> actively supported a preventive nuclear strike against Russia.

Well, even Bertrand Russell, who protested against war from WWI to the Vietnam War, advocated a preemptive nuclear strike against the USSR in 1954. The risk of nuclear war killing everyone, once the USSR had nukes, just seemed too great, I guess.

So Bertrand Russell wasn't always right, either. Fortunately, the actual politicians in charge were a bit more reasonable.

What if he was right and we live now in a world worse as a result?

What if he wasn’t right and we live now in a world better as a result?

For the curious, check this essay "Did Russell Advocate Preventive Atomic War against the USSR?": https://mulpress.mcmaster.ca/russelljournal/article/download...

I wonder if their opinions would have changed if they had been aware of the possibility this would result in nuclear winter.

You are assuming the point you are trying to prove: that von Neumann was unjustified in advocating for these things. Maybe he was just smarter than you (and me) and just had a really good argument for believing those things, given the state of the world at the time and his various priors.

Also, humans have created thousands of different and highly contradictory systems of morality over the past several thousand years. You would probably be better off not believing that you have discovered the Correct Theory of Morality.

At least in hindsight I can say with confidence that John von Neumann was wrong in this matter. Or do you really think things could have turned out better if the US had began a nuclear war?

It is one thing to say that in hindsight he held a wrong belief, and another thing entirely (especially without knowing his exact arguments and priors) to say that he held a wrong belief at the time and was not only wrong, but also therefore morally defective.

I would actually argue for the latter. Even if he might have had valid geopolitical reasons to advocate a nuclear strike (althought I highly doubt it), it would have been morally wrong nevertheless. In my opinion, there is never an ethical justification for the usage of atomic weapons. In fact, I firmly believe that the bombing of Hiroshima and Nagasaki was ethically wrong as well, but I know that other people have a different opinion on this matter.

It is very difficult to conceive of Japan having turned out any better if Kyoto had been destroyed.

I agree, but I think there are many ways of arguing that the destruction of Kyoto was justified at the time that do not involve arguing that it would make Japan better off. And like I said, there is more than one theory of morality :)