Just War Theory

Just war theory is the tradition that seeks to specify the conditions under which going to war can be justified and the moral limits on how war may be fought.

Definition

A normative framework for evaluating the morality of resorting to war and of conduct within war through a set of established criteria.

Scope

This topic covers the standard categories of just war theory: jus ad bellum (just cause, legitimate authority, right intention, proportionality, reasonable prospect of success, last resort), jus in bello (discrimination between combatants and non-combatants, proportionality, and the doctrine of double effect), and the more recently discussed jus post bellum (justice after war). It also covers the traditionalist-revisionist dispute. It describes the criteria and debates rather than judging particular wars.

Core questions

• What conditions must be satisfied for a resort to war to be just?
• What constraints govern morally permissible conduct in war?
• Are the criteria for going to war independent of those for fighting it?
• What is owed once a war has ended?

Key theories

The independence of ad bellum and in bello

The traditional view, defended by Walzer, that the justice of resorting to war and the justice of conduct in war are logically independent, so that soldiers on an unjust side can still fight justly.

Revisionist critique

McMahan argues that in bello permissions depend on ad bellum justice, so combatants fighting for an unjust cause cannot, in general, kill permissibly merely by following the rules of conduct.

History

The just war tradition developed from classical and Christian sources—Cicero, Augustine, and Aquinas—and was systematized by early modern jurists such as Grotius. Walzer's 1977 work renewed it for secular ethics, and the early-twenty-first-century revisionist movement, led by McMahan, reexamined its foundations.

Debates

Traditionalism versus revisionism

Traditionalists uphold the moral equality of combatants and the independence of the two sets of criteria, while revisionists argue moral permissions in war track individual liability and the justice of the cause.

Key figures

• Michael Walzer
• Jeff McMahan
• Brian Orend
• Thomas Aquinas

Seminal works

• walzer1977
• mcmahan2009

Frequently asked questions

What are the main jus ad bellum criteria?

Commonly listed criteria include just cause, legitimate authority, right intention, proportionality, reasonable prospect of success, and last resort.

What is the principle of discrimination?

Within jus in bello, discrimination requires distinguishing combatants from non-combatants and not making non-combatants the object of attack; debates concern its scope and the doctrine of double effect.