Comment author:Unknown
27 December 2007 10:32:40AM
1 point
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Perhaps Eliezer or someone else can check the math, but according to my calculations, if you use Nick Bostrom's SSSI (Strong Self-Sampling Assumption), and make the reference class "observers after a quantum suicide experiment", then if the prior probability of quantum immortality is 1/2, after a quantum suicide experiment has been performed with the person surviving, both the outside observer and the person undergoing the risk of death should update the probability of quantum immortality to 4/7, so that they end up agreeing.

This seems odd, but it is based on the calculation that if the probability of quantum immortality is 1/2, then the probability of ending up being an observer watching the experiment is 17/24, while the probability of being an observer surviving the experiment is 7/24. How did I derive this? Well, if Quantum Immortality is true, then the probability of being an observer watching the experiment is 2/3, because one observer watches someone die, one observer watches someone survive, and one observer experiences survival. Likewise if QI is true, the probability of being an observer surviving the experiment is 1/3. On the other hand, if QI is false, the probability of being an observer watching the experiment is 3/4 (I will leave this derivation to the reader), while the probability of being an observer surviving the experiment is 1/4.

From this it is not difficult to derive the probabilities above, that the probability of being a watcher is 17/24, and the probability of being a survivor 7/24. If you apply Bayes's theorem to get the probability of QI given the fact of being a survivor, you will get 4/7. You will also get 4/7 if you update your probabilities both on the fact of being a watcher and on the fact of seeing a survivor. So the two end up agreeing.

Intuitive support for this is the fact that if a QI experiment were actually performed, and we consider the viewpoint of the one surviving 300 successive trials, he would certainly conclude that QI was true, and our intuitions say that the outside observers should admit that he's right.

## Comments (57)

OldPerhaps Eliezer or someone else can check the math, but according to my calculations, if you use Nick Bostrom's SSSI (Strong Self-Sampling Assumption), and make the reference class "observers after a quantum suicide experiment", then if the prior probability of quantum immortality is 1/2, after a quantum suicide experiment has been performed with the person surviving, both the outside observer and the person undergoing the risk of death should update the probability of quantum immortality to 4/7, so that they end up agreeing.

This seems odd, but it is based on the calculation that if the probability of quantum immortality is 1/2, then the probability of ending up being an observer watching the experiment is 17/24, while the probability of being an observer surviving the experiment is 7/24. How did I derive this? Well, if Quantum Immortality is true, then the probability of being an observer watching the experiment is 2/3, because one observer watches someone die, one observer watches someone survive, and one observer experiences survival. Likewise if QI is true, the probability of being an observer surviving the experiment is 1/3. On the other hand, if QI is false, the probability of being an observer watching the experiment is 3/4 (I will leave this derivation to the reader), while the probability of being an observer surviving the experiment is 1/4.

From this it is not difficult to derive the probabilities above, that the probability of being a watcher is 17/24, and the probability of being a survivor 7/24. If you apply Bayes's theorem to get the probability of QI given the fact of being a survivor, you will get 4/7. You will also get 4/7 if you update your probabilities both on the fact of being a watcher and on the fact of seeing a survivor. So the two end up agreeing.

Intuitive support for this is the fact that if a QI experiment were actually performed, and we consider the viewpoint of the one surviving 300 successive trials, he would certainly conclude that QI was true, and our intuitions say that the outside observers should admit that he's right.

Interesting. If that's right, then clearly QI is wrong, because we've watched people die.