it doesn't matter whether your scenario is hypothetically possible, if it never occurs it isn't real, you lose your initial case, and that reduces your reductio ad absurdum to an in vacuo argument.

Ahh, if only it were that easy for you! But you see when you decide that your rules have to be 100% exceptionless everywhere and ALWAYS, you take on a heavy burden of proof.

For you to make this claim about the future, you have to be sure that your principle holds no matter what happens in the future. And the funny thing about the future? Lots of unexpected things happen there! Things that never happened before, and therefore according to you are not real, can all of a sudden happen for the first time! Unless of course, they are impossible. Then we can predict that they will NEVER happen.

Technological change can have moral consequences. What used to be the upper limit for potential casualties as the result of a single action has exploded in the last 100 years or so. For most of human history there was no bomb you could set that could kill more than a few people. Then in, what? the 19th C? (I'm no expert on the history of warfare) rudimentary bombs wee developed and you could kill 50-100 people. By WWII you could kill thousands with a single bomb and by 1945 you could kill hundreds of thousands. Now you can kill millions.

Deontological intuitions formed over thousands of years of history are now obsolete. A terrorist attack can result in mass casualties that are several orders of magnitude larger than anything possible in human history. In those scenarios, your intuitions fail.

The old rules no longer are valid. Never before was it even possible for a person to kill 15 million people in an instant or for one person to hold information that could save 15 million people. Now that is possible. The rules have to adjust.

What use is it to create this vanishingly unlikely scenario?

It comes in really handy when you want to debunk deontological ehtics.

I'm sorry, but that sounds like a highfalutin way of saying "the ends justify the means."

Precisely. Outcomes are what matters, not rules. Its way too easy for people to game the rules and justify horrifically bad outcomes. By sticking to outocmes, what really matters, we avoid getting played.

And I say to you again: why can't you create a scenario that justifies slavery, or genocide? And if yu can... of what worth is this philosophy?

You could but it would have to be generalizable and would have to be outweighed by an even greater good. You would have to be reduced to evil options where slavery or genocide were the lesser evils. I can't really imagine such a scenario. far less can I imagine a plausible scenario. My scenario about the terrorists getting a nuke is plausible even if improbable. But to create a scenario that justified something on the scale of genocide you would probably need a science fiction scenario, like all powerful aliens say you have to pick a race to be killed or all life on earth wil be eliminated. Then we'd have to pick a race. But that's not plausible in today's world. But a terrorist getting a nuke? That could happen.

Without such a system of morality, torture can and will quickly become normalized: how hard will it be for someone to convince themselves that they're committing an evil to prevent a far greater evil?

How hard is it for someone to convince themselves they're not breaking the rules? John Yoo convinced himself pretty well.

If you actually go to the trouble of writing out, for example, a Bayesian network for it's occurrence, even a naive one points to an absurd number of independent pre-conditions whose probabilities therefore get multiplied, resulting in a vanishingly small probability

You can take any scenario, no matter how realistic, decompose it into its component events and then decompose those even further into subevents all with their supporting conditions and then raise questions about them all and therefore "prove" that any scenario is impossible. That's a crock.

What is so hard to believe about a terrorist getting a bomb and the plot being foiled? People get busted due to surveillance all the time. You people are willfully pretending to have no imagination.

I have to run get some food. I'll be back to answer any questions.