Conflict and the Just War Theory

While both Christianity and Islam teach the importance of peace, both traditions also recognise that there are circumstances in which conflict may be necessary. The Just War theory attempts to define the conditions under which war can be morally justified. This lesson explores the origins, criteria, and religious perspectives on the Just War theory.

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What is the Just War Theory?

The Just War theory is a set of criteria that must be met for a war to be considered morally justified. It was developed primarily within the Christian tradition but has parallels in Islamic thought.

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History of the Just War Theory

Thinker	Contribution
St Augustine (354-430)	First major Christian to argue that war could be justified in certain circumstances — to restore peace and punish wrongdoing
St Thomas Aquinas (1225-1274)	Developed three main conditions for a just war: legitimate authority, just cause, and right intention
Francisco de Vitoria (1483-1546)	Added further conditions including proportionality and the protection of civilians
Modern development	The Just War criteria have been expanded and refined over centuries

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Criteria for a Just War

Jus ad Bellum (Right to Go to War)

Criterion	Explanation
Just cause	There must be a valid reason for going to war (e.g. self-defence, protecting the innocent, resisting aggression)
Legitimate authority	War must be declared by a proper authority (e.g. a government), not by individuals or private groups
Right intention	The aim must be to promote good and overcome evil, not for revenge, conquest, or economic gain
Last resort	All peaceful alternatives (diplomacy, sanctions, negotiation) must have been exhausted
Proportionality	The anticipated benefits of war must outweigh the expected harm
Reasonable chance of success	There must be a realistic prospect of achieving the just aims

Jus in Bello (Right Conduct During War)

Criterion	Explanation
Proportionality	The force used must be proportionate to the threat — no excessive destruction
Discrimination	Civilians and non-combatants must not be deliberately targeted
No prohibited weapons	Weapons that cause unnecessary suffering (e.g. chemical weapons) must not be used
Treatment of prisoners	Prisoners of war must be treated humanely

Jus post Bellum (Justice After War)

• The defeated side should be treated with fairness and dignity
• Peace settlements should address the root causes of the conflict
• Reconstruction should be supported

graph TD
    A["Just War Theory<br/>(Augustine, Aquinas)"] --> B["Jus ad Bellum<br/>(right to go to war)"]
    A --> C["Jus in Bello<br/>(right conduct in war)"]
    A --> D["Jus post Bellum<br/>(justice after war)"]
    B --> B1["Just cause"]
    B --> B2["Legitimate authority"]
    B --> B3["Right intention"]
    B --> B4["Last resort"]
    B --> B5["Proportionality"]
    B --> B6["Reasonable chance<br/>of success"]
    C --> C1["Proportionality"]
    C --> C2["Discrimination<br/>(no targeting civilians)"]
    C --> C3["No prohibited weapons"]
    C --> C4["Humane treatment<br/>of prisoners"]
    D --> D1["Fair treatment of defeated"]
    D --> D2["Address root causes"]
    D --> D3["Support reconstruction"]

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Christian Views on War

View	Position
Just War supporters	War can be morally justified if it meets the Just War criteria — most mainstream denominations accept this
Pacifists	All war is wrong — Christians should never fight. Supported by Quakers and some other groups
Realists	Sometimes war is necessary and inevitable in a fallen world

"If it is possible, as far as it depends on you, live at peace with everyone." (Romans 12:18)

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Islamic Views on War

Islam has its own criteria for justified conflict, which closely parallel the Just War theory:

Criterion	Islamic Teaching
Defensive only	War is only permitted in self-defence or to protect the oppressed
Last resort	All peaceful means must have been tried first
Legitimate authority	Only a recognised Muslim leader can declare war
No targeting civilians	Women, children, elderly, and religious leaders must not be harmed
Proportionate	Excessive force is forbidden
Accept peace	If the enemy offers peace, Muslims must accept

"Fight in the way of Allah those who fight you but do not transgress." (Surah Al-Baqarah 2:190)

"If they incline to peace, then incline to it." (Surah Al-Anfal 8:61)

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Evaluation: Is the Just War Theory Useful?

Arguments For	Arguments Against
It provides clear moral guidelines for when war is acceptable	In practice, the criteria are difficult to apply — who decides what is "just"?
It limits the destruction of war by requiring proportionality and civilian protection	Both sides in a conflict usually claim their war is just
It has influenced international law (Geneva Conventions)	Modern warfare (drones, cyber attacks) makes some criteria hard to apply
It offers a middle ground between pacifism and unlimited war	Some argue that no war can truly be "just"

Exam Tip: The Just War theory is one of the most commonly examined topics. Make sure you can list the criteria, explain them, and evaluate whether the theory is effective in practice.

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Summary

The Just War theory attempts to define the conditions under which war can be morally justified. Both Christianity and Islam recognise that while peace is the ideal, there are situations in which conflict may be necessary to protect the innocent or resist oppression. The theory provides important moral guidelines but faces challenges in practical application, particularly in the context of modern warfare.

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Worked Example: The 2003 Iraq War — Just or Unjust?

Consider this famous case study. In 2003, the United States and the United Kingdom invaded Iraq, arguing that Saddam Hussein possessed weapons of mass destruction (WMD) and posed a threat to global security. The war was controversial at the time and remains hotly debated. A parish priest, an imam and a politics teacher are asked to apply the Just War criteria.