The tract entitled _On the Unity of the Catholic Church_ is the most famous of Cyprian’s works. As the theory there developed is opposed to that which became dominant, and as Cyprian was regarded as the great upholder of the Church’s constitution, interpolations were early made in the text which seriously distort the sense. These interpolations are to-day abandoned by all scholars. The best critical edition of the works of Cyprian is by W. von Hartel in the CSEL, but critical texts of the following passage with references to literature and indication of interpolations may be found in Mirbt (Prot.), n. 52, and in Kirch (R. C.), n. 234 (chapter 4 only). Ch. 4. The Lord speaks to Peter, saying: “I say unto thee, that thou art Peter; and upon this rock I will build my Church and the gates of hell shall not prevail against it. I will give thee the keys of the Kingdom of Heaven; and whatsoever thou shalt bind on earth shall be bound also in heaven; and whatsoever thou shalt loose on earth shall be loosed also in heaven” (Matt. 16:18, 19). [To the same He says after His resurrection: “Feed my sheep” (John 21:15). Upon him He builds His Church, and to him He commits His sheep to be fed, and although. _Interpolation._] Upon one he builds the Church, although also to all the Apostles after His resurrection He gives an equal power and says, “As the Father has sent me, I also send you: receive ye the Holy Ghost: whosesoever sins ye retain, they shall be retained” (John 20:21); yet, that He might show the unity, [He founded one see. _Interpolation._] He arranged by His authority the origin of that unity as beginning from one. Assuredly the rest of the Apostles were also what Peter was, with a like partnership both of honor and power; but the beginning proceeds from unity [and the primacy is given to Peter. _Interpolation._], that there might be shown to be one Church of Christ [and one see. And they are all shepherds, but the flock is shown to be one which is fed by the Apostles with unanimous consent. _Interpolation._]. Which one Church the Holy Spirit also in the Song of Songs designates in the person of the Lord and says: “My dove, my spotless one, is but one. She is the only one of her mother, chosen of her that bare her” (Cant. 6:9). Does he who does not hold this unity of the Church [unity of Peter. _Corrupt reading._] think that he holds the faith? Does he who strives against and resists the Church [who deserts the chair of Peter. _Interpolation._] trust that he is in the Church, when, moreover, the blessed Apostle Paul teaches the same things and sets forth the sacrament of unity, saying, “There is one body and one spirit, one hope of your calling, one Lord, one faith, one baptism, one God”? (Eph. 4:4.)