Principles for becoming engaged in a Just War (jus ad bellum)

Just Cause Principle

Going to war is not justified unless for a just cause such as correcting specific acts of injustice, and defending the innocent from tyrannical aggression

• taught by Plato

Competent Authority Principle

Going to war is not justified unless initiated by the authority of those bearing responsibility for defending and preserving the common good

• began with Cicero, furthered by Augustine

Comparative Justice Principle

Going to war not justified unless for a cause more worthy than the cause opposed

• began with Augustine, furthered by Vittoria

Right Intention Principle

Going to war is not justified unless to restore peace (good order), not to punish, humiliate, win glory, or achieve a social ideal that did not previously exist

• began with Plato, furthered by Augustine

Last Resort Principle

Going to war is not justified unless no realistic non-violent options for solving the problem remain to be considered

• taught by Plato

Probability of Success Principle

Going to war is not justified if winning is futile. Going to war with no chance of winning is irrational, and using force irrationally is never right

• taught by Jesus and further developed by Vittoria

Proportionality of Projected Results Principle

Going to war is not justified unless for something worth more than the cost of achieving it (estimated in the loss of human life and property)

• Thomas Aquinas

Right Spirit Principle

Going to war is not justified unless with regret that what must be corrected can be done no other way. It is never right to go to war with glee, anger, or any attitude other one regarding war to be a tragic necessity

• Augustine