According to the teaching in Veritatis Splendor, only three things are needed to make any human act, that is, any decision or choice, objectively moral or immoral: (1) intention, (2) object, (3) circumstances. So this teaching must also apply to just war doctrine. Instead of a checklist of conditions that must be met for a war to be just, we are left with only these three fonts of morality.
1. Intention — the intended end; the purpose for which the act was chosen.
Why is the nation going to war? In other words, what is the purpose for which the war was chosen? The morality of this font (as with the other fonts) is evaluated by the love of God above all else, and the love of neighbor as self.
For example, if the reason is to defend the people of the nation from being killed or enslaved by another nation, then the intended end is good. Or, if the reason is to protect another nation from being conquered and subjugated by its neighbor, then the intention is also just.
But if the reason is to increase the power of the nation, or increase its economic profits, or take revenge for a past injury, then the intention is bad and the war would be unjust, based on the first font.
2. Moral object — the end, in terms of morality, toward which the knowingly chosen act is inherently ordered. This ordering of the act is its moral nature (or moral species). An act with a bad object is an intrinsically disordered act, and is always wrong to knowingly choose.
Some wars are intrinsically evil. A war ordered to utterly destroy another nation, or race, or ethnicity, or religion, or anything similar, would be a genocidal war, and therefore intrinsically evil and always gravely immoral. A war ordered toward enslaving another nation would also be intrinsically evil and always gravely immoral. A war which seeks revenge by killing innocent persons in the other nation is a murderous war, and is also intrinsically evil and always gravely immoral.
But if the war is ordered toward the defense of the nation, or toward the defense of another nation, which cannot defend itself without assistance, then the object is not evil and the war is not intrinsically evil. But a war which is not intrinsically evil must also be good under the other two fonts.
Obviously, a genocidal war would have not only a bad object, but also a bad intention and bad consequences. Some wars are immoral under all three fonts. Only one bad font is needed to make any act a sin. But some acts have two or three bad fonts.
3. Circumstances — the totality of the reasonably anticipated good and bad consequences for all persons affected by the act (or in this case, by the decision to go to war).
War always includes bad consequences of grave moral weight, including deaths and serious injuries to soldiers and civilians, harm to society, and vast destruction. So a just war must have reasonably anticipated good consequences of equal or greater moral weight to the reasonably anticipated bad consequences.
And so, in the checklist approach to just war theory, multiple conditions for a war to be just regard the circumstances. But no matter what list of conditions is used, the totality of the reasonably anticipated good consequences must equal or outweigh the totality of the reasonably anticipated bad consequences, or the war is unjust under the third font.
The weight of a consequence is reduced, if it is less likely, and increased if it is more likely. The weight of a consequence is reduced, if it is more remote from the decision to go to war, and increased if it is less remote (proximate).
And the harm done to innocents, whether by death or injury or displacement from their home or job, has greater weight than the harm done to enemy soldiers. However, the innocents on both sides of the conflict have the same human rights, so the harm done to innocents in the other nation is not to be given less weight, unless it is beyond the control of the government and people of the other nation.
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