Xref: utzoo comp.ai:6091 sci.philosophy.tech:2167 Path: utzoo!attcan!uunet!lll-winken!uwm.edu!rpi!zaphod.mps.ohio-state.edu!mips!apple!amdahl!kp From: kp@uts.amdahl.com (Ken Presting) Newsgroups: comp.ai,sci.philosophy.tech Subject: Re: Another letter to the New York Review Summary: Problems with the asymptotic convergence of androids Keywords: Penrose, Moravec Message-ID: <723g02AH8cU501@amdahl.uts.amdahl.com> Date: 27 Feb 90 17:58:07 GMT References: <18883@bcsaic.UUCP> <1589@skye.ed.ac.uk> <11488@venera.UUCP> <1754@skye.ed.ac.uk> <90Feb15.231415est.6212@neat.cs.toronto.edu> <2al902Zg8bnn01@amdahl.uts.amdahl.com> <3750@uceng.UC.EDU> Reply-To: kp@amdahl.uts.amdahl.com (Ken Presting) Organization: Amdahl Corporation, Sunnyvale CA Lines: 89 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.