, and so lifts it to his lips with his own hand. It has the same validity whether one portion or several portions are received from the priest at the same time.So we're seeing a clear picture: (1) the Eucharist is ordinarily offered by the priest on the tongue (although receiving by hand is acceptable, even for the laity, if the local custom permits it), (2) It's offered daily, and it's good to go daily, if possible, (3) Christ is as present in a single portion of the Eucharist as in a thousand, (4) there are feast days on the Church's liturgical calendar by this point already, and, of course, (5) the Eucharist leads to salvation.
V. St. Athanasius (c. 373 A.D.)
One of the clearest affirmations of the change in the Eucharist comes from a sermon Athanasius gave to those who had just been Baptized at the Easter Vigil, and who were about to receive First Communion. We don't know the exact date (we know he died in about 373, so it couldn't have been later than that), and we don't have the entire sermon, but from Eutyches (380 - 456), we have this fragment: (available at page 133 here):
You shall see the Levites bringing loaves and a cup of wine, and placing them on the table. So long as the prayers of supplication and entreaties have not been made, there is only bread and wine. But after the great and wonderful prayers have been completed, then the bread is become the Body, and the wine the Blood, of our Lord Jesus Christ. [...] Let us approach the celebration of the mysteries. This bread and this wine, so long as the prayers and supplications have not taken place, remain simply what they are. But after the great prayers and holy supplications have been sent forth, the Word comes down into the bread and wine - and thus His Body is confected.So before the consecration, it's bread, afterwards, it's the Body of Christ. This is plainly the language of an actual change. Besides that, we see him clearly affirming that Catholic priests are the new Levites.
VI. St. Gregory Nazianzen (c. 374 A.D.)
St. Gregory wrote a letter (Letter CLXXI) to a priest, probably his cousin, after recovering from a physical illness. Convinced his cousin's prayers benefited him, Gregory asked his cousin to pray for his recovery from all spiritual illnesses, "and loose the great mass of my sins when you lay hold of the Sacrifice of Resurrection," that is, the Eucharist. He ends the letter by asking, "cease not both to pray and to plead for me when you draw down the Word by your word, when with a bloodless cutting you sever the Body and Blood of the Lord, using your voice for the glaive." This is unambiguously about the moment of consecration, where the priest, praying the word of God from Scripture, brings down the Word of God, Jesus Christ Himself, into the Eucharist.
VII. St. Gregory of Nyssa (385 A.D.)
If you recall from Part I, Justin Martyr described the Eucharist as Christ "transmutating" us into His Body. The Greek words used were "kata metabolen," and I mentioned that they suggested Christ was "metabolizing" us. St. Gregory of Nyssa makes this point really explicitly in Chapter XXXVII of his Great Catechism. He's answering the question, "how can that one Body of Christ vivify the whole of mankind, all, that is, in whomsoever there is Faith, and yet, though divided amongst all, be itself not diminished?" How can Christ be in every Tabernacle, without reducing Himself? His answer is fascinating. He says:
Some animals feed on roots which they dig up. Of others grass is the food, of others different kinds of flesh, but for man above all things bread; and, in order to continue and preserve the moisture of his body, drink, not simply water, but water frequently sweetened with wine, to join forces with our internal heat. He, therefore, who thinks of these things, thinks by implication of the particular bulk of our body. For those things by being within me became my blood and flesh, the corresponding nutriment by its power of adaptation being changed into the form of my body.This "power of adaptation" is what we now call metabolism. So he's making explicitly the same point Justin suggested, and he mentions bread and the water/wine mixture for obviously Eucharistic reasons. He's making an important point here about why Christ used the species of bread and wine, instead of some other instrument, to establish the Eucharist. He suggests it's because we understand metabolizing those things, because we're used to consuming them on a daily basis. He then notes that Christ, the Word of God, while He walked among us, metabolized bread and wine daily, since "the body into which God entered, by partaking of the nourishment of bread, was, in a certain measure, the same with it; that nourishment, as we have said, changing itself into the nature of the body." So Christ changed bread into His Body naturally, by eating it, and wine into His Blood by drinking it. And what changed the bread into the Body of Christ? The Word: "For that Body was once, by implication, bread, but has been consecrated by the inhabitation of the Word that tabernacled in the flesh. Therefore, from the same cause as that by which the bread that was transformed in that Body was changed to a Divine potency, a similar result takes place now."
So just as in during His days walking amongst us, Christ (the Word), transformed bread into His Body, now at Mass, the words of consecration transform bread into Christ's Body. But Gregory notes that while one foreshadows the other, they're not the exact same:
For as in that case, too, the grace of the Word used to make holy the Body, the substance of which came of the bread, and in a manner was itself bread, so also in this case the bread, as says the Apostle, "is sanctified by the Word of God and prayer"; not that it advances by the process of eating to the stage of passing into the body of the Word, but it is at once changed into the body by means of the Word, as the Word itself said, "This is My Body."So the bread then ceases to be bread - not slowly, as it does in natural metabolism, but instantaneously, at the words of Christ in the consecration: "This is My Body."
Gregory draws one further application out of the connection to metabolism. Consider that bread, by itself, molds and goes bad after a few weeks, but not bread that becomes part of our bodies - we don't see an arm start molding because it was our "bread arm." No, in transforming the bread into our bodies, we create a part of us that can last as long as we do. Gregory says the same thing happens with us at the Eucharist. On our own, we rot in the ground (or in Hell), but if we're metabolized by Christ, we're preserved from this rotting:
Since, then, that God-containing flesh partook for its substance and support of this particular nourishment also, and since the God who was manifested infused Himself into perishable humanity for this purpose, viz. that by this communion with Deity mankind might at the same time be deified, for this end it is that, by dispensation of His grace, He disseminates Himself in every believer through that flesh, whose substance comes from bread and wine, blending Himself with the bodies of believers, to secure that, by this union with the immortal, man, too, may be a sharer in incorruption. He gives these gifts by virtue of the benediction through which He transelements the natural quality of these visible things to that immortal thing.He even calls this "transelementation," the term the East still uses for transubstantiation.
VIII. St. John Chrysostom (c. 387 A.D.)
The name Chrysostom means "golden-mouthed," and referred to St. John Chrysostom's beautiful preaching. He lives up to his title in this passage from his Treatise on the Priesthood, when he describes the awe and grandeur of the Mass:
For when you see the Lord sacrificed, and laid upon the altar, and the priest standing and praying over the victim, and all the worshippers empurpled with that precious blood, can you then think that you are still among men, and standing upon the earth? Are you not, on the contrary, straightway translated to Heaven, and casting out every carnal thought from the soul, do you not with disembodied spirit and pure reason contemplate the things which are in Heaven? Oh! What a marvel! What love of God to man! He who sits on high with the Father is at that hour held in the hands of all, and gives Himself to those who are willing to embrace and grasp Him. And this all do through the eyes of faith! Do these things seem to you fit to be despised, or such as to make it possible for any one to be uplifted against them?By the way, Called to Communion has a good post talking about St. John Chrysostom's view of the Liturgy as Heaven on Earth, and uses the passage which I'm quoting from here quite elegantly.
IX. St. Ambrose (c. 387-390 A.D.)
Ambrose, in Chapter VIII of On the Mysteries, goes through lots of Old Testament examples, showing how they prefigure the Sacraments - a.k.a., the "Mysteries." He then says:
We have proved the sacraments of the Church to be the more ancient, now recognize that they are superior. In very truth it is a marvellous thing that God rained manna on the fathers, and fed them with daily food from heaven; so that it is said, "So man did eat angels' food." But yet all those who ate that food died in the wilderness, but that food which you receive, that living Bread which came down from heaven, furnishes the substance of eternal life; and whosoever shall eat of this Bread shall never die, and it is the Body of Christ.
Similarly, Ambrose notes that the water the Israelites drank in the desert came from the Rock, who was Christ. And Ambrose makes a brilliant point: if these things directly from God are only foreshadowing of something bigger, that something bigger can only be God Himself. As he says, "If that which you so wonder at is but shadow, how great must that be whose very shadow you wonder at." Christ fulfills this in the Eucharist, since "light is better than shadow, truth than a figure, the Body of its Giver than the manna from heaven."
In the next chapter, Chapter IX, Ambrose directly addresses the fact that the Eucharist seems to be bread and wine:
Perhaps you will say, "I see something else, how is it that you assert that I receive the Body of Christ?" And this is the point which remains for us to prove. And what evidence shall we make use of? Let us prove that this is not what nature made, but what the blessing consecrated, and the power of blessing is greater than that of nature, because by blessing nature itself is changed.
He goes through numerous examples from Scripture, but his best is the Incarnation of Christ:
Did the course of nature proceed as usual when the Lord Jesus was born of Mary? If we look to the usual course, a woman ordinarily conceives after connection with a man. And this body which we make is that which was born of the Virgin. Why do you seek the order of nature in the Body of Christ, seeing that the Lord Jesus Himself was born of a Virgin, not according to nature? It is the true Flesh of Christ which crucified and buried, this is then truly the Sacrament of His Body.
If we can accept by faith that a Man who seems to our senses to have been the product of a sexual union is actually no mere mortal, but God Himself, born of a Virgin, then how can we balk that the Eucharist isn't what it at first seems to our senses, particularly when both the miracles of the Virgin Birth, the Crucifixion, and the Eucharist all relate to the Flesh of that Same Body?
Well, that sums it up. I may go back and fill in a few other Fathers here and there, but as a basic outline, I think that this suffices. At the very least, it shows a constant belief held from generation to generation that the Eucharist becomes the Body and Blood of Christ at the Institution, and ceases to be literal bread and wine. This Eucharist is offered in the Sacrifice of the Mass at the altar, and It saves us by offering up Christ's Once-for-All Sacrifice to God the Father on our behalf. This is clearly the view of the Catholic Church, and these views (in whole or in part) are rejected by every Protestant denomination I know of. In fact, a great many Protestants would readily call these beliefs idolatry, or at least a false Gospel. But it's through these exact same men that we know which books are in the Bible, through them that we've even heard of Jesus of Nazareth, and a great many of them paid the ultimate price of martyrdom. Plainly, to reject them is to reject the Church of the first, second, third, and fourth century, to willingly claim superior knowledge of Christ's teaching over those who preserved and taught His Gospel for centuries.