On 14 May 2015, at 20:34, meekerdb wrote:
On 5/14/2015 9:41 AM, Bruno Marchal wrote:
On 14 May 2015, at 07:13, meekerdb wrote:
On 5/13/2015 5:32 PM, Russell Standish wrote:
On Thu, May 14, 2015 at 11:26:17AM +1200, LizR wrote:
On 13 May 2015 at 18:20, Russell Standish
<[email protected]> wrote:
For a robust ontology, counterfactuals are physically
instantiated,
therefore the MGA is invalid.
Can you elaborate on this? ISTM that counterfactuals aren't, and
indeed
can't, be physically instantiated. (Isn't that what being
counterfactual
means?!)
No - counterfactual just means not in this universe. If its not
in any
universe, then its not just counterfactual, but actually
illogical, or
impossible, or something.
If "not in any universe" is meant in the Kripke sense, then
something not in any universe is something that is logically
impossible. But if "not in any universe" is meant in the MWI
sense, then counterfactuals are only those outcomes consistent
with QM but which don't happen.
OK.
I think it is only the latter kind of counterfactual that need be
considered in computations.
Not OK. You beg the question of justifying why the physical
computation wins. You then miss the comp promise of explaining the
physical form from something simpler like the combinatorial, or the
arithmetical, or the sigma_1 complete set, etc.
OK, I appreciate that. But then what does it mean that the brain
prosthesis the doctor installs must be counterfactually correct?
It means that, after the substitution is done, in case you *are* not
hungry, then in case you would be hungry, you would eat.
Is there no restriction except consistency of the possible inputs?
?
Consistent applies to any system of beliefs producing (believed)
propositions. In classical systems, consistent systems ate those not
believing in some proposition A and in ~A, or which does not believe
in the constant propositional falsity f. ~[]f, or <>t.
Unless you talk like if UDA is understood, and suggest a way to
explain physical counterfactualness in term of the physics
extracted from comp, which you assume is QM. In that case, I can
make sense of your sentence.
I'm trying to understand what "counterfactual correctness" means in
the physical thought experiments.
It means that in the physically correct mimic of the computation, like
the MOVIE, we would have the right output or the relevant circuits
behavior in case we would have made some change in the system.
Maudlin, in MGA terms, add the "Klara", physically inactive device
which would only be trigged and "restore" the counterfactual
correctness, in case a change is introduced.
But, of course, "restoring the counterfactualness at the right moment
makes you counterfactually correct, by definition, so if we accept the
physical supervenience (of consciousness on the physical activity of
the computation) then we have to accept the consciousness on MOVIE +
KLARA, which are during the experience identical, as the Klara are
inactive.
So physical supervenience makes computationalism spurious, and it is
simpler to NOT assume a physical reality at the start, and relate
consciousness to the semantic of the abstract program/person, which is
actually supported accidentally or not to this or that universal system.
This leads to the extent of Everett's formulation on the "Universal
Wave/Multiverse" to the Sigma_1 arithmetic. That one is better seen as
a web of dream emulation, as the obligatory exercise now should
consist in justifying a probability measure on them (cf the FPI).
I say more on this in an answer to another post.
Bruno
Brent
Are you defending physicalism? Or are you trying to justify the
appearance of physicalism in comp?
Sometimes, out of context, those two things can't avoid to look
similar. At some point peole should perhaps make clear all what
they assume.
Bruno
Brent
As I mentioned, a simple example is my decision between tea and
coffee. In
the MWI (or an infinite universe) there are separate branches (or
locations) in which I have both - but in the branch where I had
tea, I
didn't have coffee, and vice versa. And because those branches
can't
communicate, the road not taken remains counterfactual and non-
physical
within each branch. Isn't that enough for the MGA to not need to
worry
about counterfactuals, even in the MWI/Level whatever multiverse?
Why is communication needed?
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