Just War According to Catholic Teaching

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Just War According to Catholic Teaching
The Church teaches that military action is justified as a means of re-establishing order.

After the brutal September 11 attacks, the United States must once again wage a war in a foreign land.

As always, the problem of the legitimacy of using military action for revenge as a means of re-establishing justice comes to the fore. Thus, it is in the interest of our readers to bring to their attention the traditional Catholic doctrine on the subject.

Saint Augustine (354-430)

The great Saint Augustine provided the basis of Catholic doctrine about just war.

Considering whether war is always bad or if there are circumstances when it can be just, he wrote:

According to the Gospel of Saint Luke, Saint John the Baptist preached a baptism of penance inviting all to convert and change their lives. People from all walks of life came to him and asked what they must do to change. This precursor of Christ answered each according to his circumstances. “And the soldiers also asked him, saying: And what shall we do? And he said to them: Do violence to no man; neither calumniate any man; and be content with your pay” (Luke 3:14).

Saint Augustine comments:

If the Christian Religion forbade war altogether, those who sought salutary advice in the Gospel would rather have been counseled to cast aside their arms, and to give up soldiering altogether. On the contrary, they were told: ‘Do violence to no man . . . and be content with your pay.’ If he commanded them to be content with their pay, he did not forbid soldiering.1

Military life is therefore in itself perfectly legitimate. If the military as a cause is legitimate, so also is the military’s end: to wage war.

Nevertheless, the saint argues, there are Gospel precepts like “resist no evil,” or “turn the other cheek,” that seem to condemn the use of force and thus contradict the licitness of military life and subsequently of war.

He replies to these objections by showing how these precepts apply to the interior life and how one must be meek even when punishing another. Based on this, Moses condemned the Jewish idolaters to death, not out of personal hatred, but charity, thus preventing them from remaining in sin.

In this way, Saint Augustine’s teaching concludes that evils arising from military life and not military life itself is forbidden: “non prohibet militia, sed malitia.”

According to the holy bishop of Hippo, just war must seek to obtain or restore peace, and in this sense, it is an instrument of peace. By peace he understands the tranquility of order, the right disposition of things according to their proper end.

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Saint Augustine also defines just war as a means to re-establish and vindicate violated justice, and thus obtain peace. Therefore one can wage war to punish a nation for the violation of just order. Nevertheless, in the Augustinian concept of justice, this applies not only to the natural law of individuals and peoples, but also justice due to God as sovereign and lord. Thus both the systematic violation of natural law or the denial of the right worship of God can be motives for just war.

Likewise, just war was ordered by God Himself in many episodes narrated in the Old Testament. On the other hand, just war can also be waged against a country that refuses to punish adequately its own citizens who acted unjustly against an offended nation.

In other words, according to Saint Augustine, just war can be waged when recovering goods or legitimate situations or when restoring order and justice violated by a people.

Saint Bernard of Clairvaux (1090-1153)

Saint Bernard, the great troubadour of Our Lady, the meek mellifluous Church Doctor, was also a great orator and preacher of the Crusades, He was the official preacher of the Second Crusade.

In his famous Opusculum, “De laude novae militae” (“In Praise of the New Knighthood”), Saint Bernard addressed the Knights Templars — using Saint Augustine’s arguments on the famous reply of Saint John the Baptist to the soldiers — he wrote:

What then? If it is never permissible for a Christian to strike with the sword, why did the Savior’s precursor bid the soldiers to be content with their pay, and not rather forbid them to follow this calling?

I do not mean to say that the pagans are to be slaughtered when there is any other way to prevent them from harassing and persecuting the faithful, but only that it now seems better to destroy them than that the rod of sinners be lifted over the lot of the just, and the righteous perhaps put forth their hands unto iniquity.2

Just War According to Catholic Teaching
Saint Thomas Aquinas built upon and further developed the teachings of the Church concerning just war.

Saint Thomas Aquinas (1225-1274)

This greatest of all Church Doctors developed and completed the doctrine of just war in several aspects.

Quoting Saint Augustine, Saint Thomas returned to Saint John the Baptist’s argument favoring the legitimacy of military life and, therefore, of war and added many other points.

He introduced the concept of common good as a basic element for the licitness of war.

The military profession must have as its goal defending the public good, the poor and oppressed, the cult due to God, and the Church. Soldiers are therefore instruments of legitimate authority which prevents or punishes, even with death, the misdeeds of criminals.

Quoting the sermons of Saint Gregory the Great, he justified capital punishment as a means to avenge outraged justice, correct and instill fear in evil, and thus re-establish and guarantee both the peace of society and the Church and a nation’s stability and prosperity. Such actions are virtuous when motivated by the love of justice and charity.

For soldiers to fight in just wars, the saint explained, supernatural or divine help, which are the Virtues, is needed. The first such virtue is fortitude, a supernatural help that makes man more courageous and perseverant in the fight.

Bellicose action, he added, can only be performed with wisdom and ability, when done with prudence, which directs man’s actions in life with rectitude.

According to Saint Thomas Aquinas there are three conditions for just war:

1)  It must be declared by legitimate authority. Saint Paul says: “He beareth not the sword in vain: for he is God’s minister, an avenger to execute wrath upon him that doth evil” (Rm. 13:4).

2)  The cause must be just. He quotes Saint Augustine: “A just war is wont to be described as one that avenges wrongs, when a nation or state has to be punished, for refusing to make amends for the wrongs inflicted by its subjects, or to restore what it has seized unjustly.”

3)  It must be waged with good intention. “For it may happen that the war is declared by the legitimate authority, and for a just cause, and yet be rendered unlawful through a wicked intention. Hence Augustine says (Contra Faust. xxii, 74): ‘The passion for inflicting harm, the cruel thirst for vengeance, an unpacific and relentless spirit, the fever of revolt, the lust of power, and such like things, all these are rightly condemned in war.'”3

Subsequent Doctors

Theologians after Saint Thomas like Francisco de Vitoria (1485-1546) and Francisco Suarez (1548-1617) completed the Scholastic theory of just war with the principle of proportionality:

Besides a just cause, a summons by legitimate authority, and a right intention, these theologians teach there must be a balance between the good to be recovered or preserved, the unjust situation to be remedied or prevented, and the evils that necessarily come in the wake of war, particularly the number of deaths.

All peaceful means must be exhausted before having recourse to war.

These theologians point out that the need for justification applies only to offensive not defensive war, since the principle of legitimate defense in the face of an attack is evident.

Doctrine of the Popes

The above-mentioned doctrine of the Fathers, Doctors of the Church and theologians, was accepted and incorporated in the Magisterium of the Church as taught by the popes over the centuries.

Under the general title “Just War at the Service of the Divine Precept of Peace,” the Benedictine Monks of Solesmes, France, succinctly summarized the teaching of the popes on just war:

Order and peace can have recourse to force. However, force, in itself, is incapable of restoring peace, since peace is the fruit of the union of justice and charity.

Some enemies of justice cannot be led to accept the necessary conditions for peace without the use of force.

The importance of a certain good justifies entirely its defense by force against an unjust aggression. The Catholic Faith must be included as a most precious good. It is therefore legitimate to defend the Faith with the use of arms.4

One of the Pontifical documents referred by the Monks of Solesmes, is the Allocution to the Military Committee of the American Congress, by Pius XII, on October the 8th, 1947:

Law and order may at times have need of the strong arm of force. Some enemies of justice can be brought to terms only by force. But force should be held always in check by law and order and be exercised only in their defense. Nor is any man law into himself.5

More recent Popes have insisted on the principle of proportionality and the means to employ in the defense or recovery of a material or moral good. However, the fundamental principles were already expounded by the great doctors and popes over the centuries.


  1. Cited by Saint Thomas, Summa Theologica, II-II, q. 40 a.1
  2. Saint Bernard of Clairvaux. In Praise of the New Knighthood (Liber ad milites Templi: De laude novae militae),trans. Conrad Greenia: ORB Online Encyclopedia — Military Orders.
  3. Summa Theologica, II-II, q. 40.
  4. Moines de Solemes, La Paix Internationale, Desclee, Paris, 1956, v. I, Table Logique, P. 20.
  5. Moines de Solemes, op. cit. P. 458, n. 632.

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