(Theodosius the Squint-eyed). Dates of birth and death unknown. Leader of a 16th-century religious heresy and ideologist of the peasantry and urban poor in their struggle against the official church and the feudal order.
Feodosii Kosoi was born a bondman. In the late 1540’s he fled from Moscow to Beloozero and became a monk. Later he moved to a monastery at Novoozero, where in 1551 he began to proselytize on behalf of his “new doctrine.” Kosoi opposed such basic dogmas of Christianity as the divinity of Christ and the resurrection of the dead. He denied the existence of saints and miracles, advocated the abolishment of monasticism, and called for rejection of the practice of bowing before icons. Repudiating the official church, Kosoi preached the equality of all people; he rejected the entire system of feudal vassalage, maintained that each individual was to work for his own salvation, and called for the abolishment of war and exploitation. Kosoi’s ideas were condemned by Zenobius of Otnia. In 1553, because of his connection with M. Bashkin, Kosoi was incarcerated in a Moscow monastery. He escaped to Poland, however, and was an important influence there in the formation of the radical anti-Trinitarian movement.