# Re: MWI and Born's rule / Bruce

`On Fri, Feb 14, 2020 at 8:45 PM Alan Grayson <agrayson2...@gmail.com> wrote:`
```
> On Friday, February 14, 2020 at 2:34:59 AM UTC-7, Bruce wrote:
>>
>> On Fri, Feb 14, 2020 at 7:56 PM Alan Grayson <agrays...@gmail.com> wrote:
>>
>>> On Thursday, February 13, 2020 at 4:33:52 PM UTC-7, Brent wrote:
>>>>
>>>> On 2/13/2020 1:17 PM, Alan Grayson wrote:
>>>>
>>>> Bruce argues that the MWI and Born's rule are incompatible. I don't
>>>> understand his argument, no doubt my failing.
>>>>
>>>>
>>>> I don't think they are incompatible; it's just that the Born rule has
>>>> to stuck in somehow.  It's not implicit in the SWE and can't be derived
>>>> from the linear evolution.  Somehow a probability has to be introduced.
>>>> Once there is a probability measure, then it can be argued via Gleason's
>>>> theorem that the only consistent measure is the Born rule.
>>>>
>>>> Brent
>>>>
>>>
>>> I think what Bruce is trying to show, is that using the MWI, one CANNOT
>>> derive Born's rule as claimed by its advocates. But whether one affirms MWI
>>> or not, the only thing one has to work with is an ensemble generated by
>>> measurements in THIS world. So if you cannot derive Born's rule using a
>>> one-world theory, it would seem impossible to do so with many-worlds, since
>>> in operational terms -- what is observed -- the two interpretations are
>>> indistinguishable.  AG
>>>
>>
>> That's quite an astute observation, Alan. The thing is, we can move on
>> from there. If Many-worlds is true, all possible sets of measurements are
>> generated, and most will give different values for the probabilities. For
>> the observers getting the alternative data, there is nothing to tell them
>> that they are getting the wrong answer. MWI is incoherent.
>>
>> Bruce
>>
>
> But won't the hypothetical observers in OTHER worlds get the same
> ensembles and thus the same distributions? AG
>

No, The point of MWI is that other worlds get different data.

Bruce

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