In polemical debates over whether the first-millenium Church ever had a consensus view of Papal Infallibility, usually the letter of Saint Pope Agatho as read out during the Council of Constantinople III is cited as proof that the Church, East and West, accepted the doctrine. There are over-arching reasons that inveigh against this including the vagueness in the letter, the explicit wording of the letter being about comprehensive Roman inerrancy (something no one literally believes) and not the Vatican I doctrine, the wide use of honorifics imputed inerrancy to other authorities during the seventh century, and the reality that the Sixth Ecumenical Council did not endorse the entirety of its contents on every point* but rather its Christological teaching. I cover much of this in my book, The Rise and Fall of the Papacy. In addition to the preceding, there is a tantalizing possibility that the most explicit assertion in the letter which can be misconstrued as teaching Papal Infallibility was not originally read out during the council at all.

*This does not prove that the council would have been against what was said by Agatho. Usually a council explicitly rejects something they hear which is contrary to their views. However, it may mean what was said was not considered of primary importance and so was passed over as secondary and not reflected upon in a careful way.

A brief review of the difference between a Latin and Greek witness. As follows from Mansi 11:239-241 is the critical passage on the supposed question of Papal Infallibility in both Latin and Greek:

Quia ejus vera confessio, a Patre de coelis est revelata, pro qua a Domino omnium beatus esse pronunciatus est Petrus: qui et spirituales oves ecclesiae ab Ιpso Redemptore omnium, terna commendatione pascendas suscepit: cujus annitente praesidio, haec apostolica ejus ecclesia nunquam a via veritatis in qualibet erroris parte deflexa est, cujus auctoritatem, upote apostolorum omnium principis, semper omnis catholica Christi ecclesia, et universales synodi fideliter amplectentes, in cunctis secutae sunt, omnesque venerabiles patres apostolicam ejus doctrinam amplexi, per quam et probatissima ecclesiae Christi luminaria claruerunt. (Mansi 11:239D-E)Ὅτι ἡ αὐτοῦ ἀληθὴς ὁμολογία, ἀπὸ τοῦ πατρὸς ἐκ τῶν οὐρανῶν ἀπεκαλύφθη. ἧς ἔνεκεν ἀπὸ τοῦ Κυρίου τῶν ὅλων μακάριος εἶναι ἀπεφάνθη ὁ Πέτρος. ὃς καὶ τοῦ ποιμαίνειν τὰ πνευματικὰ πρόβατα τῆς ἐκκλησίας ἀπ’ Αὐτοῦ τοῦ Λυτρωτοῦ τῶν πάντων τῇ τρίτῃ παραθέσει ἐδέξατο. οὗ τινος ἐπινεύσαντος τῇ βοηθείᾳ, αὕτη ἡ ἀποστολικὴ αὐτοῦ ἐκκλησία, καὶ αἱ καθολικαὶ σύνοδοι πιστῶς περιπτυσσόμεναι, ἐν πᾶσιν ἠκολοῦθησαν, καὶ πάντες οἱ σεβάσμιοι πατέρες τὴν ἀποστολικὴν αὐτοῦ ἐπεσπάσαντο διδασκαλίαν, δι’ ἧς καὶ δεδοκιμασμένοι τῆς ἐκκλησίας τοῦ Χριστοῦ φωστῆρες ἔλαμψαν. (Mansi 11:240E-241A)
For his true confession was revealed from the Father in the heavens. On account of which, Peter was said by the Lord of the universe to be blessed; who received from the Redeemer of all things by a triple commendation [an order] to feed the spiritual sheep of the Church; with the assistance of Whom, this apostolic church of His has never fallen from the way of the truth into any part of error, whose authority, as that of the prince of all the Apostles, ever the whole Catholic Church and the universal synods faithfully embracing, have followed in all things, and all the reverend fathers have taken up his apostolic teaching, through which the most proved luminaries of Christ’s Church have shone forth. For his true confession was revealed from the Father in the heavens. On account of which, Peter was said by the Lord of the universe to be blessed; who received from the Redeemer of all things by a triple commendation [an order] to feed the spiritual sheep of the Church; with the assistance of Whom, this apostolic church of His and the universal synods faithfully embracing, have followed in all things, and all the reverend fathers have taken up his apostolic teaching, through which the most proved luminaries of Christ’s Church have shone forth. 

Both textual traditions preserve honorifics about Rome and are making the same overall point. The Latin, however, has a most grandiose honorific. It asserts that the Roman church “has never fallen from the way of the truth into any part of error,” a claim greatly at variance with the council’s anathema against Pope Honorius. Its absence in the Greek is thereby, at first glance, unsurprising even if it was originally found in the Latin (which is probable). In any event, if the Greek witness is against this, it demonstrates that the mind of the council’s fathers were against the idea of Rome being free from error on doctrinal questions.

Very shortly later, both the Latin and Greek speak of how:

this spiritual mother of your most tranquil empire, the Apostolic Church of Christ…has never erred from the path of the apostolic tradition, nor has she been depraved by yielding to heretical innovations, but from the beginning she has received the Christian faith from her founders, the princes of the Apostles of Christ, and remains undefiled unto the end, according to the divine promise of the Lord…therefore consider, since it is the Lord and Saviour of all, whose faith it is, that promised that Peter’s faith should not fail and exhorted him to strengthen his brethren, how it is known to all that the Apostolic pontiffs, the predecessors of my littleness, have always confidently done this very thing. (NPNF 14:331-332)

The preceding states that the “spiritual mother” has never erred, and that the identity of this mother is vaguely conflated with “Apostolic pontiffs.” However, one should recognize two things. First, Agatho does not say the Apostolic pontiffs “never erred,” but rather they never failed to “exhort” the Church. Second, consider how Agatho later invokes who the “spiritual mother” is:

Therefore the Holy Church of God, the mother of your most Christian power, should be delivered and liberated with all your might (through the help of God) from the errors of such teachers, and the evangelical and apostolic uprightness of the orthodox faith, which has been established upon the firm rock of this Church of blessed Peter, the Prince of the Apostles, which by his grace and guardianship remains free from all error, [that faith I say] the whole number of rulers and priests, of the clergy and of the people, unanimously should confess and preach with us as the true declaration of the Apostolic tradition, in order to please God and to save their own souls. (NPNF 14:337)

The spiritual mother (here, clearly the whole Church) is to be delivered from error and it is the Christian faith that remains free from it. In other words, there is a general sense in which the faith of the Church is preserved from error, and there is the reality that the Church itself struggles against errors within its own midst. This demonstrates that Agatho was not appropriating to Rome specifically a peculiar insulation from error in the second passage at the very least. However, as the Latin rendering in the first passage makes clear, he appears happy enough to at least float the idea (for reasons I believe were fitting of the genre of panegyric and the self-congratulatory tone of his letter). 

What do the varying manuscript traditions teach us? I will leave it to future research to unearth if there are profound enough internal issues with the Latin or fragmentary evidence within the earliest manuscripts contrary to later manuscripts to justify the idea that the embolden passage in the previous section is inauthentic. From the latest research on the question by Riedinger (1992), all four early Latin witnesses that include Agatho’s letter include the passage. (Concilium Universale Constantinopolitanum Tertium (680–681), Vol. 2, 63) These manuscripts are extant from approximately the early ninth century to approximately 895, (Riedinger, 1998, Kleine Schriften zu den Konzilsakten des 7. Jahrhunderts, 81) thereby placing the beginning of the tradition before the Pseudo-Isidorian Decretals or the work of Anastasius the Librarian. 

This does not make the manuscripts altogether trustworthy as Rome was no stranger to ecclesiastical forgeries for centuries, even citing a forged canon of Nicea during the 16th session of Chalcedon. Nevertheless, it would locate the sentiment of the passage within little more than a century of the sixth council’s time, reducing the probability that it would have been an outrageous statement to Roman ears during the last seventh century.

How about to Greek ears? This is where the waters get muddied. None of the Greek witnesses precede the schism. In fact, they are from considerably later. Two out of the three traditions exclude the passage. (Concilium Universale Constantinopolitanum Tertium, Vol. 2, 62) Most surprisingly, the best Greek manuscript (Parisinus Graecus 1115) is a pro-unionist manuscript which is believed to originate in eighth century Rome itself. It contains a florilegium in favor of the Filioque that was used by Bekkos of Constantinople and quotations in support of the Papalist doctrines. Though completed in 1276, Alexakis (2000) asserts it is a faithful copy of a Greek manuscript from Rome (“original manuscript”) that is dated approximately to 774/5. (“The Greek Patristic Testimonia Presented at the Council of Florence (1439) in Support of the Filioque Reconsidered,” 159) Riedinger calls it “one of the most well-known and valuable Greek manuscripts in our possession.” (Kleine Schriften…, 183) Alexakis (1996) only identifies a few of its latter folios which quote content surrounding Nicea II and later as coming from after 775. (Codex Parisinus Graecus 1115 and Its Archetype, 254-255). In review, Parisinus Graecus 1115 does not contain a complete copy of Constantinople III, but excerpts which the copyist felt were pro-Papacy. This reveals the understanding of Constantinople III not only from a pro-Unionist but also the Papal chancery of Adrian I in the 770s. They were unaware of the disputed passage in Agatho’s letter when the entire paragraph was quoted in the Greek. It appears last updated by Anastasius the Librarian himself, (Ibid., 225; 255) who apparently had left unaltered the Greek in this section.

As for the other two other Greek manuscript traditions, both are from the 13th-15th centuries. (Ibid., 184) One Greek manuscript agrees with Parisinus Graecus 1115 and another (the “Turin [Torino] Codex” and its numerous copies which are all from 16th century Italy, see Ibid.) does not, interestingly following the Latin rendering (but in Greek, obviously). More research would have to be done on the Turin Codex to find out if the passage is an insertion, what the history was behind the codex’s creation (another pro-unionist?), etcetera. This information is not presently available to me and there are several codexes with the same name. (Examples: 1, 2) The fact it can be located to Italy specifically and it appears to be of a later date that Parisinus Graecus 1115, however, is suspect. A Grecophile Italian or Greek unionist could have at this late a point simply interpolated a passage into the Greek to make it align with the Latin.

Going strictly by the scholarship and not my own speculations, the most reliable Greek lacking the passage in what is otherwise a document sympathetic to the 13th century Papacy, would be enough to conclude the Greek never had the disputed passage. However, I am not personally convinced of Alexakis’ defense of the integrity of Parisinus Graecus 1115 in all points.

This does not mean I cannot be convinced, but it is a huge pill to swallow due to the speculatory nature of Alexakis’ thesis. Alexakis asserts that we have a manuscript from 1276 which largely matches a lost manuscript from 774. However, Parisinus Graecus 1115 lacks (interpolated) passages attributed to Saint Basil’s Against Eunomius that Alexakis speculates the original lost Roman manuscript had. In response to this, Alexakis invokes the florilegium from Nicholas of Kotrone from 1264 which allegedly contains passages from the lost Roman manuscript, thereby “proving” the original did not lack this passage. (“The Greek Patristic Testimonia,” 160) Of course, Alexakis’ conjecture is possible, but clearly this is conjecture. He far from proved the case concerning whether the eighth century source from Rome actually contained the passage attributed to Basil. After all, additions (during the ninth century at least) were made to the original Roman manuscript which allegedly made it to Nicholas of Kotrone centuries later. Perhaps even the addition of Pseudo-Basil at this juncture, though we do have a ninth century manuscript with the passage. (“The Greek Patristic Testimonia,” 158, fn 32) This being the case, what Parisinus Graecus 1115 has today is not unadulterated by any measure, though surely the motive to remove the disputed section of Agatho’s letter specificially is totally lacking.

The preceding being the case, this shows that it would be an exaggeration to assert that it is morally certain that Parisinus Graecus 1115’s accounting of the Greek of Constantinople III is faithful to an earlier witness perhaps going back to both Rome and potentially even the 8th century. Is it possible? Yes. Is it the best answer scholarship has yet given? Yes. Do we lack an independent Greek witness that both disputes this and does not come from somewhere questionable, like Torino, Italy? Yes. Did the Uniate scribe and the originators of the source he used in Rome itself, lack the motive to deliberately remove the passage, thereby making its absence highly credible? Yes. Is it our best Greek witness? Yes. Is it potentially earlier than all of the Latin witnesses? Dated to 774/5, perhaps. Is there more textual research to be done? Absolutely.

Conclusion. In short, while not decisive on the question, the best extant Greek manuscript evidence implies that the teaching that Rome “has never fallen from the way of the truth into any part of error” was not original to Constantinople III, even if the passage is authentically from the Synod of Rome (680) and rightly attributed to Saint Agatho itself. The preceding implies that while extolling his own Patriarchate, Agatho wrote with deliberately lofty language perhaps intentionally meant to deflect from the recent examples of Roman capitulation on the issue of Monotheletism including Honorius’ teaching of the doctrine and Popes Eugene and Vitalian entering into communion with the Monothelites. The council itself, out of necessity due to Macarius of Antioch’s citing Pope Honorius amongst others in support of Monotheletism, had decided that Honorius (and everyone else he cited) was to be anathematized. Perhaps in making this decision, a diplomatic edit was made to Agatho’s letter (which was read out afterwards) so as not to put himself in explicit contradiction with the council’s actions. This may explain the witness of the varying manuscript traditions on this question.

It is also possible that the original Latin copy was interpolated with the disputed passage in question, as the extant Greek in the 8th century lacked it. From my perspective, which is limited, we lack a suitable motive for this unlike the speculations in the preceding paragraph. Further, there are no signs of retroversion in Agatho’s letter, because Riedinger asserts it is entirely a restoration from the original Latin. (Kleine Schriften, p. 289) I think one can safely say that the passage is original to the Latin, being that the Papal chancery in 774 was not altering the Greek lacking the same passage. If there were interpolations in this era, the Greek would have been corrupted as well.

In the end sum, quoting that the Roman church “has never fallen from the way of the truth into any part of error” as proof of Papal Infallibility is highly questionable. Doing so, when textually the passage is so uncertain in any event, speaks to the unclear historical basis of the doctrine in the first eight centuries of the Church.

The idea behind this article was inspired by “Gabriel Ramses” who provided significant resources. Additional translation and research were also provided by Evangelos Nikitopoulos and John Collorafi.