The following is taken from my final exam from my Patristic Theology class in seminary (circa 2003); we had to answer three out of five questions in essay form. This essay highlights the person and theology of Irenaeus. I will provide a brief description of Irenaeus first, and then get into the essay. This was before I ever started reading either Barth or 
Torrance in any depth. But you might see how once I did, I was already predisposed to their respective theologies vis-à-vis informing theologies like Irenaeus’ represents.
Irenaeus (ca. 130-200) was Bishop of Lyons. Most likely he grew up in Smyrna, where as a youngster he was able to listen to Polycarp. It is probable that he studied and taught at Rome. This all happened before he moved to Lyons. He also served as an important link between the Eastern and Western branch of the Church.
Irenaeus first promoted the doctrine of recapitulation, although he claimed that he received this view (in a germinal sense) from Justin Martyr. Recapitulation basically is the doctrine that states: Adam was originally created to walk in obedience with God. He disobeyed, thus all of humanity, as represented in Adam (seminally), disobeyed God with him. This obedience thrust all of humanity into a cursed life of sin. Resulting in a destroyed and alienated humanity.
Irenaeus, as derived from Romans 5, shows that Christ came as the second Adam; essentially representing all humanity. In a sense, this is a do over; Adam got it wrong, while Christ did it over and walked in perfect obedience to God. Irenaeus points out that Christ can legitimately represent all of humanity, as he uses the Luke 3 genealogy to show Christ’s line going all the way back to Adam. Therefore Christ can legitimately represent each successive generation of people, all the way from the beginning.
Christ’s perfect obedience was epitomized by his obedience unto death at the cross. He secured a restored relationship unto God because of his obedience. Therefore anyone found in Christ would have a restored relationship with God. The notion of corporate solidarity is taught here; i.e. one man representing all humanity. This teaching has been associated with the physical theory of the atonement. The idea of seminal representation. Some people oppose this idea saying that it focused on the incarnation as being redemptive, and not the actual death of Christ as redemptive. This assumption is wrong though, for in all reality the incarnation is the presupposition of the ultimate goal, which eventuates in the crucifixion — and thus redemption for all humanity (i.e. these are inter related realities).
Nevertheless, what Jesus did according to this doctrine was inaugurate a new way of life. The idea of seminal representation and corporate solidarity can be seen in the teaching of Tertullian and Augustine who both believed in original sin, and that as a result of our real representation in Adam, humanity has inherited the tainted seed from Adam. Recapitulation had an impactful effect on the teaching of the atonement, as just noted.