Bruno Marchal wrote:
On 03 Jul 2015, at 14:11, Bruce Kellett wrote:
In fact, some would say that "it is models all the way down".
I have no idea what you mean by model. But keep in mind that logicians
used it as the possible interpretation of a theory. A theory is seen as
a syntactical machine-like device to produce theorems? A model is a
structure which satisfies (interpret) those axioms and theorems of the
theory.
Yes. A word like 'model' can have many meanings in different contexts.
Physicists tend to use the term somewhat loosely to mean anything from a
simplified situation (toy model, as in 2-dimensional gravity models) to
a fully developed theory. They are less likely to use the term in the
sense of 'exemplar', as in 'a model of rectitude!'
We ultimately have nothing but models that must constantly be subject
to revision in the light of new or more evidence.
Yes, I agree with this (using models meaning theory).
The idea that we can interpret the data without using theory is due to
the facts that most of our theory are instinctive and wired up in our
brain. Without a theory, all data does not make sense. We instinctively
bet in our existence and in the existence of some reality. That is
already a theory (model, for physicists). Indeed, it is already a
theology (a part of it becomes false when assumed).
Physics is well aware that all observation is theory laden. Much of this
is hard-wired in our brains by evolution, but there is also a real sense
in which newborn babies have to learn how to observe and interpret the
world around them, developing their own models and theories of the world.
I am still waiting for your assessment of the six first steps of the
UDA, so that we can discuss step 7 and step 8 at ease.
In brief, it seems that the early steps are about developing a theory in
which consciousness can be split up into moments that are integrated
over to make up the continuous experience, memory being the linking
feature. This is a preparation for interpretation of the realization of
existence in the UD.
I have problems with the one-dimensional 'model' of personal identity
that is used here. Personal identity is multi-dimensional, and identity
over time is a complicated function of these dimensions. Something
important seems to be lost with hanging everything on memory. Also, the
first person perspective merges into the third person perspective
imperceptibly as we include awareness of our bodies and surroundings.
Pure introspection will never get us anywhere. However, once you move
the dovetailer into Platonia, these early stages of the argument do not
establish anything significant. (See below.)
It seems to me that you did understand step seven, as you got the point
by yourself once (and present it as a problem for comp, but you ignored
that that was the point). The UDA *is* a problem for the
computationalist: to eliminate the white rabbits, or equivalently to
justify the laws of physics.
You have not really responded to my suggestion that the laws of physics,
and the elimination of white rabbits, are already implicit in the UD --
we just go to the computation that computes the whole universe, from its
inception to indefinitely in the future. If we consider only
distinguishable histories, this is a finite computation up to any given
epoch, so is necessarily present in the dovetailer. Why not use it?
There is then no difficulty in extracting physics -- it is just there,
complete.
This might not explain anything beyond that which is explained by the
assumption of primitive physicality, but then, I don't think that comp
actually does explain anything, anyway.
The ontological commitment toward a
primitive physical reality simply does no more work after step 8 (MGA,
or Maudlin).
Step 8 and the MGA do not prove anything.
Bruce
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