Tangential: This argument comes up a lot, and I get that it's a specific example to make a general point, but are we that confident that removing Hitler from the equation means no Holocaust? It can't be denied that he had significant influence, but Nazis existed without him and antisemitism was widespread in Germany at least as far back as its founding. Am I wrong to think Hitler's contribution was not necessary for that outcome?

The novel "Time and Time again" by Ben Elton explores the possibility of averting of the world wars via time travel. I really enjoyed the book and would recommend. Without wanting to spoil anything, I would say it broadly agrees with your thesis.

> but are we that confident that removing Hitler from the equation means no Holocaust?

No.

Afaik, Hitler was instrumental in making Nazi party big and popular. They became big due to his speaking abilities. Antisemitism was widespread all around Europe. Germany was not the most antisemitic one - the Jews were running to Germany from Easter Europe.

The nazi party was not the only competitor for power and among those, it was only genocidal by ideology. Germany could end up as military dictatorship - there would be imperialism but it would not be the same. It could end up as actual democratic country too. But, the party that won were Nazi and there, Hitler was the one who made that party big.

Imagine in 1900 if people had some technology that would make the earth vanish into nothingness in 2050, after everyone currently alive had died. Would it have been morally neutral for them to deploy that technology, since the only people it would affect are nonexistent hypothetical people?

On your specific points:

> you have to also count and subtract the deaths they will cause

Agreed.

> A few of those children might turn out to be be murderers. Others will cause accidents, maybe big ones. Others still will have consumption habits that snuff out future lives.

That's right: each person that comes into existence has some chance of making the world worse for others, and some chance of making it better. I think that overall new people are a positive contribution, especially if you consider their own enjoyment of life, but if you think it's the other way then it's completely to reasonable count "more people will be born" as a negative feature of a policy.

> Imagine if Adolf Hitler's mother had died in some accident before he had been conceived and born; how would you tally the accident?

When looking at moral questions you're generally concerned with decisions: do I try jump in to help with this accident in front of me? Do I give money to this person that seems to need it more than I do? Do I advocate for this policy? It's not clear to me what sort of moral question your hypothetical corresponds to, since at the time of the accident (or before that if we're considering the value of some sort of policy that might have affected the chance of her dying) no one knows that it's her child in particular that would end up causing such enormous harm.

Basically, what you're asking is if we plant a time bomb, does it become morally neutral at a certain, sufficiently long time value, whereby it doesn't kill anyone who is alive today?

That time could be a lot shorter than 150 years. Say a one-year-long time bomb kills someone's newborn infant, and only that infant. When the bomb was planted, that infant hadn't yet been conceived. Of course that bomber is going behind bars.

I find the arguments in these areas absurd and not absurd in almost equal measure, but I don't think your argument is a strong one against.

If we bite the hook then the thing we care about is something like expected value.

That only applies for non-actualized future events. We tally the accident of Hitler's mother's death according to the probabilistic expected value of her contribution, which was approximately the same as any other woman of her time and place.

> Imagine if Adolf Hitler's mother had died in some accident before he had been conceived and born; how would you tally the accident?

As a pretty positive development. But kinda, none of us have predictive abilities like that.