Irenaeus was a 2nd-century bishop of Lyons in modern-day France. He knew Polycarp, who was a disciple of the Apostle John. He, therefore, serves as a significant witness to the early Church’s development, especially as it was consolidating itself against divergent groups. In his monumental Against Heresies, Irenaeus counters the various Gnostic groups, which misconstrued foundational beliefs of the Christian Faith, like the Incarnation of Christ.
Thanks to Irenaeus, we get an astonishingly clear look at the Faith of the second-century Church. What follows are twelve topics derived from his work Against Heresies. A straightforward reading of the selected quotes is sufficient to show that the early church was indeed the Catholic Church. From fundamental beliefs like the Trinity and Incarnation to the nature of the Church and its leadership in Rome, to the Eucharistic presence of Jesus and the role of Mary, Irenaeus reveals that the faith in continuity with the original Apostles was the Catholic Faith.
12 Points In St. Irenaeus’ Against Heresies That Show The Catholic Church Was The First Church
1. THE TRINITY: GOD, HIS WORD & HIS SPIRIT
Contrary to the caricatures of God on display in today’s secular world, Irenaeus offers a sophisticated notion of God that is as robust as that of later Medieval philosophy. God is the entirely “simple” being (that is, without parts) who just is His own intelligence, reason, and the like. He is immaterial Spirit:
Because he is pure being and goodness—the “source of all that is good”—Irenaeus can say that human fulfillment is precisely found in God. God does not need us, and we can contribute nothing to God. Instead, to follow and serve God is the “glory of man” (Against Heresies 4:14).
That God is intelligent implies the existence of His Word, the reason of God, that is eternally present to Him. Along with the Spirit, the Word is in some sense distinct yet equally present to God. Here Irenaeus is clearly articulating the substance of the doctrine of the Trinity, even without using that word. For Irenaeus, the revelation of God as Father, Son, and Spirit forms the unifying structure of the Christian Faith. (In fact, he often summarizes the Faith in a way that resembles the later Creeds.):
“The rule of truth which we hold, is, that there is one God Almighty, who made all things by His Word, and fashioned and formed, out of that which had no existence, all things which exist. […] He who, by His Word and Spirit, makes, and disposes, and governs all things, and commands all things into existence….For with Him were always present the Word and Wisdom, the Son and the Spirit, by whom and in whom, freely and spontaneously, He made all things […] I have also largely demonstrated, that the Word, namely the Son, was always with the Father; and that Wisdom also, which is the Spirit, was present with Him, anterior to all creation.” –Against Heresies 4:20
2. JESUS CHRIST: THE WORD MADE FLESH
Throughout Irenaeus’ writings, he explicates the importance of the Incarnation—of the eternal Word of God becoming man in Christ. Many of the quasi-Christian knockoffs of the second century, the Gnostics, misconstrued the Incarnation. Unlike those sensational documentaries that air on the History Channel—or even unfortunate blockbusters like The Da Vinci Code—that claim the divinity of Christ was some centuries-later upgrade, Christ’s divinity was proclaimed from the very beginning of the Faith. With Irenaeus, you have an “average Joe” bishop proclaiming the truth about 150 years before the Council of Nicaea:
Why would God become man? Irenaeus has plenty to say about this; in fact, he does so in a very beautiful way, as will be expressed below as well. Because the Word of God just is the eternal image of God the Father, the Word’s becoming man in Christ is just God’s way of revealing Himself to man. By becoming man, God invites all persons into relationship: And for this purpose did the Father reveal the Son, that through His instrumentality He might be manifested to all (Against Heresies 4:6).
As Irenaeus also goes at pains to show, the Incarnation was prefigured by and is the fulfillment of the Old Testament. Countering those Gnostics who put a sharp wedge between the Old Testament and New Testament—something even many modern Christians are tempted to do—Irenaeus instead shows that the entire story of Scripture reveals God’s one plan of salvation. The Old Testament is only fully understood in light of Christ; but it thereby remains important all the more:
“And for this reason, indeed, when at this present time the law is read to the Jews, it is like a fable; for they do not possess the explanation of all things pertaining to the advent of the Son of God, which took place in human nature; but when it is read by the Christians, it is a treasure, hid indeed in a field, but brought to light by the cross of Christ, and explained, both enriching the understanding of men, and showing forth the wisdom of God and declaring His dispensations with regard to man, and forming the kingdom of Christ beforehand.” –Against Heresies 4:26
3. RECAPILULATION & REDEMPTION: HOW CHRIST SAVES US
Irenaeus offers a description of salvation that is far more comprehensive—and arguably more beautiful—than what we are used to. For many Christians, salvation means God’s rescuing of the human race from sin by means of the Cross. Irenaeus certainly assents to this. But salvation involves much more. By becoming man, God transforms all of creation and brings it to its perfection:
This work of salvation is not only achieved by the Cross but the entire life of Christ. Even more, for Irenaeus, the Cross is not just an instrument of atonement but the manifestation of Christ’s obedience, which undoes our disobedience through Adam onward: In the second Adam, however, we are reconciled, being made obedient even unto death (Against Heresies 5:16).
By the Incarnation, the Eternal Word of God’s enters into His creation—the same creation that was made by the very same Word, in the first place! God does so that “He might sum up all things in Himself.” By becoming man, Christ restores man himself, who has been disfigured by sin:
“For in times long past, it was said that man was created after the image of God, but it was not [actually] shown; for the Word was as yet invisible, after whose image man was created, Wherefore also he did easily lose the similitude. When, however, the Word of God became flesh, He confirmed both these: for He both showed forth the image truly, since He became Himself what was His image; and He re-established the similitude after a sure manner, by assimilating man to the invisible Father through means of the visible Word.” —Against Heresies 5:16
4. SALVATION: TRANSFORMED BY CHRIST
According to Irenaeus, our salvation is a life-long journey that begins in Baptism. While some Christians may consider Baptism to be of symbolic significance only, Irenaeus understands it to be the very means by which one is “regenerated” or born anew in the Spirit (e.g., in Against Heresies 3:17). Now, this new life is not a one-time event but a process as we continue to receive God’s grace and grow in love of God:
“For He did not set us free for this purpose, that we should depart from Him…but that the more we receive His grace, the more we should love Him. Now the more we have loved Him, the more glory shall we receive from Him, when we are continually in the presence of the Father.” —Against Heresies 4:13
Whereas some Christians have emphasized faith as opposed to good works, Irenaeus maintains that we must “bring forth fruit.” Those who are awarded eternal life are those who have “preserved in His love” and have “kept his commandments.” Indeed, Irenaeus envisions the real possibility of walking away from Christ through grave sin: By clinging to sin, one may “cast out the Spirit.”:
“But if they cast out the Spirit, and remain in their former condition, desirous of being of the flesh rather than of the Spirit, then it is very justly said with regard to men of this stamp, That flesh and blood shall not inherit the kingdom of God.”
—Against Heresies 5:10
One’s ultimate salvation, therefore, is not a matter of securing Heaven at some initial point of conversion. Instead, the Christian life is lifelong. Thankfully, though, this is not something we do of ourselves: We trust in Christ to bring us to full maturity in the Spirit.
5. LIFE IN CHRIST: THE CHRISTIAN WAY
The new life offered to the believer in Christ is one that expands our obligation to love God and neighbor. But, notes Irenaeus, this obligation is tied to our freedom as “sons” (and daughters) of God. Irenaeus echoes Christ’s teaching in the Sermon on the Mount, which is a call to eradicate sin on its most basic level: “not only from evil deeds, but even from the desire after them.” The Christian, born into a new way of life, should be opposed to those things that lead to addiction and vice. Life in the Spirit should lead to self-control and temperance.
Note that the Christian way is not just a list of arbitrary rules. For Irenaeus, a life opposed to the Spirit is in fact “contrary to reason,” for one becomes like “swine and dogs” instead of what we are meant to be in Christ (Against Heresies 5:8).
Irenaeus highlights how the Christian Way is a transformation not only of oneself but one’s relationship to others. That is, Christianity is inherently ordered to the transformation of society. He notes a specific concern for those in need, and he suggests the Christian’s radical call to “share all [one’s] possessions with the poor.” The Christian’s disposition should be one of mercy towards all—regardless of “their evil intentions”:
“[He told us] to share all our possessions with the poor; and not to love our neighbors only, but even our enemies; and not merely to be liberal givers and bestowers, but even that we should present a gratuitous gift to those who take away our goods.”
—Against Heresies 4:13
6. THE EUCHARIST: SACRIFICE AND SPIRITUAL FOOD
Among all the topics covered in this post, this is one of the most important for Christians to consider. The Eucharist is one of those rites that virtually all Christian traditions celebrate, yet it is one that is subject to very diverse interpretations. For some Christians, perhaps many in the USA, the Eucharist is a purely symbolic reality. Because of this, the Eucharist is not central to the Faith, and it is certainly not critical to one’s salvation.
Very different is Irenaeus’ understanding. For this bishop, the Eucharist is no mere symbol. By the power of the Word of God, it is “no longer common bread”: It is the very flesh and blood of Christ. Of course, Irenaeus knew perfectly well that the Eucharist appears like bread and wine to the senses. But the deeper reality is Christ’s very presence:
Irenaeus can also confess the Eucharist to be the “pure sacrifice” of the Church; after all, it is Christ Himself! Speaking of the Eucharist as a sacrifice will sound very foreign to many Western Christians. But Irenaeus nevertheless professes that which was a given in the second century, namely, that the Eucharist is the “new oblation of the new covenant”:
“He took that created thing, bread, and gave thanks, and said, “This is My body.” And the cup likewise, which is part of that creation to which we belong, He confessed to be His blood, and taught the new oblation of the new covenant; which the Church receiving from the apostles, offers to God throughout all the world, to Him who gives us as the means of subsistence the first-fruits of His own gifts in the New Testament, concerning which Malachi, among the twelve prophets, thus spoke beforehand.”
—Against Heresies 4:17
“The oblation of the Church, therefore, which the Lord gave instructions to be offered throughout all the world, is accounted with God a pure sacrifice, and is acceptable to Him; not that He stands in need of a sacrifice from us, but that he who offers is himself glorified in what he does offer, if his gift be accepted.” —Against Heresies 4:18
Already apparent from the above, Irenaeus clearly associates the Eucharist with our salvation. Just as Christ in John’s gospel tells us to partake of his flesh and blood for eternal life, so Irenaeus—one link (through Polycarp) away from the Apostle John—affirms as much:
“ For as the bread, which is produced from the earth, when it receives the invocation of God, is no longer common bread, but the Eucharist, consisting of two realities, earthly and heavenly; so also our bodies, when they receive the Eucharist, are no longer corruptible, having the hope of the resurrection to eternity.” —Against Heresies 4:18
7. THE CHURCH: VISIBLY ONE & CATHOLIC
To say that the Church is “visibly one” is to say that the Church has a determinate constitution that allows it to endure throughout time. This means that the Church is not some vague union of believers as a term like “Christianity” might instead imply. No, for Irenaeus, the Church is bound to a common faith and governance and therefore unites Christians throughout the world. That Christians throughout the world are so united permits Irenaeus to say that this universal Church proclaims the faith “as if she possessed only one mouth.”:
“As I have already observed, the Church, having received this preaching and this faith, although scattered throughout the whole world, yet, as if occupying but one house, carefully preserves it. She also believes these points [of doctrine] just as if she had but one soul, and one and the same heart, and she proclaims them, and teaches them, and hands them down, with perfect harmony, as if she possessed only one mouth. For, although the languages of the world are dissimilar, yet the import of the tradition is one and the same…”
“[…] the Catholic Church possesses one and the same faith throughout the whole world, as we have already said.” —Against Heresies 1:10
Irenaeus is not naive. He knows there are divergent groups claiming to have the real scoop on Christ. His entire work Against Heresies is an attempt to counter the various heresies of his time. However, he is able to distinguish the true Church from these breakaways by the simple fact that the latter “are of much later date.” For him, the true Church is that which is in continuity with the Church of the Apostles. And for Irenaeus, division is abhorrent. Denominationalism is counter to the nature of the Church; one wonders what Irenaeus would say about today’s thousands upon thousands of competing groups:
“Now all these [heretics] are of much later date than the bishops to whom the apostles committed the Churches; which fact I have in the third book taken all pains to demonstrate. […] But the path of those belonging to the Church circumscribes the whole world, as possessing the sure tradition from the apostles, and gives unto us to see that the faith of all is one and the same.” —Against Heresies 5:20
8. APOSTOLIC SUCCESSION: CONTINUITY IN THE CHURCH
The continuity of the Church is ensured by the succession of bishops going all the way back to the Apostles. For Irenaeus, this is not just a fact-of-the-matter—an interesting historical datum—but is instead rooted in the very structure of the Church. After all, the New Testament proclaims the Apostles to be the “foundation” of the Church; these same men, Irenaeus tells us, delivered “their own place of government” to still other men, the Bishops:
“Wherefore it is incumbent to obey the presbyters who are in the Church—those who, as I have shown, possess the succession from the apostles; those who, together with the succession of the episcopate, have received the certain gift of truth, according to the good pleasure of the Father. But [it is also incumbent] to hold in suspicion others who depart from the primitive succession, and assemble themselves together in any place whatsoever…” —Against Heresies 4:26
For Irenaeus, Christianity is not a matter of assembling “together in any place whatsoever.” Indeed, says Irenaeus, those “who depart from the primitive succession” fall away from the truth of the Faith and communion with the Church. After all, Apostolic Succession is not just a means of establishing the Church’s leadership. Even more, the successors of the Apostles are those who have “received the certain gift of truth.” As the Apostles first delivered the faith to the Church, so their successors continue to guard it.
9. THE PRIMACY OF ROME: CENTER OF UNITY
Irenaeus proclaims the central place of the Church of Rome in no uncertain terms. In countering the Gnostic heretics, Irenaeus presents the Roman church as the chief example of orthodoxy. He clarifies that this “preeminent authority” is based in its apostolic foundation in Peter and Paul. With this church, he says, “every church should agree.” That is quite the claim for Rome:
“Since, however, it would be very tedious, in such a volume as this, to reckon up the successions of all the Churches, we do put to confusion all those who, in whatever manner, whether by an evil self-pleasing, by vainglory, or by blindness and perverse opinion, assemble in unauthorized meetings; [we do this, I say,] by indicating that tradition derived from the apostles, of the very great, the very ancient, and universally known Church founded and organized at Rome by the two most glorious apostles, Peter and Paul; as also [by pointing out] the faith preached to men, which comes down to our time by means of the successions of the bishops. For it is a matter of necessity that every Church should agree with this Church, on account of its preeminent authority.”
—Against Heresies 3:3
This emphasis on the Roman church is not just due to its historical basis in the Apostles. Instead, its authority is continued in the succession of bishops. After listing the bishops of Rome through Eleutherius in his own day, Irenaeus can claim that it is by this succession that the “tradition from the apostles” and “the preaching of the truth” has “come down to us.” Irenaeus identifies the succession of the Roman bishops as the “most abundant proof” of authentic, orthodox faith. The central place of the bishop of Rome, the Pope, is already on full display:
The blessed apostles, then, having founded and built up the Church, committed into the hands of Linus the office of the episcopate […] Eleutherius does now, in the twelfth place from the apostles, hold the inheritance of the episcopate. In this order, and by this succession, the ecclesiastical tradition from the apostles, and the preaching of the truth, have come down to us. And this is most abundant proof that there is one and the same vivifying faith, which has been preserved in the Church from the apostles until now, and handed down in truth. —Against Heresies 3:3
10. THE RULE OF FAITH: HOW WE KNOW THE CONTENT OF CHRISTIANITY
How do we know what the Christian Faith is, anyways? Many Christians today might be quick to point out the Bible. And surely, the written Word of God is of prime importance to the Christian. Irenaeus certainly upheld the Scriptures as authoritative—even as the official canon was still being determined. But Irenaeus points to a larger context, of which the Scriptures only form part. For Irenaeus, the content of the Faith can be discerned from the teaching of the Church, which delivers the Apostolic Tradition, including Scripture, in its entirety:
“True knowledge is [that which consists in] the doctrine of the apostles, and the ancient constitution of the Church throughout all the world, and the distinctive manifestation of the body of Christ according to the successions of the bishops, by which they have handed down that Church which exists in every place, and has come even unto us, being guarded and preserved without any forging of Scriptures, by a very complete system of doctrine, and neither receiving addition nor [suffering] curtailment [in the truths which she believes…” —Against Heresies 4:33
Irenaeus gets to the heart of the matter when he asks: What should we do when a question of faith arises? That is, how do we settle a dispute over what is authentic Christianity? Again, many Christians today may think it is simply a matter of searching through the Bible. But Irenaeus knew that his Gnostic opponents used Scripture too. Therefore, says Irenaeus, Apostolic Tradition is key. What matters is what the Apostles actually taught; or, more specifically, the teaching of those who legitimately succeed the Apostles in their ministry. Here is where Rome comes into play. Because of its “preeminent authority,” Irenaeus tells us, all churches must agree with the Church of Rome. Already in the second century, the Roman church is a kind of arbiter of the Faith:
“For it is a matter of necessity that every Church should agree with this Church, on account of its preeminent authority […] In this order, and by this succession, the ecclesiastical tradition from the apostles, and the preaching of the truth, have come down to us.” —Against Heresies 3:3
11. COMMUNION OF SAINTS: FROM MARY TO MARTYRS
Because of their role in God’s plan of salvation, some believers are set apart as special examples of the Christian life. For Irenaeus, this includes the prophets and patriarchs of the Old Testament; it also includes the Apostles and their close associates, like Polycarp, a martyr and bishop from whom Irenaeus learned. In fact, martyrs quickly became model believers—the first saints recognized as part of the heavenly Church who even now pray for those on Earth. That some Christians should be emulated more than others is at least suggested by the fact that some Christians are indeed holier than others: Those in Heaven receive a “suitable dwelling place” according to the extent of one’s sanctity, which, as we saw above, means one’s response to grace and love for God (Against Heresies 5:13).
For Irenaeus, the Mother of Christ, Mary, is a key player in salvation history. She was not just a vessel from which Christ received His humanity. No—for Irenaeus, Mary’s obedience is the very “cause of our salvation.” Just as Christ is the New Adam—something Scripture itself states—so Mary is the New Eve, affirms Irenaeus. As our first parents led to the sinful state of humanity, so the “Second” Adam and Eve restore our dignity. In a telling image, Irenaeus says that “the knot of Eve’s disobedience was loosed by the obedience of Mary.”:
“And even as [Eve], having indeed a husband, Adam, but being nevertheless as yet a virgin having become disobedient, was made the cause of death, both to herself and to the entire human race; so also did Mary, having a man betrothed [to her], and being nevertheless a virgin, by yielding obedience, become the cause of salvation, both to herself and the whole human race…
“And thus also it was that the knot of Eve’s disobedience was loosed by the obedience of Mary. For what the virgin Eve had bound fast through unbelief, this did the virgin Mary set free through faith.” —Against Heresies 3:22
“And if the former did disobey God, yet the latter was persuaded to be obedient to God, in order that the Virgin Mary might become the patroness of the virgin Eve. And thus, as the human race fell into bondage to death by means of a virgin, so is it rescued by a virgin; virginal disobedience having been balanced in the opposite scale by virginal obedience.” —Against Heresies 5:19
What Irenaeus says here is veneration of Mary in its most basic and pure form; it acknowledges Mary’s place in God’s plan of salvation. Implicit, too, is the supreme sanctity of Mary: She is the opposite of Eve, the first woman to sin. In a sense, the doctrines of the Immaculate Conception and Assumption of Mary are just further elaborations of what Irenaeus already teaches.
12. CONSUMMATION IN CHRIST: NEW CREATION, NEW BODIES
For Irenaeus, the end of all things is really the consummation of God’s purpose for His creation. This world is but a taste of what is to come. Indeed, contrary to the modern caricatures that depict Heaven as a kind of disembodied state, our true destiny is bodily existence in the realm of the “New Heaven and New Earth”—that is, the transformed Universe in full harmony with Christ. Irenaeus sees creation and its consummation as a wonderful story tied together by God’s Word. As God created all things through his Word, so He redeems man and brings all things—the entire Universe—into communion with Himself.
Quite obvious throughout Irenaeus’ work is his emphasis on the Resurrection of the dead. We are not just souls; to be human is to be embodied—albeit in a glorified and transfigured state:
“[…]it is manifest that the souls of His disciples also, upon whose account the Lord underwent these things, shall go away into the invisible place allotted to them by God, and there remain until the resurrection, awaiting that event; then receiving their bodies, and rising in their entirety, that is bodily, just as the Lord arose, they shall come thus into the presence of God.” —Against Heresies 5:31
“But when this [present] fashion [of things] passes away, and man has been renewed, and flourishes in an incorruptible state, so as to preclude the possibility of becoming old, [then] there shall be the new heaven and the new earth, in which the new man shall remain [continually], always holding fresh converse with God.”
—Against Heresies 5:36
Even so, humans have the freedom to choose or reject God—to love him and our neighbor or to abandon that love and focus inward. Echoing the words of Christ, Irenaeus envisions the radical possibility of hell, which is eternal. But just as Heaven is often misconstrued today, so is hell. Irenaeus reminds us that hell is not some arbitrary punishment inflicted by an angry God. Instead, hell is freely chosen self-exclusion from God—the natural outcome of which is suffering. “Separation from God is death,” says Irenaeus, just as “separation from light is darkness.” There is a modern trend in some Christian circles to get rid of hell—or to at least assert no one goes there. Irenaeus would rebuke this notion and remind fellow Christians that the ability to choose un-love and reject God is very real:
“But on as many as, according to their own choice, depart from God, He inflicts that separation from Himself which they have chosen of their own accord. But separation from God is death, and separation from light is darkness; and separation from God consists in the loss of all the benefits which He has in store. […] God, however, does not punish them immediately of Himself, but that punishment falls upon them because they are destitute of all that is good. Now, good things are eternal and without end with God, and therefore the loss of these is also eternal and never-ending.” —Against Heresies 5:27
Any person who would like to grow in a comprehensive understanding of the Christian worldview should consult Irenaeus of Lyons. His conception of the Faith is cosmic: Christ the Word creates the entire Universe, redeems it, and will ultimately glorify it. Irenaeus offers beautiful insights into Christ’s work of redemption, namely, the recapitulation of creation. He also provides a clear example of the early Church’s self-understanding: That is, it is a visible body united throughout the world and united in a common faith.
Anyone who wants to discern what early Christianity was truly like—and how it compares to the various claims of today’s Christians—should consult this early bishop. Whereas modern Christians diverge on key issues like the nature of the Eucharist, the meaning of salvation, the role of the Pope, and the importance of Mary, Irenaeus offers straightforward answers that, in turn, typify the beliefs of the post-apostolic Church.
St. Irenaeus of Lyons, pray for us that the Church may again have “but one soul, and one and the same heart,” as you observed in your time.
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