The blog Cor ad cor loquitor has posted a summary retrospective discussion into whether or not the bombings of Hiroshima and Nagasaki were morally permissible, and provided many viewpoints both new and old. Some of the comments go into the apparently endless military and strategic details which accompanied the close of WWII and are, I suppose, an engaging pastime. But the briskness with which relevant highly official Catholic teaching — a million times weightier than any individual's view — is quickly blown aside, or not even engaged, is not so pleasing.

This teaching is, of course, from the teaching document Gaudium et Spes, where, in 1965, the worldwide Catholic Bishops, formally assembled under the guidance of the Pope, made this declaration:

Every act of war directed to the indiscriminate destruction of whole cities or vast areas with their inhabitants is a crime against God and humanity, which merits firm and unequivocal condemnation.

Two commenters sideline this teaching by considering only one particular meaning for "indiscriminate", one saying: "The U.S. atom bomb drops were not indiscriminate destruction of cities. They were ostensible military targets…" So perhaps the Bishops are thought to be teaching the blindingly obvious: Don't destroy whole cities for no reason at all? Or were they only re-teaching the simplistic: Don't directly target civilians? (If shooting one innocent civilian is wrong, it's not much of an ethical stretch to conclude that destroying an entire city of them is also wrong.)

I do not think Bishops in Council make such trivial points; they had larger goals in mind. Their declaration would be a peculiar historical time to teach the obvious. And the Bishops clearly took care to highlight that particular declaration within the rest of the document, though filled with many other important matters.

So what are the Bishops saying? We can pick out some things:

What is condemned is an act. No moral reckoning is included for the reasons, motivations, or goals of the act however good or bad — the act is condemned regardless of those.

What is the act that is condemned? Clearly it is some kind of indiscriminate destruction. So then, we must determine what destruction is sometimes not permitted, and then exactly in what kind of indiscriminate way the destruction must never be carried out.

The what is easy to determine: the document declares that in some circumstances we cannot destroy "entire cities or extensive areas along with their population".

More critical is to determine in what sense indiscriminate should be taken. Indiscriminate in what way? Here the Bishops have provided the necessary context in a closely preceding paragraph of their document:

The proliferation of scientific weapons has immeasurably magnified the horror and wickedness of war. Warfare conducted with such weapons can inflict immense and indiscriminate havoc which goes far beyond the bounds of legitimate defense. Indeed, if the kind of weapons now stocked in the arsenals of the great powers were to be employed to the fullest, the result would be the almost complete reciprocal slaughter of one side by the other, not to speak of the widespread devastation that would follow in the world and the deadly after-effects resulting from the use of such weapons.

The Bishops have their eye on the indiscriminate effects of the weapons. That is their sense for indiscriminate. (In the context of the sixties the weapons were nuclear, but they do not limit what they say to just those weapons; for technology moves ever onwards.) And the effects of nuclear weapons are indeed indiscriminate; a re-reading of the harrowing eyewitness account given by Father Siemes of the bombing of Hiroshima provides ample evidence of this. Soldiers, mothers, kintergarten children, farmers, priests, nuns, tram passengers, Japanese, Koreans, Germans, Protestant girls, peasants, professors, theology students: all victims alike.

Nuclear weapons have this effect because of the extensive area affected by the direct blast, and the even larger area, over an extended period of time, that will be affected by fallout. There are some very small nuclear weapons which, by careful design, probably do not have such extensive effects, and might be usable in a narrowly localizable and thus discriminate way. Presumably the Bishops are not addressing that case. But the Hiroshima-sized weapons are large enough that, when used against a populated city, they must affect population of large areas. That is the indiscriminate act that the Bishops condemn.

Subsequent to Gaudium et Spes, it is not possible to claim that, because a city or an area has a military target within it, it is moral to attack the population of the whole city, or the whole area, in order to destroy the military target. Such an indiscriminate act is condemned, regardless of the motive for it.

(And given the condemnation of such an act, any use of the double effect principle in order to support the Hiroshima and Nagasaki bombings is ruled out, since that principle can never be used where the action under consideration is already known to be morally wrong.)