More can be written, and I'm not sure whether this gets enough towards the philosophical and moral bases, but you might like to start with "Is it true that the U.S. dropped flyers around Japan as a warning to the Japanese civilians before they bombed Hiroshima and Nagasaki?" by restricteddata. He quickly debunks that idea, but then discusses bombing of cities, including contemporary thinking. He also replied in "Did the US *have* to nuke Japan in WWII?". But that has more tactical / worldly thinking, like a mention of previous firebombing and of political concerns.

I can mention that these discussions are from the more general FAQ section, "The atomic bombs, aka questions /u/restricteddata has answered, with answers by the obvious one, /u/t-o-k-u-m-e-i, /u/The_Alaskan, and Various. But these cover other aspects, like the Japanese reaction and such, so that's of interest only if you want to know other things about the environment.

This is not to discourage discussion. More questions, data and debate are welcome. Are any of these useful?

There are two things here. One is the factors that went into the "decision(s)." There are many. Books that cover (and argue) over them include:

• Rhodes, The Making of the Atomic Bomb

• Gordin, Five Days in August

• Hasegawa, Racing the Enemy

• Alperovitz, The Decision to Use the Atomic Bomb

• Frank, Downfall

And many, many, many more. There is no single book that encompasses the literature, though I think Hasegawa's book is the one I tend to recommend over all the others, because it does a lot of work.

But I am not sure those books will get at the root of your question, which is about the relative influence of Enlightenment-style rationals on the various people involved in such a decision.

For what it is worth, I think it is kind of a mixed bag. The typical ways to justify the bombings after the fact are decidedly pre-Enlightenment arguments: the principle of "double effect" (essentially "ends justify the means" — the "saved lives" justification), and the closely-related notion of "just war" (the "the Japanese were horrible in their own conduct and that justified just about whatever you want in return" arguments).

There were, however, also modes of reasoning that do trace very well to the Enlightenment, though in my reading they apply less specifically in the case of the atomic bombs and more generally to questions about aerial bombing and the ideologies that went with it. (Sven Lindqvist's A History of Bombing is a great read on the latter.) Basically these are philosophies of how you win wars, what the point and purpose of war is (a big topic), and under what conditions you are allowed to do things like drop explosives on people from mechanical contraptions. These logics have traditionally traced themselves to much darker, Enlightenment philosophies about the value of technology and civilization, the willingness to dominate and exterminate "brutes" from above, and sort of pseudo-psychological rationales for why total bombardment might be an effective route to getting surrender (sort of the Blitzkrieg from the air). I think of all of these as very Enlightenment and post-Enlightenment in their articulation, and they have a very different "feel" than the sorts of justifications that are typically traced to Aquinas. And you also have things that seem like a blend, e.g., the view of some scientists that the best hope for the long-term future of the world was making the first use of the atomic bombs as terrible as possible, so that the world would get its act together and outlaw war moving forward (obviously this did not occur). Is the latter an elaborate, technological, internationalist version of the principle of double effect, or something else? I don't know.

I am not a moral philosopher or a theologian; I am sure there is much more to say on this from that perspective. But I do think that saying that the Enlightenment enabled these things without remorse (and we have bypassed the question of whether there was remorse; it's complicated) is not quite fair to the Enlightenment (it is not like massacres of civilians started being a thing only in the 18th century), but at the same time, I suspect you can trace specifically Enlightenment-style philosophies as well in the "mix" of how people justified these things (obviously the connection to high technology and the deep presence of technical experts in these conversations plays a role in making this a very post-Enlightenment issue).