Kosmas 17 was a deacon, notarios and kouboukleisios of the patriarch of Constantinople; in 787 he was one of the patriarchal officials present as readers at the Second Council of Nikaia (the Seventh Ecumenical Council); he is styled Κοσμᾶς ὁ εὐλαβέστατος διάκονος καὶ νοτάριος καὶ κουβουκλείσιος τοῦ εὐαγοῦς πατριαρχείου or similar: Mansi XII 1038, XII 1042, XII 1078, XIII 13, XIII 40, XIII 73, XIII 92, XIII 160 (twice), XIII 188, XIII 189, XIII 413. At the first session, on 24 September 787, he read out passages from the Life of St Sabas, the Ecclesiastical History of Theodoros Lector and the Acts of the Council of Chalcedon: Mansi XII 1038-1039, 1042. At the second session, on 26 September 787, he read out the letter sent to the patriarch Tarasios 1 by the pope, Hadrian I (Hadrianos 1): Mansi XII 1078. At the fourth session, on 1 October 787, he read passages from Gregory of Nazianzos, Maximos Homologetes, the Life of Symeon Stylites the Younger and a letter from pope Gregory II (Gregorios 72) to the patriarch Germanos I (Germanos 8): Mansi XIII 13 (Gregory), XIII 40 (Maximos Homologetes), XIII 73-77 (Symeon Stylites), XIII 92 (Pope Gregory). At the fifth session he read from Cyril of Jerusalem and Symeon Stylites the Younger: Mansi XIII 160. At this session he produced a copy of the Old Testament which he had found in the patriarchal library and showed a scholion defending the veneration of icons, which iconoclasts had attempted to erase; it was still legible and he read it out: Mansi XIII 188. He also produced a work on the martyrs, found by him in the treasury of the oratories of the patriarchate, from which a section dealing with the image of Kamouliana "not made by hand" had been removed: Mansi XIII 189. At the eighth session (in the palace of the Magnaura in Constantinople), he read out the definition of the faith adopted by the Council: Mansi XIII 413.

(Publishable link for this person: )