Today, in Against the Heresies 1.10, we encountered an important piece of Irenaeus’ theology, recapitulation or anakephalaiosis. Here is what Unger writes in his notes:

The word anakephalaiosis expressed a capital idea in Irenaean theology. … It must convey the idea of being brought to a head as a unifying principle and of somehow resuming all things. This process of recapitulation of all things begins with the Incarnation and will be completed with the glorification of the body, yet because the Word preexisted creation and was in the planning, and was operative from creation on, the Incarnate Word recapitulates all things. He summarizes in Himself all creation and unites all people and angels too to HImself as under one Head, and in so doing He duplicates, or resumes, the acts of Adam either by similarity or by opposition.

Dominic J. Unger, St. Irenaeus of Lyons: Against the Heresies. New York: Paulist, 1992, pp. 185-186.