Diversity was a mark of mid-second century Christianity with different groups adopting different gospels as their supreme authority. Questions were asked such as whether the divinity of Christ was taught in the gospel according to Matthew, and whether it was not simpler and no less religious to hold Jesus to be merely the son of his father Joseph; what measure of authority attached to the letters of Paul, how one could answer Marcion's exclusive acceptance of a text of Luke's gospel from which references to fulfilled Old Testament prophecy had been removed as Judaistic interpolations, or his belief that Paul was the only apostle emancipated from Judaism and deserving recognition.
Born probably about 140, Irenaeus constitutes a major link between the Church of his own time, spread throughout the Roman Empire and beyond, and the heroic age of the past with Bishop Polycarp of Smyrna who could recall St John, who had shown the heretic Marcion the door, and who had visited Bishop Anicetus of Rome to defend the tradition of Asia Minor concerning the celebration of Easter, achieving peace with the recognition of diversity. Like other Greeks from Asia Minor, Irenaeus moved to the Rhône valley. He was probably author of the moving account of the inhuman persecution inflicted by order of Marcus Aurelius on the Christians of Lyon and Vienne in 177, preserved in the Church History of Eusebius of Caesarea. Continuing controversy between Rome and Asia Minor about the calculation of Easter Day and the form of the preceding fast drew him in to write a conciliatory letter to Pope Victor inviting him to be tolerant of diversity. That was hard for Victor to do for the reason that at Rome there were migrant Christians from Asia Minor, and it seemed hard to tolerate differences within one city. It seemed an advertisement of disunity. Victor's bid for uniformity was supported by several bishops in the Greek East. The disagreement was the earliest instance of tensions between Greek east and the west, the latter being still Greek-speaking.
Irenaeus' greatest work was a five-part argument against gnosticism, especially against the followers of Valentinus. In its original form his was the least