You're given the option to torture everyone in the universe, or inflict a dust speck on everyone in the universe. Either you are the only one in the universe, or there are 3^^^3 perfect copies of you (far enough apart that you will never meet.) In the latter case, all copies of you are chosen, and all make the same choice. (Edit: if they choose specks, each person gets one dust speck. This was not meant to be ambiguous.)
As it happens, a perfect and truthful predictor has declared that you will choose torture iff you are alone.
What do you do?
How does your answer change if the predictor made the copies of you conditional on their prediction?
How does your answer change if, in addition to that, you're told you are the original?
No it isn't, it's a statement about the universe: If you smoke, you'll get lesions. It's written into the specification of the universe; what decision theory you use doesn't change the characteristics of the universe.
No. You don't get to specify a universe without the kind of causality that the kind of CDT we use in our universe depends on, and then claim that this says something significant about decision theory. Causality in our hypothetical works differently.
No it isn't.
No it isn't. In terms of CDT, we can say that smoking causes the gene; this isn't wrong, because, according to the universe, anybody who smokes has the gene; if they didn't, they do now, because the correlation is guaranteed by the laws of the universe. No matter how much work you prepared to ensure you didn't have the gene in advance of smoking, the law of the universe says you have it now. No matter how many tests you ran, they were all wrong.
It may seem unintuitive and bizarre, because our own universe doesn't behave this way - but when you find yourself in an alien universe, stomping your foot and insisting that the laws of physics should behave the way you're used to them behaving is a fast way to die. Once you introduce a perfect predictor, the universe must bend to ensure the predictions work out.
What kind of causality is this, given that you assert that the correct thing to do in smoking lesions is refrain from smoking, and smoking lesions is one of the standard things where CDT says to smoke?
"A causes B, therefore B causes A" is a fallacy no matter what arguments you put forward.
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