The just war tradition in Christianity and its continuing relevance

What is a just war?

A just war is a war which is declared for right and noble reasons and fought in a certain way. A just war is not a war that is ‘good’ as such. It is a war that Christians feel to be necessary or 'just' in the circumstances, when all other solutions have been tried and have failed. It is a necessary evil and a last resort.

Christianity is not a pacifist religion, although there are pacifists in most Christian denominations. Some Christian groups - eg the Religious Society of Friends (Quakers) - oppose war in all circumstances.

Most Christians would support a war if it were justified by just war standards.

The just war theory was first developed by St Thomas Aquinas. Aquinas was one of the most influential theologians of the last 1,000 years. The theory set out conditions against which to judge the following:

  • whether or not a war should be waged - jus ad bellum (Latin for 'right to war')
  • if a war could be justified, and how it should be waged - jus in bello (Latin for 'the law in waging war')

Aquinas's conditions for a just war – jus ad bellum

  • The war must have a just cause - eg against invasion or for self-defence - and not to acquire wealth or power.
  • The war must be declared and controlled by a proper authority, eg the state or ruler.
  • The war must be fought to promote good or avoid evil, with the aim of restoring peace and justice after the war is over.

Later conditions developed by other Christians - jus in bello

  • The war must be a last resort when all peaceful solutions have been tried and failed, eg negotiation.
  • The war should be fought with proportionality. There should be just enough force to achieve victory over legitimate targets, ie civilians should be protected.
  • The good which is achieved by the war must be greater than the evil which led to the war.
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The just war theory, with some amendments, is still used by Christians and others today as a guide to whether or not a war can be justified.