One might ask Bob, what is the measure of Universes in which a Bob finds M but heeds
M' without being suicidal or at least hazardous to his own health? At any rate, Bob
could hardly have reached in sound mind & body the cognitive height of many-worlds
ideas without heeding M instead of M'. "Why not stick with them's what brung you,
Bob?" (Also, it seems to me that Bob might well have to be at least partially heeding
familiar M in order to function well enough to try to heed M'.)
Of course, Bob could quip, "Denial is not just a river in Egypt." To some extent, we
all stick to one or another interpretation in spite of the interpretation's apparent
incoherence, & in spite of apparent contrary evidence. The fact that the incoherence
or contrariness may be merely apparent is the temptation (we revise core ideas more
reluctantly than others, & rightly so) -- the temptation to go wrong & persist even
against a wind of disconfirming information. There is no surefire formula to avoid
errors in any of these directions. There's open-mindedness (good) & there's flakiness
& wishy-washyness (bad.) There's respect for what has stood the test of time so far
(good) & there's dogmatism (bad). (As a practical matter, as regards knowingly to play
by a different set of rules than that of the reality which one lives -- it seems to me
that psychologically & biologically we are constituted so that we can't do that unless
we are insane, & unlikely to be argued back to sanity.!
- Ben Udell
Hal Finney writes:
>Wei Dai writes:
>> Now suppose that two people, Alice and Bob, somehow agree that a measure M is the
>> objectively correct measure, but Bob insists on using measure M' in making
>> decisions. He says "So what if universe A has a bigger measure than universe B
>> according to M? I just care more about what happens in universe B than universe A,
>> so I'll use M' which assigns a bigger measure to universe B." What can Alice say to
>> Bob to convince him that he is not being rational? I don't see what the answer
>> could be.
>How about if she whacks him on the head? Maybe that would knock some sense into him.
>Seriously, she could confront him with the reality that in the universe branch they
>are in, measure M works, while M' does not. Reality, whether in the form of a knock
>on the head or more peaceful interactions, is not subjective.
>Now, true, there would be branches in the multiverse where M' worked while M did not.
> Believers in objective measure would say that those branches are of low measure and
>so "don't matter", but as you point out, Bob can argue symmetrically that this branch
>where he is stuck with Alice and M has worked is also, to him, of low measure.
>But we can solve this conundrum while retaining symmetry. Rationality should demand
>allegience to the observed measure. It is irrational to cling to a measure which
>has been rejected repeatedly by observations. If classical definitions of rationality
>don't have this property, we should fix them. Bob is irrational to hold to M' in a
>universe whose observations reveal M.
>Now, this will demand that in White Rabbit universes, ones where the quantum or
>thermodynamic laws just happen to fail due to bad luck, a rational person would have
>to abandon his (correct!) belief in a lawful universe and come to believe
>(incorrectly!) in miracles. However this is actually a reasonable requirement, since
>we are stipulating that such
miracles have been observed.