The distinction between Christianity and Christendom is not widely understood. Christianity is the faith of those who seek to follow Jesus of Nazareth and declare him to be the Son of God - a claim in direct contention with Caesar's progeny.
The result is a religion of radical reconciliation, communal meals, reversing social expectations and blessing the poor. In contrast, Christendom is what Christianity became when it got mixed up with the Roman Empire.
It was an unlikely alliance. Some early Christians like Tertullian defined Christianity self-consciously in opposition to the values of the Roman state. After all, it was the Romans that murdered Christ in the first place.
Early Christians had been pacifists and had refused to serve in the army. In contrast, the Romans were a highly militarised and authoritarian culture that had subdued most of the known world by force.
Christianity became the official religion of the Roman Empire with the conversion of the emperor Constantine in AD 312 at the battle of Milvian Bridge, after which the church began to back pedal on the more radical demands of the adult Christ.
The Nicene Creed, what came to be the official version of Christianity, was composed in AD 325 under the sponsorship of Constantine. The creed conveniently skips over the political aspects of Christ‚Äôs teaching, jumping from birth to death:
‚ÄúWho for us and for our salvation came down from heaven. And was incarnate of the Holy Ghost and of the Virgin Mary and was made man; was crucified also for us under Pontius Pilate, suffered and was buried; and the third day rose again according to the Scriptures.‚Äù
It was Constantine who decided that 25 December was to be the date on which Christians were to celebrate the birth of Christ and it was Constantine who ordered the building of the Church of the Nativity at Bethlehem. Christmas ‚Äì a festival completely unknown to the early church ‚Äì was invented by the Roman emperor.
The question for Christians is whether the Roman Empire effectively subdued Christianity and absorbed it into the imperial cult. As many have argued, the ethics and theology of Christendom might be said to bear precious little resemblance to the simple and radical faith of a carpenter from Galilee.
And it‚Äôs certainly the case that Christianity has been readily appropriated for the defence of, for example, the divine right of kings and the feudal ordering of society.
Within a century of Constantine‚Äôs conversion, St Augustine would develop the novel idea of just war, trimming the church‚Äôs originally pacifist message to the needs of the imperial war machine.
From Constantine onwards, the radical Christ worshipped by the early church would be pushed to the margins of Christian history to be replaced with the infinitely more accommodating religion of the gurgling baby and screaming victim. Neither version of Jesus was able to disturb the Empire with political rhetoric.
Yet it should be perfectly obvious to anyone who has actually read the Christmas stories that the gospel regards the incarnation as challenging the existing order.
The pregnant Mary anticipates Christ‚Äôs birth with some fiery political theology: God ‚Äúhas brought down the powerful from their thrones and lifted up the lowly, he has filled the hungry with good things and sent the rich away empty‚Äù, she blazes.
Born among farm labourers, yet worshipped by kings, Christ announces an astonishing reversal of political authority. The local imperial stooge, King Herod, is so threatened by rumours of his birth that he sends troops to Bethlehem to find the child and kill him. Herod recognised that to claim Jesus is lord and king is to say that Caesar isn‚Äôt.
The story of Christmas, properly understood, asserts that God is not best imagined as an all-powerful despot but as a vulnerable child, born into a disgraced family of asylum seekers. It‚Äôs a statement about the truly subversive nature of divine power.
But in the hands of Christendom, Christmas became a way of distracting attention from the teachings of Christ. It became a form of religion that concentrates on things like belief in the virgin birth while ignoring the fact that the gospels are much more concerned about the treatment of the poor and the forgiveness of enemies.
If it‚Äôs true that Christendom has held Christianity captive for several centuries, there may be hope for a more radical Christianity in the whole process of secularisation.
For what secularisation specifically attacks is state religion, the religion of Christendom. Post-Christendom provides an opportunity for a very different Christian voice to emerge. A Christianity whose priorities are much more those of the prophetic Jesus ‚Äì good news to the poor, freedom to the captive, sight to the blind.
This is a slightly revised version of an article which first appeared in Socialist Worker newspaper.