What is recapitulation theory?

Irenaeus of Lyons, answered from the texts and cited to the page.

Irenaeus of Lyons answers

The Word of God, who made man in the beginning, became man himself, and in doing so gathered up into himself the whole of what he had made. That is what I mean by recapitulation. He did not take a new formation, nor flesh from some other substance, but the very handiwork of the Father, that which had perished in Adam; and he set it right by going through it again, where it had gone wrong.

Mark first that the thing lost and the thing saved must be the same. If the Lord had taken flesh of some other order, he would not have summed up human nature in his own person, nor could he be called flesh at all; flesh is a transmission of what was moulded at the first from the dust.¹ So the Word took flesh and blood after the way of the original formation, saving in his own person at the end what had in the beginning perished in Adam.²

The apostle holds to the same: if the flesh were not in a position to be saved, the Word of God would in no wise have become flesh.³ Then the pairs, which are where the argument lies. Adam had his substance from virgin soil, not yet tilled, and was formed by the hand of God, that is, by the Word. So the Word, recapitulating Adam in himself, rightly received a birth from Mary, who was as yet a virgin.

God did not take dust again, but wrought so that the formation should be made of Mary, that there might not be another formation called into being, but that the very same one should be summed up, the analogy preserved.⁴ Hence Eve is summed up in Mary, that a virgin should be a virgin's intercessor, and by a virgin's obedience undo the disobedience of a virgin.⁵

And the trespass that came by the tree was undone by the tree of obedience, when the Son of man, hearkening to God, was nailed to it.⁶ By one man's disobedience sin entered and death obtained a place; so by the obedience of one man, righteousness introduced shall cause life to fructify in those who were dead.⁷ Nor does it stop at Adam's children.

He had to save that very man created after the image and likeness, for it is absurd to say that the first to suffer captivity was not rescued by him who conquered the enemy, while his children were.⁸ The enemy is not conquered if the old spoils remain with him. So salvation is not one episode set among others. The whole long history of the flesh is summed up and carried through in the Lord, so that mortality is swallowed up by immortality.

Sources

1. But if the Lord became incarnate for any other order of things, and took flesh of any other substance, He has not then summed up human nature in His own person, nor in that case can He be termed flesh.

   Against Heresies, Book V

2. nor would the Lord have summed up these things in Himself, unless He had Himself been made flesh and blood after the way of the original formation [of man], saving in his own person at the end that which had in the beginning perished in Adam.

   Against Heresies, Book V

3. For if the flesh were not in a position to be saved, the Word of God would in no wise have become flesh.

   Against Heresies, Book V

4. It was that there might not be another formation called into being, nor any other which should [require to] be saved, but that the very same formation should be summed up [in Christ as had existed in Adam], the analogy having been preserved.

   Against Heresies, Book III

5. Eve summed up in Mary, that a virgin should be a virgin's intercessor, and by a virgin's obedience undo and put away the disobedience of a virgin.

   The Demonstration of the Apostolic Preaching

6. the trespass which came by the tree was undone by the tree of obedience, when, hearkening unto God, the Son of man was nailed to the tree

   The Demonstration of the Apostolic Preaching

7. For as by one man's disobedience sin entered, and death obtained [a place] through sin; so also by the obedience of one man, righteousness having been introduced, shall cause life to fructify in those persons who in times past were dead.

   Against Heresies, Book III

8. it is too absurd to maintain, that he who was so deeply injured by the enemy, and was the first to suffer captivity, was not rescued by Him who conquered the enemy, but that his children were

   Against Heresies, Book III