À (At) 11:23 +0100 15/03/99, Marchal écrivait (wrote) :
>>[Gilles:]
>>...In all your thought experiment you seem to
>>assume that it is possible to reproduce *exactly* the behaviour of a
>>physical system (the brain) with some detailed computation.
>
>[Bruno]
>This is indeed my working hypothesis. To be precise I suppose there is a
>level of description of myself such that I survive through a digital
>substitution made at that level. I don't care if the level corresponds to
>the quantum state of the entire cosmos or just the local concentration of
>neurone's neurotransmettor ...
...
>Indeed, but this is true even for an appendicite operation.
>I mean that, BY DEFINITION, if COMP is correct, and if the level of
>substitution is correct then I will come back from the hospital with the
>same feeling of someone coming back after a succesfull operation.
>Of course it is an event in my life, and my life will diverge from the
>possible life I would have had having not go to the hospital.
I think my concerns start right there. What's the meaning of "I survived
through a digital substitution?" As you said yourself, the question of
identity is subjective. It works well in our world because we have no way
to do this kind of operation. As you say yourself, it would be impossible
to decide whether the survival is true or not if such substitutions would
be feasible.
I'll try to put it in other words. Suppose that the progress of technique
has made this kind of operation feasible. Now assume that you are a judge
and that somebody complains after such an operation, because he thinks that
the substitution has been missed. Could you give an objective criterium to
decide if this complaint is founded? Sure not. This man would probably have
changed compared to before his operation, but it can be attributed to
normal psychological consequences of what happened. The surgeon (computer
scientist ?) could argue he had well done the job, but this cannot be
proved. Note that it is impossible that the patient feel different : he
can't remember his former state, so he has no way to test if he has
"really" changed. His complaint could only be founded by qualitative,
exterior measurements maybe from his relatives, who have their own
subjectivity. So what to decide? (I guess that if such operation became
feasible, there would be indeed a lot of such trials, especially in US!)
I try here to precize the nature of the differences between our points of
view. You seem to admit that this property (COMP) could be true without
being provable, like some mathematical propositions. What I think (that's
probably why you describe me as a physicalist!) is that assertions about
the real world (including, but not only, comp!) are neither provable, nor
true in a mathematical sense. They are all approximations applied to human
categories, that do not describe "exactly" the reality. So in fact (I guess
that I am just telling what Kant said two centuries ago, although my
philosophical formation is rather limited!)) any "ontological" or
"metaphysical" theory (like that of big programmer!) is useless.
Propositions about the world are worthwhile (and for me deserve the world
"explanation") only if they relate together some apparent features of the
world with sufficient accuracy and predictive power. We are free to define
our categories accordingly. I do not take the Universe for granted. I think
our discourse about the world is subjective and that any proposition about
its real nature (I put in this category God, the Big programmer or N !) is
desperately devoid of usefulness, because not testable and not falsifiable.
So for me "COMP" is neither true not false : you have to better define its
operational sense to see "how far" it is true. I recognize that your
reasoning is true if you admit that something like COMP can be (really)
true.
However I do not know any example where ontological reflexions have allowed
to make anything real. Furthermore we may have different "epistemological"
points of view.
For example a very important step would be to succeed in building
"thinking machines", say like Turing, machines which you could discuss
with. I think this step is feasible. What I think is that they will never
be used to "replace" somebody, first because it is tremendously more
complicated to duplicate (and as I tried to convince you, impossible to
duplicate *exactly*) a highly organized system that to let a simple one
self-organize (what nature has made for all of us), and second because it
will raise so difficult questions about identity that we would promptly
abandon this way! So most probably such machines would be like a new,
artificial (living??) species with its own individuals, all different from
each others (because I think that consciousness can exist only with a
personal history) and of course from us. This is hopefully a testable
prediction!
In all case I am very happy to have this kind of discussion with you; even
if I don't share all you premises, it helps me a lot to clarify these
issues, including my own positions!
Cheers
Gilles
Received on Wed Mar 17 1999 - 00:33:52 PST
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