This concludes ONE magazine’s series on the Eastern churches, which began with a profile of the Orthodox Church of Eritrea in January 2005. Of the 47 articles, all but one were authored by Mr. La Civita.

The Patriarchal Church of Constantinople — the Ecumenical Patriarchate — ranks as primus inter pares, “first among equals,” in the worldwide Orthodox communion of churches. The present incumbent, Bartholomew I, Archbishop of Constantinople, New Rome and Ecumenical Patriarch, exercises no authority over other Orthodox churches or patriarchs. Yet his prerogatives include second in honor after Rome among the ancient sees of the church; the right to hear appeals between clergy if invited; and the right to ordain bishops outside defined canonical boundaries.

Not all accept this status. Some canonists (particularly those associated with the powerful Orthodox Patriarchate of Moscow) challenge the ecumenical patriarch’s leadership. They assert the medieval claim “Two Romes have fallen. A third — Moscow — yet stands. A fourth there shall not be.” The Turkish government rejects any global role of the ecumenical patriarch, citing only his leadership for the few thousand Orthodox Christians who remain in Turkey; most live in what is today called Istanbul.

Bartholomew I, nevertheless, enjoys international stature. He exercises varying degrees of authority over some 3.5 million Orthodox Christians in Turkey, northern Greece and those scattered beyond the traditional canonical boundaries of the ancient patriarchates, including the Americas, Oceania and Western Europe. And environmentalists have nicknamed him the “Green Pope” for his advocacy of and commitment to environmental conservation. Tradition attributes the apostle Andrew as the founder of the church of Constantinople. But its link to Caesar would catapult it to prominence within Christendom, rivaling even Rome.

Favor. Recognizing the ascendance of his empire’s eastern provinces, the Roman emperor Constantine I moved his capital from Rome to Byzantion, a Greek port straddling Europe and Asia. On 11 May 330, the emperor solemnly christened his “new Rome” as a Christian capital and ordered the elite of old pagan Rome to move there.

In addition to the usual civic structures and monuments, Constantine built elaborate churches, including a cathedral dedicated to Christ as Hagia Sophia, “the Wisdom of God,” that served as his personal chapel; and Hagioi Apostoloi, the church of the Holy Apostles, where he was later buried. These sanctuaries took on immense significance for the development of the church in late antiquity.

This development coincided within the confluence of cultures in the eastern shores of the Mediterranean. As Christianity grew and embraced converts from the Greek, Jewish, Persian, Roman and Syriac cultures, debate raged regarding the nature of Jesus, his relationship to the Father and how to preach and practice the Gospel. Competing schools of theology and philosophy evolved.

Greek-speaking theologians from the church of Alexandria in Egypt utilized allegory to explain Jesus’ divinity and humanity. Syriac-speaking theologians from the church of Antioch in Syria fashioned an understanding of Jesus that stressed his humanity. Seen as complementary today, these different approaches clashed, threatening to disrupt the unity of the Roman Empire, which took on a Christian character even as it maintained its Roman identity.

In the interests of peace, unity, catholicity in practice and consensus in governance, Constantine and his successors convoked “ecumenical” (from the Greek, oikoumene, meaning of the inhabited world) councils, bringing together bishops and theologians from throughout the empire and beyond.

At the first council, held in Nicaea in 325, the fathers formulated the Christian creed that, with some modifications, is recited to this day in churches worldwide. The council fathers also recognized as an “ancient custom” the patriarchal authority of the bishops of Rome, Alexandria and Antioch, granting them jurisdiction over large swaths in the empire.

But as Constantinople increased in size and wealth, so did the prestige of its bishop. And with the support of the emperor and his household, the capital’s bishop began to press for patriarchal recognition. In 381, the fathers of the Council of Constantinople conferred primacy in the east to the bishop of Constantinople, stating in its third canon that “the bishop of Constantinople shall have the prerogative of honor after the bishop of Rome since the city of Constantine is the New Rome.”

The fathers of the Council of Chalcedon in 451 confirmed the position of the bishop of Constantinople, recognizing the city as the “residence of the emperor and the Senate” and establishing it as a patriarchate with jurisdiction over Asia Minor and Thrace. In its controversial canon 28, the council went further and organized the church into the so-called “Pentarchy,” ranking the patriarchates of Rome, Constantinople, Alexandria, Antioch and Jerusalem. While it was understood in the east that Rome held the place as first among equals, the popes did not recognize Constantinople until the Council of Florence in 1439.

As church and state mingled increasingly in Constantinople, the authority of its patriarch swelled. His close relationship to the emperor and his household encouraged other bishops to identify him as the “ecumenical” (meaning at the center of the empire, from the Greek oikos, meaning of the household) patriarch.

In 586, John IV of Constantinople assumed the title “ecumenical patriarch,” which Pope St. Gregory the Great rejected for its ambitions of universal jurisdiction. While John and his successors denied such objectives, the authority of the ecumenical patriarchs did grow to include the Balkans, once subject to the Roman pontiffs, and to those areas outside the control of the ancient patriarchates — “among the barbarians.”

Expansion. Even as the power and reach of the eastern Roman (later understood as “Byzantine”) Empire declined — civil strife, schism, the rise of Islam and the iconoclastic controversy all took their toll — Constantinople continued to lure covetous clan leaders who desired the power and wealth of this dazzling cosmopolitan city.

In 852, one ambitious pagan prince, Boris, ascended the Bulgar throne. He manipulated Byzantium’s emperor in the east and courted the pope in the west, using as leverage his interest in the Christian faith. Boris eventually adopted Byzantine Christianity in 864, but he relentlessly pursued a policy of independence for his fledgling church and state. Vacillating between Constantinople and Rome, Boris’s politics hardened a split between the two churches, each of which claimed jurisdiction over the Balkans. Known as the Photian Schism — coinciding with tenure of Photios I as ecumenical patriarch — it underscored the deepening rift between the “Orthodox” East and the “Catholic” West and foreshadowed the eventual divorce between the two.

Meanwhile, in the Central European principality of Greater Moravia, Latin missionaries worked among the realm’s Moravian Slavs, introducing the Latin rites of the Roman church and advocating closer ties with Moravia’s enemies: the Germanic princes of the Holy Roman Empire. To counter these efforts, Prince Rastislav of Moravia petitioned the Byzantine emperor, Michael III, to provide Slav-speaking missionaries to work among his people.

In 862, Michael III and Photios I sent two Greek brothers, Cyril and Methodius. They devised an alphabet for the Slavonic vernacular, translated Scripture, developed a Slavonic liturgy and transcribed the first Slavic code of civil law. Despite support from the papacy, the brothers’ work generated hostility among the Latin bishops, who drove Cyril and Methodius from Moravia, deposed Rastislav and, in 886, banished their followers.

Two of their disciples, Clement and Naum, found refuge in Boris’s Bulgaria. There, they furthered the cultural, linguistic and spiritual works of Cyril and Methodius and realized Boris’s goal of an independent church, yet it adhered to the Byzantine liturgical rites and traditions of Constantinople.

Schism. The Arab Muslim occupation of Alexandria, Antioch and Jerusalem (which began in the seventh century) heightened the position of the ecumenical patriarchate of Constantinople among the Eastern churches and set it on a course of conflict with the church of Rome. By the second millennium of the Christian era, the two churches had parted ways — culturally, liturgically, philosophically, politically and theologically — even as they remained in full communion.

Calling themselves “Romanoi,” meaning Roman in Greek, the Byzantines proudly retained their Roman identity within the context of a Hellenistic culture inherited from ancient Greece. The Byzantines spoke Greek, utilized a vocabulary shaped by Greek culture and advanced ancient Greek ideals.

Perhaps the greatest remaining example of this culture is the Divine Liturgy of St. John Chrysostom and the Byzantine rites of the patriarchal church of Constantinople. Though these liturgical practices originated in the churches of ancient Palestine and Syria, they matured in Constantinople’s Great Church of the Hagia Sophia, which the Emperor Justinian rebuilt and dedicated in 537 with the words, “Solomon, I have surpassed thee!”

The Great Church of Constantinople became a metaphor for heaven. The very structure itself — domes, vaults, arcades, columns, mosaics and silk hangings — evoked the heavenly sanctuary inhabited by God. This “cosmos church for a cosmic liturgy” evolved over the ages, and Byzantine ecclesiastical architecture, as well as its liturgical rites, were adopted by Slavic Christians and adapted by monks from Egypt to Syria.

While Byzantine liturgies developed — taking on influences as diverse as Armenian, Coptic and Syriac — its ecumenical patriarchs stood fast against innovations from the Latin West that it defined as uncanonical. Some of these innovations were cultural and disciplinary, but Rome’s alteration of the creed with the addition of the word, filioque, Latin for the belief that the Holy Spirit “proceeds from the Father and the Son,” remains a factor dividing the Catholic and Orthodox churches.

Ecumenical Patriarch Photios I rejected the filioque as a theological error and as uncanonical; no changes to the creed, he argued, could be made without the summoning of an ecumenical council. His successors ceased to commemorate the popes in the Divine Liturgy, particularly after Rome incorporated the filioque into the Mass in the 11th century, an action that symbolized the breakdown between Constantinople and Rome.

The official schism between the Catholic and Orthodox churches is usually tied to the anathemas between the pope and the ecumenical patriarch in the summer of 1054. Most scholars agree, however, that the anathemas were invalid — Pope Leo IX had died two months before his own legate placed a letter on the altar of the Hagia Sophia excommunicating Michael I. They also believe the anathemas severed communion between two leaders not their churches. Though Pope Paul VI and Ecumenical Patriarch Athenagoras I lifted these anathemas in Jerusalem in 1965, their dramatic gesture did not heal the schism.

To the Orthodox East, the capture of Byzantine Constantinople by Catholic knights of the Fourth Crusade in 1204, their pillage of its churches and palaces, and the pope’s sanctioning of a Latin emperor and a Latin patriarch in the city of Constantine marks the definitive divorce between the Orthodox East and the Catholic West. In 1261, the Byzantines retook their capital city, but within its gates they discovered a city in decline, despoiled by greed and neglect.

Until the Ottoman Turks stormed the city’s walls in May 1453 and killed the last emperor of the Romans, the Byzantines sought to restore their empire, their glories, their churches and their culture. In order to enlist the assistance of the Catholic West — cash and arms were in short supply — the emperors sought the restoration of union between the two churches. Popes summoned councils in Lyon (1274) and Florence (1439), but the unity achieved deteriorated soon after the Byzantine legation returned to Constantinople.

Ethnarchs. The Islamic Ottoman Turkish Empire, which succeeded the Byzantine state in 1453, developed a sophisticated governing structure in which to govern its non-Muslim peoples, or dhimmi in Arabic. Non-Muslim communities, in exchange for their loyalty to the sultan, were granted freedom of worship, guaranteed legal protection and exempted from laws binding Muslims, such as dietary restrictions. Barred from serving in the sultan’s army — paying a poll tax (jizyah in Arabic) instead — non-Muslims served the sultan in government, particularly in the diplomatic corps. And while many grew rich and influential at court, especially after the 17th century, all experienced some restrictions.

The sultan appointed a national leader for each group, usually the ranking hierarch of the religious community. This national leader, or ethnarch, reported to the sultan directly. The ethnarch had enormous power within the community and was free to establish his own courts and judges, create and enact personal and religious laws, and collect and distribute taxes.

As ethnarch of the Ottoman Orthodox Christian community, the ecumenical patriarch grew in standing. Though deprived of his church — the Great Church of the Hagia Sophia had been converted into a mosque, its mosaics whitewashed, its altars removed, its sanctuary lights extinguished — the ecumenical patriarch took on the trappings of the Byzantine emperors and his court, including the imperial standard of the last dynasty, the double-headed eagle.

Collecting wealth and acquiring power over other Orthodox churches, particularly in the Balkans, the ecumenical patriarchs and the Greek community dominated the Christian communities of the Ottoman Empire. In the Balkans, this fueled Bulgarian, Romanian and Serbian resentment for the “Phanariots” (after the Phanar quarter, the location of the ecumenical patriarchate), who suppressed the ambitions of the Balkans as they championed their own.

The Greek war of independence in the early 19th century put the ecumenical patriarchate in a difficult position. As ethnarch, he swore fealty to the sultan and exacted that same loyalty from the community over which he presided. But, his inclinations were to support his own peoples’ dreams of a restored Greek state.

The sultan reacted quickly after successful Greek rebellions in the Peloponnese. After he celebrated the Divine Liturgy on Easter Sunday (10 April 1821), Ecumenical Patriarch Gregory V was arrested and hanged from the gate of the patriarchal compound, which to this day remains sealed in his memory.

In 1833, the government of the newly created Kingdom of Greece declared the Orthodox Church there independent of the ecumenical patriarchate and submitted it to the leadership of the king. In 1850, the ecumenical patriarch recognized its autonomy and established the metropolitan archbishop of Athens as its head.

Today. Ten years of near constant warfare — the Balkan Wars (1912-13), World War I (1914-18) and war between Greece and Turkey (1919 to 1922) — weakened the ecumenical patriarchate, depriving it of territory and people. But the worst was yet to come.

In 1923, the Treaty of Lausanne called for the exchange of populations, forcing Turks out of Greece, and Greeks out of Turkey. Overnight, Greek communities present in Asia Minor since the third century before Christ disappeared. More than 1.5 million Orthodox Greeks settled in Greece proper. Though exempt, Istanbul alone lost some 300,000 people and several hundred thousand died in the melee. Anti-Greek riots in Istanbul in 1955 emptied the city of those few who remained.

Present-day Istanbul — from the Greek, eis ten polin, meaning “to the city” — shares little with its former incarnation as Constantinople. Once cosmopolitan, it is now a homogeneous metropolis of some 15 million people. Almost all of its inhabitants — 97 percent — are Muslims, ethnic Turks or Kurds. The empty churches of the Greeks, and the shell of the Hagia Sophia, cast ghostly reminders of ages past, when the city served as the capital of two great civilizations.