During Christianity’s early years, as the church moved from being a series of transitional movements to a collection of settled institutions, a blurring occurred in the distinction between Pax Christi, the kind of peace made possible by Jesus the Son of God, and Pax Romana, the kind of peace made possible by the Emperor and his progeny.
In fact they were very different. The former was based on the sacrificial love of a community of disciples. It was prepared to lay down life for the sake of right, but not take it. The latter, by contrast, consisted of armed quietude and occupation.
Moreover, the very person of Jesus embodied a direct challenge to the violent basis of imperial power. The title "Son of God" was one used by the Emperor for his own heir, seeking to invest his earthly domination with a divine aura. In using the title for their Saviour, early Christians were claiming primacy for the power of love over the love of power.
However, over time, many Christian communities learned to "make peace" of a different kind with the type of ruling authority that ended up killing Jesus - but which could not quench the endless life enfleshed in him.
It would be foolish to blame all of this on Constantine and the Edict of Milan, signed with Licinius, which proclaimed religious toleration across the Roman Empire. Nevertheless, what happened in CE 313 lead to the establishment of Christianity alongside other beliefs and an increasing acceptance of the ethics of Caesar as the defining ‘reality’.
This proved a fateful shift, and for over 1700 years, "majority churches", including Catholic and Protestant ones in the West and the Orthodox of the East, have accepted (with varying degrees of enthusiasm) a variety of deals whereby the ruling worldly order is blessed in exchange for power, privilege and protection.
It is this era that is ending in Britain and elsewhere in Europe. The establishment of the Church of England under the Crown is the residual, attenuated vestige of this settlement, along with bishops in an unelected second parliamentary chamber and a raft of arrangements (including, until recently, blasphemy laws) which are gradually being unravelled in public life.
Post-Christendom, says Stuart Murray in his book which launched the Paternoster Press series under that title, “is the culture that emerges as Christian faith loses coherence to a society that has been definitively shaped by the Christian story and as the institutions that have been developed to express Christian convictions decline in influence.”
Many Christians are upset about this loss of Christianity’s ‘cultural power’ within society. But the other way of looking at it is that it represents a great opportunity to recover the moral and spiritual vision of the church as a discipleship community - one seeking to witness to the way of Christ not by being a functionalist institution propping up the social order, or a world-denying sect, leaving it untouched; but an agent of transformation alongside those who the crucified and risen Jesus identified with most – the last, the lost and the least.
The shift to a post-Christendom situation, while uncertain and difficult in many ways, therefore involves the possibility of a relocation of the church from the centre to the margins (where it first grew); from majority to minority; from settlement to sojourning; from privilege to plurality; from institution to movement, and from maintenance to mission.
The biggest change, as far as Christian peacemaking is concerned, is that it means re-instituting the category of ground up witness above that of top-down control. If the Gospel of peace is to have credibility, we must respond to those who are saying “don’t tell me, show me”.
The word ‘witness’ comes from the New Testament word martyria, from which we get ‘martyrdom’ – being prepared to lay down life for what is true, rather than to compel or dominate others. This is personally and politically highly demanding. It is the way adopted by Christian Peacemaker Teams (CPT), for example, who seek to ‘get in the way’ of war, violence and oppression and to work non-violently with those searching for alternatives, rather than simply waiting for governments and guerrillas to ‘give peace a chance’ or pleading with them from the sidelines.
After Christendom there is both fresh hope and fresh challenge for Christian peacemaking. The core question is: “how is peace written into the fabric our lives and our Christian commitment?”, not “OK, I’m a Christian. Now, what sort shall I decide to be, a pacifist or a just warrior?”
If 'just war' means “just another war”, the defence of “Christian Empire” or the overwhelming conformity of the church to an ethic promulgated by the modern delegates of Caesar, then it is the wrong path.
If, however, it is a way of moving away from violence those who cannot yet recognise the fullness of the peace Christ offers – a kind of Christian equivalent to the lex talionis (the Jewish law for limiting retribution), then it has a role to play. Not as an end in itself, but as part of a journey whose destiny is the shalom, the just-peace, that is realised in and as the Body of Christ, shaped by Jesus and the great Hebrew prophets.
The point is this: the Body of Christ is a broken body offered unconditional life by God, not life grabbed at the expense of entrapping others in death. To be baptised into this body is to share a life in Christ that is brought about by grace not guns.
To me it makes no sense at all to claim be joined to a New Community through baptism, to pass from death to life with Christ, and still to be willing to kill other members of that same, redeemed body; or indeed to kill others on behalf of the body (and thus betray its meaning and origins).
When we understand what our baptism really means, Christian peacemaking becomes received as the essence of Christian faith, not an “ethical add on” or the conclusion of a squabble about certain New Testament passages.
So after Christendom we are called to reassess in a core sense what it means to be church, to be that body; what is means to be a peacemaker rather than just a refuser of war (a passivist); what political realism looks like in the face of Christ, rather than in the image of the Imperial Order and its realpolitik.
A new, costly boldness becomes possible on this basis. Having lost our investment in the ruling order, we as people of faith are freed to live out a different way, communally and politically, which does not have to wait for the permission or approval of ‘the powers that be’. To be the "fellowship of reconciliation" we proclaim and long for, in other words, and to devise strategies to show how political order can be rebuilt on that basis.
This is an abbreviated version of a talk given to the Fellowship of Reconciliation (FoR - http://www.for.org.uk/ ) England's Annual Council in Oxford earlier in 2008. The author has also contributed a chapter, along with Tim Nafziger, to 118 Days: Christian Peacemaker Teams held hostage in Iraq, edited by Tricia Gates Brown and available here: http://tinyurl.com/3z6pqm  Later in 2008, he will publish Threatened with Resurrection: The difficult peace of Christ.
(c) Simon Barrow is co-director of Ekklesia. He blogs at http://faithinsociety.blogspot.com  and his website is at http://www.simonbarrow.net . His latest book Fear or Freedom? Why a warring church must change  is published by Shoving Leopard / Ekklesia.