Caius (2), an ecclesiastical writer at the beginning of the 3rd cent., according to late authority, a presbyter of the Roman church. Eusebius mentions but one work of his, to which he refers four times ( H. E. ii. 25, iii. 28, 31, vi. 20), and from which he gives some short extracts. This was a dialogue purporting to be a report of a disputation held at Rome during the episcopate of Zephyrinus (a.d. 201–219) between Caius and Proclus, a leader of the sect of Montanists.
This dialogue is mentioned by the following writers, who may, however, have only known it from the account given by Eusebius:—Hieron. de Vir. Ill. 59; Theod. Haer. Fab. ii. 3; iii. 2, where the present text, doubtless by a transcriber's error, reads Patroclus instead of Proclus (Niceph. Call. H. E. iv. 12, 20; Photius, Bibl. 48). Only the last of these attributes any other work to Caius. Theodoret says that he wrote against Cerinthus, but is probably referring to a part of the dialogue in question.
In the short fragments preserved, Proclus defends the prophesyings of his sect by appealing to the four daughters of Philip, who with their father were buried at Hierapolis; Caius, on the other hand, offers to shew his antagonist at the Vatican and on the Appian Way the tombs of the apostles "who founded this church." That Caius should have conducted a disputation at Rome does not of itself prove that he, any more than Proclus, permanently resided there. Yet the expression cited conveys the impression that he did; and Eusebius was apparently of that opinion, for elsewhere (vi. 20), having mentioned that Caius only counted St. Paul's epistles as thirteen, omitting that to the Hebrews, he adds that even in his own time "some of the Romans" did not ascribe that epistle to the apostle. It is just possible that we are still in possession of the list of genuine apostolic writings which Eusebius (l.c. ) intimates that Caius gave, in order to rebuke the rashness of his opponents in framing new Scriptures. Muratori attributed to Caius the celebrated fragment on the canon published by him, which concludes with a rejection of Montanist documents.
But it is difficult to believe that if this were the list referred to by Eusebius, he would not have quoted it more fully. Among the heretical writings rejected by Caius was a book of Revelations (Eus. ii. 25) purporting to be written by a great apostle and ascribed by Caius to Cerinthus, in which the author professes to have been shewn by angels that after the resurrection Christ's kingdom should be earthly, that men should inhabit Jerusalem, should be the slaves of lusts and pleasures, and should spend a thousand years in marriage festivities. The strongest reason for thinking that the book intended is the canonical book of the Revelation is that Dionysius of Alexandria (Eus. H. E. vii. 25) asserts that some of his predecessors had maintained that the Apocalypse is the work of Cerinthus, and describes their views in language strongly resembling that of Caius.
There had been much speculation respecting Caius himself (s.v. D. C. B. 4-vol. ed.); and Lightfoot, in his Apostolic Fathers (Clement of Rome, vol. ii. p. 377), questions his existence. But Dr. Gwynn, of Dublin, pub. in Hermathena VI. some fragments of Capita adv. Caium, written by Hippolytus, which he had discovered in Cod. Mus. Brit. Orient. 560. These passages shew that he had attacked the Apocalypse of St. John, and treated the book as inconsistent with the Holy Scriptures. Harnack (Herzog. 3 ) thinks it not improbable that he had treated the Apocalypse as a work of Cerinthus; and as he would be at one in this opinion with the Alogi of Asia Minor, a connexion between him and them may be supposed. Nothing more is known with certainty of him (cf. Zahn, Gesch. des N. T. Kanons, ii. 985 seq.).