On Sep 17, 2012, at 3:39 PM, Craig Weinberg <whatsons...@gmail.com>
On Monday, September 17, 2012 9:24:23 AM UTC-4, stathisp wrote:
On Sep 16, 2012, at 10:42 PM, Craig Weinberg <whats...@gmail.com>
set has subsets, and we can limit our discussion to these subsets.
example, if we are interested only in mass, we can simulate a human
perfectly using the right number of rocks. Even someone who believes
in an immortal soul would agree with this.
No, I don't agree with it at all. You are eating the menu. A
quantity of mass doesn't simulate anything except in your mind.
Mass is a normative abstraction which we apply in comparing
physical bodies with each other. To reduce a human being to a
physical body is not a simulation is it only weighing a bag of
I'm just saying that the mass of the human and the mass of the rocks
is the same, not that the rocks and the human are the same. They
share a property, which manifests as identical behaviour when they
are put on scales. What's controversial about that?
It isn't controversial, but I am suggesting that maybe it should be.
It isn't that there is an independent and disembodied 'property'
that human body and the rocks share, it is that we measure them in a
way which allows us to categorize one's behavior as similar to
another in a particular way.
Think of the fabric of the universe being like an optical illusion
where colors change when they are adjacent to each other but not if
they are against grey. There is no abstract property being
manifested as concrete experiences, only concrete experiences can be
re-presented as abstract properties.
Yes, but there are properties of the brain that may not be relevant
behaviour. Which properties are in fact important is determined by
experiment. For example, we may replace the myelin sheath with a
synthetic material that has similar electrical properties and then
test an isolated nerve to see if action potentials propagate in the
same way. If they do, then the next step is to incorporate the nerve
in a network and see if the pattern of firing in the network looks
normal. The step after that is to replace the myelin in the brain
rat to see if the animal's behaviour changes. The modified rats are
compared to unmodified rats by a blinded researcher to see if he can
tell the difference. If no-one can consistently tell the difference
then it is announced that the synthetic myelin appears to be a
functionally identical substitute for natural myelin.
Except it isn't identical. No imitation substance is identical to
the original. Sooner or later the limits of the imitation will be
found - or they could be advantages. Maybe the imitation myelin
prevents brain cancer or heat stroke or something, but it also
maybe prevents sensation in cold weather or maybe certain amino
acids now cause Parkinson's disease. There is no such thing as
identical. There is only 'seems identical from this measure at this
Yes, it's not *identical*. No-one has claimed this. And since it's
not identical, under some possible test it would behave differently;
otherwise it would be identical.
Not in the case of consciousness. There is no reason to believe that
it is possible to test quality of consciousness. What might seem
identical to a child may be completely dysfunctional as an
adolescent - or it might be that tests done in a laboratory fail to
reveal real world defects. We have no reason to believe that it is
possible for consciousness to be anything other than completely
unique and maybe even tied to the place and time of its instantiation.
But there are some changes which make no functional difference.
Absolutely, but consciousness is not necessarily a function, and
function is subject to the form of measurement and interpretation
If l have a drink of water, that changes my brain by decreasing the
sodium concentration. But this change is not significant if we are
considering whether I continue to manifest normal human behaviour,
since firstly the brain is tolerant of moderate physical changes
But a few milligrams of LSD or ricin (LD100 of 25 µg/kg) will have a
catastrophic effect on normal human capacities, so that the brain's
tolerance has nothing to do with how moderate the physical changes
are. That's a blanket generalization that doesn't pan out. It's folk
and secondly people can manifest a range of different behaviours and
remain recognisably human and recognisably the same human. In other
words humans have certain engineering tolerances in their
components, and the aim in replacing components would be to do it
within this tolerance. Perfection is not attainable by either
engineers or nature.
Engineering may not be applicable to consciousness though. There is
tolerance for the extension of consciousness - if you injure your
spine, we could engineer a new segment, just like we could replace
your leg with a prosthetic, but there is not necessarily a
replacement for the self as a whole. A prosthetic head that doesn't
replace the person is not necessarily a possibility. You assume that
a person is a structure with interchangeable parts. I think it is an
experience which is inherently irreducible and non-transferable.
As is the nature
of science, another team of researchers may then find some deficit in
the behaviour of the modified rats under conditions the first team
not examine. Scientists then make modifications to the formula of the
synthetic myelin and do the experiments again.
Which is great for medicine (although ultimately maybe
unsustainably expensive), but it has nothing to do with the
assumption of identical structure and the hard problem of
consciousness. There is no such thing as identical experience. I
have suggested that in fact we can perhaps define consciousness as
that which has never been repeated. It is the antithesis of that
which can be repeated, (hence the experience of "now"), even though
experiences themselves can seem very repetitive. The only seem so
from the vantage point of a completely novel moment of
consideration of the memories of previous iterations.
Here is where you have misunderstood the whole aim of the thought
experiment in the paper you have cited. The paper assumes that
identical function does *not* necessarily result in identical
consciousness and follows this idea to see where it leads.
I understand that, but it still assumes that there is a such thing
as a set of functions which could be identified and reproduced that
cause consciousness. I don't assume that, because consciousness
isn't like anything else. It is the source of all functions and
appearances, not the effect of them. Once you have consciousness in
the universe, then it can be enhanced and altered in infinite ways,
but none of them can replace the experience that is your own.
Do you think if your brain were cut in half, but then perfectly put
back together that you would still be conscious in the same way?
What if cut into a thousand pieces and put back together perfectly?
What if every atom was taken apart and put back together?
What if every atom was taken apart, and then atoms from a different
pile were used to put you back together?
What then if the original atoms were put back, would they both
experience what it is like to be you?
Does the identity of one's atoms matter or are they interchangable?
If the identity is not what matters, what is it that does?
> This is the point of the thought experiment. The limitations of
all forms of
> measurement and perception preclude all possibility of there ever
> such thing as an exhaustively complete set of third person
behaviors of any
> What is it that you don't think I understand?
What you don't understand is that an exhaustively complete set of
behaviours is not required.
Yes, it is. Not for prosthetic enhancements, or repairs to a
nervous system, but to replace a nervous system without replacing
the person who is using it, yes, there is no set of behaviors which
can ever be exhaustive enough in theory to accomplish that. You
might be able to do it biologically, but there is no reason to
trust it unless and until someone can be walked off of their brain
for a few weeks or months and then walked back on.
The replacement components need only be within the engineering
tolerance of the nervous system components. This is a difficult task
but it is achievable in principle.
You assume that consciousness can be replaced, but I understand
exactly why it can't. You can believe that there is no difference
between scooping out your brain stem and replacing it with a
functional equivalent as long as it was well engineered, but to me
it's a completely misguided notion. Consciousness doesn't exist on
the outside of us. Engineering only deals with exteriors. If the
universe were designed by engineers, there could be no consciousness.
I don't access an exhaustively complete
set of behaviours to determine if my friends are the same people from
day to day, and in fact they are *not* the same systems from day to
day, as they change both physically and psychologically. I have in
mind a rather vague set of behavioural behavioural limits and if the
people who I think are my friends deviate significantly from these
limits I will start to worry.
Which is exactly why you would not want to replace your friends
with devices capable only of programmed deviations. Are simulated
friends 'good enough'. Will it be good enough when your friends
convince you to be replaced by your simulation?
I assume that my friends have not been replaced by robots. If they
have been then that means the robots can almost perfectly replicate
their behaviour, since I (and people in general) am very good at
picking up even tiny deviations from normal behaviour. The question
then is, if the function of a human can be replicated this closely
by a machine does that mean the consciousness can also be
replicated? The answer is yes, since otherwise we would have the
possibility of a person having radically different experiences but
behaving normally and being unaware that their experiences were
The answer is no. A cartoon of Bugs Bunny has no experiences but
behaves just like Bugs Bunny would if he had experiences. You are
eating the menu.
-- Stathis Papaioannou
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