Just War

Bec Owens


St Augustine wrote two criteria for Just war, but Aquinas is credited for writing them clearly and adding the philosophy. He also contributed the third criteria, ‘right intention’. Other Christian philosophers debated new criteria over the next 500years and eventually, five rules were agreed


The war must be started and controlled by the state or its ruler (e.g. a king). This is called the ‘legitimate ruling authority'.

This tends to rule out most civil wars and terriost campaigns as the ruling authority may be in question or because there is no process for determining the people's will regarding the war. The condition goes back to Aquinas and before him, Augustine.


There must be a just cause with a chance of winning e.g. In World War 2, the allies decided the cause was just, and defended countries from German attack.

This does not necessarily rule out hopeless wrs if the values involved are important enough, but again demands a careful assessment of the consequences.


War must be a last resort after all options have been negotiatiated such as statements of intent, negotiations, police actions short of open warfare and have a good chance of excess. For example, in World War 2, the allies believed they had tried all means of negotiation and have been duped.


The war must be to promote good and overcome evil. Peace and justice must be restored quickly. This involves weighing any justice of the cause against the evils of violence, destruction, suffering and death that will inevitably flow from war. The good must outweigh the evil.


Only enough force should be used as is absolutely necessary to achieve peace. Innocent civilians should not be attacked. The good to be achieved must never be out of proportion to the means used.


The reasons for going to war must be good in themselves. they must not be conquest for the sake of exploiting the enemy's territory or people, but self-defence against a real and present threat. This condition goes back to Aquinas and before him, Augustine.


There must be no unresasonable conditions, such as unconditional surrender, cession of territory or means of livelihood, added to the original war aims.