In the following paragraph the theologian Duncan Forrester explains how just war thinking is ethical and has become divorced from theological reflection:
Just war theory is a way of thinking which has its roots in pre-Christian classical philosophy and Christian metaphysics. It is ethical rather than theological, and precisely because it does not presuppose any religious commitment or involve an explicit dogmatic element it often commends itself as peculiarly appropriate in a secular age. But for centuries just war thinking was conducted within the theological framework, and when it is detached from that framework it becomes liable to subtle but significant modification. The theological frame affirmed that war and violence call for repentance and need forgiveness, despite the fact that in a fallen world we must expect conflict to take place. Thus the Norman knights who triumphed at the Battle of Hastings in a cause that had been declared just by the Pope himself were still required to do penance for having shed human blood. Just war considerations were used to discourage recourse to violence (ius ad bellum) and to promote restraint in the conduct of war (ius in bello) within the general theological assumption that all participation in war is sinful. The greater the distance that developed between the theology of war and the ethics of the just war the easier it became to regard war as sometimes good, or even holy, rather than always inherently sinful. As just war theory was increasingly detached from classical Christian theology and grafted on to a modern, more optimistic view of human nature and the world, it could offer little effective resistance to the acceptance or glorification of war which springs from seeing the modern ideological war as a Manichean confrontation of absolute good and absolute evil. A theory once intended to express an abhorrence of war often became a means of justifying it.From: Duncan B. Forrester, ‘The Theological Task’, in Ethics and Defence: Power and Responsibility in the Nuclear Age, ed. Howard Davis (Oxford: Basil Blackwell, 1986), 31–32. Reprinted as Duncan B. Forrester, ‘The Theological Task’, in Forrester on Christian Ethics and Practical Theology: Collected Writings on Christianity, India, and the Social Order, Ashgate Contemporary Thinkers on Religion: Collected Works (Farnham: Ashgate, 2010), 358–59.
This implies that Christian thinking about war can take place within a theological framework and that in doing so we can recapture a fuller picture of war and peace than a merely ethical one. To place the problem of war within theology opens up new discussions about the problem of war and the promotion of peace. This is theological work worth pursuing and worth funding.