Augustine of Hippo provided the church with a number of crucial phrases. We have the phrase ex nihilo, meaning that creation was made out of nothing. Another phrase that Augustine gave us is not only important for the church but actually one that’s important for political philosophy. The Latin expression is jus ad bellum, or “just war.”
Augustine’s thinking on the topic grew out of his circumstances. In 410, as the Visigoths were laying waste to Rome, the Romans blamed the Christians and their refusal to participate in the civic religion for the city’s downfall. Augustine wrote an apologetic response: The City of God. In this book, Augustine provides helpful guidance for thinking about what it means to be a Christian in challenging times. But he also sketches out his idea of a just war. He laid out two components to his theory of just war: the first concerned legitimate reasons for going to war, and the second concerned how a state or a military ought to conduct itself in order to wage war in a just manner.
These were important questions for Christians. Many Christians up until Augustine’s day were pacifists, based on their reading of the sixth commandment—“Thou shalt not kill.” Augustine thought about the issue a little bit differently. His reading of the New Testament, and particularly regarding Christians’ obligation to the state as outlined in Romans 13, led him to believe that the state does have an obligation in waging war. So he moved away from a pacifist understanding of war. But how are we as Christians to approach the topic of war from a Christian perspective? This is where Augustine helps us. The first thing he does is ask how we are to think about war and about the point of war. It sounds counterintuitive, but this is what Augustine says: “We wage wars because we are interested in peace. It is ultimately peace that we seek, not war, and war is a means not to itself, but it is a means to peace.” He goes on: “For it is the wrongdoing of the opposing part which compels the wise man to wage just wars, and this wrongdoing, even though it gave rise to war, should still be a matter of grief to man because it is man’s wrongdoing. Let everyone, then, who thinks with pain on all these great evils—so horrible, so ruthless—acknowledge that this is misery.” Augustine is saying that war is misery, but it is necessary for peace.
In thinking about war, Augustine lays out criteria for a just war, reasons why a nation should go to war. He makes the case that, first of all, war should be a last resort. Are there other options? States should exhaust diplomatic options before going to war. He then asks, what are the parameters of war? He talks about whether the war will end once the cause for the war is avenged and the reason for the war is accomplished. He asks if there has been a wrong committed that warrants a war. Then he asks, is force used properly? In a war, there should be a distinction between combatants and noncombatants, and civilians should be protected. In asking these questions, Augustine helped us as Christians to think about just war.