Why did one word in the Creed divide East and West?

What the Creed of 381 says

The creed most churches call the Nicene Creed is, strictly, the Niceno-Constantinopolitan Creed. The Council of Nicaea in 325 confessed the full divinity of the Son, and the Council of Constantinople in 381 expanded the article on the Holy Spirit. In its Greek original, that article confesses the Spirit as the Lord and giver of life, who proceeds from the Father [1]. The wording echoes Jesus' words in John's Gospel: "the Spirit of truth who proceeds from the Father" (John 15:26, BSB) [2].

No one disputes that the words "and the Son" were not in the text agreed in 381. Western editions of the councils print the creed without them [1].

How the word entered the Latin Creed

The addition first appears in the acts of the Third Council of Toledo, in Spain, in 589, where it was used against Arianism, the teaching that the Son is less than the Father [3]. From Spain it spread into the Frankish lands [3]. In 809 a council called by Charlemagne at Aachen approved its use, after Frankish monks in Jerusalem had been accused of heresy for singing it [3].

Rome did not follow at first. Pope Leo III accepted the doctrine behind the phrase but refused to add it to the Creed, on the ground that the councils had forbidden additions to their text [3][1]. He had the Creed engraved without it on two silver shields, one in Greek and one in Latin, and placed them at the tomb of St. Peter [1]. The first time a pope used the expanded Creed at Mass was in 1014, when Benedict VIII agreed to the request of the German king Henry II at his coronation [3][1].

Why the East objected

Eastern theologians raised two objections. The first was about authority: a creed agreed by an ecumenical council should not be changed by one part of the Church alone [5]. The second was about theology. Eastern teaching holds that the Father is the single source within the Trinity, and the addition seemed to make the Son a second source of the Spirit [5].

In 867 Patriarch Photius of Constantinople, in an encyclical letter to the other Eastern patriarchs, named the filioque among the gravest errors of the Latin Church, accusing the West of altering the Creed in heresy [3][12]. The dispute became tied up with quarrels over papal authority and church rule [5]. On 16 July 1054 the papal legate Cardinal Humbert left a bull of excommunication on the altar of Hagia Sophia; it condemned Patriarch Michael Cerularius, the Greek teaching on the Holy Spirit, the marriage of Greek priests and the Greek use of leavened bread, and the patriarch's synod excommunicated the legates in reply [12]. The filioque was one charge among several, and the excommunications were lifted by Pope Paul VI and Patriarch Athenagoras I on 7 December 1965 [12]. Historians stress that the division grew over centuries and that no single event caused it [6].

Why the West defended it

Western theology, drawing on Augustine, holds that the Spirit is the bond of love between the Father and the Son, and that the Son shares in the Spirit's procession because he shares everything with the Father. Scripture calls the Spirit "the Spirit of His Son" (Galatians 4:6, BSB) [7]. Catholic teaching does not make the Father and the Son two separate sources: the Catechism says the Spirit proceeds from both "as from one principle", and that the Father remains the first origin [13]. On that reading, "and the Son" guards the Son's equality with the Father, which is why Toledo used it against Arianism [3]. Most Protestant churches inherited the Western Creed with the filioque, and for Catholics and most Protestants it remains part of ordinary teaching [8].

Recent steps

In 1875 a conference at Bonn of Old Catholics, Orthodox and Anglicans treated the phrase as an unauthorized addition to the Creed [3]. In 1995 a Vatican document set out the Catholic position afresh, and Orthodox theologians, among them Metropolitan John Zizioulas, responded to it [9]. On 25 October 2003 the North American Orthodox-Catholic Theological Consultation, after four years of study, unanimously adopted "The Filioque: A Church-Dividing Issue?" [10]. Noting that the Vatican had affirmed the normative value of the Creed of 381 in its original Greek, it recommended that the Catholic Church use that text, without the filioque, in catechesis and worship [10][4]. This was the consultation's advice, not a change in Catholic doctrine or liturgical law.

On 28 November 2025, at Iznik, the site of ancient Nicaea, Pope Leo XIV and Ecumenical Patriarch Bartholomew of Constantinople marked the council's 1,700th anniversary and, in a service the Holy See Press Office records as including the recitation of the Nicene-Constantinopolitan Creed [14], recited it together without the filioque [11]. The Catholic Mass in the West still uses the Creed with the phrase.

What this means for the reader

When Catholics and most Protestants say "who proceeds from the Father and the Son" and Orthodox Christians say "who proceeds from the Father", they are reciting two forms of the same creed. The difference concerns both how the Trinity is described and who may change a creed, and for over a thousand years the churches have debated both.