Early Life and Formation
Philotheus was born around 1300 in Thessalonica. His mother was a Jewish convert to Orthodox Christianity. The surname Kokkinos, meaning 'red-haired,' was attributed by the historian Nicephorus Gregoras to his fiery and wild appearance, though it likely represented his actual family name.
He studied under Thomas Magister (died 1347), described as one of the most learned men of his time, and showed exceptional aptitude in both theological and secular studies. He entered monastic life early, beginning at Mount Sinai before relocating to Mount Athos.
Monastic Career on Athos
At the Vatopedi monastery on Athos, Philotheus developed a significant relationship with Savvas the New of Kalymnos (died 1350), a Fool-for-Christ whom he later memorialized as a biographer. He subsequently moved to the Great Lavra, where he formed a close relationship with Saint Gregory Palamas, became his biographer, and emerged as a devoted follower of hesychasm.
He composed the Hagiorite Tome in 1339 while still on Mount Athos. It served as the manifesto of the Athonite monks, articulating how the saints participate in the divine and uncreated Light beheld at the Transfiguration.
Ecclesiastical Offices
In 1340 Philotheus was appointed abbot of the Monastery of Philokalou in Thessalonica. In 1344 he was recalled to the Great Lavra as its hegumen. In 1347 Patriarch Isidore I appointed him Metropolitan of Heraclea in Thrace.
His first patriarchate ran from August 1353 to December 1354, by appointment of co-Emperor John VI Kantakouzenos; he was deposed following John V Palaiologos's consolidation of power. His second patriarchate ran from 8 October 1364 to August 1376, after he was recalled upon the death of Callistus I on 8 February 1364; he was deposed when Emperor Andronikos IV Palaiologos ascended the throne.
Defense of Hesychasm
Philotheus wrote extensively against the anti-hesychasts and against Western scholasticism, particularly opposing the theology of Thomas Aquinas. He participated in the Hesychast Council of 1351 and authored its Acts, formally endorsing Palamite theology. The council met in six patriarchal sessions between 1341 and 1351, with its final session on 28 May 1351.
During his second patriarchate he led the synod of 1368 that formally canonized Gregory Palamas, designating the Second Sunday of Great Lent as Palamas's feast day, and personally composed the Church's services to him. At the same synod he condemned Prochoros Kydones. The 1368 synod later achieved ecumenical status when the 2016 Council of Crete granted it universal authority as the Fifth Council of Constantinople. Philotheus is venerated alongside Photius I, Mark of Ephesus, and Gregory Palamas as a Protector of Orthodoxy.
Liturgical Codification
The scholar Robert F. Taft affirmed that the liturgical codification of the eucharistic service of the Great Church reached its full form in the diataxis of Philotheus I. His rubric book, completed before 1347, eventually became normative throughout the Byzantine churches and was incorporated into Demetrius Ducas's 1526 editio princeps of the liturgy.
Relations with the Slavic Churches
Around 1354 envoys from Philotheus's patriarchate visited Saint Sergius of Radonezh, urging the adoption of communal monastic rules; the Trinity monastery adopted the Studite Constitution, facilitating the spread of hesychasm to Russia. In 1375 he recognized the Serbian Patriarchate of Pec, and that same year he consecrated Cyprian as Metropolitan of Kiev, Lithuania, and Russia.
Relics & Shrines
Following his deposition in 1376, Philotheus entered exile and reposed in 1379 in Constantinople. His tomb at the Monastery of Akatalyptos Maria Diakonissa (the Theotokos Kyriotissa, now the Kalenderhane Mosque) became a place of many miracles and a pilgrimage site.
