On 5/25/2015 9:31 AM, Bruno Marchal wrote:
On 25 May 2015, at 03:27, meekerdb wrote:
On 5/24/2015 5:05 AM, Pierz wrote:
On Sunday, May 24, 2015 at 4:02:42 PM UTC+10, Brent wrote:
On 5/23/2015 9:58 PM, Pierz wrote:
On Saturday, May 23, 2015 at 8:36:40 PM UTC+10, Liz R wrote:
I'm not sure why comp would predict that physical laws are invariant
for all
observers. I can see that it would lead to a sort of
super-anthropic-selection effect, but surely all possible observers
should
exist somewhere in arithmetic, including ones who observe different
physics
(that is compatible with their existence) ?
I really must dig up the old thread! But I'm not saying comp does entail
invariant physics for all observers, just that if there are different
physics,
the substitution level must be very low indeed. Think of the original
scenario in
the UDA: a person in Washington is suddenly annihilated, and then
duplicated in
Helsinki and Moscow (or whatever). That operation creates a 50% probability
of
finding oneself in Helsinki or Moscow. But the ultimate point of the UDA is
that
one's actual probability of finding oneself in Helsinki or Washington
depends on
the total measure of /all/ virtual environments within which that observer
is
instantiated in an environment that looks like one of those cities. One
can't
isolate a particular virtual system from the trace of the UD. So you can't
create
an arbitrary physics in an environment that looks like either city (or
anywhere).
Well you can, but any observer will always find their own physics to be the
measure of *all* their continuations in arithmetic. So there can't be an
environment that is like Helsinki or Moscow at some point but that has
different
physical laws. Carry this logic over to the scenario of a person standing
in an
empty room - the physics the person experiences will be the measure of all
such
identical persons standing in empty rooms.
"Experiencing physics" I think needs some explication. If experiencing only
refers to consciously thinking propositions, then one may not be
experiencing much
physics: the world seems 3D with colors, there's a mild temperature, air
smells
OK,... One doesn't directly, consciously experience the 2nd law, or the
Born
rule. The "laws of physics" are human inventions to describe and predict events.
They're not out there in Nature; which is why we have to revise them from time to
time as we find more comprehensive, more accurate "laws".
OK, but it doesn't seem relevant to the argument. We experience a world predictable
and stable in certain ways that, now we're so sophisticated, we formalise into the
science of physics. Bruno's claim is that these regularities are not intrinsic
properties of some primary stuff, but emergent from the computational properties of
observers - namely how often various continuations of those observers crop up
relatively to one another in the abstract space of all possible continuations. I'm
trying to make an admittedly difficult point about whether or not observers in
different places can experience different physics within this paradigm, and if so, how
that relates to "substitution level". If you're worried about people "experiencing
physics" let's just concentrate on observers who go to the trouble of doing physics
experiments. It really doesn't matter.
My point was that most people's conscious experience most of the time could be
accommodated within a large range of physics. For example Newtonian physics seems
intuitive while quantum mechanics isn't; but we think QM is the better theory. But
Bruno claims that his theory implies QM and not Newtonian mechanics. So if people
consciously experienced a Newtonian universe (which they once thought they did) would
that falsify comp or would it just imply that the UD can instantiate Newtonian universes.
Which it can't. So, a Newtonian universe would have refute comp, and indeed even
locality as the Newtonian universe is not local. But of course, a computationalist could
say, that the "newtonian character is illusory, and that by looking closer we will
discover ... something like QM.
So you are claiming that it would be impossible to have a conscious being that experienced
a Newtonian universe - that this would produce a logical contradiction?
Brent
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