13. Moreover it suffices Us to be able to affirm without peril that at whatever time the practice of praying by name for the Roman pontiff at Mass was finally accepted by the Greek Church, this practice was definitely in force in Greek churches many centuries before schism broke out, and was only broken off after the fatal separation. A letter dated 1053 of Peter, patriarch of Antioch, to Michael Cerularius, the well-known reviver of the Photian schism, survives. This letter is published in Greek and Latin by Joannes Baptista Cotelerius in the second volume of his Monument. Eccles. Graec. Michael had said that he was surprised that Peter of Antioch himself as well as the bishops of Alexandria and Jerusalem mentioned the Roman pontiff in the sacred diptychs (p. 140 of the abovementioned volume). But Peter most sharply rebuked the rashness of the maddened man in showing that both at Antioch and at Constantinople, the commemoration of the Roman pontiff had never been omitted up to his time: "Of these matters I too am an unexceptionable witness, as are the many others who with me hold high office in the Church, that in the time of Lord John (patriarch of Antioch), the Pope at Rome, also called John, was included in the sacred diptychs. Furthermore, when I came to Constantinople forty-five years ago I found that under Patriarch Sergius the Pope was mentioned at holy Mass along with the other Patriarchs."

It is said in addition that no discussions on restoring unity were ever begun without the acceptance of the prior condition that the commemoration of the Roman pontiff should be included in the sacred liturgy, nor was a union which had been agreed on regarded as complete until the previous condition had actually been put into effect. The clear result of all this is that the Latin and Greek churches agree in recognizing and affirming that the commemoration implies a profession of due subjection to the Roman pontiff as head of the Church, and of a willingness to remain in the unity of the Church. On the other hand the omission of this commemoration signifies the intention of steadfastly espousing schism.