Stathis Papaioannou writes: > Hal, > >I should add that I don't believe in QTI, I don't believe that we are > >guaranteed to experience such outcomes. I prefer the observer-moment > >concept in which we are more likely to experience observer-moments where > >we are young and living within a normal lifespan than ones where we are > >at a very advanced age due to miraculous luck. > > Aren't the above two sentences contradictory? If it is guaranteed that > somewhere in the multiverse there will be a million year old Hal > observer-moment, doesn't that mean that you are guaranteed to experience > life as a million year old?
I don't think there are any guarantees in life! I don't see a well defined meaning about anything I am guaranteed to experience. I am influenced by Wei Dai's approach to the fundamental problem of what our expectations should be in the multiverse. He focused not on knowledge and belief, but on action. That is, he did not ask what we expect, he asked what we should do. How should we behave? What are the optimal and rational actions to take in any given circumstances? These questions are the domain of a field which, like game theory, is a cross between mathematics, philosophy and economics: decision theory. Classical decision theory is uninformed by the AUP, but it does include similar concepts. You consider that you inhabit one of a virtually infinite number of possible worlds, which in this theory are not real but rather represent your uncertainty about your situtation. For example, in one possible world Bigfoot has sneaked up behind you but you don't know it, and in other worlds he's not there. You then use this world concept to set up a probability distribution, and make your decision based on optimal expected outcome over all possible worlds. Incorporating the multiverse can be done in a couple of ways. I think Wei proposed just to add the entire multiverse as among the possible worlds. Maybe we live in a multiverse, maybe we don't. The hard part is then, supposing that we do, how do we rank the expected outcomes of our actions? Each action affects the multiverse in a complex way, being beneficial in some branches and harmful in others. How do we weight the different branches? Wei proposed to treat that weighting as an arbitrary part of the user's utility function; in effect, making it a matter of taste and personal preference how to weight the multiverse branches. I would aim to get a little more guidance from the theory than that. I would first try to incorporate the measure of the various branches which my actions influence, and pay more attention to the branches with higher measure. Then, I think I would pay more attention to the effects in those branches on observers (or observer-moments) which are relatively similar to me. However, that does not mean I would ignore the effects of my actions on high-measure branches where there are no observers similar to me (i.e. branches where I have died). I might still take measures such as buying life insurance for my children, because I care about their welfare even in branches where I don't exist. Similarly, if I were a philanthropist, I might take care to donate my estate to good causes if I die. These considerations suggest to me an optimal course of action in a multiverse, or even in a world where we are not sure if we live in a single universe or a multiverse, which is arguably the situation we all face. It rejects the simplicity of the RSSA and QTI by recognizing that our actions influence even multiverse branches where we die, and taking into consideration the effects of what we do on such worlds. There is still an element of personal preference in terms of how much we care about observers who are very similar to ourselves vs those who are more different, which gives room for various philosphical views along these lines. And in terms of your question, I would not act as though I expected to be guaranteed a very long life span, because the measure of that universe is so low compared to others where I don't survive. Hal Finney