Symeon the New Theologian was a Byzantine Christian mystic and theologian born around 949 AD in Galatia, modern-day Turkey. He is known for his deep spiritual writings and emphasis on personal experience of God, which set him apart from other theologians of his time. His works often focused on the importance of the Holy Spirit and the transformative power of divine grace. Symeon became a monk and later the abbot of the Monastery of St. Mamas in Constantinople. He faced opposition from church authorities due to his views, but his teachings influenced later Christian mysticism. He is recognized as a saint in both the Eastern Orthodox Church and the Roman Catholic Church.