He was a disciple and scribe of St John Chrysostom. About the year 426 he was ordained Bishop of Cyzicus, but was unable to take up his see because another had been unlawfully elected in his place, so he remained in Constantinople. Around 428, Nestorius was made Patriarch of Constantinople, and almost immediately began teaching his blasphemous doctrine that the holy Virgin could not be called Theotokos, "God-bearer," but only Christotokos, "Christ-bearer." Proclus resisted this teaching forcefully, once giving a sermon in the presence of the heretical Patriarch, defending the Orthodox teaching concerning the Theotokos. Proclus was elevated to the throne of Patriarch of Constantinople in 434, after Nestorius had been deposed and the Orthodox teaching clearly proclaimed in an Ecumenical Council. It was Proclus who persuaded the Emperor Theodosius the Younger to have the holy relics of his teacher St John Chrysostom returned to Constantinople, and who received them on their triumphal return to the city. He reposed in peace in 447.