He was a supporter of St. Gregory Palamas and became a follower and advocate of the form of contemplative prayer called Hesychasm, and the Orthodox theology of uncreated Grace. As a writer of note, Philotheus wrote works on the theology of the Uncreated Energies of God and refuted the scholastic philosophy that was then current in the Western church. His most famous work, written in 1339, was the "Hagiorite Tome", the manifesto of the Athonite monks on how the saints partake of the Divine and uncreated Light that the Apostles beheld at the Transfiguration of Jesus.