Ioannes 15 was the representative of Antioch at the Ecumenical Council called by Eirene 1 in 785; he was the synkellos of the patriarch of Antioch and is described as a holy man distinguished for his learning and his conduct: Theoph. AM 6277 (καὶ ἤνεγκαν ἐκ μὲν Ἀντιοχείας Ἰωάννην τὸν μέγαν καὶ περιβόητον λόγῳ καὶ ἔργῳ ἁγιωσύνης μετέχοντα καὶ σύγκελλον τοῦ πατριάρχου Ἀντιοχείας γεγονότα). See Treadgold, Revival, p. 398, n. 88.

He arrived in time to attend the Council in the Church of the Holy Apostles in Constantinople on 7 August 786 (according to Theophanes; the correct date was 31 July, see Grumel, Regestes, n. 355): Theoph. AM 6278. He and Thomas 4 remained at Constantinople until the Council was reconvened at Nikaia in October (actually September) 787: Theoph. AM 6279 (τοὺς δὲ Ῥώμης καὶ ἀνατολικοὺς ἐκ προσώπου).

At the Second Council of Nikaia (the Seventh Ecumenical Council) he and Thomas 4, priests and monks, were the representatives of the apostolic sees of the eastern diocese (Ἰωάννου καὶ Θωμᾶ τῶν εὐλαβεστάτων πρεσβυτέρων, μοναχῶν καὶ τοποτηρητῶν τῶν ἀποστολικῶν θρόνων τῆς ἀνατολικῆς διοικήσεως): Mansi XII 994-XIII 486 (Ioannes 15 represented Antioch, Thomas 4 Alexandria). They were sent in response to a letter to the patriarchs and clergy of Antioch, Alexandria and Jerusalem from the patriarch of Constantinople, Tarasios 1, asking for representatives to be sent to help restore church unity: Mansi XII 1126-1127, XIII 459. They were the synkelloi of the patriarchs of Antioch and Alexandria and are named in the letter from the two patriarchs as representing them and the patriarch of Jerusalem; described as orthodox and lovers of peace (τοὺς θεοφιλεῖς ἀδελφοὺς ἡμῶν Ἰωάννην καὶ Θωμᾶν ζήλῳ θείῳ τῆς ὀρθοδόξου κεκοσμημένους πίστεως, δύο ἁγίων καὶ μεγαλων (sic accents as μεγάλων) πατριαρχῶν ὁμοψύχους συγκέλλους γενομένους, οὐ μὴν ἀλλὰ καὶ τῆς ἁγιοποιοῦ ἡσυχίας ὄντας ἐραστάς): Mansi XII 1131.

A monk, priest and synkellos, he represented Theodoretos 1, the patriarch of Antioch, and Elias 12, the patriarch of Jerusalem (the textual reading is doubtful, possibly a variant of Ailia, but the see is identified from the Acts of the Council, see above) at the Second Council of Nikaia: Ignatios, Vita Tarasii 28, cf. Photius, Ep. 1, lines 374ff (I 13 Laourdas-Westerink). (Ioannes 15 and Thomas 4, monks and priests, represented the apostolic sees of the East at Nikaia), Ep. 2 (I 40ff. Laourdas-Westerink).

They brought letters from the bishops and clergy of the Oriental diocese: Mansi XII 1007 (παρὰ τῶν ἀρχιερέων καὶ ἱερέων τῆς ἀνατολικῆς διοικήσεως, διὰ Ἰωάννου τοῦ εὐλαβεστάτου μοναχοῦ καὶ συγκέλλου γενομένου τοῦ πατριαρχικοῦ θρόνου Ἀντιοχείας καὶ Θωμᾶ πρεσβυτέρου καὶ ἡγουμένου). They attended the first seven sessions, from 24 September to 13 October 787, and presumably the last also, on 23 November: Mansi XII 994, 1051, 1114, XIII 1, 157, 204, 365, 413. Styled Ἰωάννης ὁ εὐλαβέστατος μοναχὸς καὶ πρεσβύτερος καὶ τοποτηρητὴς τοῦ ἀποστολικοῦ θρόνου Ἀντιοχείας: Mansi XII 1019; Ἰωάννης ὁ εὐλαβέστατος μοναχός τε καὶ τοποτηρητὴς τῶν ἀνατολικῶν ἀρχιερέων or similar: Mansi XII 1022, 1031, 1034, XIII 24, 40, 53, 57, 61, 64, 65, 69, 72, 89, 133 (Ἰωάννης ἐλέῳ Θεοῦ πρεσβύτερος καὶ πατριαρχικὸς σύγκελλος, τὸν τόπον ἐπέχων τῶν τριῶν ἀποστολικῶν θρόνων, Ἀλεξανδρείας, Ἀντιοχείας, καὶ Ἱεροσολύμων), XIII 164, 168, 173, 189, 196, 197.

At the first session Ioannes 15 proposed that the writings of the Fathers be consulted in order to discover how former heretics should be received back into the Church: Mansi XII 1019. He spoke several times during this session: Mansi XII 1022, 1031, 1034. At the second session he spoke of church unity, welcoming the convening of the Council and approving the content of the statements from pope Hadrian I (Hadrianos 1) in favour of the traditional veneration of icons: Mansi XII 1086-1087 (Ἰωάννης ὁ θεοφιλέστατος πρεσβύτερος καὶ πρεσβευτὴς τῆς ἀνατολικῆς διοικήσεως). During the third session he spoke in favour of the readmission of heretics who had repented; later he and Thomas 4 asked for the letter sent by Tarasios 1 to the bishops and clergy of Alexandria and Antioch to be read to the Council: Mansi XII 1115-1119, cf. XII 1127 (bearer of the letter). At the fourth session, during a discussion on the human form of angels, he noted that God himself had appeared in that form to Jacob: Mansi XIII 8. He also observed that the angel depicted driving off barbarian hordes in a picture admired by John Chrysostom was none other than the angel of the Lord who smote the Assyrians at Jerusalem one night: Mansi XIII 9. He made observations on several other occasions during this session: Mansi XIII 9 (since pictures helped Gregory of Nyssa, how much more would they help the ignorant and unlearned), 20 (pictures speak louder than words, and artists are like advocates of the written - συνήγοροί εἰσι τῶν γεγραμμένων), 24 (the evidence read to the Council shows that the icons of saints work miracles and perform cures), 40 (evidence read out from Maximos Homologetes (Maximos 10) showed not only that icons were necessary but had equal power with the Gospels and the Holy Cross), 53 (he approved the orthodoxy of a passage from Leontios of Neapolis and then produced a codex of a work by Anastasios of Antioch, which he himself had unearthed in Constantinople in the house of the silentiarios Prokopios 5 and which he claimed corresponded to another copy which they had in the East), 57 (on the parallels between the veneration of images of the emperor and of Christ), 61 (it was better to break one's oath than to keep it when doing so meant the destruction of icons; some iconoclasts, he said, still felt bound by the oaths they had taken), 64 (he asked for the question of their oaths to be further investigated, but Tarasios 1 ruled that the matter had been already dealt with sufficiently), 65 (SS Kosmas and Damian performed miracles through their images), 69 (he produced a codex containing a sermon of Basil, which he had brought from the East to be read out), 72 (he criticised the logic of the iconoclast council over its attitudes to icon veneration, in the light of remarks read out from St Basil), 89 (he had personally seen and frequently honoured the icon of the Theotokos at Jerusalem mentioned in the Life of Maria the Egyptian). Later he subscribed the statements read out from the Fathers in support of the traditional veneration of icons: Mansi XIII 133. At the fifth session also he made a number of remarks: Mansi XIII 164 (Samaritans were worse than other heretics and those who rejected icons were so bad that they deserved to be called Samaritans also), 168 (the Fathers saw that those who rejected the incarnation, such as Jews and Samaritans, also rejected the veneration of icons; iconoclasts were therefore like them), 173 (the so-called Itineraries of the Apostles represented Lykomedes as crowning an image of the apostle John, just like the pagans crowned their idols; he compared the iconoclasts to Nebuchadnezzar, the Samaritans, the Jews, the pagans and the Manichees as rejecting the incarnation and anathematised them and their writings; he also proposed, and the Council agreed, that no further copies of this work be made, and existing copies be destroyed), 189 (the result of book burning and icon breaking by the iconoclasts had in fact only been to reveal the Truth more clearly). Introduced to the Council at the end of the fifth session by the patriarch Tarasios 1, he narrated his account of the origins of the iconoclast movement (cf. Yezid 2): Mansi XIII 196-200. At the close of the session he called out blessings for the role played by Nikaia in the history of the Church and the triumph of orthodox belief: Mansi XIII 200-201. At the seventh session he subscribed the statement of the faith adopted by the Council: Mansi XIII 380 (Ἰωάννης ἐλέῳ Θεοῦ πρεσβύτερος καὶ πατριαρχικὸς σύγκελλος, τόν τόπον ἐπέχων τῶν τρῖων ἀποστολικῶν θρόνων, Ἀλεξανδρείας, Ἀντιοχείας καὶ Ἱεροσολύμων) (= XIII 133, quoted above). He is alluded to but not named in a letter of Theodore the Stoudite (Theodoros 15), according to which he had no authority at Nikaia, and consequently the Council could not be ecumenical: Theod. Stud., Ep. 38, lines 63-66. Later he accompanied Tarasios 1 when the patriarch was summoned before the emperor (Constantine VI (Konstantinos 8)) for opposing his plans to divorce his wife and remarry; he was then an old man (τὸν γηραιὸν Ἰωάννην): Vita Tarasii 43, lines 2-5 (he is identified as the representative of the East at the Council). He also opposed the emperor's wishes and advised him strongly not to continue, and for this suffered abuse and threats from imperial officials; neither he nor Tarasios 1 would agree to the emperor's wishes and finally they were expelled from his presence: Vita Tarasii 45, lines 1-11.

(Publishable link for this person: )