What Wei Dai means by “valuing extra copies in other quantum branches” is two things:
(Weak version:) The fact that A values B and C, where B and C are possible ‘future selves’ of A.)
(Strong version:) The fact that B values C, where C is B’s “counterpart in a quantum counterfactual world”.
Now, there’s an argument to be had about whether (2) should be true, even assuming (1), but right now this simply muddies the waters, and it will be much clearer if we concentrate on (1).
So, A valuing his own continued existence means A wanting it to be true that B and C, his possible future selves (in different counterfactual worlds), are both alive. A would not be very happy with B being dead and C being alive, because he would say to himself “that means I have (e.g.) a 1⁄2 chance of dying”. He’d much rather that B and C were both alive.
However, A might think like this: “If the Many Worlds Interpretation is true then it’s wrong to say that either B or C but not both will exist. Rather, both of them exist independently in separate universes. Now, what’s important to me is that my mind continues in some form. But I don’t actually need both B and C for that to happen. So if Roko offered me $100 in exchange for the instantaneous, painless death of B I’d quite happily accept, because from my perspective all that will happen is that I’ll receive the $100.”
Presumably you disagree with this reasoning, right? Even if MWI is true? Well, the powerful intuition that causes you to disagree is what Wei is talking about. (As he says, giving up that intuition is the position of “quantum immortality”.)
The fact that Wei states “the strong version” when “the weak version” would have sufficed is unfortunate. But you will completely miss the point of the debate if you concentrate solely on the difference between the two versions.
Er, what evidence exactly am I supposed to be updating on?
The supplied evidence for 1 (“We value extra copies in other quantum branches”) seems feeble. Most people are totally ignorant of the MWI. Most people lived before it was invented. Quantum theory is mostly an irrelevance—as far as people’s values goes. If—astonishingly—evidence of wavefunction collapse was ever found, people would carry on caring about things much as before—without any breakdown of morality—despite the loss of practially everything in other worlds. That thought experiment seems to demonstrate that most people care very little about copies of themselves in other worlds—since they would behave much the same if scientists discovered that those worlds did not exist.
Maybe there are somewhere a bunch of people with very odd values, who actually believe that they really do value copies of themselves in other worlds. I can think of at least one fellow who thinks like that—David Pearce. However, if so, this hypothetical silent mass of people have not stood up to be counted here.
OK, I’ll try again, from the beginning:
What Wei Dai means by “valuing extra copies in other quantum branches” is two things:
(Weak version:) The fact that A values B and C, where B and C are possible ‘future selves’ of A.)
(Strong version:) The fact that B values C, where C is B’s “counterpart in a quantum counterfactual world”.
Now, there’s an argument to be had about whether (2) should be true, even assuming (1), but right now this simply muddies the waters, and it will be much clearer if we concentrate on (1).
So, A valuing his own continued existence means A wanting it to be true that B and C, his possible future selves (in different counterfactual worlds), are both alive. A would not be very happy with B being dead and C being alive, because he would say to himself “that means I have (e.g.) a 1⁄2 chance of dying”. He’d much rather that B and C were both alive.
However, A might think like this: “If the Many Worlds Interpretation is true then it’s wrong to say that either B or C but not both will exist. Rather, both of them exist independently in separate universes. Now, what’s important to me is that my mind continues in some form. But I don’t actually need both B and C for that to happen. So if Roko offered me $100 in exchange for the instantaneous, painless death of B I’d quite happily accept, because from my perspective all that will happen is that I’ll receive the $100.”
Presumably you disagree with this reasoning, right? Even if MWI is true? Well, the powerful intuition that causes you to disagree is what Wei is talking about. (As he says, giving up that intuition is the position of “quantum immortality”.)
The fact that Wei states “the strong version” when “the weak version” would have sufficed is unfortunate. But you will completely miss the point of the debate if you concentrate solely on the difference between the two versions.
Tim sometimes morphs into an “I won’t update” bot during debates.
Er, what evidence exactly am I supposed to be updating on?
The supplied evidence for 1 (“We value extra copies in other quantum branches”) seems feeble. Most people are totally ignorant of the MWI. Most people lived before it was invented. Quantum theory is mostly an irrelevance—as far as people’s values goes. If—astonishingly—evidence of wavefunction collapse was ever found, people would carry on caring about things much as before—without any breakdown of morality—despite the loss of practially everything in other worlds. That thought experiment seems to demonstrate that most people care very little about copies of themselves in other worlds—since they would behave much the same if scientists discovered that those worlds did not exist.
Maybe there are somewhere a bunch of people with very odd values, who actually believe that they really do value copies of themselves in other worlds. I can think of at least one fellow who thinks like that—David Pearce. However, if so, this hypothetical silent mass of people have not stood up to be counted here.