If you only ever learn one concept from the early Fathers, learn this one. It will do more for your reading of Scripture than any other single idea I know.
The word is recapitulation. The man is St. Irenaeus of Lyons, writing in the second century, and his great work Against Heresies is in the Fathers Library in full.
What the word means
To recapitulate is to sum up, to gather under one head, to go back over something and take it up again.
Irenaeus's claim is that Christ does this with the entire human story. He does not simply pay a debt and leave the history behind Him untouched. He goes back through it. He takes up human life at every point where it went wrong, and He lives it rightly.
Adam disobeys at a tree. Christ obeys at a tree. Adam is the head of a race that dies. Christ is the head of a race that lives. Eve's disobedience is answered by the Theotokos's obedience, and Irenaeus makes exactly that comparison. Israel fails in the wilderness for forty years. Christ is in the wilderness forty days and does not fail.
Christ is not only the remedy for the story. He is the story done properly.
Why he was arguing for it
Remember the rule from the article on reading the Fathers. Find out who he is arguing with. The title tells you: Against Heresies.
The Gnostics taught that the God of the Old Testament was a lesser and often malicious being, that the material world was a mistake, and that Christ came from a different and higher God to rescue spirits out of the mess. On that view the Old Testament is at best a record of someone else's failure.
Recapitulation destroys that. If Christ takes up the human story and completes it, then that story was His all along. The God who made Adam is the God who becomes the second Adam. The material world He entered is the world He made, and He entered it with a real body precisely because bodies are His.
So this is not a devotional flourish. It is a weapon, forged for a specific fight, and the fight was over whether creation and the Old Testament belong to our God.
What it does to your Bible
Here is the practical payoff, and it is enormous.
Most people who grow up with the Bible carry around two books that do not obviously belong together. There is an Old Testament full of strange laws and violence, and a New Testament about Jesus, and the connection is a handful of prophecies you were told to look up.
Recapitulation makes it one book. Every figure in the Old Testament who partly does what a man should do is pointing at the one who will do it completely. Isaac carrying the wood. The bronze serpent lifted up. Jonah three days in the deep. The Passover lamb. These are not decorative coincidences that clever preachers noticed later. On Irenaeus's account, they are what the story is for.
The typology tables on this site lay a great deal of this out passage by passage. Go through them once with recapitulation in your head and they stop looking like a party trick and start looking like the architecture of the thing.
The line everyone knows
The formula most people have heard is St. Athanasius's: God became what we are so that we may become what He is. That is the greatest conclusion of the life of Christ ever written down in one sentence.
Irenaeus is working the same ground earlier, and the two belong together. The Word descends so that man might ascend. That descent is not a rescue mission that touches down and leaves. It goes all the way to the bottom of human life, through birth, growth, hunger, weariness, betrayal, death and the grave, taking each one up and healing it by living it.
Which is why theosis is not an exotic add on to Christianity. It is the point. We are taken out of the pit we have dug for ourselves and given the opportunity to become the saints God called us to be, and the reason that is possible is that Christ has already been through every inch of the ground we are standing on.
One note, since I have been strict about this elsewhere. That summary sentence about descent and ascent is my own way of putting Irenaeus, and you will find similar phrasings in editorial summaries. Do not quote it as his words. Go read Against Heresies and find his own.
Where to start
Against Heresies is long and the early books spend a great deal of time describing Gnostic systems in detail so he can take them apart. That is heavy going for a first read.
- Read what is attached to Scripture first. Select verses in the reader and read the Irenaeus entries in the Church Fathers section, then follow the links into the full work.
- Then read the typology tables with recapitulation in mind.
- Then go into Against Heresies itself in the Fathers Library, starting with the later books where the positive argument is heaviest.
Adam at a tree. Christ at a tree. Once you see it you will see it everywhere, and you will never read the Old Testament as somebody else's book again.