The famous work of the great holy father of the Western Church of the 3rd century, Hieromartyr Cyprian, Bishop of Carthage (210-258), “The Book of the Unity of the Church” (251) has an ecclesiological content and is relevant at all times in the life of the earthly Church. Written after the persecution of Christians by Emperor Decius in 250, which led to disorder within the Western Church - a whole series of schisms and unrest, which St. Cyprian considers it an invention of the devil, it became the reason for expressing the doctrine of the Church as such and its main property - unity, the violation of which by people is a grave sin. Published in: Works of the Hieromartyr Cyprian, Bishop of Carthage. A book about charity and almsgiving. M.: Pilgrim, 1999. (Library of Fathers and Teachers of the Church. Book 6). pp. 232-251.