The Orthodox Church consists historically of the local Churches of the Eastern Roman empire, including Constantinople, Alexandria, Antioch and Jerusalem, as well as the Churches that came into being as a result of their missions. During the first millennium of Christianity, this communion included the Church of Rome. It is important to remember that the Orthodox and Roman Catholic Churches, as well as Rome's Protestant offshoots, all share a common ancestry in the one, universal Christian communion of the early centuries.

The Christian mission, as it is described by Luke in Acts and in Paul's Epistles, spread rapidly through the territories of the Roman empire. Orthodox tradition holds that it spread beyond the Roman world even in the apostolic period, with St Thomas travelling as far as southern India, converting many people along the way. Most of the more distant missions, such as Georgia, Armenia and Ethiopia, however, were probably achieved in the fourth or fifth centuries after the Roman empire had finally adopted Christianity as its state religion, following the conversion of Constantine I. By this time, the Church, which had earlier been an illegal, minority organisation within a predominantly pagan society, was slowly becoming the dominant force in shaping government laws and social traditions. The Roman empire, consisting of its Eastern and Western halves, became a fully Christian state: it was believed to be sanctioned by God, with its emperors or kings fulfilling special duties as God's representatives in the secular realm.

WHAT IS AN ICON?

The Greek word eikon simply means 'image', but the word has come in Orthodox tradition to mean much more than simply a pictorial representation of a religious subject. Every icon, whether it depicts Christ, the Word and Son of God, Mary the Mother of God, a saint, or a biblical scene or feast, represents a confession of faith and a witness to the Incarnation. This is because the icon is a symbol, which manifests something greater than its physical limits allow. Like the written word, an icon expresses divine truth in a manner that humans can perceive and understand. As St John of Damascus asserted in the eighth century, when Orthodox Christians 'venerate images, it is not veneration offered to matter, but to those who are portrayed through matter in the images'.

An 'icon' usually means a portable wooden panel, painted either with encaustic wax (especially before about the seventh century) or with egg tempera. However, the term refers in its widest sense also to the images portrayed in frescoes or mosaics on church walls, on sacerdotal vestments, altar vessels, Gospel and liturgical book covers, crosses and other media. Panel icons may be made not only on wood, but also on ivory, metal, textile and many other materials. Icons may serve decorative or pedagogic purposes, in addition to acting as liturgical or devotional objects. All of these forms of icons, however, share one important characteristic: they offer a window into eternal meaning and are thus worthy of honour and devotion. Such honour is not offered to the icon itself, but to what it represents.

Of all the artisanal productions preserved from the time since Constantine I (the Great) began calling Byzantium, the capital of the old eastern Roman empire, by a new name (Constantinople – Constantine’s polis, or city), probably the most familiar today are icons and buildings such as Hagia Sophia. But it is arguable that Byzantine books should share pride of place.

Across the imperial centuries, Greek manuscripts – usually deluxe copies of the Gospels or service books, but also theological treatises such as the copy of Dionysius the Areopagite sent to Louis the Pious in 827 – served as valuable diplomatic gifts. After the fall of Constantinople to the Ottoman Turks in 1453 they were collected by humanist scholars, particularly, though not exclusively, for the ancient Greek authors whose texts they preserved; and by the French kings who saw themselves as the successors to the Byzantine emperors and surrounded themselves with the trappings of their purported ancestors. Beyond the role of Greek manuscripts in cultural history, their contents – and decoration – are important as testimony to the ways medieval Byzantines ordered and arranged their thoughts, and for the ways that images were used to reinforce and shape the world of the largely urban elite who had access to, and could actively read, books.