Arguments for Just War

By Simon Falk, Catholic University of America

I recently watched a debate about just war between two Catholics and two Conservative Anabaptists.[1] There were some very interesting arguments on both sides, and I thought there was a lot to be learned from watching it. It is my goal in this article to try and summarize the arguments of both sides about just war and the implications of their positions. It also reveals a difference in how each side sees Scripture and Tradition, which is important but too large a topic for one single article. It is important to keep in mind that the Catholic Church upholds a just war theory, while the Anabaptists are pacifists and thus do not. It is not required of Catholics to hold a just war theory, but it has been presented as worthy of belief. Also of importance is the fact that the Anabaptists do not believe Christians should be involved in government whatsoever, thus they do not vote or run for public office. While this position is relevant to the debate, it is also somewhat of a separate issue, so I will try to only deal with it as needed. I conclude that though both positions have their merit, war can indeed be justified in concordance with the positions of the Church Fathers and careful interpretation of Scripture.

The arguments for the position called biblical nonresistance are taken from various passages of Scripture. Jesus seems to forbid war in the Sermon on the Mount: “But I say to you, offer no resistance to one who is evil. When someone strikes you on your right cheek, turn the other one to him as well” (Mt 5:39). When Peter draws his sword to defend Jesus in the Garden of Gethsemane, Jesus says to him, “Put your sword back into its sheath, for all who take to the sword shall perish by the sword” (Mt. 26:52). Commenting on this passage, Tertullian says: “In disarming Peter, Christ disarmed all soldiers.”[2] Jesus says we should love our enemies (Mt. 5:44), and killing is not loving one’s enemies. The simple interpretation of this is that Jesus does not want Christians to fight.

St. Paul also seems to share this interpretation of Jesus’ view on war. We are citizens of heaven as Philippians 3:20 says, and if Christians were to go to war for an earthly nation, there is the possibility of killing other Christians who are members of a different earthly nation. Heaven is not only for when we die. The Kingdom of God is here and now; thus, Christians should not fight in war as faithful citizens of Heaven. St. Paul and the Early Church Fathers see that Christians should be involved instead in spiritual warfare. St. Paul says, “For our struggle is not with flesh and blood but with the principalities, the powers, with the world rulers of this present darkness, with the evil spirits in the heavens” (Eph 6:11). Therefore, Christians are called to warfare, but of the spiritual kind.

However, the just war theory would interpret the Scripture verses quoted above differently. The Sermon on the Mount was not given to government officials, nor did Jesus give blueprints for a system of government that Christians must participate in. Someone holding a just war theory could indeed take the words of Jesus seriously and affirm that martyrdom is an act of virtue, and martyrs do “turn the other cheek” and “offer no resistance to one who is evil.” However, the logical reason for just war would be what is called in moral theology the principle of double effect. If a person is confronted by a violent aggressor who is threatening to kill an innocent person and the only way to stop that aggressor is lethal force, then the intent is not killing but the preservation of another’s life. It is true Jesus said love our enemies, but he also said love our neighbor. How can we love our neighbor, then, if we do nothing to stop his death at the hands of a violent attack?

The just war theorist would claim to have good reasons to believe that Jesus did not mean that all governments in all situations should do nothing when confronted with war or violence. Just war theorists claim to find support in the preaching of John the Baptist that Christ did not forbid all war: “Soldiers also asked him, ‘And what is it that we should do?’ He told them, ‘Do not practice extortion, do not falsely accuse anyone, and be satisfied with your wages” (Lk 3:14). One can see here that John does not command soldiers to quit their jobs, and he even calls them to be content with their wages. Jesus praises John as the greatest among those born of women,[3] so if John had made a grievous error in not telling soldiers to quit their profession, would Jesus have said such a thing? St. Augustine also notes this, and St. Thomas Aquinas cites Augustine on this question as well.[4]

Support for the just war theory can also be found in St. Paul’s letter to the Romans. When speaking of government St. Paul says, “But if you do evil, be afraid, for it does not bear the sword without purpose; it is the servant of God to inflict wrath on the evildoer” (Rom 13:4). It could be interpreted from the text that this refers to the government using force for internal affairs such as with violent criminals in one’s own country. St. Paul does not merely note this as a fact of life but goes so far as to say that the government can be God’s servant in inflicting punishment upon evildoers.

It seems clear from this passage that Scripture approves of the use of the sword by legitimate governments to control their own internal threats. However, does this not also mean that a legitimate government could take up the sword against external threats as well? St. Thomas Aquinas makes an argument in support of just war in the Summa Theologica, laying out three requirements[5]: warriors in a just war should be commanded by a true governmental authority; a just cause is necessary; and there must be a proper intention. St. Paul’s affirmation that the government can use the sword to punish an evil one is in accord with the first requirement, and this may be why St. Thomas insists on having the proper authority for declaring war. The principle of double effect is seen in the latter two requirements because both the goal and intentions should be morally good, though they may create undesired effects.

There seem to be powerful arguments on both sides. The non-resistant position has the words of Jesus at face value, to love thy enemy. Also, St. Paul redirects our focus to the spiritual identity of the Christian, and the spiritual war to be fought. Knowing this, how can one go to war for an earthly nation and kill others? Finally, the horror and bloodshed of war is truly a terrible thing. How can any Christian who loves peace participate in such a thing? On the other side, Jesus was not mandating public policy at the Sermon on the Mount. Therefore, did He really mean that no government in any situation can use force to defend itself? The Bible is not a systematic theology book, but a Christian should have a moral system based on Scripture to make right and just decisions. If good arguments can be made for the principle of double effect, using force may be necessary to defend others as the best way to love your neighbor, and thus war can be justified with the proper goal and intentions.


[1] “It’s Just War”- Should Christians Fight? Debate on March 28, 2014. Found online.

[2] On Idolatry, 19

[3] see Lk 7:28

[4] Summa Theologica, Second Part of the Second Part, Question 40, Article 1

[5] Summa Theologica, Second Part of the Second Part, Question 40, Article 1

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