1 John has sometimes been interpreted as a polemic against a Cerinthian heresy. This rests partly on patristic stories about John’s near-encounter with Cerinthus at a bathhouse, and it implies that the opponents in 1 John are proto-gnostics who teach a semidocetic christology.

But patristic critics didn’t only accuse Cerinthus of gnostic teaching. Some described him as a judaizing heretic.

A third-century text attached to Tertullian’s Prescription against Heretics (the author is known as Pseudo-Tertullian) says (in Raymond Brown’s summary) that “Cerinthus taught that the world was created by angels (instead of by a demiurge) who also was responsible for the giving of the law. Pseudo-Tertullian also reports that the Ebionites (a Jewish Christian movement) were the successors of Cerinthus in some of their ideas.”

Dionysius Bar Salibi (d. 1171), basing his opinion on lost works of Hippolytus, had a similar view of Cerinthus. Again Brown: “Dionysius tells us that Gaius (or Caius), a learned ecclesiastic of Rome at the end of the second century . . . , is supposed to have denied that John wrote either Revelation or GJohn, works really composed by Cerinthus. Hippolytus, we are told, disproved this claim of Gaius on the principle that the doctrine of Cerinthus was quite unlike that of GJohn, e.g., Cerinthus taught the necessity of circumcision, that the creator was an angel, that Jesus was not born of a virgin, and that eating and drinking certain things were forbidden.”

Epiphanius of Salamis’s Panarion (375) records similar details of Cerinthus’s teaching. He links him with the Nazoraeans, a Jewish sect, as well as the Ebionites, he says that Cerinthus was one of the troublemakers in Acts 15. For him, Cerinthus was “the founder of a Jewish Christian sect that remained faithful to circumcision and other observances of the Law; for them Jesus was the Messiah but human and not to be worshipped.”

Brown evaluates this mixed evidence - Cerinthus was a gnostic (Irenaeus) and Cerinthus was a Judaizer - and concludes that the former is more reliable. Perhaps, though, it’s a mistake to set these off against each other. Perhaps Judaizing and gnosticism are more deeply connected than they appear.