Irenaeus's late-second-century catalog and refutation of the Valentinian Gnostic system, written to expose its Aeon-mythology as a corruption of apostolic teaching and to set the true faith of the worldwide Church against it.
Against Heresies, Book I is Bishop Irenaeus of Lyons's detailed exposition of the Gnostic school of Valentinus and its offshoots, written around 180 CE at the request of a friend who wanted to understand — and refute — the sect's teachings. Irenaeus opens by explaining his method: rather than argue in the abstract, he will lay out the Valentinians' own doctrine in full so that its absurdity becomes self-evident, comparing their elaborate reinterpretations of Scripture to writers who stitch together lines of Homer to make the poet seem to be speaking about something he never addressed. The bulk of the book narrates the Valentinian myth in careful, almost ethnographic detail: an invisible Father called Bythos ("Depth") and his consort emit thirty Aeons in paired male-female generations, filling out a heavenly Pleroma; the youngest Aeon, Sophia, oversteps her place and falls into passion and ignorance, and her expelled offspring Achamoth becomes the origin of the material world, fashioned unknowingly by a lesser craftsman, the Demiurge, who is identified with the God of the Old Testament.
From there Irenaeus tracks how the various Valentinian teachers — Ptolemy, the numerologist Marcus with his letter-and-number mysticism, and others — used this cosmology to reread the Gospels and the Law allegorically, finding hidden references to their Aeons in details like the twelve-year-old Jesus in the Temple, the twelve apostles, or the eight persons saved in Noah's ark. He then broadens the survey backward and outward: to Simon Magus, whom he treats as the fountainhead of all heresy; to Saturninus, Basilides, Carpocrates, Cerinthus, and Cerdo; and to a wide array of libertine and ascetic offshoot sects, cataloging their distinctive claims about the Demiurge, the true unknown Father, and the fate of the soul. Set against all of this, in chapter 10, stands Irenaeus's own summary of "the preaching of the faith" as received by the Church "dispersed across the entire world" — one God, one Christ, one Spirit — which he insists is held identically by churches in Germany, Spain, Gaul, the East, and Egypt, regardless of how eloquently or plainly it is expressed.
Book I matters historically because it is one of the fullest surviving primary accounts of second-century Gnosticism, preserved almost entirely through Irenaeus's hostile summary rather than through the Gnostics' own writings (many of which survive only in fragments or were rediscovered at Nag Hammadi in 1945, allowing modern scholars to check his reporting). It is also an early, explicit statement of a normative "rule of faith" and of catholicity — the claim that a single apostolic teaching underlies a geographically scattered Church — that would become foundational for later Christian orthodoxy and for the developing biblical canon.
“Error, indeed, is never displayed in its own naked form, lest, once exposed, it be at once seized; but craftily arraying itself in an attractive dress, it contrives, absurd as it is even to say, to appear — through outward semblance — more true than the truth itself to the more simple-minded, who are thus deceived.”
— Book I — Preface
“They say that there exists, in invisible and indescribable heights, a certain perfect Aeon who existed before all else. Him they call Proarche, and Propator, and Bythos; and they say he is invisible, and such that no thing can grasp him.”
— Book I — Chapter 1
“The Church, though dispersed across the entire world, all the way out to earth's furthest bounds, received from the apostles and from their disciples this single faith: in God the Father, ruler of all, who fashioned heaven and earth and sea and all things held within them; and in one Christ Jesus, God's Son, who took on flesh for the sake of our deliverance;”
— Book I — Chapter 10
“And the churches founded in Germany believe and hand down nothing different, nor do those established among the Iberians, nor among the Celtic peoples, nor in the eastern lands, nor within Egypt's borders, nor across Libya, nor those established in the middle regions of the world;”
— Book I — Chapter 10
“Since we hold the standard of truth — namely, that a single all-powerful God exists, who fashioned everything through his Word, shaping and producing all that exists out of what did not exist, so that it might come to be”
— Book I — Chapter 22
It is Irenaeus of Lyons's late-second-century work exposing and refuting the Gnostic teachings of Valentinus and related sects. Book I is devoted mainly to laying out their cosmology of Aeons, Sophia's fall, and the origin of the material world in painstaking detail, then broadening to survey earlier and related heretical teachers before summarizing the Church's own "rule of faith."
Irenaeus was bishop of Lyons in Gaul. He explains in the preface that he wrote at a friend's request, having personally met Valentinian teachers and studied their doctrine, so that its "most monstrous and deepest mysteries" could be made plain and refuted rather than left to spread unchallenged.
In Valentinian teaching as Irenaeus reports it, the Pleroma ("Fullness") is the invisible spiritual realm containing thirty Aeons — paired divine beings emitted successively from the first principle, Bythos ("Depth"). The youngest Aeon, Sophia, falls into disordered passion, and the consequences of her fall, worked out through her offspring Achamoth, become the mythological origin of the created, material world.
He compares their method to writers who stitch together isolated lines of Homer into a new speech, so that the naive assume Homer actually composed it for that purpose. He argues the Valentinians and the numerologist Marcus do the same with the Gospels and the Law, finding their Aeon-numbers in details like the twelve-year-old Jesus in the Temple or the eight people saved in Noah's ark, when the texts were never about that system at all.
Simon the Samaritan, described using Luke's account of a sorcerer who amazed Samaria, is treated by Irenaeus as the historical root from which all later heresies descended, including Saturninus, Basilides, Carpocrates, Cerinthus, and Cerdo, whom Book I surveys in turn after finishing with the Valentinians.
In chapter 10 he sets out a creed-like summary of apostolic teaching — one God the Father who made heaven and earth, one Christ Jesus incarnate for human deliverance, and the Holy Spirit who spoke through the prophets — and argues that this same faith is held identically by churches across Germany, Spain, the Celtic lands, the East, Egypt, and Libya, regardless of differences in language or the eloquence of any individual teacher.
It is one of the fullest ancient accounts, though a hostile one; much of what is known about Valentinus's followers survives chiefly through Irenaeus's detailed summaries rather than the Gnostics' own writings, many of which are lost or survive only in fragments and later discoveries such as the Nag Hammadi texts.
Yes. After finishing with the Valentinian system and Marcus's numerology, Book I moves through Simon Magus, Saturninus, Basilides, Carpocrates, Cerinthus, Cerdo, and a range of unnamed offshoot sects, including libertine groups and groups that reinterpreted figures like Cain and Judas favorably.
Against Heresies — Book II · Against Heresies — Book III · Against Heresies — Book IV · Against Heresies — Book V