"This one fact, that a Great Council, universally received afterwards without hesitation throughout the Church, and presided over by papal legates, pronounced the dogmatic decision of a Pope heretical, and anathematized him by name as a heretic is a proof, clear as the sun at noonday, that the notion of any peculiar enlightenment or inerrancy of the popes was then utterly unknown to the whole Church" [including the West as represented by the papal legates] (J. von Dollinger, The Pope and the Council (Boston: Roberts, 1870), p. 61). [Roman Catholic historian]
From C. J. Hefele, A History of the Councils of the Church (Edinburgh: Clark, 1896), Volume V, pp. 181-187:
"It is in the highest degree startling, even scarcely credible, that an Ecumenical Council should punish with anathema a Pope as a heretic! That, however, the sixth Ecumenical Synod actually condemned Honorius on account of heresy, is clear beyond all doubt, when we consider the following collection of the sentences of the Synod against him:
At the entrance of the thirteenth session, on March 28, 681, the Synod says:
"After reading the doctrinal letter of Sergius of Constantinople to Cyrus of Phasis (afterwards of Alexandria) and to Pope Honorius, and also the letter of the latter to Sergius, we found that these documents were quite foreign to the apostolic doctrines, and to the declarations of the holy Councils and all the Fathers of note, and follow the false doctrines of heretics. Therefore we reject them completely, and abhor them as hurtful to the soul. But also the names of these men must be thrust out of the Church, namely, that of Sergius, the first who wrote on this impious doctrine. Further, that of Cyrus of Alexandria, of Pyrrhus, Paul, and Peter of Constantinople, and of Theodore of Pharan, all of whom also Pope Agatho rejected in his letter to the Emperor. We punish them all with anathema. But along with them, it is our universal decision that there shall also be shut out from the Church and anathematized the former Pope Honorius of Old Rome, because we found in his letter to Sergius, that in everything he followed his view and confirmed his impious doctrine." Towards the end of the same session the second letter of Pope Honorius to Sergius was presented for examination, and it was ordered that all the documents brought by George, the keeper of the archives in Constantinople, and among them the two letters of Honorius, should immediately be burnt, as hurtful to the soul.
Again, the sixth Ecumenical Council referred to Honorius in the sixteenth session, on August 9, 681, at the acclamations and exclamations with which the transactions of this day were closed. The bishops exclaimed: "Anathema to the heretic Sergius, to the heretic Cyrus, to the heretic Honorius, to the heretic Pyrrhus"
Still more important is that which took place at the eighteenth and last session, on September 16, 681. In the decree of the faith which was now published, and forms the principal document of the Synod, we read: "The creeds (of the earlier Ecumenical Synods) would have sufficed for knowledge and confirmation of the orthodox faith. Because, however, the originator of all evil still always finds a helping serpent, by which he may diffuse his poison, and therewith finds fit tools for his will, we mean Theodore of Pharan, Sergius, Pyrrhus, Paul, Peter, former bishops of Constantinople, also Honorius, Pope of Old Rome, Cyrus of Alexandria, etc., so he failed not, by them, to cause trouble in the Church by the scattering of the heretical doctrine of one will and one energy of the two natures of the one Christ." After the papal legates, all the bishops, and the Emperor had received and subscribed this decree of the faith, the Synod published the usual (logos prosphoneticos), which, addressed to the Emperor, says, among other things: "Therefore we punish with exclusion and anathema, Theodore of Pharan, Sergius, Paul, Pyrrhus, and Peter; also Cyrus, and with them Honorius, formerly bishop of Rome, as he followed them." In the same session the Synod also put forth a letter to Pope Agatho, and says therein: \'91We have destroyed the effort of the heretics, and slain them with anathema, in accordance with the sentence spoken before in your holy letter, namely, Theodore of Pharan, Sergius, Honorius.
In closest connection with the Acts of the sixth Ecumenical Council stands the imperial decree confirming their resolutions. The Emperor writes: "With this sickness (as it came out from Apollinaris, Eutyches, Themistius, etc.) did those unholy priests afterwards again infect the Church, who before our times falsely governed several churches. These are Theodore of Pharan, Sergius the former bishop of this chief city; also Honorius, the Pope of old Rome the strengthener (confirmer) of the heresy who contradicted himself. We anathematise all heresy from Simon (Magus) to this present ...we anathematise and reject the originators and patrons of the false and new doctrines, namely, Theodore of Pharan, Sergius...also Honorius, who was Pope of Old Rome, who in everything agreed with them, went with them, and strengthened the heresy."
It is clear that Pope Leo II also anathematized Honorius in a letter to the Emperor, confirming the decrees of the sixth Ecumenical Council, in his letter to the Spanish bishops, and in his letter to the Spanish King Ervig.
Of the fact that Pope Honorius had been anathematized by the sixth Ecumenical Synod, mention is made by the Trullan Synod, which was held only twelve years after.
Like testimony is also given repeatedly by the seventh Ecumenical Synod; especially does it declare, in its principal document, the decree of the faith: "We declare at once two wills and energies according to the natures in Christ, just as the sixth Synod in Constantinople taught, condemning ...Sergius, Honorius, Cyrus, etc." The like is asserted by the Synod or its members in several other places.
To the same effect the eighth Ecumenical Synod expresses itself. In the Liber Diurnus the Formulary of the Roman Chancery (from the fifth to the eleventh century), there is found the old formula for the papal oath according to which every new Pope, on entering upon his office, had to swear that "he recognised the sixth Ecumenical Council, which smote with eternal anathema the originators of the heresy (Monotheletism), Sergius, Pyrrhus, etc., together with Honorius" (C. J. Hefele, A History of the Councils of the Church (Edinburgh: Clark, 1896), Volume V, pp. 181-187).
"The following points are established by the best documentary evidence:
1. Honorius taught and favored in several official letters (to Sergius, Cyrus, and Sophronius), therefore ex cathedra, the one-will heresy. He fully agreed with Sergius, the Monotheletic patriarch of Constantinople. In answer to his first letter (634), he says: “Therefore we confess one will (qevlhma, voluntas) of our Lord Jesus Christ.”623 He viewed the will as an attribute of person, not of nature, and reasoned: One will, therefore only one will. In a second letter to Sergius, he rejects both the orthodox phrase: “two energies,” and the heterodox phrase: “one energy” (ejnevrgeia, operatio), and affirms that the Bible clearly teaches two natures, but that it is quite vain to ascribe to the Mediator between God and man one or two energies; for Christ by virtue of his one theandric will showed many modes of operation and activity.624 The first letter was decidedly heretical, the second was certainly not orthodox, and both occasioned and favored the imperial Ekthesis (638) and Type (648), in their vain attempt to reconcile the Monophysites by suppressing the Dyotheletic doctrine.625
...Various attempts have been made by controversialists to save the orthodoxy of Honorius in order to save the dogma of papal infallibility. Some pronounce his letters to be a later Greek forgery.626 Others admit their genuineness, but distort them into an orthodox sense by a nonnatural exegesis.627 Still others maintain, at the expense of his knowledge and logic, that Honorius was orthodox at heart, but heretical, or at least very unguarded in his expressions.628 But we have no means to judge of his real sentiment except his own language, which is unmistakably Monotheletic. And this is the verdict not only of Protestants,629 but also of Gallican and other liberal Catholic historians.630
2. Honorius was condemned by the sixth oecumenical Council as “the former pope of Old Rome,” who with the help of the old serpent had scattered deadly error.631 This anathema was repeated by the seventh oecumenical Council, 787, and by the eighth, 869.
...Here again ultramontane historians have resorted to the impossible denial either of the genuineness of the act of condemnation in the sixth oecumenical Council,632 or of the true meaning of that act.633 The only consistent way for papal infallibilists is to deny the infallibility of the oecumenical Council as regards the dogmatic fact.634 In this case it would involve at the same time a charge of gross injustice to Honorius.
3. But this last theory is refuted by the popes themselves, who condemned Honorius as a heretic, and thus bore testimony for papal fallibility. His first success or, Severinus, had a brief pontificate of only three months. His second successor, John IV., apologized for him by putting a forced construction on his language. Agatho prudently ignored him.635 But his successor, Leo II., who translated the acts of the sixth Council from Greek into Latin, saw that he could not save the honor of Honorius without contradicting the verdict of the council in which the papal delegates had taken part; and therefore he expressly condemned him in the strongest language, both in a letter to the Greek emperor and in a letter to the bishops of Spain, as a traitor to the Roman church for trying to subvert her immaculate fate. Not only so, but the condemnation of the unfortunate Honorius was inserted in the confession of faith which every newly-elected pope had to sign down to the eleventh century, and which is embodied in the Liber Diurnus, i.e. the official book of formulas of the Roman church for the use of the papal curia.636 In the editions of the Roman Breviary down to the sixteenth century his name appears, yet without title and without explanation, along with the rest who had been condemned by the sixth Council. But the precise facts were gradually forgotten, and the mediaeval chroniclers and lists of popes ignore them. After the middle of the sixteenth century the case of Honorius again attracted attention, and was urged as an irrefutable argument against the ultramontane theory. At first the letter of Leo II. was boldly, rejected as a forgery as well as those of Honorius;637 but this was made impossible when the Liber Diurnus came to light.
The verdict of history, after the most thorough investigation from all sides and by all parties remains unshaken. The whole church, East and West, as represented by the official acts of oecumenical Councils and Popes, for several hundred years believed that a Roman bishop may err ex cathedra in a question of faith, and that one of them at least had so erred in fact. The Vatican Council of 1870 decreed papal infallibility in the face of this fact, thus overruling history by dogmatic authority. The Protestant historian can in conscience only follow the opposite principle: If dogma contradicts facts, all the worse for the dogma" Schaff, History of the Christian Church, Vol IV: Mediaeval Christianity AD. 590-1073, § 113 "The Heresy of Honorius."