Irenaeus (c. 130–c. 202 AD) has such a refreshing view of God’s purpose in saving humanity. He richly exposits Scripture, does theology within living memory of the disciples of the Lord, and does not have to unfold the baggage that 2,000 years of church history has loaded up unto theological notions.
In the first place, he follows Paul in Romans 5 who identities Adam as a type for Jesus. The genealogy in Luke also shows Jesus’ relationship with Adam. In this case, Luke ties the end to the beginning—reminding of Origen’s dictum that the end is like the beginning.
This parallelism is vital for Ireneaus because the Word of God shaped all things and in way co-dwelled with them since the beginning through the prophets and on. And being the maker of all things (the Father created all things through his Word), he then enters into creation.
He becomes what he created. And as a true human being, he absorbs the whole history of humanity from Adam to him into himself. The Word sums up all things that belong to him, in himself, being the eschatological human, the new Adam.
Why might he do this? Well, because is good. But also because he foresaw human sin. So that which he created, he saves.
He liberates them from the enemy, Satan and Death. But at the heart, he—in himself—unites or reconciles humanity with God.
Since all humanity is in him by way of summary, he can on behalf of humanity overcome sin and share with them the greatest gift: adoption as sons.
By so mixing Adam’s race and the divine Word in himself, he becomes the representative of humanity and reconciles it with God. We become in Christ what he is in relationship to God: a son. We by adoption; he by nature.
Whatever our Head then gains, the body too receives.
Obviously, more could be said. And I am sure Ireneaus has said more in other places; it’s important to remember that he claims to speak in accord with what the churches teach as the Spirit supports her through the teaching of the apostles.
Ireneaus studied under Polycarp in Smyrna whom John the apostle appointed as bishop there. And Ireneaus often claims to follow and even cites Polycarp and other elders of the church to demonstrate continuity with the apostles and their teaching.
It would take a radical skepticism to accuse Irenaeus of making this all up. I have no doubt that he did learn from Polycarp and knew how the apostles preached the Gospel.
As a Greek speaker who trained in Asia Minor where many disciples of the Lord had done their work, it stands to reason that Ireneaus would have deep insight into scriptural teaching.
And it stands to reason that his living commentary of the apostles’ words and the disciples of the apostles’ words would help him to know God’s revelation in ways that we could learn from.