Exchange and Deification

The “wonderful exchange” — the Son takes what is ours so as to give us what is his — has its birthplace in St. Irenaeus. In the preface to Against Heresies Book V he writes that the Word “did, through His transcendent love, become what we are, that He might bring us to be even what He is Himself.” This formula, grounded in recapitulation, passes to Athanasius — who gives it its most famous shape — and into the whole theosis tradition. For Irenaeus the content of salvation is incorruption and immortality, and his most concrete proof is Eucharistic: bodies nourished by the body and blood of Christ cannot finally remain corruptible, but will rise.

Tradition: Pan-Orthodox (Church Father)

The Exchange Formula’s Birthplace

The admirabile commercium, the “wonderful exchange,” is one of the great structuring ideas of Orthodox soteriology, and its classic patristic ancestor is Irenaeus. At the opening of Book V — the book devoted to the resurrection and the saving work of Christ in the flesh — he states it with unforgettable economy. The believer is to follow

the only true and steadfast Teacher, the Word of God, our Lord Jesus Christ, who did, through His transcendent love, become what we are, that He might bring us to be even what He is Himself. (Against Heresies V, preface; trans. ANF 1)

This is the wording verified and used elsewhere in this compendium (see Theosis and Theosis in Athanasius). Its structure is an exchange: the Word descends into our condition (“become what we are”) in order to raise our condition into his (“bring us to be even what He is”). It is not a symmetrical barter but a one-way gift of love — Christ assumes our mortality so as to give us his life.

Irenaeus states the same logic at greater length in Against Heresies 3.19.1, where the exchange is spelled out as the reason for the Incarnation itself:

For it was for this end that the Word of God was made man, and He who was the Son of God became the Son of man, that man, having been taken into the Word, and receiving the adoption, might become the son of God. For by no other means could we have attained to incorruptibility and immortality, unless we had been united to incorruptibility and immortality. (Against Heresies 3.19.1; trans. ANF 1)

Here the exchange is tied directly to recapitulation (see Anakephalaiosis): the Son becomes Son of man so that men, taken up into him, might become sons of God by adoption. The asymmetry the later tradition will guard is already present — we become sons of God by adoption and participation, not by becoming God in essence.

Lineage to Athanasius and the Theosis Tradition

Irenaeus’ formula is the headwater of a stream that runs through the whole Greek patristic tradition. Athanasius, a century and a half later, inherits it and gives it its most famous and lapidary form: “He became man that we might become god” (On the Incarnation 54). The dependence is explicit in the scholarly tradition and acknowledged in this compendium: Athanasius inherits “the wonderful exchange from Irenaeus and gives it its most famous formula” (see Theosis in Athanasius, which traces the exchange’s “classic patristic ancestor” to Irenaeus, Against Heresies V, preface).

From Athanasius the formula passes to the Cappadocians, to Cyril of Alexandria, to Maximus the Confessor, and ultimately to the Palamite articulation of deification as participation in the divine energies (not the essence) — the safeguard that keeps theosis from collapsing into pantheism. Irenaeus stands at the source of all of this. What he supplies is not yet the essence–energies distinction (that clarification comes much later) but the fundamental grammar: God becomes what we are so that we might share what he is, by grace and adoption (see Theosis for the developed doctrine).

It is worth noting how Irenaeus already guards the asymmetry that the later tradition will make precise. In Against Heresies 3.19.1 he speaks of “the gift of adoption,” and warns against those who “despise the incarnation of the pure generation of the Word of God, [and] defraud human nature of promotion into God” (Against Heresies 3.19.1; trans. ANF 1). “Promotion into God” and “adoption” are gift-language: the deified are sons by adoption, sharing the Son’s relation to the Father by grace, whereas the Son is what the Father is by nature. The exchange is therefore never a fusion of essences. Irenaeus’ favourite scriptural anchor for this is Psalm 81[82]:6 — “I said, You are all the sons of the Highest, and gods” — which he reads, not as conferring divine nature, but as naming the adoptive sonship given to those who “received the gift of adoption” through the incarnate Word (Against Heresies 3.19.1). The same biblical text will recur throughout the patristic theosis tradition for exactly this reason.

Incorruption as the Content of Salvation

For Irenaeus, the goal named by the exchange is concrete: incorruption (aphtharsia) and immortality (athanasia). Fallen humanity is in bondage to death; salvation is the gift of incorruptible life. This is the burden of 3.19.1: “by no other means could we have attained to incorruptibility and immortality, unless we had been united to incorruptibility and immortality… so that the corruptible might be swallowed up by incorruptibility, and the mortal by immortality” (Against Heresies 3.19.1; trans. ANF 1).

Incorruption is not a reward bolted onto human nature from outside; it is the restoration of what humanity was made for and lost. Those who reject the incarnate Word “remain in mortal flesh, and are debtors to death, not obtaining the antidote of life” — the pharmakon of immortality being communion with the incorruptible Word himself (Against Heresies 3.19.1; trans. ANF 1). Deification, for Irenaeus, is incorruption: to be made a son of God by adoption is to be made incorruptible, raised beyond the reach of death. This keeps his theosis firmly anti-Gnostic and creational — the goal is not the soul’s escape from the body but the body’s own clothing with incorruption.

The Eucharistic Argument

Irenaeus’ most striking and original argument for the salvation of the flesh is Eucharistic, and it turns the Gnostic denial of the flesh’s salvation on its head. If, as the Gnostics held, the flesh is incapable of incorruption, then the Eucharist makes no sense; but the Eucharist is the body and blood of Christ; therefore the flesh that receives it must be capable of incorruption. The bread of the earth, receiving the invocation, becomes the Eucharist; so too our bodies, receiving the Eucharist, are made incorruptible:

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 4.18.5; trans. ANF 1)

He presses the same argument in Book V, this time anchored in 1 Corinthians 10:16. If the flesh is not saved, then the cup is not really the communion of Christ’s blood and the bread not the communion of his body — which is absurd:

But if this indeed do not attain salvation, then neither did the Lord redeem us with His blood, nor is the cup of the Eucharist the communion of His blood, nor the bread which we break the communion of His body… He has acknowledged the cup (which is a part of the creation) as His own blood, from which He bedews our blood; and the bread (also a part of the creation) He has established as His own body, from which He gives increase to our bodies. (Against Heresies 5.2.2; trans. ANF 1)

And the conclusion, in 5.2.3, draws the resurrection out of the Eucharist directly:

our bodies, being nourished by it [the body and blood of the Lord], and deposited in the earth, and suffering decomposition there, shall rise at their appointed time, the Word of God granting them resurrection to the glory of God, even the Father, who freely gives to this mortal immortality, and to this corruptible incorruption. (Against Heresies 5.2.3; trans. ANF 1)

The argument is exact and complete: bodies that are nourished by Christ’s incorruptible body are made sharers in its incorruption, and so cannot finally stay in the grave. The Eucharist is thus the physical pledge of the resurrection — the exchange formula enacted at the altar, where the believer literally receives “what He is” into “what we are.” Irenaeus’ Eucharistic realism is wholly bound up with his anti-Gnostic insistence on the goodness of the flesh and the unity of creation and redemption (see The Eucharist; on the same passages, Behr, Irenaeus of Lyons; Osborn, Irenaeus of Lyons, ch. 11).

It is no accident that this Eucharistic argument comes in the same books where Irenaeus defends the resurrection of the flesh against the Gnostics. For him the two stand or fall together. If the flesh cannot be saved, the Eucharist is a fraud and the resurrection a fiction; but the Church does offer Christ’s body and blood, and her bodies are nourished by them — therefore the flesh is destined for incorruption. The “two realities, earthly and heavenly” that constitute the Eucharist (Against Heresies 4.18.5) mirror the two realities, divine and human, united in the incarnate Word: in both, the heavenly takes up the earthly without destroying it, and raises it. The sacrament is thus the recapitulation enacted in miniature, the exchange formula made edible.

In sum, the exchange that Irenaeus first names — “He became what we are, that He might bring us to be what He is” — is no abstract slogan. Its content is incorruption, its source is the recapitulating Incarnation, its heir is Athanasius and the whole theosis tradition, and its surest proof, for Irenaeus, is the Eucharist that already nourishes mortal flesh with the immortal body of the Lord.

References

Irenaeus of Lyon. Against Heresies (Adversus Haereses) 3.19.1; 4.18.5; 5, preface; 5.2.2–3. Translated by Alexander Roberts and William Rambaut. In Ante-Nicene Fathers, vol. 1. Buffalo: Christian Literature Publishing, 1885.
Athanasius. On the Incarnation 54 [PG 25:192B]. Translated by John Behr. Popular Patristics Series 44b. Crestwood, NY: St. Vladimir’s Seminary Press, 2011.
Behr, John. Irenaeus of Lyons: Identifying Christianity. Oxford: Oxford University Press, 2013.
Osborn, Eric. Irenaeus of Lyons. Cambridge: Cambridge University Press, 2001.
Steenberg, M. C. Irenaeus on Creation: The Cosmic Christ and the Saga of Redemption. Leiden: Brill, 2008.