Path: utzoo!utgpu!watserv1!watmath!att!bellcore!bellcore-2!rutgers!cs.utexas.edu!sdd.hp.com!usc!venera.isi.edu!smoliar From: smoliar@vaxa.isi.edu (Stephen Smoliar) Newsgroups: comp.ai Subject: Re: Hayes vs. Searle Summary: still worrying about symbols Message-ID: <14385@venera.isi.edu> Date: 21 Jul 90 14:31:13 GMT References: <129.26a5feab@csc.fi> Sender: news@venera.isi.edu Reply-To: smoliar@vaxa.isi.edu (Stephen Smoliar) Organization: USC-Information Sciences Institute Lines: 65 In article <129.26a5feab@csc.fi> ylikoski@csc.fi writes: > >The human brain attaches semantics to neuron impulse trains and its >symbols. I would claim that if we build a computer system that attaches >semantics to its symbols in the same way as the human brain attaches >semantics to its symbols, then we have a computer program that >understands. > This argument assumes that the human brain HAS symbols (or, at least, that is implied through the use of the possessive "its"). There is no evidence that this is the case. I think it would be fair to say that the point is still up for debate, just like the premise that the human brain "has" mental images. It seems to me that the only reason we are arguing about symbols is because they are critical in Searle's argument. This is because Searle is bound and determined that his precious concept of "understanding" should not be related to behavior. By factoring behavior out of the problem, he feels secure in being left with a problem of interpreting symbol structures. This still strikes me as specious. Machines behave; and they don't "have" symbol structures. WE invent symbol structures in order to explain and predict machine behavior, but I defy anyone to find any symbols in the inner guts of any machine architecture! (This is why Newell deals with the "symbol level" as the highest layer of description of a computer architecture. It is the layer through which we, as humans, can understand what is going on in all the lower layers.) Likewise, I think it very unlikely that we are going to find any symbols in the architecture of the brain (and, to make life even more interesting, we are probably NOT going to find the elegant hierarchy of layers which Newell invokes in describing computer architectures). Back when he was working on the ENTSCHEIDUNGSPROBLEM, Turing discovered that symbols were a great lever for understanding computational behavior. By the time Church offered up his famous thesis, many researchers had made the same discovery. Church's thesis argues that since it is always the same computational behavior, all these different symbolic perspectives are, in some sense, equivalent. It does NOT argue that any computing agent must actually possess such symbol structures. This is a subtle point; and it seems to have escaped Searle, thus leading him to say all sorts of silly things about symbols which fly in the face of any objective observation of either machine or human behavior. > >2) Many agencies in John's Society of Mind possess capabilities >involving Rolle's theorem: for example his Inference agency knows how >to utilize Rolle's theorem while proving simple theorems. > This part of Antti's argument I can accept. However, close inspection of Minsky's text will reveal that he, too, does not expect his agencies to embody symbol structures. He discusses how various constructs which WE would deal with as symbol structures may be implemented with his agencies, but his argument essentially extrapolates on the idea that we can implement an "interpreter" for "machine code" out of electronic hardware. Anything we try to say about "understanding Rolle's theorem" ultimately reduces to how those agencies behave. Any symbol structures we invoke are merely an abstraction to facilitate the description of that behavior. ========================================================================= USPS: Stephen Smoliar USC Information Sciences Institute 4676 Admiralty Way Suite 1001 Marina del Rey, California 90292-6695 Internet: smoliar@vaxa.isi.edu "It's only words . . . unless they're true."--David Mamet