After receiving some classical education and much biblical knowledge, Irenaeus migrated to Gaul from Asian Minor. Mission to Rome (probably brings a letter of recommendation regarding imprisoned Christians of Vienne & Lyon to bishop Eleutherios urging a more tolerant attitude towards montanists) where he knew Polycarp of Smyrna. He became bishop of Lyon after 177, replacing the martyr Pothinus. There he tried to evangelize the Celts native to Gaul, but his main opponents were Gnostics. Little else is known of his life (martyrdom is late and lacks any basis).
Though he wrote much more (known from Eusebius's HE), the only extant texts belonging to the Bishop of Lyon are Against Heresies and Demonstration of the Apostolic Preaching. AH: The five volumes comprising this work, written ca. 180, are primarily against Valentinian Gnosticism. Books I-II diagnose heresy, especially Gnostic heresy. I. Elegcoj. (Here he presents the grand myth of world generation and world reintegration that he attributes to the Ptolomean and traces its connections to the doctrine of Valentinus. All "heretical schools" can be traced down to their origin in Symon Magus). II Serial discussion of Valentinian doctrines (many repetitions): Pleroam and creator (1-11), aeaons (12-19), numbers (20-28), last things and demiurge (29f.), supplementary material on other Gnostic schools (31-35).
Books III-V (are they an afterthought in I's plan?) replace Gnosticism with true knowledge of universally available Christian faith handed down in the true apostolic church. III: doctrines of the one true God and his Christ. IV: the unity of the divine oikonomia V. redemption of the human creature in its sarx.
DAP(Epideixis tou apostolikou kerigmatos): This smaller work presents a summary sketch of Christian doctrine in 100 chapters as delineated in AH III-V. Other fragments are Letter to Pope Victor, letter to the Alexandians, to Florius. Treatise on the number eight.
Key terms in I's theology such as oikonomia and anakephalaisosis had their origin in Greek grammar and rhetoric. His thought is best exemplified in AH. In it we see that the criteria for orthodoxy are the canon tes aletheias and the regula fidei. These consisted primarily in confession of the plan of salvation(oikonomia) as revealed in Scripture and passed down through the generations from the Apostles through catechesis. The main loci in salvation history are the disobedience of Adam, the incarnation, the sending of the Spirit, and the resurrection of the body. Christ's mission suits I's definition of the nature of humanity: human is flesh. Christ came in the flesh to redeem fleshly man because this restored the relationship between Creator and creation. His doctrine can be subsumed under the notion of unity (of OT & NT and their gods, of Christ, of human being).
He is the first theologian that has fully mastered the totality of the traditional data. His influence falls from the 4c onwards, eclipsed by the doctors that illuminated the church at that time. AH loses its relevance with the new challenges and almost disappears. Only in 16c with Erasmus regains relevance and starts growing increasingly. He was one of the first to formulate the definition of Christ as two natures in one person. That AH, especially, was widely read is evidenced by the multiple translations extant. I.'s work was much quoted in the early church's literature. His sources besides the Apostolic Fathers (Ign, Clem,) are Justin and TheoAnt. Irenaeus had immense influence on ClAlex, Ath, SA.
Most quoted Father after SA in the CVII; offers clue to regain the unity of theology and strengthen links between exegesis, dogma and spirituality. His historical view of the world, his conception of progressive economy of salvation of humanity, his doctrine of the universal recapitulation in X. Especially attractive is his optimistic and biblical spirituality of incarnation, body, Spirit.
I. Pleroma
Unity of Church opposed [10-22:RF] Presentation
II. Refutation of Valentinian theses on Pleroma Refutation
Emission of Aeons
Numbers
Consummation of world + demiurge
Non-Valentinian theses Simon + Carpocrates
Basilides (nr of heavens)
"Gnostic" (plurality of gods).
[truth of Scriptures 1-5]
III. One God Creator [6-15] Creation & Christology
One Christ (human + divine) - Recapitulation [16-23]
Concl.
IV. God author of OT + NT Bible
OT: prophecy of NT
V. Resurrection of the Flesh Anthropology (+ cr)
God Creator = Father