Hal wrote

> Lee Corbin writes:
> > Why not instead adopt the scientific model?  That is, that
> > we are three-dimensional creatures ensconced in a world 
> > governed by the laws of physics, or, what I'll call the
> > "atoms and processes" model. About observer-moments, I would
> > say what LaPlace answered to Napoleon about a deity:
> > "I have no need of that hypothesis".
> 
> Observer moments are more than a hypothesis, they are our raw experiences
> of the world.  It is more the world that is the hypothesis to explain
> the observer moments, than vice versa.  "I think, therefore I am... an
> observer moment," as Descartes meant to say.

Yes, I had overstated my case. Thanks for the correction. Still,
on a certain literal level, I meant what I said: as an *hypothesis*,
I have no need of observer-moments (any more, say, that I would
require the existence of telephones as part of a scientific
*hypothesis*). But I regret implying that I thought they did not
exist.

> However, given the strong evidence we have for the world's existence and
> the explanatory power it gives for our experience, I don't think there
> is a problem with treating it as fundamental.  This leads to a model of
> world -> observers -> observer-moments.

Yes, thank you. This is exactly the ontology I had in mind. As another
example, laws-of-physics -> atoms-and-minerals -> telephone-sets.
I have no need of an hypothesis that begins with either observers,
observer-moments, or consciousness.

> A key point is that the mapping is not just one-to-many.  It is
> many-to-many.  That is, an observer moment is shared among multiple
> observers; and an observer exists in multiple worlds.

Certainly. This is the usual point of view from the MWI.

You continue:

> [i]  observers merge whenever information is forgotten. And they
>      diverge whenever information is learned.
> [ii] observers exist in any world which is consistent with their
>      observations. 

Basically, yes. But your second point, which I've labeled (ii),
I think has to be modified in this direction: while it's true
that I am "in" any universe where I'm observing exactly the
same sights, sounds, and tactile sensations (regardless of their
actual histories), it's necessary that it be *me* there, and
not Joe Schmoe. This is accomplished by introducing a second
axis that is calibrated by how similar are the internal reactions
of the entity to mine.

Now the set of my observations lies on a continuum (e.g.,
if the colors I'm seeing become too garish or the shapes I'm
seeing become too unfamiliar, then it's less an observer-moment
that *I'm* having and more one that someone else is having).

Likewise, the set of my internal reactions to my observations
lie on a continuum. Sure, there are Lee Corbins with tails
who are seeing exactly what I'm seeing and typing exactly what
I'm typing, but some of them are a lot angrier and more upset
than I am at having been corrected, and so the coefficient of
personal identity falls off along this axis too with distance.

> I see both views - worlds as primary, or observers and observer-moments as
> primary - as playing an important role in understanding our relationship
> to the multiverse.

Please explain why observers and observer-moments should sometimes
be regarded as primary. They're completely derivative in my ontology.
Of course, it's extremely common for derivative entities, like marks
on a whiteboard exhibiting mathematical relationships, or telephone-sets,
or DNA, to be important along the road of making further predictions
and affording further explanations. But still, all those things,
(like "observers" and "observer-moments" for me) don't feel
fundamental. Not as fundamental, for example, as the Standard Model.

You then outline a nice program for making computations based
upon observer-moments.

> ...
> This approach seems to require acknowledgement of the fundamental
> importance both of worlds and observer-moments.  We use worlds to
> calculate measure; we use observer-moments to constrain the set of worlds
> that we occupy, now and in the future.  A world-only approach would seem
> to pin us to a single world and not recognize that we span all worlds
> which contain identical observer-moments;

Well, I was taking "world-only" to include all our best theories
of physics, in particular QM. And the MWI interpretation of QM
of course leads us to observer-moments. It didn't occur to me to
restrict "world" to just one spacetime.

Lee

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