🚀 go-pugleaf

In article <3750@uceng.UC.EDU> dmocsny@uceng.UC.EDU (daniel mocsny) writes:
>In article <2al902Zg8bnn01@amdahl.uts.amdahl.com> kp@amdahl.uts.amdahl.com (Ken Presting) writes:
>> . . . If nobody
>>noticed and described "that certain something", then no way can we build
>>it into anything.  But if we can build it, we can also program it.
>
>I disagree. The analog builders might "get lucky," and be able to
>reproduce their success even though they can't explicate any
>programmable underlying mechanism.

Good point, I should have explicitly qualified "build" with
"deliberately".  But even this qualification won't, by itself, rescue
my point altogether -

>You don't have to have any idea of how to simulate combustion before
>you can invent gunpowder and conquer nations. . . .

I can think of an even more damaging example.  Natural selection has
"built" an intelligent organism, by trial and error, and certainly did
not start out with any understanding of the phenomenon it was destined
to produce.

> . . . {A} recipe for
>gunpowder is a reproduceable, logical description of the process, but
>it is nowhere near complete enough *by* *itself* to allow a computer
>to reproduce much of the sensory information an observer would obtain
>from watching you mix up a big batch of gunpowder and set a match to
>it.
>
>The real world contains many useful phenomena that give us an enormous
>head start in the game of artificially creating complex sensory
>experiences. Trying to recreate the same sensory experiences via
>logical computation and general-purpose actuators is vastly harder,

This comment strikes at the heart of my mistake.  A general-purpose
computer is easy enough to imagine, and not so hard to make.  But now
that I think about it, I am convinced that a general-purpose *actuator*
is clearly impossible.  The picture I drew of a deductive simulator
controlling a robot would require an actuator that could take any
assertion about the state of a human body and *poof* cause it to be the
case that some congregation of atoms has that very state.  Short of Star
Trek's transporter, the idea is absurd.

So let me backpedal a bit.  I need to start with a special purpose
transducer which can drive a dedicated actuator.  I can recite a standard
story here, for example a two-way radio inside the skull of a suitably
decerebrated (ouch) human body, which is the "actuator".  The transducers
might be electrodes (or better, electrically controlled neurotransmitter
dispensers) connected to the remains of a spinal column, with
corresponding neurotransmitter sensors connected to efferent neurons from
the retina, skin, etc.

Endocrine "signals" from the rest of the body are also important in brain
function, and we would like our robot also to respond appropriately to
various psycho-active drugs.  Fortunately, current technology provides us
with a suggestive example of general-purpose chemical sensors in the
form of gas chromatographs, PET and MRI scanners, etc, so it is perhaps
conceivable that future development (and especially miniaturization)
will result in devices capable of encoding the various chemical events
to which the brain is sensitive.

Of course, since I have described a body which is physically altered, it
is trivial to identify observable differences between the robot and a
normal human.  Just X-ray its head.  So my tidy picture of abritrarily
accurate calculations subverting increasingly careful or protracted
measurements needs an indefinite number of ad-hoc exceptions.  If we
want our robot to make a reasonable showing in (say) a Total Turing Test,
we'd have to make it very shy of radiologists, and who knows what else.

To rescue my final conclusion, that any detectable deviations between the
model and a real human are eliminable, I must add the assumption that
sensor and actuator technology will progress without limit.  This is much
more problematic than assuming that the deductive simulation can be
made arbitrarily precise.

I consider the failure of this story to be a reductio of all proposals
to guage the success of AI in terms of indistinguishability from humans.
The problem is not that there is some threshold of accuracy that androids
can never reach.  Rather, the problem is that sensor and actuator
technology will necessarily progress at a finite pace, always leaving
some detectable difference between the robot and the real thing.  As long
as we refrain from analyzing intelligence, we will be hard pressed to
find principled grounds on which to ignore objections that the detectable
differences show the failure of our implementation.

In a future post, I will discuss Dan's objections to my hasty disposal of
empiricism.  The main idea is that measurement enforces theory-dependence.

In the meantime, my thanks to Dan for a stimulating objection.