Just War and Pacifism

Just War and Pacifism

The ethics of war is one of the oldest and most consequential areas of moral philosophy. Can war ever be morally justified, or is all violence inherently wrong? This lesson examines the just war tradition — from its origins in Augustine and Aquinas through to modern international humanitarian law — and contrasts it with the pacifist tradition, particularly Christian pacifism and the witness of the Quakers. The lesson also considers the challenges posed by modern warfare, including nuclear weapons, terrorism, and humanitarian intervention.

The Just War Tradition: Origins

The just war tradition holds that war, while always regrettable, can sometimes be morally justified — and that when it is waged, it must be conducted according to strict moral rules. The tradition has its roots in ancient philosophy (Cicero, Aristotle) and was developed systematically by Christian theologians.

• St Augustine of Hippo (354–430) is regarded as the father of just war theory. Writing in the context of the declining Roman Empire, Augustine argued that war could be justified to restore peace, protect the innocent, and punish wrongdoing. Christians, he held, could serve as soldiers without sin, provided the war was authorised by legitimate authority and waged with the right intention (love of neighbour, not hatred or greed). Augustine\'s key insight was that the use of force could be an act of love — defending the innocent from aggression is a form of neighbour-love.
• St Thomas Aquinas (1225–1274), in the Summa Theologica (II-II, Q.40), systematised just war theory by establishing three conditions that must be met for a war to be just:
  • Legitimate authority (auctoritas principis): War must be declared by a legitimate sovereign authority — not by private individuals or groups.
  • Just cause (causa justa): There must be a genuine wrong to be righted — typically aggression, the violation of rights, or the defence of the innocent.
  • Right intention (intentio recta): The war must be waged with the intention of establishing peace, not for conquest, revenge, or material gain.

Jus ad Bellum — Justice of Going to War

Later thinkers expanded Aquinas\'s three conditions into a more comprehensive set of criteria for determining whether it is just to go to war (jus ad bellum):

• Just cause: War must be fought for a morally legitimate reason — self-defence against armed attack, protection of the innocent from genocide or ethnic cleansing, or the recovery of territory unjustly seized. Aggressive war — war waged to conquer, dominate, or exploit — is never just.
• Legitimate authority: The decision to go to war must be made by the proper governmental authority. In modern international law, this typically means either a state acting in self-defence (Article 51, UN Charter) or military action authorised by the UN Security Council.
• Right intention: The aim of the war must be to establish a just and lasting peace, not to pursue national aggrandisement, economic gain, or revenge.
• Last resort: War is justified only when all peaceful alternatives — diplomacy, negotiation, economic sanctions, mediation — have been exhausted or are clearly futile.
• Proportionality: The anticipated benefits of the war (e.g., ending aggression, preventing genocide) must outweigh the expected costs (military and civilian casualties, destruction, economic disruption).
• Reasonable chance of success: It is unjust to wage a war that has no reasonable prospect of achieving its objectives, as this would entail pointless suffering and death.

Jus in Bello — Justice in the Conduct of War

Even when a war is justly entered, it must be fought justly. Jus in bello governs the conduct of hostilities:

• Discrimination (non-combatant immunity): Combatants must distinguish between military targets and civilian non-combatants. Deliberate attacks on civilians are always prohibited. This principle is codified in the Geneva Conventions (1949) and their Additional Protocols (1977).
• Proportionality in means: The force used must be proportionate to the military objective. The use of excessive or indiscriminate force — such as the carpet-bombing of cities or the use of chemical weapons — violates jus in bello.
• No intrinsically evil means: Certain weapons and tactics are inherently immoral — including biological weapons, chemical weapons, torture, and the deliberate targeting of hospitals, schools, or places of worship.
• Treatment of prisoners: Prisoners of war must be treated humanely and not subjected to torture, degrading treatment, or summary execution (Third Geneva Convention, 1949).

Jus post Bellum — Justice After War

An increasingly important component of just war theory is jus post bellum — the moral obligations that arise after the conclusion of hostilities:

• Just peace terms: The peace settlement must be proportionate and not vindictive. The Treaty of Versailles (1919), which imposed crippling reparations on Germany, is widely cited as an example of unjust peace terms that contributed to the rise of Nazism and the Second World War.
• Reconstruction: The victorious power has a moral obligation to assist in the reconstruction of the defeated state — restoring infrastructure, governance, and civil society.
• Accountability: War crimes and crimes against humanity must be investigated and prosecuted. The Nuremberg Trials (1945–46), the International Criminal Tribunal for the former Yugoslavia (1993–2017), and the International Criminal Court (established 2002) embody this principle.
• Reconciliation: Long-term peace requires reconciliation between former enemies — truth commissions, reparations, and processes of national healing.