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Medieval Sourcebook
Michael Kerularios: Letter to Patriarch Peter of Antioch (concerning Schism of 1054)   
Sometime in June or July 1054.

Michael Keroularios, the most holy archbishop of Constantinople, New Rome, and ecumenical patriarch, to Peter, most holy patriarch of God's City, Antioch.  Sometime in June or July 1054.  The Greek text is in J.P. Migne, ed., Patrologia graeca vol. 120, columns 781-796.

In the footnotes, I have attempted to provide both a recent secondary reference which could be used to find additional bibliography for the scholars and research-paper-writing students; and an open-source reference such as Wikipedia for those who are only a little curious.  Please keep in mind that open-source references must be read critically.  For example, while many articles on Wikipedia are irreproachable, some are out-of-date, tendentious, or inaccurate. [Tia M. Kolbaba]


9.  Now a rumor has reached our ears that the pope is commemorated in the diptychs not only by Your Perfection1, but also by the bishops of Alexandria and Jerusalem.2  I would not think that such ignorance could exist--especially, above all others, in Your Incomparable Virtue.  For you know that from the sixth holy and ecumenical council to the present the commemoration of the pope has been excised from the sacred diptychs of our holy churches.3  [This is] because the pope of that time, Vigilius4, did not want to come to that council, nor to anathematize what Theodoret wrote against the orthodox faith and against the twelve chapters of St. Cyril, or the letter of Ibas.5  And from then until now the pope has been cut off from our holy and catholic church.  For this reason, the rumor that patriarchs are commemorating the pope is wholly incredible to us--not so much concerning the patriarchs of Jerusalem and Alexandria as concerning Your Wide Wisdom and Singular Prudence.

10.  Moreover, [we have also heard] that the two aforementioned bishops not only accept people who partake of the unleavened bread [in the Eucharist], but also themselves celebrate the divine mystery with unleavened bread.6  Since we have no-one at hand whom we might question about them in this matter, and since we cannot otherwise trust other people with it, we are entrusting the whole of the investigation to Your Holiness, so that when you have examined the matter thoroughly you may let Our Mediocrity know. . . .

11.  Skleros, the most illustrious Proedros and Dux of Antioch has given us a copy of your letter to the [bishop] of Grado, also known as Aquileia.  When we read this, we found that it treated, for the most part, only of unleavened bread, omitting the other Roman errors, which are much more serious.  If, perhaps, Our Mediocrity has written in this way to Your Holiness what we wrote to [Skleros] concerning these things, still we have never explained any of these to the Pope himself or to any of his bishops, except for the letter of which we are now sending you a copy.  For it seems from their letters and deeds that they are wholly lovers of falsehood and meddlers. But you know very well that the Romans are not spitted on only one pike--the one regarding unleavened bread, which is clearly known to all--but on many and various ones.  On account of the following it is necessary to avoid them.7

12.  Their Judaizing8 practices are as follows:  the aforementioned accusation regarding azymes; eating the meat of beasts that have been strangled;9 shaving;10 observing the Sabbath;11 eating unclean meats;12 monks eating pork fat and all the skin right down to the meat;13 behaving in the same manner in the first week of Lent, Cheese-fare Week, as in the week before;14 eating meat on Wednesday and cheese and eggs on Friday, but fasting all day on the Sabbath.15
Beyond these [Judaizing practices] such things as the following are also true:  reasoning badly and dangerously, they have made some sort of addition to the holy creed, so that it is as follows:  "...and in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father and the Son."16  And in the divine service they intone, "One holy, one Lord, Jesus Christ, in the glory of God the Father, with the Holy Spirit."17

13.  They forbid the marriage of priests.  That is, those who have wives cannot take up the dignity of the priesthood, but those who wish to be priests must be unyoked.18  Two brothers [are allowed to] marry two sisters.19  During the liturgy, at the time for taking communion, one of the celebrants eats the unleavened bread and then he kisses the others.20  Their bishops wear rings on their hands, as if, indeed, they took their churches as brides, and they say that they wear [the ring] as a pledge.21  Bishops, going forth to battle, stain their hands with blood, killing and being killed.22  As many have reported to us, they perform holy baptism by baptizing the candidates with only one immersion, invoking the name of the Father and of the Son and of the Holy Spirit. Also, they fill the mouths of the baptized with salt. 23 Wrongly receiving the apostolic saying which reads, "A little leaven leavens the whole loaf," they have written it down thus:  "A little leaven corrupts the whole loaf."  Thus they try, through this little occasion of a word, to set aside the yeast which raises the leavened bread.24

14.  They do not adore the relics of the saints.25  Some of them do not venerate icons, either.26 They accept neither our fathers, teachers, and high priests--I mean Gregory the Theologian, Basil the Great, and the Divine Chrysostom, along with other saints whom they enumerate--nor any of their teaching.27  They do also other things which it would be a great work to enumerate one by one.  Therefore, if they live in such a way and, enfeebled by such customs, dare these things which are obviously lawless, forbidden, and abominable, then will any right-thinking person consider that they are at all to be included in the category of the orthodox?  I think not.  But let those who declare that they think rightly while acting in this way take their part, but let us never envy them their concord and consent.  Let us not be so insane.  Let us not utterly take leave of our senses.

15.  We have related these things briefly so that Your Perfection, being able to know the practices of these men, might not think that they err only in the matter of the unleavened bread, just as we ourselves have thus far understood.  And so that, recognizing also their extraordinary inferiority, you might reckon them with those whom they deserve.  But more grave and more insupportable than all of these, that which also displays most clearly their dementia, is the following: they say that they will not travel here so that they might be taught or hold discussions, but rather for teaching and persuading us to hold their dogmas.  These things they say also with overweening arrogance and impudence.


1 In Byzantine letters, the letter writer often uses elaborate honorific names for his addressee, such as "Your Perfection", "Your Incomparable Virtue."  Compare the English use of "Your Majesty," "Your Highness," or "Your Honor."

2 The Orthodox Churches of Byzantium kept lists of the leaders of other churches whom they prayed for in regular worship services.  These lists, often referred to as "the diptychs," included only those churches and their leaders who were considered orthodox.  Therefore, to "commemorate a bishop in the diptychs" was to say that you considered him orthodox.  In other words, Keroularios is arguing here that the bishop of Rome, the Pope, is not orthodox and should not be commemorated in the prayers of orthodox churches.  See

3 The Sixth Ecumenical Council, also known as the Third Council of Constantinople, was held in Constantinople in 680-681 CE.

4 Actually, Vigilius (537-555) was pope during the Fifth Ecumenical Council, which took place in 553.  The pope at the time of the Sixth Ecumenical Council was Agatho (678-681).  Keroularios is talking here about the events and condemnations at the Fifth Ecumenical Council.  See Richard Price, trans. and comm., The Acts of the Council of Constantinople of 553, with Related Texts on the Three Chapters Controversy (Liverpool:  Liverpool University Press, 2009).

5 Again, these are events of the Fifth Ecumencial Council, rather than of the Sixth.  The condemnations referred to are those known as the "Three Chapters"; see Price, Acts of the Councils of … 553; also Celia Chazelle and Catherine Cubitt (eds), The Crisis of the Oikoumene. The Three Chapters and the Failed Quest for Unity in the Sixth-Century Mediterranean (Turnhout 2007).  (There is also a Wikipedia article on the Three Chapters, but as of 2019 it is biased and out-of-date.)

6 One of the differences between the ritual of the Eastern Orthodox Churches and the Roman Catholic churches is the kind of bread used in the Eucharist (also called the Mass, the Divine Liturgy, and the Lord's Supper).  The Orthodox Churches use leavened bread; the Roman Catholic churches use unleavened bread (wafers). Tia Kolbaba, The Byzantine Lists.  Errors of the Latins (Urbana:  University of Illinois Press, 2000), 37-39.  A pretty balanced and mostly accurate account online:

7 What follows is one of the earliest lists of Latin errors—a kind of text that becomes more common as time goes on.  Kolbaba, Byzantine Lists, for explanations of each of accusations and analysis of their sources, meanings, and implications.

8 The history of the term "Judaizing" among Christians to condemn other Christians whom they suspect of heresy is long and complicated.  For this context, it is primarily necessary to know that most practices identified by medieval Christian authors as "Judaizing" have little or nothing to do with real Jewish practices and much more to do with Christian fears and projections. 

9 Eating meat that has not been bled properly is forbidden in the New Testament (Acts 15:19-20, 28-29), and by various church laws thereafter.  Kolbaba, Byzantine Lists, 35-37.

10 As a general rule, Greek men wore long beards, and Latin men shaved.  Greek priests were almost invariably bearded, while many Latin priests were cleanshaven.  See Giles Constable, “Introduction. Beards in History,” in Apologiae Duae.  Gozechini Epistola ad Walcherum.  Burchardi, ut videtur, Abbatis Bellevallis Apologia de Barbis, ed. R.B.C. Huygens (Corpus Christianorum, Continuatio Medievalis 62; Turnholti, 1985), pp. 46-130.  Kolbaba, Byzantine Lists, 56-57.  A bit over-the-top and inaccurate in some historical details, this article is nevertheless a fun open-source account of the facial-hair differences of opinion:

11 It is not clear what Keroularios means by this, but see his complaints about Sabbath fasting below, including note 15.

12 According to the New Testament and most church law, no meat was unclean for Christians, but see Kolbaba, Byzantine Lists, 35-37, 145-162 for Byzantine complaints about what Latin Christians eat.

13 Monks of the eastern churches generally observed an entirely vegetarian diet, while some monks in the Latin West were allowed limited amounts of meat, including lard.  All of this varied greatly from monastery to monastery, so wholesale comparisons are generally wrong.  See Kolbaba, Byzantine Lists, 46-47.

14 The differences between the length of Lent in the Latin and Greek churches are complicated and have a complicated history.  For a general discussion, see Kolbaba, Byzantine Lists, 41-43.

15 Saturday was generally observed as a feast day in the orthodox eastern churches and as a fast day in the Latin churches.  See Kolbaba, Byzantine Lists, 34-35; The Dictionary of the Middle Ages (New York:  Charles Scribner's Sons, 1989), vol. 5, 18-19, "Fasting, Christian"; The Oxford Dictionary of the Christian Church, 2nd ed. (New York:  Oxford University Press, 1974), vol. 3, 1237-1238, "Saturday"; The Oxford Dictionary of Byzantium (New York:  Oxford University Press, 1991), vol. 2, 779-780, "Fasting" and vol. 3, 1977, "Sunday."

16 For the controversy about the addition to the creed, see A. Edward Siecienski, The Filioque.  History of a Doctrinal Controversy (Oxford: Oxford University Press, 2010).

17 See Kolbaba, Byzantine Lists, 65.

18 In the Byzantine Orthodox Church, a man could be married before he was ordained to the priesthood.  In the western churches, there seems always to have been a strong preference that ordained clergy be unmarried and celibate, although clerical celibacy was not universally observed.  In the eleventh century, at the very time this text was written, the reformers of the Latin Church were leading a push to remove all married priests from the priesthood and enforce celibacy for the clergy.  Kolbaba, Byzantine Lists, 39-40.

19 In the Byzantine Orthodox Church, the marriage of two brothers to two sisters was considered incestuous.  On differences in the marriage laws between the Roman and Constantinopolitan Churches, see Kolbaba, Byzantine Lists, 44-46.

20 This is perhaps a complaint about the frequency with which no one attending a Latin Mass took communion except the priest, in part because there could be many Masses each day in a Latin Church, and the Greek Church did not allow multiple Eucharists in a day.  See Kolbaba, Byzantine Lists, 54-56.

21 Eastern bishops did not wear rings, while rings were part of the regalia of Latin bishops, and were interpreted precisely as Keroularios reports.  See Kolbaba, Byzantine Lists, 53; Oxford Dictionary of Byzantium vol. 1, 185-186, "Arrha Sponsalia."

22 This is another complicated topic.  In general, Byzantines were more adamant than Latins about clerics taking no part in war, but there were exceptions.  See Kolbaba, Byzantine Lists, 48-51.

23 The Byzantine Orthodox Church insisted that baptism include three full immersions.  By the 11th century, Latin practice was quite different from Greek practice, and sometimes included only one immersion, or even no full immersion.  Kolbaba, Byzantine Lists, 43-44.

24 This is a return to the question of unleavened bread in the Eucharist—see note 6 above.

25 This is not true in the case of the Latins, but is an accusation frequently launched against heretics of all kinds.  Kolbaba, Byzantine Lists, 51.

26 Also not true, although it is true that icons play a smaller role in Latin devotion than they do in Greek.  Kolbaba, Byzantine Lists, 51-52.

27 The three bishops mentioned here are Gregory of Nazianzus (329-390 CE), Basil of Caesarea (330-379), and John Chrysostom (c. 349-407) are revered in the Greek Orthodox Church as "the Three Holy Hierarchs." All three are also recognized as saints and Fathers of the Church in the Latin Church, but it is true that their icons, their cults, and their theological works are more influential and more revered in the East.  Kolbaba, Byzantine Lists, 64.

Translation and notes © Tia M. Kolbaba, April 2019