Against Heresies or Refutation.

        Irenaeus was not only an active missionary churchman; he was also one of the leading Christian writers of his day, and his work describing and attacking the heretical movements of his times is the most important work of its kind that has come down to us from the second century. (We do not possess Justin's treatise Against All Heresies or the writings of Theophilus Against Marcion and Against Hermogenes). He set out, it is true, to deal with the Gnostic heresy and called his book a Refutation of Gnosticism (“Gnosis falsely so called,” cf. I Tim. 6:20, where the same phrase is used). But, as he advanced, the work grew under his hand, and, before he had finished, he had covered not only Gnosticism in its various forms (Books I and II) but had presented the sound Christian position as he understood it (Books III-V).

        Irenaeus appeals to the fact that some churches of apostolic foundation had maintained an unbroken tradition of sound Christian teaching and so should, when he wrote, be trustworthy centers of the faith as the apostles had taught it. As he was writing in the West, he pointed to the Roman church as such a center and appealed to its tradition of Christian truth through an unbroken line of bishops in support of the standard type of Christianity (Haer. iii. 3. 2). He gores a list of these Roman bishops reaching down from the days of the apostles to his own contemporary Eleutherus (iii. 3. 3), in whose episcopate, A.D. 175-89, he evidently wrote his third book, and probably all five books, of his work.

        Irenaeus also appealed to a Christian scripture, not only an Old Testament and the Four Gospels (iii. II. 8) but the Acts (iii. 12. 15) and the letters of Paul. In fact, Irenaeus is the first Christian writer who can be shown to have had something like what we understand by the New Testament, at least in its earliest form of twenty-two books-four gospels, the Acts, thirteen letters of Paul (including the three Pastorals, to Timothy and Titus), I John and I Peter, the Revelation of John, and the Shepherd of Hermas. With Irenaeus, Christians began to call these books “scriptures” just as they did the Jewish books of our Old Testament.

        In these more constructive books of his Refutation, Irenaeus still has his eye on the heretics, for he occasionally deals with the positions of Marcion, the Ebionites, and others. His book has been well described as a treasure house from which later writers on the heresies drew. He himself was indebted for material to Justin, from whose book Against Marcion he quotes (iv. 6. 2), to Hegesippus, and probably to Theophilus. His own work, on the other hand, was later used by the anti-heretical writers Hippolytus and Epiphanius. He was the most important anti-Gnostic writer of antiquity. His practice of quoting characteristic passages from the writings of leading schismatics that have since disappeared makes him an invaluable source of information about them, although of course he is writing polemic, not dispassionate descriptions. And the positive statement of Christian views that forms more than half his great book reveals developer of Christian thought.

        It is a curious fact that so important a book as Irenaeus' treatise should have disappeared, but in its original Greek form it has nowhere been found; except for quotations from it in later writers, our knowledge of it is largely dependent upon an early Latin translation of it, which is extant in numerous manuscripts. There is also an Armenian version of Books iv and v,[56] besides fragments of a Syriac translation. Some portions of the Greek original are known, quoted in the pages of Hippolytus, Eusebius, and Epiphanius or unearthed in fragmentary papyri now chiefly at Jena. But one, found at Oxyrhynchus, is believed to have been written in the late second or early third century, so that it is almost contemporary with Irenaeus.[57]