When is a war just, for Aquinas? (ST II-II, q. 40, a. 1)

Summa article explained, no. 5. A paraphrase and reading guide, not a translation.

The short answer. Aquinas says three things are necessary for a war to be just: the authority of the sovereign who commands it, a just cause (those attacked deserve it because of some fault, such as refusing to right a wrong), and a right intention (to advance good or avoid evil, aiming at peace). A wicked intention can still make it unlawful.

Where this sits in the Summa

Question 40 belongs to the treatise on charity in the Second Part of the Second Part. War is treated among the vices opposed to peace, which is an effect of charity. That placement is the first lesson: Aquinas asks about war as a question of love of neighbour and peace, not of strategy. The question has four articles: whether it is always sinful to wage war (a. 1), whether clerics may fight (a. 2), whether ambushes are lawful (a. 3), and whether one may fight on holy days (a. 4).

The objections

Aquinas lets the Gospel speak first.

1. "All that take the sword shall perish with the sword" (Matthew 26:52). Punishment is only for sin, so war is sinful.
2. "Do not resist evil" (Matthew 5:39) and "Not revenging yourselves" (Romans 12:19). War goes against a divine precept.
3. War is contrary to peace. Only sin is contrary to an act of virtue.
4. Tournaments are forbidden. The Church denied church burial to those killed in tournaments. If the exercise of war is forbidden, war itself seems sinful.

Sed contra

Augustine, in his letter to Marcellinus: if Christianity forbade war altogether, the soldiers who asked John the Baptist for advice would have been told to lay down their arms. Instead they were told, "Do violence to no man... and be content with your pay" (Luke 3:14). He did not forbid soldiering.

Respondeo: three conditions

1. The authority of the sovereign. A private person may not declare war, because he can seek redress from a superior's court, and he has no right to summon the people to arms. Those entrusted with the common good may use the sword against wrongdoers within (Romans 13:4) and so also against enemies without. Augustine (Contra Faustum xxii, 75): the power to declare and counsel war belongs to those who hold supreme authority.
2. A just cause. Those attacked must deserve it on account of some fault. Augustine's formula: a just war avenges wrongs, as when a nation must be punished for refusing to make amends for wrongs its subjects committed, or to restore what it seized unjustly.
3. A right intention. The belligerents must intend the advancement of good or the avoidance of evil. Aquinas quotes a text he attributes to Augustine (the Dominican translators note it is in fact from canon law, not Augustine): true religion counts as peaceful those wars waged not for aggrandisement or cruelty but to secure peace, punish evildoers and uplift the good. And from Contra Faustum xxii, 74, the things rightly condemned in war: "the passion for inflicting harm, the cruel thirst for vengeance, an unpacific and relentless spirit, the fever of revolt, the lust of power".

The conditions are cumulative. A war declared by the right authority, for a just cause, can still be rendered unlawful by a wicked intention.

The replies

• To the first. To "take the sword" is to arm yourself to take a life without the command or permission of lawful authority. To use it on the authority of the sovereign or a judge is not to take it but to use it as commissioned.
• To the second. Those precepts should always be held in readiness of mind, so that we are ready not to resist when that is right. But sometimes we must act otherwise for the common good, or even for the good of those we fight.
• To the third. Those who wage war justly aim at peace, and oppose only the evil peace. Augustine to Boniface: "we go to war that we may have peace."
• To the fourth. Not all martial exercises are forbidden, only the disordered and dangerous ones that end in killing or plunder.

Two neighbouring texts worth reading with it

• Ambushes (q. 40, a. 3). Deceiving the enemy by telling something false or breaking a promise is always unlawful: there are rights of war and covenants that bind even among enemies (Ambrose). Concealing your plans is lawful. The same line between lying and keeping back the truth appears in the article on lying (II-II, q. 110, a. 3).
• Self-defence (q. 64, a. 7). One act can have two effects, only one intended. Defending your life may have the effect of killing the attacker. The act is lawful if the intention is to save your life and the force is proportionate; more violence than necessary makes it unlawful. This article is the usual starting point for what later moralists called the principle of double effect.

How it lines up with the Catechism

The Catechism treats war under "safeguarding peace" (CCC 2302-2317). It calls for every effort to avoid war (2308) and sets out "strict conditions for legitimate defense by military force" (2309), all to hold at once: the damage inflicted by the aggressor must be "lasting, grave, and certain"; all other means of ending it must have proved "impractical or ineffective"; there must be "serious prospects of success"; and the use of arms must not produce "evils and disorders graver than the evil to be eliminated", where "the power of modern means of destruction weighs very heavily". It names these as "the traditional elements enumerated in what is called the 'just war' doctrine", and says their evaluation belongs to the prudential judgment of those responsible for the common good.

It adds that the moral law stays valid during conflict (2312), that non-combatants, the wounded and prisoners must be treated humanely and that orders to commit genocide must be resisted (2313), and that indiscriminate destruction of cities and their inhabitants "is a crime against God and man" (2314).

Common misreadings

• "Aquinas invented just war theory." He builds on Augustine, whom he quotes at every step, and on canon law.
• "Aquinas has seven criteria." He names three. Proportionality, last resort and probability of success, as listed today, come from the later tradition and are now set out in CCC 2309.
• "Just cause means any national interest." In the article it means a fault that deserves redress: a wrong not righted or something seized unjustly.

How to work this article in Aquinian Studio

Take a contested case and put it in disputation form: "Whether a war of pre-emption can have a just cause?" Aquinian distinguishes the terms first, orders the authorities from Scripture through Augustine, Aquinas and the Catechism, and states the strongest objection before it determines. Investigate then tests the determination in a second pass. It reasons with authority; it does not become authority, and it does not decide for a government or a conscience. Check named passages against the primary text before formal use. aquinian.com. New accounts start with 150 free credits, no card.

FAQ

What are Aquinas's three conditions for a just war? The authority of the sovereign, a just cause, and a right intention (Summa Theologiae II-II, q. 40, a. 1).

Does the Catholic Church still teach just war? Yes. The Catechism sets out strict conditions for legitimate defence by military force in CCC 2309 and calls them the traditional elements of the "just war" doctrine.

Is lying to the enemy allowed in a just war? Not according to Aquinas. Concealing plans is lawful, but telling something false or breaking a promise is always unlawful (Summa II-II, q. 40, a. 3).

Sources

Summa Theologiae II-II, q. 40, aa. 1 and 3, and q. 64, a. 7, Fathers of the English Dominican Province translation (1920), newadvent.org/summa/3040.htm and 3064.htm. Catechism of the Catholic Church 2302-2317, vatican.va/archive/ENG0015/__P81.HTM.