To begin with, it must be understood that Just War doctrine is a development of apostolic teaching.  In other words, it follows from certain implications of the teaching of Jesus and the apostles, but the New Testament writers don’t discuss it directly.  That’s not sinister, it’s just how human thought works. So, for instance, Jesus and the apostles never said one word forbidding us to fire a .38 revolver into an innocent person’s head.  Likewise, Jesus and the apostles never said one word commanding us to drive on the correct side of the road. But they did say that the fifth commandment forbids murder.  So when revolvers and death-dealing automobiles were invented, the Church could develop its teaching to include the fact that shooting innocents in the head and reckless driving are sins even though the New Testament says nothing about these things.  In short, times change, but certain things don’t change.  And depending on how things change, the Church’s practical application of the things that don’t change can change as well.

So with Just War doctrine.  Just War doctrine was only fashioned as a concession to human weakness centuries after the apostles. In the early centuries of the Church, Christians typically refused to serve in the military, seeing no reason at all to serve a pagan Caesar who was an open and persecuting enemy of Christians.  Indeed, in the face of violent persecution from the pagan state, the New Testament bears witness to a radical degree of non-violence.  Peter, having learned his lesson about taking up the sword (even in self-defense) in the Garden of Gethsemane, writes to a Church suffering horrors under Nero and tells them not “Stand Your Ground” but:

Beloved, do not be surprised at the fiery ordeal which comes upon you to prove you, as though something strange were happening to you. But rejoice in so far as you share Christ’s sufferings, that you may also rejoice and be glad when his glory is revealed. If you are reproached for the name of Christ, you are blessed, because the spirit of glory and of God rests upon you. But let none of you suffer as a murderer, or a thief, or a wrongdoer, or a mischief-maker; yet if one suffers as a Christian, let him not be ashamed, but under that name let him glorify God. For the time has come for judgment to begin with the household of God; and if it begins with us, what will be the end of those who do not obey the gospel of God? And

“If the righteous man is scarcely saved,
where will the impious and sinner appear?”

Therefore let those who suffer according to God’s will do right and entrust their souls to a faithful Creator. (1 Peter 4:12–19)

In this, Peter sounds nothing like a National Sword Association spokesman urging Good Guys with Swords to stab Bad Guys with Swords and exactly like his Master who rebuked him with the words, “Put your sword into its sheath; shall I not drink the chalice which the Father has given me?” (John 18:11).

But as the Roman Empire Christianized over the next three centuries after Peter, believers began to wonder about their responsibilities in defending, not themselves, but other innocents who were the victims of aggression. They did so because, as Paul pointed out, it was the job of Caesar to ensure the protection of the common good with, among other things, the sword (cf. Romans 13). So when Caesar himself became Christian, it became necessary for the Church to ponder this issue and to eventually formulate Just War doctrine as a reasonable approach to this question of competing goods.

In short, Just War doctrine has never been a dogma but is rather a set of good faith prudential attempts to navigate a chaotic and bloody world. It is a set of “rule of thumb” moral calculations rooted in the gospel that both forbids murder but understands that Caesar “does not bear the sword in vain” (Romans 13:4).  It is a wise distillation of human judgments that tries to think with the Sacred Tradition handed down from the apostles, but it is not Sacred Tradition itself. As such, Just War doctrine is subject to revision as circumstances and technologies change.

Legitimate and Illegitimate Developments of Just War Doctrine

That said, we must clearly understand what is and is not meant by that.  What is not meant is, “Because Just War doctrine is not dogma but a set of prudential guidelines, we can feel free to abandon it and commit war crimes if we like.”  Never forget, prudential judgment is about how best, not whether, to obey the Church’s teaching.  The Church’s guidance is not a game of “Simon Peter Says” in which only dogmatic pronouncements matter and every other piece of moral guidance can be accepted or rejected depending on how it accessorizes our politics and ideology. There are legitimate and deeply illegitimate forms of revision to Just War doctrine, which we weigh by evaluating the unchanging aspects of divine revelation.  Very simply, anything that makes it easier to kill innocents or otherwise assault human dignity without just cause is an illegitimate revision of Just War doctrine, because the bedrock of all Just War doctrine is the fifth commandment:  You shall not murder (Exodus 20:13).

Conversely, an example of a (possible) legitimate development of Just War doctrine is the issue facing the Church with the advent of modern warfare: namely, the question raised by Pope St. John Paul II concerning whether the Church can tolerate war at all anymore:

Today, the scale and the horror of modern warfare – whether nuclear or not – makes it totally unacceptable as a means of settling differences between nations. War should belong to the tragic past, to history, it should find no place on humanity’s agenda for the future.[1]

Pope Benedict XVI concurred with this and said that “given the new weapons that make possible destructions that go beyond the combatant groups, today we should be asking ourselves if it is still licit to admit the very existence of a ‘just war.’”[2]

Note how Pope Benedict phrases that.  Prudential judgment is about carefully weighing a range of possibilities in light of the Tradition and even more carefully taking a practical step.  It is not about careening off in some direction and declaring your decision to be a one-size-fits-all dogma for all of time and eternity.  Benedict is not laying out a doctrine or even a policy for the Church.  He is simply probing some possibilities of what the Spirit may be saying to the Church in light of the signs of the times.

The point is, the Church—always skeptical about war and only indulging Just War doctrine as a concession to human weakness and never as an ideal—will never ever revise Just War doctrine to say, “On second thought, if you feel like it, go ahead and launch nukes if you are afraid.  You gotta break some eggs to make an omelet!” Rather, she is already pondering the possibility that there may no longer be such a thing as a just war at all.

Making War Hard

Consider the way Just War doctrine is formulated. The conditions of a Just War are these, according to the Catechism (2309):

• the damage inflicted by the aggressor on the nation or community of nations must be lasting, grave, and certain;
• all other means of putting an end to it must have been shown to be impractical or ineffective;
• there must be serious prospects of success;
• the use of arms must not produce evils and disorders graver than the evil to be eliminated. The power of modern means of destruction weighs very heavily in evaluating this condition.

This part of Just War doctrine is called ius ad bellum.  It refers to the conditions under which states may legitimately resort to war. Notably, not just one or two or a majority of these criteria must be met, but all four.  Fail to fulfill even one and your war is unjust.

At this point, some might object, “If so, then Just War doctrine makes it extremely difficult to go to war!”

Bingo!  Exactly!  The key to understanding Just War doctrine is that it is and always has been designed as a series of restraints intended to make going to war as difficult as possible. The whole point is to restrain the human appetite for mayhem, vengeance, murder, and destruction that sinfully yearns for an excuse to be unleashed.  It was formulated by the Church for that express purpose because war kills the creature made in the image and likeness of God for whom Christ suffered, bled, and died. It sees war, not as something you get to do if you can successfully jump through these four hoops, but as a thing a nation may tragically be forced to do if all four of these conditions apply.  And (mark this), that necessarily means that if a nation goes to war unjustly it is committing mass murder and, therefore, mortal sin.

Now the very first requirement of Just War doctrine is that all Just War must be an act of defense against an aggressor who has attacked you, not a preventive blow against somebody you fear might attack in the future.  War, to be just, must be a last and not a first resort for the same reason you may shoot a burglar who has broken into your house to attack you, but you cannot sit on your front porch and shoot passersby because you don’t like the look of them and fear they may burgle your house someday.

Preventive war, being neither a response to an actual act of aggression nor a last resort is itself an act of aggression.  It should be as morally desirable to Christians as the thought of amputating one’s own healthy leg because you fear that in five years you might step on a nail and get gangrene.  War means innocents will die and be made widows, widowers, and orphans. Indeed, as all pro-life people should know, it means that unborn children will die along with their mothers.  That is why Joaquin Navarro-Valls, speaking on behalf of Pope St. John Paul II, said, “Whoever decides that all peaceful means available under international law are exhausted assumes a grave responsibility before God, his own conscience and history.”[3]

And that, in the end, is why arguing that the silence of the Catechism on preventive war makes it okay is as nonsensical as arguing that the silence of the Catechism on testing rat poison on orphans makes that okay.

That said, it should also be noted that Cardinal Ratzinger’s comment on the silence of the Catechism about preventive war was not intended to be an exhaustive critique of the American case for war, but simply to point out what any serious Catholic should have seen as obvious: that if the war proposed by the Bush Administration could not pass even the first and most rudimentary test of justice, it did not matter whether it passed the three other criteria for a Just War, just as when a new car explodes upon turning the ignition key, you don’t bother asking whether the brakes work, the accelerator sticks, or the steering wheel turns.

Still and all, it is worth noting that, in addition to the fact that preventive war clearly violated the first criterion of Just War doctrine, the war did not, in fact, meet any of the Church’s criteria for a Just War. That is why two popes and all the bishops of the world refused to back it.

And that is why it was a catastrophic failure of the “pro-life” movement in the US when it committed itself (with the exception of the despised and ostracized Consistent Life Ethic/Seamless Garment folk) to support the war in open defiance of the Church’s clear teaching.  Assuring themselves that the myths of the Five Non-Negotiables, of Opposition to Abortion Taking Away the Sins of the World, and of “Anything Goes” Prudential Judgment gave them a license to kill hundreds of thousands in a war the Church unequivocally condemned, the “pro-life” movement took its first truly definitive step into the realm of haereses by committing itself, not merely to ignore, but to actively fight the Church on behalf of the GOP—and to use the unborn as human shields to do it. Once again, the unborn were pitted against, rather than related to, the lives the GOP did not care about. Once again, the “pro-life” movement committed itself to the fantasy that a Republican administration was just about to magick away abortion if only we would do evil that good may come of it. And once again that fantasy was betrayed as abortion rates that had plummeted under Clinton flatlined and even spiked a little under Bush.

It would be the first, but by no means the last, step the “pro-life” haereses would take to embrace Consequentialism in a matter of clearly grave and intrinsic evil and thereby continue to corrode their hearts and minds in pursuit of worldly power at the cost of their souls.

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[1] Pope St. John Paul II, Pentecost Homily, Coventry, UK, May 30, 1982. Available on-line at http://www.vatican.va/content/john-paul-ii/en/homilies/1982/documents/hf_jp-ii_hom_19820530_ coventry.html as of December 3, 2019.

[2] “Challenging the Just War Theory” by Tony Magliano, National Catholic Reporter, September 1, 2014. Available on-line at https://www.ncronline.org/blogs/making-difference/challenging-just-war-theory as of December 4, 2019.

[3] Alan Cowell, “Threats and Responses: World Reaction; A Worried World Shows Discord,” New York Times, March 19, 2003.  Available on-line at https://www.nytimes.com/2003/03/19/world/threats-and-responses-world-reaction-a-worried-world-shows-discord.html as of October 5, 2023.