Irenaeus

The teachers Irenaeus wrote against claimed a tradition handed down privately to those capable of receiving it, alongside the ordinary teaching given to everyone else. His answer is procedural rather than speculative, and it is the reason the book mattered.

If the apostles had a hidden doctrine, he argues, they would have entrusted it to the men they put in charge of the churches, and those men and their successors are known by name and can be listed. He lists them for Rome, and points to Smyrna and Ephesus. What those churches teach openly, and have taught continuously, is therefore the measure. A doctrine that appears in the second century with no public line behind it is new, whatever it claims about its origins.

Alongside this he sets the rule of truth, the summary of belief a candidate receives at baptism, and uses it as a frame that determines how scripture may be read. His illustration is exact: a mosaic portrait of a king can be taken apart and the same tiles reassembled into a fox or a dog, and the person who has done it can still say that every tile is original. Heretical reading, on his account, does not add material, it rearranges it.

The same instinct produced his insistence that there are four Gospels and only four, which is the earliest surviving statement of the number, and his doctrine of recapitulation, that Christ passes through every stage of human life and repairs it from inside, with Mary answering Eve at the point where the damage began.

Against Heresies does not survive in its original Greek except in fragments and quotations. What survives entire is a very literal Latin translation, wooden enough that scholars can often reconstruct the Greek behind it, plus an Armenian version of part. For seventeen centuries its first book, a systematic description of the Valentinian teaching of Ptolemaeus with its thirty aeons and its fallen Sophia, was effectively the only detailed account of second century Gnostic teaching that anyone had, and it was written by a man whose purpose was to refute it.

The discovery of the Nag Hammadi codices in Egypt in 1945 put primary texts in front of readers for the first time. The result was mixed for his reputation and interesting either way. His reporting turned out to be substantially accurate, and one of the recovered works corresponds closely enough to a system he describes that his summary can be checked against it line by line. His framing, that these were late innovations by named individuals departing from a single earlier faith, is what the recovered library made harder to sustain, since it shows a wider and less orderly range of second century Christian writing than his account implies.

He is also remembered for a use of his authority that his polemics do not predict. When the bishop of Rome moved to cut off the churches of Asia over the date of Easter, Irenaeus wrote urging him not to, on the ground that the difference in practice was old and had not previously broken communion. Eusebius, who preserves the letter, notes that he lived up to his name, which means peaceable.