Valentinus (Gnostic) in the context of "Irenaeus of Lyons"

Irenaeus (/ɪrɪˈneɪəs/ or /ˌaɪrɪˈniːəs/; Ancient Greek: Εἰρηναῖος, romanized: Eirēnaîos; c. 125 – c. 202 AD) was a Greek bishop noted for his role in guiding and expanding Christian communities in the southern regions of present-day France and, more widely, for the development of Christian theology by opposing Gnostic interpretations of Christian Scripture and defending orthodoxy. Originating from Smyrna, he had seen and heard the preaching of Polycarp, who in turn was said to have heard John the Evangelist.

Chosen as Bishop of Lugdunum, now Lyon, Irenaeus wrote his best-known work Against Heresies around 180 as a refutation of gnosticism, in particular that of Valentinus. To counter the doctrines of the gnostic sects claiming secret wisdom, he offered three pillars of orthodoxy: the scriptures, the tradition said to be handed down from the apostles, and the teaching of the apostles' successors. He is the earliest surviving witness to regard all four of the now-canonical gospels as essential.

Valentinianism was one of the major Gnostic Christian movements. Founded by Valentinus (b. c. 100 CE – d. c. 165 CE) in the 2nd century, its influence spread widely, not just within the Roman Empire but also from northwest Africa to Egypt through to Asia Minor and Syria in the east. Later in the movement's history, it broke into Eastern and a Western schools. The Valentinian movement remained active until the 4th century, declining after Emperor Theodosius I issued the Edict of Thessalonica in 380, which established Nicene Christianity as the state religion of the Roman Empire.

No evidence exists that Valentinus was labeled a heretic during his lifetime. Irenaeus of Lyons, who was the first patristic source to describe Valentinus's teachings—though likely incompletely and with a bias toward the time's proto-orthodox Christianity—did not finish his apologetic work Against Heresies until the latter 2nd century, likely sometime after Valentinus's death. The rapid growth of the Valentinian Gnostic movement—named eponymously after Valentinus—after his death prompted early Christian thought leaders, such as Irenaeus and later Hippolytus of Rome, to write apologetic works against Valentinus and Valentinianism, which conflicted with proto-orthodox theology. Because the proto-orthodox camp's leadership encouraged the destruction of Gnostic texts writ large, most textual evidence regarding Valentinian theology and practice comes from its critics—particularly Irenaeus, who was highly focused on refuting Valentinianism.

Cerdo (Ancient Greek: Κέρδων) was a Syrian Gnostic who was deemed a heretic by the Early Church around the time of his teaching, circa 138 AD. Cerdo started out as a follower of Simon Magus, like Basilides and Saturninus, and taught at about the same time as Valentinus and Marcion. According to Irenaeus, he was a contemporary of the Roman bishop Hyginus, residing in Rome as a prominent member of the Church until his forced expulsion therefrom.

He taught that there were two gods, one that demanded obedience while the other was good and merciful. According to Cerdo, the former was the God of the Old Testament who had created the world. He also said that the latter God was superior but that he was only known through his son, Jesus. Like later Gnostics, he was a docetist who rejected the bodily resurrection of the dead.