Proclus was Archbishop of Constantinople in the first half of the fifth century, remembered above all as a defender of the title Theotokos ("Mother of God") for the Virgin Mary and for his role in restoring honor to his predecessor Saint John Chrysostom. The tradition received in the synaxaria presents him as a disciple and scribe of Chrysostom, who ordained him deacon and priest; some modern scholarship instead places his formation chiefly under Archbishop Atticus of Constantinople (406-425), whom he served as secretary, and regards the close personal link to Chrysostom as having been emphasized in later centuries. Either way, Proclus rose within the clergy of the capital as a noted preacher.
He was consecrated bishop of the dependent see of Cyzicus around the year 426 by Patriarch Sisinius, but he was unable to take up residence there. According to the synaxarion the people had already chosen another bishop before his arrival; other accounts attribute his exclusion to Nestorian opposition. He therefore remained in Constantinople, where he continued to preach and where the decisive episode of his life unfolded.
While Nestorius held the archiepiscopal throne and had begun teaching that the Virgin should not be called Theotokos, Proclus delivered, by tradition around 429-430 and in Nestorius's own presence, a celebrated homily on the Incarnation that openly defended the title Theotokos. The sermon was later incorporated into the Acts of the Council of Ephesus (431), at which Nestorius was condemned and deposed, and it became one of the most renowned Marian sermons of the early Church. Although Proclus himself was not present at Ephesus, Saint Cyril of Alexandria acknowledged the weight of his preaching against the Nestorian teaching.
Following the death of Maximianus, Proclus was enthroned as Archbishop of Constantinople in 434 and governed the Church for about twelve years, until his death around 446-447. His episcopate was marked by moderation: he sought to reconcile divided parties rather than to prolong conflict, and he was esteemed for his ascetic manner of life, his care for the poor and downtrodden, and his preaching. A substantial body of homilies and letters has been transmitted under his name.
