Barlaam of Seminara

Barlaam of Seminara was a Basilian monk, theologian, humanist and mathematician, probably born around 1290 in Seminara, Calabria, in a Greek-speaking Orthodox setting. He is remembered above all for his dispute in the Byzantine Empire with Gregory Palamas over Hesychasm, the mystical tradition of prayer in the Eastern Orthodox Church.

By the 1320s he had settled in Constantinople, where he gained the favour of church and political circles and was given a teaching post at the university under Emperor Andronicus III. He went on diplomatic missions to Naples, Paris and Avignon, where he met Petrarch. His writings include treatises against the Latins and a Greek work on arithmetic covering whole numbers, fractions and sexagesimal fractions.

He held that God is ultimately unknowable: the divine manifestations, such as the light of Mount Tabor, were created effects rather than God's essence. On this basis he criticised the Hesychast monks for what he saw as passivity and for claiming to perceive an uncreated light. Palamas answered with his Triads, which became a foundation of Byzantine mysticism. Barlaam was excommunicated in 1341 and later joined the Catholic Church. His legacy lives on mainly through the controversy, which shaped how Western writers understood Byzantine mysticism.