"Orthodoxy: More Than an Empire (900-1700)" is the title of this chapter.
Crises and Crusaders (900-1200)
At the millennium, Constantinople, with somewhere around 600,000 residents, was easily the biggest city in the known world. It was a time of relative strength and prosperity in the eastern empire. However, it was also a time of theological challenge, exemplified by Symeon "the New Theologian" who argued that true ordination came from God and not from men; that authority was rooted in character, not in office; that power was the result of godly simplicity, not worldly sophistication.
The eleventh century also saw Constantinople trying to fend off Muslim encroachment. "The most decisive battle in the Byzantine confrontation with the Seljuk Turks was at Manzikert in Asia Minor in 1071, at which the reigning Emperor Romanus was not only crushingly defeated, but suffered the humiliation of being taken prisoner" (470). His successor, Alexios "repeatedly appealed to Western leaders for help against various enemies, and in 1095 for the first time he was given a serious hearing. It as this request which led [Pope] Urban II to launch the publicity campaign which triggered the First Crusade" (470). The Crusades had the effect of increasing tension between East and West. The presence of armies from the West in and around Constantinople unnerved the East. At times, mayhem against Muslims spilled over into violence against Byzantines. The two sides had long since lost their ability to comprehend each other. And the papacy was increasing its claim to a universal monarchy.
The Fourth Crusade and its Aftermath (1204-1300)
MacCulloch singles out the Fourth Crusade because of its focus: "attacks on Constantinople in 1203 and 1204, horrible deaths in quick succession for a series of Byzantine emperors, including the little-regarded Alexios, the trashing of the Christian world's wealthiest and most cultured city--in short, countless incentives for centuries of Orthodox fury against Catholics" (474). The Byzantine Empire was forever damaged. In early response, a few "statelets" sprang up, the most impressive one at Nicaea in the mountains of Asia Minor. The rulers of Nicaea were the ones who recaptured Constantinople from the Latins in 1261. "Even though Constantinople was restored to Byzantine control . . . , the empire's unity, that fundamental fact of Byzantine society from Constantine the Great onwards, never again became a reality" (477).
Orthodox Renaissance, Ottomans and Hesychasm Triumphant (1300-1400)
The post-1261 Byzantine Empire was never the same, and it experienced disintegration and pressure as a result of "a new branch of Turkish tribes who had carved out for themselves a principality in north-west Asia Minor and who survived a determined effort by the Byzantines to dislodge them in a significant victory in 1301. Their warlord leader was called Osman, and they took their name of Ottomans from him" (483).
As MacCulloch points out, it's ironic that this age saw a good bit of interchange between East and West. He discusses the similarities and differences of the liturgies and physical features of the two great Churches. A good number of Latin texts by Augustine and Thomas Aquinas were translated into Greek during this period.
At this same time, the East "was convulsed by a dispute about the validity of a style of mystical prayer known as Hesychasm" (487). Hesychasm connotes the idea of silence and stillness, like an ancient form of Quakerism. Its main proponent was Gregory Palamas taught that this form of prayer enabled the worshipper to reach visions of divine light, to see the Holy Spirit as it were. On the other side was Barlaam who cited the Maximus tradition, according to which the essence of God is unknowable. Ironically, both of them cited newly-translated Latin theological texts. Ultimately, Barlaam's side lost the debate and Gregory triumphed. By 1341, Barlaam was condemned as a heretic. So he went west and joined the Roman Catholics!
Hopes Destroyed: Church Union, Ottoman Conquest (1400-1700)
By the end of the fourteenth century, the last emperors in Constantinople had resigned themselves to being vassals of the Ottoman sultan. Appeals to the West were and would have been futile. The hostility between the two had been growing for a long time. The Great Papal Schism of 1378, in which two and then three different people were claiming to be Pope, revealed that Catholicism had major problems of its own.
The fifteenth century witnessed an attempt on the part of the two sides to mend the rift. But from the standpoint of the East, issues like the Catholic doctrine of Purgatory, their use of unleavened bread, and the powers and claims of the papacy, made the gap impossibly wide. In its homeland, Orthodoxy withered under Muslim domination.