On 5/6/2015 8:54 PM, Bruce Kellett wrote:
meekerdb wrote:
Pretty good list.
On 5/6/2015 6:23 PM, LizR wrote:
With profound and sincere apologies to Bruno, some people distinguish these two items,
so I thought it might be worthwhile trying to marshall the arguments in one place, and
give them simple names as per the objections to the Chinese Room I seem to recall
seeing in one of DRH's books - "The Systems Reply" and so on.
So, why do some folks consider that "comp1" doesn't lead to "comp2" ?
1. "Arithmetical Realism is wrong" - the view that maths is something we made up. This
might be true, but imho it has (so far) failed to convincingly explain away that pesky
"unreasonable effectiveness".
I've never understood the "unreasonable effectiveness" argument. ISTM that the
effectiveness is evidence that we made it up. First, since /*we*/ are creatures of
this world what */we/* make will have some effectiveness in this world just because of
evolution and natural selection. Second, much of mathematics was invented specifically
to solve problems in this world - so is it any surprise that it's effective? Third,
there is a lot of "game" mathematics that is only effective in proving things about an
invented realm.
I am with you here. I think it was Lee Smolin who said recently that the effectiveness
of mathematics in describing the physical world is greatly over-rated. As Brent says,
mathematics is about as effective as you would expect for something that we made up to
explain our experience of the world. It is not "unreasonably effective" because, for
example, there is no closed form solution for the simplest three-body problem in
Newtonian gravity.
I would say the best argument for arithmetical realism (especially arithmetic) is that
it is ubiquitous and facts about it seem to be discovered. But I don't think this is
strong argument.
No, it is quite weak because once you have chosen the axioms, the theorems that can be
deduced from these by using the assumed rules of inference are independent of what
anybody thinks about them. It is just like an invented game such as chess in this regard.
I must admit that I do take exception to Bruno's oft-repeated saying that "if you accept
that 2+2=4 independent of you or me then you believe in arithmetical realism". That is
disingenuous in the extreme, because he then goes on to use the term "realism" with
respect to arithmetic in ways that do not follow from the simple tautology "2+2=4".
Accepting that tautologies are true independent of people, depending only on the
definition of the terms involved, is a far cry from realism about arithmetic.
2. "Pronouns" - only one person takes this seriously, and has been unable to convince
anyone else (so far) but in theory there might be something wrong with using pronouns
when talking about matter duplication (or AI programme duplication, or MWI
experimenter duplication...)
I think there is something wrong with */some/* uses of pronouns. What's wrong is that
they implicitly assume that there is an entity with temporal continuity that can be
identified as "you". But this depends on a theory of personal identity that become
problematic in the presence of duplicating machines. Bruno seems to say that if M and
W have the same memories about all events prior to t, then M and W are the same person,
or maybe just the same person before t? But do they have to have ALL the same
memories; aren't their degrees of sameness? And is it really only memories?
Duplication is better understood for a computer based AI, but that opens the
possibility of duplicating exactly the same memory, but having a slight variation in
the processor.
However I don't think these seriously impact the argument because personal identity is
really based on bodies and Bruno's theory proposes to replace our concept of bodies
with something based on computation anyway.
But he plans to extract the physical world, with bodies in all their messiness, from
computations anyway. So he cannot simply discard bodies as of no relevance to the
concept of personal identity. Bodies exist in his world as much as in ours. Basing
personal identity solely on the content of memories is seriously impoverished.
3. "Everything in the light cone" - the view that consciousness is necessarily an open
system, of which any description must take into account all past influences that may
impinge on it. This is more interesting and persuasive than the first two, imho, but
personally I don't think it's relevant, since if one is going to make a recording of a
series of conscious states one can (in principle) isolate the brain from the outside
world by making a "cut" where signals from the world turn to nerve impulses. One then
has to "merely" record everything at that interface, and all the computations going on
in the brain in response to that input.
The "brain in a vat" scenario. That is always a possibility and I do not think that
Bruno has adequate defenses against solipsism. He criticized me for being defeatist when
I said that we normally just ignore such possibilities and get on with our lives because
we can't do anything about it anyway. But he can't rule out solipsism either.
But note that the meaning, the reference, of those computations in the brain depend on
the brain not being isolated in the past. Some of them even depend on the evolutionary
history of the species of that brain.
This is true, but can be overcome by enclosing the brain in a vat and feeding artificial
stimuli that mimic some external world.
Ah, but there's subtle point in that "some". Suppose we fed the brain the digital screen
signal of "World of Warcraft" and let it drive the inputs to the game controller. Because
my brain and senses evolved in this world (3+1 spacetime, photons,...), if it were fed the
GPU output from WoW my brain would reject it as noise. If the brain was to realize my
consciousness it would have to be fed a simulation of this world, not just some world.
4. The "Necessity of couterfactuals" - the view that any conscious being needs to be
able to handle counterfactuals. This is true in real life, of course, but perhaps not
if one is trying to create a recording of a conscious state. Maudlin goes into this in
his "Olimpia and Klara" thought experiment, in which he constructs a Library of
Babel's worth of completely unnecessary machinery to handle the counterfactuals, then
refrains from actually using it. Istm that this applies to the MGA as well - there is
no actual necessity to deal with cases that don't arise when one is repeatedly running
the same deterministic computer programme, hence this ability isn't needed when
replaying a recording of consciousness.
I don't know which side of this I come down on. But from one point of view the
requirement that consciousness be instantiated by a computation, not just a playback,
leads by extension to the ELC theory.
My feeling is that the whole deal with counterfactuals is just a diversion. If
consciousness can be implemented on a computer, then one can run the same program with
the same inputs any number of times, and one only ever recreates the same conscious
experiences -- there are not different conscious moments for each run, and
counterfactuals play no part in repeats, they only come into play when you run with
different inputs, which is not the case under consideration. Hence, a recording (which
is equivalent to the original program) will, when replayed, also generate the conscious
experience. The point here being that it has to be replayed on physical equipment, just
as the original program was run on physical equipment. So MGA does not eliminate the
need for the physical: rather, it reinforces the conclusion that the physical is
indispensable.
Besides, I have always found this insistence on counterfactual correctness ironic for
people who believe in MWI and happily abandon counterfactual definiteness when they
explain the EPR correlations. The argument in MWI is that experiments that are not
performed do not have definite results. Exactly the same is true for the MGA. Hence
counterfactuals are irrelevant.
5. The "Argument from incredulity" - the whole idea is preposterous, so there simply
must be something wrong somewhere! This is yet to be proven for all of modern science,
most of which has been subjected to it at some point.
The argument from incredulity has more punch when it's being used against a reductio.
It's like saying accept my incredible theory or else you'll have to believe this
absurdity.
The 'argument from incredulity' was raised against Bruno's interpretation of the MGA. He
claimed a contradiction, but really all that was established was that he found the
results of not believing his interpretation to be absurd. This is not a valid argument
-- what is absurd to one person may well be quite reasonable to another.
And, for completeness...
6. The "pee-pee" argument, which makes fun of the terminology and insults the ideas
without making any constructive points. I will lump into this arguments that because
we don't have matter duplicators the whole thing fails, and similar ideas. I think we
can dismiss these without further ado.
For convenience, and because I know we like making up our own terminology, I have
given these all handy abbreviations, namely ARW, PN, ELC, NOC, INC and TPPA.
Is there anything I've missed?
I think ultrafinitism is another possibility. And it's not often mentioned, but it's
also possible that consciousness is a computation that depends on the continuum (after
all quantum mechanics does).
Yes, that. But I think the strongest argument against the theory is that it doesn't
actually give you a physical world. There is a claim that we can extract the physical
world by "interviewing the machine", but it is not really clear what this means, and
until such interviews give useful physics, then the model has to be regarded as of
dubious utility.
The point is that normal scientific practice requires any theory to be measured against
its empirical success. But if a claimed theory of everything has no empirical successes
at all, that is definitely a strong argument against it. If the theory doesn't work,
there must be something wrong with it, even if it is not easy to put your finger on
exactly where the theory went wrong.
But I think we have identified enough weak points in the theory that we need not be too
concerned about the final demolition -- the theory will simply fail to attract any
substantial body of believers.
Well my hope would be somewhat different: that the theory attract some experts in
mathematical and modal logic who can either pull some new empirical prediction out of it
or show that is impossible. I don't know enough modal logic to judge. For example it
seems illogical to me to say a world is not accessible from itself; and this is an axiom
that has consequences for the modal logic.
Brent
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