perm filename NYRB[PUB,TES] blob
sn#075088 filedate 1973-11-27 generic text, type T, neo UTF8
00100 .PAGE FRAME 45 HIGH 69 WIDE
00200 .AREA TEXT LINES 4 TO 42
00300 .TITLE AREA FOOTING LINE 45
00400 .DOUBLE SPACE
00500 .FONT 1 "NGR40"
00600 .FONT 2 "NGR30"
00700 .TURN ON "%"
00800 .EVERY FOOTING(,%1{PAGE}%*,)
00900 .NEXT PAGE
01000 .SELECT 1
01100 .CENTER
01200 ARTIFICIAL INTELLIGENCE LABORATORY
01300 STANFORD UNIVERSITY
01400 CALIFORNIA,94305.%2
01500 .FILL
01600
01700
01800
01900 .VERBATIM
02000
02100
02200 November 23rd.
02300
02400
02500
02600 Dear Sirs,
02700
02800 .FILL
02900 Bernard Williams' review of Dreyfus WHAT COMPUTERS CAN'T DO
02902 was very welcome, because workers in the field of Artificial
02904 Intelligence [AI] seem unable or unwilling to defend themselves
02906 against Dreyfus' attacks on their work, and so ought to be grateful
02908 for a philosopher prepared to champion them.
02910
02912 However, there is a slight confusion near the center of
02914 Williams' discussion that needs comment, since it is precisely the
02916 elimination of endemuc miuddle that is the refreshment a philosopher
02918 might have brought to the laborers in the mechanical vineyard of AI.
02920 Dreyfus' thesis is that distinctive human abilities cannot be
02922 simulated by a digital computer, and Williams meets much of this
02924 argument head on. But throughout his review he makes use of a
02926 distinction between "simulating a human activity ", on the one hand,
02928 , in the sense of producing the relevant behavior in a machine
02930 (playing chess , say) and "producing the behavior in the way humans
02932 do it" on the other.
02934
02936 This distinction, though widely accepted in AI, is almost
02938 wholly without content, and moreover was not needed by Williams for
02940 his excellent attack on Dreyfus' much publicised arguments.
02942
02944 Williams introduced the distinction (p. 36) when he
02946 contrasted AI and Cognitive Simulation [CS] : where CS is said to
02948 take "tips from the ways humans actually solve problems". That
02950 should of course have been: "takes tips from the ways humans SAY
02952 they solve problems" since no one has the least idea how brains solve
02954 problems, nor even any clear idea of what it would be like to know.
02956 Given that fact, the AI-CS distinction begins to look rather weak .
02958 Next Williams says ". . . for AI researchers the aim is not to
02960 solve problems "the way we do", but just to get a machine to solve
02962 problems"(p. 38).
02964
02966 By his suggestion that one MIGHT try to get a machine to
02968 solve problems the way we do, Williams endorses the distinction
02970 again, and is also utterly unfair to the motivation of many, if not
02972 most, AI workers. For their aim is to simulate intelligent
02974 problem-solving activity as a way of understanding it, not just as a
02976 way of solving the problems. Moreover , at present that is the only
02978 way in which we CAN understand mysterious processes like thinking :
02980 by simulating them. It may be second best but it is all there is.
02982 And when Williams writes near the end (p. 40) ". . . and if
02984 construct [an artificial organism] is what we do. . . . . then
02986 we understand it" he seems to appreciate the last point.
02988
02990 But immediately after the last quotation Williams falls
02992 straight back into the muddle in his peroration ". . . This is the
02994 direction in which in which content can be found for the notion that
02996 a machine. . . . . . . . might solve problems . . . . .
02998 as we do". But this is merely rhetorical, for he has shown no
03000 direction at all. Indeed, if he had , he would have given conceptual
03002 thinking a gigantic push forward, since at the present time no one
03004 has any serious suggestion as to what it would be like to discover
03006 the "language in which the brain processes information" , and hence
03008 how we "really" solve problems"? To see this one only has to
03010 realise the problem of discovering the language in which a computer
03012 was really processing a problem, if one had no more to go on than the
03014 contents of the computer's registers. It would be an almost
03016 impossible code cracking job, even though we know all the high level
03018 computer languages to which the changes of state could conceivably
03020 correspond. In the case of the brain we have no such information.
03022
03024 Williams seems in his review to give his blessing to a
03026 fundamental muddle in AI: he could have ignored it , since he did
03028 not need it to deal with Dreyfus, or have cleared it up. Instead he
03030 endorsed it.
03032
03034 One additional point is germane: Williams refers more than
03036 once to the "result" that any analog process can be simulated on a
03038 digital computer. This is very important to any discussion of
03040 Dreyfus, who holds(1) that the human activities in question cannot be
03042 simulated by digital means , though (2) they can perhaps be simulated
03044 by analog means. Clearly this "result" closes the gap between
03046 Dreyfus' (1) and (2) to vanishing point , and so suggests Dreyfus is
03048 contradicting himself. .
03050
03052 But there may be a loophole in this anti-Dreyfus argument:
03054 for like all such formal proofs, the result inquestion holds only for
03056 the class of objects defined in the proof. There may well be
03058 entities or systems that are analog devices in the common sense
03060 meaning of the term, though are not covered by the result. In
03062 particular, it is still an open question whether or not the
03064 three-body problem can even be recursively approximated by digital
03066 means. If it should turn out not to be so, then any three bodies, in
03068 virtue of their mutual gravitational attraction , would form a device
03070 not simulable by a digital computer. It may be a little hard to see
03072 how such a device could be used to simulate human behavior but it
03074 would constitute an important theoretical looophole in that
03076 particular argumant against Dreyfus' general claims.
11700
11800
11900
12000 .VERBATIM
12100
12200 Sincerely,
12300
12400
12500
12600 Yorick Wilks.
12650
12652
12654
12656
12658 To: The editors
12660 New York Review of Books.
12662
12700 .FILL