The Filioque: How One Word Split the Church—and Whether It Still Has To

"And in the Holy Spirit, the Lord and life-giver, who proceeds from the Father, who with the Father and the Son is together worshipped and together glorified, who spoke through the prophets."

— The Niceno-Constantinopolitan Creed, as confessed by the First Council of Constantinople (381). The original Greek reads tò ek toû Patròs ekporeuómenon—"who proceeds from the Father." There is no "and the Son."

One Word, One Schism

There is no shorter fault line in the history of Christianity than the filioque. It is a single Latin word—filioque, “and from the Son”—tucked into one clause of the Nicene Creed. And yet that word has been blamed, for the better part of a millennium, for the deepest and most enduring division in the Christian world: the estrangement of the Latin West (Roman Catholicism) from the Greek East (Eastern Orthodoxy).

The dispute is genuinely about something. When Western Christians confess that the Holy Spirit “proceeds from the Father and the Son,” and Eastern Christians confess that he “proceeds from the Father,” they are making claims about the inner life of God himself—about the eternal relations among the Father, the Son, and the Holy Spirit. This is not church bureaucracy. It is the doctrine of the Trinity at its most refined and most vertiginous point.

But the filioque is also a case study in how theology, language, politics, and wounded pride can braid themselves together until a question that might have been resolved by careful translation becomes a casus belli. My own conviction—and I will lay out the evidence rather than just assert it—is that the two traditions have been closer all along than the polemics suggested, and that the most authoritative Catholic statement on the question, issued in 1995, concedes nearly everything the East was right to insist upon. Whether that makes the filioque a resolved question or merely a softened one is something each reader can weigh by the end.

Let us begin where the creed began.

What the Creed Actually Said in 381

In 325, the Council of Nicaea confronted the Arian denial that the Son is fully God and confessed the Son to be homoousios—“consubstantial”—with the Father.⁠³ But Nicaea said almost nothing about the Holy Spirit. It ended its creed abruptly: “And in the Holy Spirit.” Full stop.

It fell to the First Council of Constantinople in 381 to expand that bare clause into a confession of the Spirit’s full divinity, against a party (the Pneumatomachoi, “Spirit-fighters”) who denied it. The council produced the creed Christians of every tradition still recite—the Niceno-Constantinopolitan Creed—and its article on the Spirit reads, in the original Greek:

καὶ εἰς τὸ Πνεῦμα τὸ Ἅγιον, τὸ Κύριον καὶ Ζωοποιόν, τὸ ἐκ τοῦ Πατρὸς ἐκπορευόμενον, τὸ σὺν Πατρὶ καὶ Υἱῷ συμπροσκυνούμενον καὶ συνδοξαζόμενον…

And in the Holy Spirit, the Lord and life-giver, who proceeds from the Father, who with the Father and the Son is together worshipped and together glorified…⁠⁴

The phrase to watch is tò ek toû Patròs ekporeuómenon—“who proceeds from the Father.” There is no “and the Son.” The creed confesses the Spirit’s origin from the Father, and there it stops.

That silence was not an oversight; it tracks the language of Jesus himself. And it is freighted with a Greek technical term—ekporeuómenon, from ekporeúomai—that will turn out to carry most of the weight in the entire controversy. Hold that word in mind. We will return to it, because the whole question of whether the filioque is an error or a translation problem hinges on it.

The Biblical Evidence

The creed’s procession language comes from a single verse. On the night before he died, Jesus told his disciples:

When the Advocate comes whom I will send you from the Father, the Spirit of truth that proceeds from the Father, he will testify to me. (John 15:26)⁠⁵

The Greek verb behind “proceeds” is ekporeúetai—the same root the creed uses. This is the one place in Scripture where the Spirit’s “procession” is named directly, and it names the Father as the source. The East has always read the creed as simply quoting Jesus: the Spirit proceeds from the Father, full stop, because that is what the Lord said.

Honesty requires a caveat here that Catholic apologists sometimes skip. The Church’s own study Bible, the New American Bible (Revised Edition), notes on this verse that the Spirit “comes from both Jesus and the Father in mission, with no reference here to the eternal procession of the Spirit.”⁠⁶ In other words, John 15:26 is, on a careful reading, describing the Spirit’s mission—his being sent in time—rather than directly teaching his eternal origin within the Trinity. The verse is a starting point for both sides, not a proof-text that settles the matter.

What complicates the East’s clean reading is the rest of the New Testament. The same Gospel of John has Jesus say of the Spirit, “He will take from what is mine and declare it to you,” immediately adding, “Everything that the Father has is mine” (John 16:14–15). After the resurrection, Jesus “breathed on” the disciples and said, “Receive the holy Spirit” (John 20:22)—an act the Western tradition reads as the Son himself bestowing the Spirit. And Paul calls the Spirit “the spirit of his Son” (Galatians 4:6) and “the Spirit of Christ” (Romans 8:9).⁠⁷

So the biblical data pull in two directions at once. The Spirit “proceeds from the Father,” and yet the Spirit is also “of the Son,” sent by the Son, breathed by the Son. The entire history of the filioque is, in a sense, the history of how the Greek East and the Latin West each tried to hold both of those truths together—and reached for different language to do it.

The Greek Fathers: Through the Son

The Greek Fathers built their Trinitarian theology around what they called the monarchy of the Father—from mon-archē, “single source.” The Father is the one archē anarchos, the principle-without-principle; the sole pēgē, fountain, of both the Son (by generation) and the Spirit (by procession). This is the cornerstone of Eastern theology, and it is the lens through which the East reads any talk of the Spirit proceeding “from the Son”: such talk sounds, to Greek ears, like positing a second source in the Godhead, dividing the one fountain into two.

But the Greek Fathers were not content to leave the Son out of the Spirit’s eternal life entirely. They reached for a preposition: the Spirit proceeds from the Father through the Son—dia toû Huioû. Basil the Great wrote that the Spirit, “through the Son, who is one, he is joined to the Father, who is one, and by himself completes the Blessed Trinity.”⁠⁸ Cyril of Alexandria, the great fifth-century champion of orthodoxy, spoke freely of the Spirit as proceeding “from the Father and the Son” and as the Spirit who “flows from the Father in the Son.”⁠⁹

The most precise statement comes from John of Damascus, the eighth-century systematizer of Greek theology, who drew the line exactly where the East still draws it:

And we speak likewise of the Holy Spirit as from the Father, and call Him the Spirit of the Father. And we do not speak of the Spirit as from the Son: but yet we call Him the Spirit of the Son… And we confess that He is manifested and imparted to us through the Son.⁠¹⁰

There is the Eastern position in one breath: not “from the Son” as to origin or cause, but genuinely “of the Son,” “through the Son,” resting on the Son and given through him. The Son is not a second source; but neither is he irrelevant to the Spirit’s eternal procession. The Greek Fathers guarded the Father’s monarchy with one hand while affirming a real eternal relationship between the Son and the Spirit with the other.

Keep that distinction—origin versus manifestation, cause versus order—in view. It is the hinge on which reconciliation will eventually turn.

The Latin Fathers: From the Father and the Son

The Latin West developed along a parallel but distinct track, and its great architect was Augustine of Hippo. In his monumental work On the Trinity (De Trinitate), Augustine taught plainly that the Holy Spirit proceeds from the Father and the Son. But—and this is the part Eastern polemics usually omit—he built in exactly the safeguard the Greeks demanded.

Augustine first grounds everything in the Father. “The Father is the beginning (principium) of the whole divinity,” he writes; the Spirit, who proceeds from Father and Son, “is referred back to Him from whom the Son was born.”⁠¹¹ Then he qualifies the double procession with a crucial adverb:

God the Father alone is He from whom the Word is born, and from whom the Holy Spirit principally proceeds. And therefore I have added the word principally, because we find that the Holy Spirit proceeds from the Son also. But the Father gave Him this too… whatever He gave to the only-begotten Word, He gave by begetting Him.⁠¹²

This is the decisive Latin move. The Spirit proceeds from the Father principaliter—“principally,” as from the source—and only communiter, “in common,” from the Son, because the Father gave the Son the power to spirate the Spirit in the very act of begetting him.⁠¹³ The Son’s role in the Spirit’s procession is itself a gift from the Father. The Father remains the ultimate origin. Augustine, in other words, affirmed the filioque and the monarchy of the Father in the same paragraph.

Augustine was not alone. Hilary of Poitiers, Ambrose of Milan—“the first to formulate the filioque,” in one Vatican assessment—and Pope Leo the Great all confessed an eternal procession from the Father and the Son.⁠¹⁴ And by the late fifth or early sixth century, a Latin creed of southern Gaul known as the Athanasian Creed (the Quicumque vult, despite its name not by Athanasius) stated the doctrine without hedging: “The Holy Spirit is from the Father and the Son: not made, nor created, nor begotten, but proceeding.”⁠¹⁵

So the filioque was not a medieval novelty smuggled in by power-hungry popes, as it is sometimes portrayed. It was the settled teaching of the Latin Fathers centuries before it became a creedal controversy. The problem was never simply whether the West believed it. The problem was how it got into the creed—and what it sounded like in Greek.

Maximus the Confessor: The Bridge

Before we follow the word into the creed, we should pause on the single most important witness in the entire debate—a Greek saint who saw the collision coming and tried to defuse it four centuries early.

In the 640s, the Byzantines were alarmed to receive a synodal letter from Rome that spoke of the Spirit proceeding from the Son. To Greek ears, this sounded like the heresy of two sources. Maximus the Confessor—a monk of impeccable Eastern credentials, who would later have his tongue and right hand cut off for defending orthodoxy against imperial pressure—wrote a letter from Rome explaining what the Latins actually meant:

On this basis they showed that they themselves do not make the Son Cause (Aitia) of the Spirit. They know, indeed, that the Father is the sole Cause of the Son and of the Spirit, of one by generation and of the other by ekporeusis—but they explained that the latter comes (proienai) through the Son, and they showed in this way the unity and the immutability of the essence.⁠¹⁶

This is the bridge. Maximus tells his fellow Greeks: the Latins are not saying what you fear. They do not make the Son a cause (aitia) of the Spirit; they confess, as you do, that the Father is the sole cause. Their “from the Son” is a statement about the Spirit’s coming-forth through the Son in the one divine essence—not a claim that the Son is a second fountainhead. The Latin “procession” and the Greek “through the Son,” Maximus argues, point to the same reality.

I do not want to overstate the case, because the Letter to Marinus is itself contested ground. Catholics from Bessarion at the Council of Florence onward have read it as proof that the filioque is compatible with Greek theology. Many Orthodox read it the opposite way: Maximus proves that the Latins of his day did not mean a causal filioque—and therefore the later, hardened, medieval filioque is precisely not what Maximus was defending. The text is a genuine crux, and an honest treatment has to present it as one. But its mere existence is remarkable: a Greek Father, in the seventh century, telling the East that the Western formula need not divide the Church. He was, tragically, ignored.

How One Word Entered the Western Creed

The doctrine was old. The creedal addition was new, and it crept in through the back door of the Latin West—not by papal decree, but by regional liturgical drift.

The conventional story locates the first creedal use at the Third Council of Toledo in 589, when the Visigothic kingdom of Spain renounced Arianism and returned to Catholic orthodoxy. But here scholarship counsels caution. Whether the filioque actually stood in the creed as recited in 589, or was inserted into the council’s records by a later editor, is genuinely disputed; the phrase is securely attested in the Spanish creed only by the later seventh century.⁠¹⁷ The Vatican’s own 1995 study acknowledges that the Councils of Toledo between 589 and 693 perhaps “did not insert it in the Symbol of Nicaea-Constantinople,” and that the addition is securely documented in the West only from the end of the eighth century.⁠¹⁸

What is clear is that the interpolated creed spread through Spain into the Frankish lands, and that Charlemagne’s court promoted it aggressively. A synod at Aachen in 809 defended the filioque and pressed Rome to adopt it.⁠¹⁹ And here the popes did something that ought to embarrass anyone who imagines Rome as the eager innovator: Pope Leo III refused. He affirmed the doctrine of the filioque as true, but declined to insert the word into the creed, out of respect for the original text and concern for unity with the East. According to the tradition, he had the creed engraved—without the filioque—on two silver shields, in Greek and Latin, and set up at Saint Peter’s, precisely to preserve the unaltered text.⁠²⁰

Rome held that line for two centuries. It was not until 1014, when the emperor Henry II came to Rome for his imperial coronation and requested it, that Pope Benedict VIII finally allowed the creed to be sung at the papal Mass with the filioque.⁠²¹ Rome was the last holdout in the Latin West, not the instigator. By the time it yielded, the East had a real grievance: a word had been added to an ecumenical creed without an ecumenical council.

Ephesus and the “No New Creed” Problem

That grievance had a canonical edge, and it is the strongest card in the Eastern hand. At the Council of Ephesus in 431, the assembled bishops decreed:

It is unlawful for any man to bring forward, or to write, or to compose a different (hetéran) Faith as a rival to that established by the holy Fathers assembled with the Holy Ghost in Nicæa.⁠²²

For the Orthodox, this is decisive: the Council of Ephesus forbade any alteration of the creed, full stop. The West added a word. Therefore the West broke the canon. The theological question of whether the filioque is true is, on this reading, almost secondary; the West had no authority to touch the creed at all, and certainly not unilaterally.

The Catholic response distinguishes between composing a rival faith and clarifying the existing faith. Ephesus, the argument runs, condemned the production of a competing creed—its immediate target was a Nestorian baptismal formula—not the legitimate development of a phrase that makes the original faith more explicit against a new error. Whether that distinction holds is exactly what is in dispute, and a fair-minded observer has to concede that the East has the more natural reading of the bare words of the canon. The West’s better argument is not that Ephesus permits the addition, but that the content of the filioque was already the faith of the Fathers, and that the real fault was procedural and jurisdictional: not what was added, but who added it, and how.

Photius, 1054, and the Hardening

The filioque became a weapon in the ninth century, in the hands of one of the most brilliant men ever to occupy the see of Constantinople: the patriarch Photius. In his Mystagogy of the Holy Spirit, Photius mounted the first systematic Greek attack on the filioque as not merely an illicit addition but a theological error.⁠²³

The history here is tangled, and it is easy to get wrong—so much so that the two sides cannot even agree on how to number the councils. A council at Constantinople in 869–870 deposed Photius; the Catholic Church counts it as the Fourth Council of Constantinople and an ecumenical council. A different council, at Constantinople in 879–880, restored Photius, recited the creed without the filioque, and condemned additions to it; the Eastern Orthodox count that council as the genuine eighth ecumenical council. Same city, adjacent years, opposite verdicts, rival numbering. Anyone writing about this period has to keep the two councils rigorously distinct, because conflating them produces nonsense.⁠²⁴

And then there is 1054—the date everyone “knows” as the year of the Great Schism. The popular story is that the filioque split the Church in 1054. The popular story is wrong on both counts. The mutual excommunications of 1054, when Cardinal Humbert laid a bull of excommunication on the altar of Hagia Sophia and Patriarch Michael Cerularius excommunicated the legates in return, turned mostly on other matters: papal authority, jurisdiction over southern Italy, and whether the Eucharist should use leavened or unleavened bread. The filioque was a secondary charge. And in a detail that would be comic if it were not so consequential, Humbert’s bull accused the Greeks of having removed the filioque from the creed—apparently unaware that it had never been in the original text at all.⁠²⁵ Nor did 1054 feel, at the time, like a final rupture; it was experienced as one more quarrel in a long series. The schism hardened gradually over the following centuries, sealed less by Humbert’s bull than by the sack of Constantinople by Western crusaders in 1204.

The lesson is one I keep relearning about Church history: the dramatic dates are usually less decisive than the slow accumulation of estrangement behind them.

The Reunion Councils: Lyons and Florence

Twice the medieval Church tried to heal the breach, and twice it defined the filioque with precision—aiming, each time, to answer the Eastern fear of “two sources.”

At the Second Council of Lyons in 1274, the Church confessed that “the Holy Spirit proceeds eternally from the Father and the Son, not as from two principles but as from one single principle (tamquam ex uno principio).”⁠²⁶ That phrase—from one principle—is the whole Catholic answer to the monarchy concern: the Father and the Son spirate the Spirit not as two competing sources but as one. The union of Lyons collapsed almost immediately, repudiated by the Byzantine clergy and faithful who had not been consulted.

The more thorough attempt came at the Council of Florence in 1439, whose bull of union Laetentur Caeli remains the most developed Catholic definition. It declared:

The Holy Spirit is eternally from the Father and the Son and has His essence and His subsistent being both from the Father and the Son, and proceeds from both eternally as from one principle and one spiration… we declare that what the holy Doctors and Fathers say, namely, that the Holy Spirit proceeds from the Father through the Son, tends to this meaning, that by this it is signified that the Son also is the cause, according to the Greeks, and according to the Latins, the principle of the subsistence of the Holy Spirit, as is the Father also.⁠²⁷

Notice what Florence does: it explicitly identifies the Greek “through the Son” with the Latin “from the Son,” and declares them equivalent. This was the high-water mark of reunion—signed by the Greek delegation, including the emperor. And it, too, collapsed when the delegates returned home to a Constantinople that overwhelmingly rejected the union. Within fourteen years the city had fallen to the Ottomans, and the question of reunion became, for centuries, moot.

Aquinas and the Theological Heart

Between Lyons and Florence stands the theologian who gave the Latin position its most rigorous form. Thomas Aquinas, in the Summa Theologiae, defends the filioque not by piling up proof-texts but by an argument from the very structure of Trinitarian relations.⁠²⁸

The argument runs like this. The three divine persons are not distinguished by anything in the divine essence, which they share wholly and equally; they are distinguished only by their relations of origin, and relations distinguish only when they stand in opposition (as “father” and “son” do). Now the Son and the Spirit must be really distinct persons. But if the Spirit did not proceed from the Son, there would be no relation of opposition between them—and therefore, Aquinas argues, no way to tell them apart as persons. As he puts it: “the Holy Ghost is from the Son. For if He were not from Him, He could in no wise be personally distinguished from Him.”⁠²⁹

Crucially, Aquinas insists this does not exclude the Father’s primacy or even contradict the Eastern formula. “The Greeks themselves,” he notes, “recognize that the procession of the Holy Ghost has some order to the Son; for they grant that the Holy Ghost is the Spirit ‘of the Son,’ and that He is from the Father ‘through the Son.’” And he concedes the Eastern point directly: even if one says the Spirit “proceeds from the Father alone,” the Son “would not thereby be at all excluded; because as regards being the principle of the Holy Ghost, the Father and the Son are not opposed to each other.”⁠³⁰ The Father and Son are not two principles, Aquinas concludes, but one principle of the Spirit—the same conclusion Lyons and Florence would define.⁠³¹

The Two Words That Aren’t the Same

Here is the part most popular explanations of the filioque get wrong—or skip entirely—and it is the single most important thing to understand about the whole controversy. The Greek and Latin words for “procession” do not mean the same thing. The entire dispute is, to a degree that is almost embarrassing, a translation problem.

Recall the Greek verb in the creed: ekporeúesthai, the noun ekpóreusis. In the technical vocabulary the Cappadocian Fathers forged, this word means specifically origination from the ultimate source—procession from the Father alone as the principle-without-principle of the Trinity. By definition, in Greek, the Spirit cannot “ekporeúesthai from the Son,” because that would make the Son a second ultimate source. When an Orthodox Christian hears the filioque rendered into Greek as ek toû Patròs kaì toû Huioû ekporeuómenon, he hears a heresy—and he is right to reject it.

The Latin verb procedere is far broader. It means simply “to come forth,” and it covers any relationship of origin whatsoever—including the Son’s coming-forth from the Father and the Spirit’s coming-forth from both in the one divine essence. When a Latin says the Spirit procedit from the Father and the Son, he is not making a claim about ekpóreusis at all. He is making the broader claim that the Spirit receives the one divine nature from the Father and, through the Father’s gift, from the Son.

The mischief began with the Latin Bible. When the Latin scriptures—the Vulgate and the Old Latin versions before it—translated John 15:26’s ekporeúetai with the broad Latin procedit, and the creed’s ekporeuómenon with procedentem, they created what the Vatican would later call “a false equivalence… between the Oriental theology of the ekporeusis and the Latin theology of the processio.”⁠³² Two words that meant different things were treated as one. For a thousand years, East and West argued past each other—each defending a truth the other was not actually denying. The East was defending the Father’s unique status as sole cause; the West was affirming the Son’s role in the Spirit’s coming-forth in the shared essence. Both were right. They were answering different questions in the same words.

The 1995 Clarification: Rome’s Remarkable Concession

In 1995, after a homily in which Pope John Paul II called for clarifying the filioque “in order to highlight its full harmony with what the Ecumenical Council of Constantinople of 381 confesses,” the Pontifical Council for Promoting Christian Unity issued a study document with the unglamorous title The Greek and Latin Traditions Regarding the Procession of the Holy Spirit. It is, in my judgment, one of the most important ecumenical texts of the twentieth century, and it concedes—officially—almost everything the East was right to insist on.⁠³³

The document affirms, in language no Eastern theologian could improve upon, that “the Father alone is the principle without principle (archē anarchos)… the sole source (pēgē) of the Son and of the Holy Spirit,” and that “the Holy Spirit therefore takes his origin from the Father alone (ek monou tou Patros) in a principal, proper and immediate manner.” It distinguishes the two words precisely: “The Greek ekporeusis signifies only the relationship of origin to the Father alone as the principle without principle of the Trinity. The Latin processio… is a more common term, signifying the communication of the consubstantial divinity from the Father to the Son and from the Father, through and with the Son, to the Holy Spirit.”⁠³⁴

From this it draws the conclusion that the filioque, “in fact, situated in a theological and linguistic context different from that of the affirmation of the sole monarchy of the Father,” does not contradict the Father’s role as sole origin of the Spirit’s ekporeusis. And then it makes the gesture that matters most in practice: it affirms that Rome “has refused the addition of kai tou Huiou”—“and the Son”—“to the formula ek tou Patros ekporeuomenon of the Symbol of Nicaea-Constantinople in the Churches, even of Latin rite, which use it in Greek. The liturgical use of this original text remains always legitimate in the Catholic Church.”⁠³⁵

Read that carefully. The Catholic Church officially holds that the creed without the filioque—the creed of 381, exactly as the Orthodox confess it—is fully legitimate, and that the filioque should never be added to the Greek text, where it would be heretical. The filioque is a feature of the Latin creed, expressing a truth in a Latin idiom, and Rome has explicitly refused to impose it on the Greek confession. That is not a fudge. It is a recognition that both traditions, in their own languages, confess the same faith.

Where Things Stand Today

So is the filioque still church-dividing? Here the Orthodox themselves divide, and the division is instructive.

On one side stands what is sometimes called the rigorist position, associated above all with the twentieth-century theologian Vladimir Lossky and, in a sharper key, John Romanides. For them the filioque is not a misunderstanding to be cleared up but a genuine triadological error—the taproot of everything that went wrong in Western theology, a confusion of the persons that subordinates the Spirit and must be repudiated, not merely explained.⁠³⁶

On the other side stands a moderate position with deep roots in Orthodox scholarship. Its classic statement is the Theses on the Filioque published in 1898 by the Russian church historian Vasily Bolotov, who argued that “from the Father and the Son,” “from the Father through the Son,” and “from the Father alone” are all theologoumena—permissible theological opinions—rather than defined dogmas, and that the filioque is therefore not an impedimentum dirimens, a church-dividing obstacle, to reunion.⁠³⁷ Metropolitan Kallistos Ware, the most widely read Orthodox theologian in the English-speaking world, came to hold a version of this view: that the dispute, properly understood, is more a matter of emphasis and language than of opposed dogmas.⁠³⁸

Meanwhile the practical landscape has quietly shifted in the direction of reconciliation. The Eastern Catholic Churches—communions in full union with Rome that retain their own Byzantine, Syriac, and other liturgical traditions—generally do not recite the filioque, exactly as Rome’s 1995 document anticipates.⁠³⁹ And at joint celebrations with the Ecumenical Patriarch—most notably in 1995 and again in 2004—the Creed has been professed in its original Greek form, without the filioque.⁠⁴⁰

My own view, for whatever a layman’s conviction is worth, is that the filioque is a real difference that has been miscast as a contradiction. The East is right that the Father is the sole source of the Godhead, and right to guard that truth jealously; the West has now said so officially. The West is right that the Son is not a bystander to the Spirit’s eternal life, and the East has always half-said so with its own “through the Son.” What divides Catholics and Orthodox today is not, at bottom, the doctrine of the Spirit’s procession—on which Rome has conceded the decisive point—but the older and harder question of who has the authority to define the faith and amend the creed. The filioque was always more a symptom than a disease. The disease is the question of the papacy, and that is a subject for another day.

The Catechism of the Catholic Church puts the hope as well as anyone could. The Eastern and Western ways of confessing the Spirit, it says, are a “legitimate complementarity” which, “provided it does not become rigid, does not affect the identity of faith in the reality of the same mystery confessed.”⁠⁴¹ One word divided the Church. It need not, I think, divide it forever.

Frequently Asked Questions

Footnotes

1. 1. The date 1014 for Rome's liturgical adoption is confirmed by the Pontifical Council for Promoting Christian Unity, The Greek and Latin Traditions Regarding the Procession of the Holy Spirit (1995): "Rome only admitted it in 1014 into the liturgical Latin version of the Creed." Reprinted in L'Osservatore Romano, Weekly Edition in English, September 20, 1995, p. 3; available at EWTN.com.

2. 2. PCPCU, The Greek and Latin Traditions (1995). The phrase "remains always legitimate in the Catholic Church" refers to the creed in its original Greek form without the filioque.

3. 3. On Nicaea (325) and the term homoousios, see the Arian heresy and Nicene Creed. The Council of Nicaea's creed ended its third article simply "And in the Holy Spirit," leaving the Spirit's divinity to be elaborated at Constantinople in 381.

4. 4. Greek text and English of the Niceno-Constantinopolitan Creed (381), procession clause, from Early Church Texts, earlychurchtexts.com. The verb is ekporeuómenon (from ekporeúomai); even the early Latin transmission rendered it "a Patre procedentem," without filioque.

5. 5. John 15:26, New American Bible (Revised Edition), United States Conference of Catholic Bishops. The Greek ho parà toû Patròs ekporeúetai ("who proceeds from the Father") uses the same verb as the creed.

6. 6. NABRE footnote on John 15:26 (USCCB): the Spirit "comes from both Jesus and the Father in mission, with no reference here to the eternal procession of the Spirit." The verse is widely read by modern exegetes as describing the Spirit's economic mission rather than directly teaching his immanent (eternal) origin.

7. 7. John 16:14–15; John 20:22; Galatians 4:6; Romans 8:9 (NABRE). The Western tradition leaned especially on "He will take from what is mine… Everything that the Father has is mine" (John 16:14–15) and on the post-resurrection insufflation (John 20:22). Already Tertullian, Adversus Praxean 25, cited John 16:14 to ground the Son's role in the Spirit's coming-forth.

8. 8. Basil of Caesarea, On the Holy Spirit 18.45 (Sources chrétiennes 17 bis, p. 408), as cited in the PCPCU, The Greek and Latin Traditions (1995). On the Cappadocian "monarchy of the Father," see also Gregory of Nazianzus, Oration 31.8, which calls the Spirit "a middle term between the Unbegotten and the Begotten" (Sources chrétiennes 250, p. 290).

9. 9. Cyril of Alexandria, Thesaurus (PG 75, 585A) and (PG 75, 577A), cited in PCPCU, The Greek and Latin Traditions (1995). The Vatican document stresses that even Cyril, who uses the broader verb proienai of the Spirit's relation to the Son, never uses ekporeuesthai of that relation—reserving the technical term for the Spirit's origin from the Father alone.

10. 10. John of Damascus, An Exposition of the Orthodox Faith (De Fide Orthodoxa) 1.8, trans. S. D. F. Salmond, Nicene and Post-Nicene Fathers, Series 2, vol. 9; available at NewAdvent.org. John also writes that the Spirit "proceeds from the Father and reposes in the Word" (De Fide Orthodoxa 1.7, PG 94, 805B).

11. 11. Augustine, On the Trinity (De Trinitate) 4.20.29, trans. Arthur West Haddan, Nicene and Post-Nicene Fathers, Series 1, vol. 3; available at NewAdvent.org: the Father is "the beginning (principium) of the whole divinity."

12. 12. Augustine, De Trinitate 15.17.29 (NPNF 1, vol. 3), NewAdvent.org.

13. 13. Augustine, De Trinitate 15.26.47 (NPNF 1, vol. 3; the passage is numbered 15.25.47 in the Migne Patrologia Latina, PL 42, 1094–1095): the Spirit proceeds "from the Father principally (principaliter)… yet in common (communiter) from both." The Catechism of the Catholic Church quotes this passage at no. 264.

14. 14. See PCPCU, The Greek and Latin Traditions (1995), which cites Hilary of Poitiers, De Trinitate 12 (PL 10, 471) and 8.20 (PL 10, 251A); Ambrose of Milan, De Spiritu Sancto 1.11.120 (PL 16, 733A), calling Ambrose "the first to formulate the filioque"; and Leo the Great, Sermons 75.3 and 76.2 (PL 54, 402, 404).

15. 15. The Athanasian Creed (Quicumque vult), Spiritus Sanctus a Patre et Filio: non factus, nec creatus, nec genitus, sed procedens. On its non-Athanasian, Latin, late-fifth- or early-sixth-century southern Gaulish origin, see The Catholic Encyclopedia, "Athanasian Creed," NewAdvent.org; the authoritative Latin text is in Denzinger-Hünermann no. 75.

16. 16. Maximus the Confessor, Letter to Marinus of Cyprus (PG 91, 136A–B), as translated in PCPCU, The Greek and Latin Traditions (1995). The letter dates from around 645–646 and responds to Byzantine alarm at a synodal letter from Rome. Its interpretation is contested: Catholics read it as proof the filioque is compatible with Greek theology; many Orthodox read it as proof that the seventh-century Latins did not mean a causal filioque.

17. 17. On the disputed status of the filioque at the Third Council of Toledo (589): A. E. Burn (1908) first argued that the phrase was interpolated into the council's records by a later hand. See the discussion in Bernd Oberdorfer, Filioque: Geschichte und Theologie eines ökumenischen Problems (Göttingen: Vandenhoeck & Ruprecht, 2001), and the survey in A. Edward Siecienski, The Filioque: History of a Doctrinal Controversy (Oxford: Oxford University Press, 2010), the standard English-language history of the question.

18. 18. PCPCU, The Greek and Latin Traditions (1995): the filioque "was confessed… by the Councils of Toledo in Visigothic Spain between 589 and 693 (DS 470, 485, 490, 527, 568)… If these Councils did not perhaps insert it in the Symbol of Nicaea-Constantinople, it is certainly to be found there from the end of the eighth century."

19. 19. The Synod of Aachen (809), convened under Charlemagne, defended the liturgical use of the filioque and forwarded the matter to Rome. See Siecienski, The Filioque, chap. 5; PCPCU, The Greek and Latin Traditions (1995), citing Mansi 14, 17.

20. 20. On Pope Leo III's refusal (c. 810) to insert the filioque into the Roman creed while affirming its doctrinal truth, and the tradition of the silver shields engraved with the unaltered creed in Greek and Latin set up at St. Peter's, see Siecienski, The Filioque, chap. 5. The precise wording of the shield inscriptions circulates in variant forms in the secondary literature and should be checked against a critical edition of the Liber Pontificalis before being quoted verbatim.

21. 21. In 1014, at the request of Emperor Henry II (crowned in Rome that February), Pope Benedict VIII permitted the Creed to be sung with the filioque at the papal Mass for the first time. See PCPCU, The Greek and Latin Traditions (1995); Siecienski, The Filioque, chap. 5.

22. 22. Council of Ephesus (431), Canon 7, trans. Henry R. Percival, The Seven Ecumenical Councils, Nicene and Post-Nicene Fathers, Series 2, vol. 14; available at CCEL. Percival's notes record that the canon's immediate target was a rival (Nestorian-tinged) baptismal creed, which grounds the Catholic argument that it forbade composing a competing faith rather than clarifying the existing one.

23. 23. Photius of Constantinople, Mystagogy of the Holy Spirit (ninth century), the first systematic Greek treatise against the filioque, arguing for procession "from the Father alone." See Siecienski, The Filioque, chap. 6.

24. 24. The Council of 869–870 (which deposed Photius) is reckoned by the Catholic Church as the Fourth Council of Constantinople and the eighth ecumenical council; the Council of 879–880 (which restored Photius and read the Creed without the filioque) is reckoned by the Eastern Orthodox as the genuine eighth ecumenical council. Catholic and Orthodox historians assess the relationship between the two councils and the degree of Pope John VIII's assent to the latter differently; see Siecienski, The Filioque, pp. 99–104.

25. 25. On the mutual excommunications of 1054 and the secondary place of the filioque among the charges, see the Great Schism; and Siecienski, The Filioque, chap. 7. Cardinal Humbert's bull notoriously accused the Greeks of having deleted the filioque from the creed, evidently unaware it was never in the original Greek text.

26. 26. Second Council of Lyons (1274), Constitution on the Procession of the Holy Spirit: the Spirit proceeds "from the Father and the Son, not as from two principles but as from one single principle (tamquam ex uno principio)" (Denzinger-Schönmetzer no. 850). See Norman P. Tanner, ed., Decrees of the Ecumenical Councils (London: Sheed & Ward; Washington, DC: Georgetown University Press, 1990), 1:314.

27. 27. Council of Florence (1439), bull Laetentur Caeli, trans. in Heinrich Denzinger, The Sources of Catholic Dogma, trans. Roy J. Deferrari, no. 691 (older Denzinger nos. 1300–1301); see also Tanner, Decrees, 1:526–528. Florence explicitly identifies the Greek "through the Son" with the Latin "from the Son."

28. 28. Thomas Aquinas, Summa Theologiae I, q. 36, "The person of the Holy Ghost," trans. Fathers of the English Dominican Province; available at NewAdvent.org. Article 2 asks whether the Spirit proceeds from the Son; article 3, whether through the Son; article 4, whether the Father and Son are one principle of the Spirit.

29. 29. Aquinas, Summa Theologiae I, q. 36, a. 2, corpus.

30. 30. Aquinas, Summa Theologiae I, q. 36, a. 2, corpus and ad 1. The "Father alone" concession (ad 1) is significant: Aquinas grants that "from the Father alone" does not exclude the Son, since Father and Son are not opposed as principle of the Spirit.

31. 31. Aquinas, Summa Theologiae I, q. 36, a. 4, corpus, citing Augustine, De Trinitate 5.14: "the Father and the Son are not two principles, but one principle of the Holy Ghost."

32. 32. PCPCU, The Greek and Latin Traditions (1995): "Since the Latin Bible… had translated Jn 15:26… by 'qui a Patre procedit,' the Latins translated the ek tou Patros ekporeuomenon of the Symbol… by 'ex Patre procedentem'… In this way, a false equivalence was involuntarily created… between the Oriental theology of the ekporeusis and the Latin theology of the processio."

33. 33. Pontifical Council for Promoting Christian Unity, The Greek and Latin Traditions Regarding the Procession of the Holy Spirit (1995), prefatory note recording John Paul II's request in his homily of June 29, 1995, in the presence of Ecumenical Patriarch Bartholomew I. The document describes itself as "an authoritative interpretation," not a new dogmatic definition.

34. 34. PCPCU, The Greek and Latin Traditions (1995).

35. 35. PCPCU, The Greek and Latin Traditions (1995): "the Catholic Church has refused the addition of kai tou Uiou to the formula ek tou Patros ekporeuomenon of the Symbol of Nicaea-Constantinople in the Churches, even of Latin rite, which use it in Greek. The liturgical use of this original text remains always legitimate in the Catholic Church."

36. 36. Vladimir Lossky, The Mystical Theology of the Eastern Church (Crestwood, NY: St. Vladimir's Seminary Press, 1976; orig. French ed. 1944), treats the filioque as a fundamental error; John Romanides pressed a similarly rigorist line. The characterization of their positions here follows the standard secondary literature, including Siecienski, The Filioque, chaps. 10–11.

37. 37. Vasily Bolotov, "Thesen über das 'Filioque': Von einem russischen Theologen," published anonymously in the Revue internationale de théologie (1898), in the context of Orthodox–Old Catholic reunion dialogue. Bolotov classified the procession formulas as theologoumena rather than dogmas and held the filioque to be no impedimentum dirimens to reunion.

38. 38. Kallistos (Timothy) Ware, The Orthodox Church, new ed. (London: Penguin, 1993), presents the moderate Orthodox view that the dispute is substantially one of emphasis and terminology, distinguishing it from the rigorist line. Ware's own position shifted over his career; the characterization here reflects his mature, conciliatory treatment.

39. 39. PCPCU, The Greek and Latin Traditions (1995): Rome refuses the filioque in the Greek text "even of Latin rite," and "the liturgical use of this original text remains always legitimate in the Catholic Church." Eastern Catholic Churches in full communion with Rome generally retain the original creed without the filioque, consistent with this principle.

40. 40. At the papal liturgies for the Feast of Saints Peter and Paul attended by Ecumenical Patriarch Bartholomew I—notably June 29, 1995, and again in 2004—the Niceno-Constantinopolitan Creed was professed in its original Greek form, without the filioque. The 1995 occasion is the same visit that prompted John Paul II's request for the clarification cited above.

41. 41. Catechism of the Catholic Church, no. 248, citing the Eastern "through the Son" and the Western "filioque" as a "legitimate complementarity"; available at vatican.va. See also CCC nos. 246–247.