One of the claims of the Roman Catholic Church is that the Pope was seen by the entire ancient church both east and west as the infallible head of the Church. They say that when he makes official pronouncements about the faith and morals he is kept from erring by the Holy Spirit.
We Orthodox counter that claim in part by saying that Pope Honorius was found by the sixth council of the Church (Third Council of Constantinople 680-681) to be a heretic for saying that Jesus only had one will instead of two. Roman Catholics counter this by saying that the East put that in the council, but they never agreed with it. They say either that Honorius’ writings were misunderstood by the East, or that they were personal musings, and were never meant to be an official pronouncement.
The following shows that every Roman Catholic Pope from the 8th to 11th centuries had to denounce Pope Honorius as a heretic before they could ascend the throne of St. Peter. Since no pope would be officially denounced as a heretic unless he had made an official declaration on the faith, it would be impossible for these popes to denounce Honorius and still believe that the Roman Catholic Church had always taught that their bishops were infallible.
According to the Catholic Encyclopedia the Liber Diurnus Romanorum Pontificum is:
A miscellaneous collection of ecclesiastical formularies used in the papal chancery until the eleventh century. It contains models of the important official documents usually prepared by the chancery; particularly of letters and official documents in connexion with the death, the election, and the consecration of the pope; the installation of newly elected bishops, especially of the suburbicarian bishops; also models for the profession of faith, the conferring of the pallium on archbishops, for the granting of privileges and dispensations, the founding of monasteries, the confirmation of acts by which the Church acquired property, the establishment of private chapels, and in general for all the many decrees called for by the extensive papal administration.
The Catholic Encyclopedia says this about Formula 84 of the Liber Diurnus:
Lucas Holstenius was the first who undertook to edit the Liber Diurnus. He had found one manuscript of it in the monastery of Santa Croce in Gerusalemme at Rome, and obtained another from the Jesuit Collège de Clermont at Paris; but as Holstenius died in the meantime and his notes could not be found, this edition printed at Rome in 1650 was withheld from publication, by advice of the ecclesiastical censors, and the copies put away in a room at the Vatican. The reason for so doing was apparently formula lxxxiv, which contained the profession of faith of the newly elected pope, in which the latter recognized the Sixth General Council and its anathemas against Pope Honorius for his (alleged) Monothelism.
The relevant paragraph of Formula 84, as translated by a friend of mine, says the following:
The authors were in actuality defending the new heretical doctrines of Sergius, Phyrrhus, Paulus, and Petrus of Constantinople, and were in agreement with Honorius, who expanded his perverse fix for the problem.
In listing Pope Honorius with other heretics that newly elected Popes had to denounce upon their elevation to the throne of St. Peter, the Liber Diurnus shows that the Roman Catholic Church, at least until the 11th century, did not see its Popes as infallible.