To fully appreciate the richness of Byzantine heritage, it is essential to understand their religion, as the majority of the architectural and artistic masterpieces surviving today were created in a religious context. Furthermore, today’s Orthodoxy is its direct continuation. Christianism, along with the Roman identity, was at the core of the Byzantine’s identity. How did it shape the Byzantine society, putting an end to centuries of paganism? How was it defined, and how did it evolve into the Orthodoxy? And what influence did it ultimately have on Byzantine history? To understand this progression, one must back to the end of the Roman period.

The rise of Christianity in the Eastern Roman Empire.

When Constantine founded Constantinople, he wasn’t yet a Christian. He authorized Christianity in 313 but initially built temples to the Roman gods in his new capital, even before the first churches. It was only at the end of the 4th century that Christianity became the official and only permitted religion. The emperor then designates himself as “the emperor of the Romans” and adds to this title that of “faithful in Christ the God.” He is God’s lieutenant on earth, the foremost Christian, and ultimately, the head of the Church.

From tolerance to sole religion, Christianity rapidly imposed itself on the masses of the Roman East. It even surpassed the empire’s borders within nearby regions, and sometimes even far-reaching areas of the Persian Empire. Yet, paganism long resisted within the high and educated ranks of the urban aristocracy and disappeared only gradually. Justinian did not dare to close the Academy of Athens until 529, and the temple of Philae in Egypt remained active until the 7th century.

In parallel, once their religion was authorized, Christians no longer opposed Roman identity. Their leaders, the bishops, were members of the aristocracy raised in the paideia, the ancient schooling system. Many were enthusiasts of Neoplatonic philosophy and ancient rhetoric. They quickly became the best defenders of Roman identity and reconciled its heritage with Christian thought.

The difficult birth of a unified Christian doctrine.

The division of the church at the time of Constantin.

The message of Christ was meant to be universal, therefore the final aim of the christianity is to encompass the oikoumene (literally, the inhabited world), meaning the whole humanity. Nonetheless, the reality was more complex. The core of the christian belief itself is complex, preaching one God but in three persons (the Father, the Son, and the Holy Spirit). In the first centuries, a vast corpus of scriptures, including many apocryphs, circulates in the christian communities. The new religion was also confronted with the ancient world’s diversity, with beliefs sometimes rooted in local places for centuries, with powerful and well-established schools of thought. To add to the complexicty, the christian communities, divided and clandestine, were, in fact, having different practices, interpretations, and even sometimes beliefs.

By authorizing the new religion, and beyond the question of his personal convictions, Constantine made a primarily political choice. He sought to gain the support of what appeared to be the most dynamic segment of his empire’s population. Consequently, he could not tolerate Christians tearing each other apart. Therefore, he convened the first council at Nicaea. An ecumenical council normally gathers enough bishops and is viewed as speaking for the whole community. Constantine had it presided over by his representatives. No one contested this role, since he was responsible for the authorization of the new religion. At that time, ideology also considered the emperor a god. Although he was not seen as such by Christians, he was nevertheless the legitimate representative of God on earth. This idea remains strong in the Orthodox tradition: the emperor, as God’s lieutenant on earth, convenes and presides over councils.

The Arianism dispute and the first concile of Niceae.

The main controversy of the time centered on the relationship between the three components of the Trinity (the Father, the Son, and the Holy Spirit). Arius, a priest from Alexandria, advocated for a strict monotheism: according to him, the Son was a creation of the Father. His doctrine is known as Arianism. It was condemned by the Council of Nicaea, which proclaimed that the Father, the Son, and the Holy Spirit are of the same substance: this is known as the Nicene Creed. However, this did not really solve the problem. Constantine himself recalled Arius from exile as early as 328, and several of his successors were Arians. Arianism spread in many regions of the East and among the Germanic peoples outside the empire’s borders. It was not until nearly a century later, with the second ecumenical council of Constantinople convened by Theodosius in 381, that the issue was resolved.

Nestorianism and Monophysism.

Nestorianism and the first Council of Ephesus.

A new controversy arises on Christ’s nature: fully God and fully human. It divides East for centuries. Initially, two main schools of thought opposed each other: those of Antioch in Syria and Alexandria in Egypt. Nestorius, a priest of Antioch who became patriarch of Constantinople in 428, rejects Christ’s birth from a woman. The Virgin isn’t Theotokos but Christotokos: Nestorianism. Cyril of Alexandria opposes, defending Mary’s divine motherhood. The Council of Ephesus in 431 condemns Nestorianism but doesn’t erase it. Nonetheless, Cyrille and his school manage to push a more rigorist view of the christian dogm, tending to a stronger monotheism.

The rise of Monophysism.

According to this belief, during the Incarnation, the human nature of Christ merges into the Divinity: there is only one (monos in Greek) nature (physis in Greek) left: this is monophysitism. Cyril was able to impose this doctrine during a new council held at Ephesus in 449. Political considerations then intervene. The new emperor, Marcian, who ascended the throne in 450, did not want to alienate Rome, which was less sympathetic to Monophysitism, and the part of the empire that was then the most threatened. He convened a new council at Chalcedon, on the Asian side facing Constantinople, which condemned Monophysitism in 451. Despite this, Monophysitism prevailed in the eastern provinces, in Syria and Egypt in particular. The holding of the council at Chalcedon, located on the Asian side facing the capital, even suggests that the population of Constantinople might have leaned towards Monophysitism at that time. But the crisis was too deep to be resolved so easily. The population, especially in the countryside, found themselves in contempt of the bishop and the tax collector sent from Constantinople, and Monophysitism became the vehicle for the revival of local Coptic or Syriac cultures. This situation was not without danger, at a time when the Persian Empire was a formidable enemy in the East, quickly replaced by the Arabs.

Furthermore, Monophysitism reached even the Constantinopolitan elites. Justinian’s wife, Empress Theodora, was Monophysite. Several emperors followed suit. Others, especially in the early 7th century when the empire was struggling against the Persians and the Avars, attempted unsuccessfully to find compromises. The problem was ultimately resolved by the loss of the Monophysite regions, conquered in about a decade by newcomers: the Muslim Arabs, who would change the religious landscape of the Near East and Africa.

The veneration of the images and the iconoclastic crisis.

The veneration of the images.

The divine law given to Moses forbids graven images, the representation of God’s creatures, and the worship of them. These commandments are strictly followed by the Jewish and Muslim religions, and by the most rigorous Christians. This results in the absence of sculptures, even in the round, in the churches of Eastern Christianity, and contributes to the disappearance of the art of statuary inherited from antiquity, reducing it to a minor art in Byzantium.

However, there is not unanimous agreement on representations in the form of painting or mosaic, and from the earliest days of Christianity, images are present in churches. Indeed, they serve to illustrate the sacred history for a mostly illiterate population, thus providing access to the Holy Scriptures indirectly. According to the Fathers of the Church (the great theologians of the 4th and 5th centuries), these images are not objects of any particular devotion, unlike the imperial portraits present in the empire, which are venerated and honored with lights and incense. At the time, the only objects that were worshipped were the relics of martyrs, and later of holy men.

But from the 6th century onwards, the situation changes. Portraits of holy men are made during their lifetime. Images, like relics, acquire miraculous powers. They first spread in the private sphere, then become public and take on considerable importance. Some images are even reputed to be acheiropoieta, not made by human hands. Others are carried in procession, such as that of the Protectress of Constantinople before the walls of the capital during the siege by the Avars in 626. The image thus acquires power in itself and becomes an intermediary between God and men in place of the emperor, whose military defeats and loss of the greater part of the empire have deprived him of much of his credibility. The idea of seeking help from these objects is all the more prevalent because the belief in the presence of divine forces in these material objects is deeply rooted in the Greco-Roman world, long before Christianity.

The first iconoclasm, the councils of Hieria and Nicaea.

Leo the Isaurian, who ascended the throne in 717, aimed to rally support during the Arab siege of Constantinople. He decided to remove images from churches and worship starting in the 730s, aligning with his clergy’s concerns, especially in Asia Minor. His victories against the Arabs allowed him, and later his son Constantine V, to enforce this doctrine at the Council of Hiereia in 754. Iconoclasm became the empire’s official doctrine. The issue centered on whether Christ could be represented in images, extending to the Virgin and saints. Theologically, if the image shows both natures of Christ, it confuses them, making it Monophysite. If it depicts only Christ’s human nature, it separates them, making it Nestorian. Iconoclasm only allowed symbolic representations of divinity: the Cross, the Eucharist, and the Word.

Facing imperial policy, voices are raised in defense of images. The main figure of the movement is John of Damascus, a former caliphate official who retired to a monastery in Palestine. Located outside the Empire, he can write freely. In his view, the incarnation makes God representable: Christ is the icon of the Father. He turns the iconoclastic argumentation: since Christ is perfectly man, he can be represented; otherwise, one is a monophysite, because one confuses the two natures. If one can represent Christ, one can represent the Virgin and the saints. To counter the accusation of idolatry, John distinguishes the image, a material object, and what it represents. The image is not the object of a cult, but of a simple veneration. The honor that is given to it goes back to what it represents. These two conceptions of the divine prove to be irreconcilable.

However, the victories won by the iconoclast emperors Leo III and Constantine V give them increased authority. The Byzantine ecclesiastical hierarchy ends up bending to the imperial will and its progressive renewal is in favor of iconoclasts. The only serious opponents are the monks who are refractory to iconoclasm. One of the reasons for their resistance is that many monasteries live on the pilgrims who are attracted to them by the images and relics they hold. The emperors have the monks of the resistant monasteries secularized and dispersed. Constantine V organizes a mockery at the Hippodrome of Constantinople where the monks and nuns, stripped of the monastic habit and returned to the world, are paraded on the track by couple, a man and a woman, holding hands, to signify that they are reintegrating into ordinary society. The persecutions are more vexatious than violent. Those whom the later iconodule sources make martyrs, such as Stephen the Younger, are in fact condemned for conspiracy or for lèse-majesté (Stephen thus reconstituted a dissolved monastery in prison, and trampled on a coin with the imperial effigy).

However, the entire population does not support iconoclasm. It also faces opposition from the papacy, which turns to the Carolingians, threatening the last Byzantine possessions in Italy. To break this isolation, Empress Irene, regent in the name of her son Constantine VI, decides to restore the cult of images. She convenes a new council, with the support of the pope, at Nicaea in 787 – the population of Constantinople is uncertain because it has become majority iconoclast.

The second iconoclasm and the definitive restoration of images.

However, the iconodule emperors who succeed one another suffer defeats after defeats against the Bulgars. In 813, they even besiege Constantinople and the panicked population rushes to the tomb of Constantine V, iconoclast but victorious. In 815, Leo V reinstates the Council of Hieria, while admitting that the cult of icons cannot be called idolatry. His two successors pursue this policy, the ecclesiastical hierarchy is again purged and a few monks enter into resistance again. But this second iconoclasm does not have the vigor and unity of the first. In 843, another empress, Theodora, regent for her son Michael III, has the cult of images definitively restored, an event that has since been celebrated as a feast in the Orthodox Church.

The consequences of this crisis are deep and lasting, both for the life of the Byzantines and for their art. Portable icons multiply in homes, and their models are standardized. The walls of the churches are again covered with frescoes and mosaics, according to a program that is gradually fixed: the Christ Pantocrator is imposed in the dome and the Virgin in the apse, the portraits of the saints flourish on the walls. In parallel, the pilgrimage of relics experiences a new boom.