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From: aarons@syma.sussex.ac.uk (Aaron Sloman)
Newsgroups: comp.lang.lisp
Subject: Re: Is this the end of the lisp wave?
Summary: nobody ever thought lisp was the language of thought
Message-ID: <4178@syma.sussex.ac.uk>
Date: 13 Jan 91 02:10:27 GMT
References: <2456@paradigm.com> <22573@well.sf.ca.us> <96861@aerospace.AERO.ORG> <5256@idunno.Princeton.EDU>
Organization: School of Cognitive & Computing Sciences, Sussex Univ. UK
Lines: 67

eliot@phoenix.Princeton.EDU (Eliot Handelman) writes:

> Path: syma!icdoc!ukc!mcsun!uunet!cs.utexas.edu!uwm.edu!linac!att!rutgers!njin!princeton!phoenix!eliot
> Date: 12 Jan 91 08:40:55 GMT
> Sender: news@idunno.Princeton.EDU
> Organization: Princeton University, New Jersey
>
> ;>Common LISP effectively died from obesity.
> ;
> ;*And* still managed to leave out "neq".
>
> It died because it was linked to AI and that died. The whole beauty of
> list processing was that at one time it was seriously believed that
                                             ^^^^^^^^^^^^^^^^^^^^
> thought was essentially list processing, and if you toss in recursion
> you can accomodate self-consciousness too. A lisp machine was a machine
> whose resident language was "the logic of thought." No one believes this
> anymore,....

Actually, having been involved with AI since about 1969 I don't
think I've ever met any serious thinker who believed this.

I keep finding people who say AI is dead because the AI people
believed X and X has been proved wrong, when in fact X is so
obviously false that nobody ever would have believed it, except
perhaps a few badly taught students, and people on the fringes
trying to understand a difficult discipline and latching onto
simplified slogans because they couldn't see what was really going
on. (I once read a draft report by a social scientist commenting on
the UK "Alvey" advanced IT program, in which it was claimed that AI
was more or less defined by the use of Lisp. Fortunately, the final
report benefited from some informed criticism.)

All the people I talked to in the AI field in the early days were
very clear that there was a difference between what they were trying
to implement and how they were implementing it, although it was
agreed that sometimes making the distinction was not easy (hence the
occasional confused person who called a program a theory).

Choice of language and data-types was clearly an implementation
detail. For example, things that used to be done with property lists
in the early days are now often done using hash-tables because the
latter are much more efficient than long property lists. Also, some
of the things that lisp-ers do with lists are done in Prolog using
terms.

What many people in AI have believed is that intelligent systems
don't just manipulate vectors or lists but hierarchically structured
representations, i.e. that understanding, perceiving, thinking,
planning, and the like require the ability to cope with things
composed of parts with relationships between them, where the parts
are also composed of parts with relationships, etc. (This belief was
also shared by many linguists).

I don't think anything that has turned up in recent years has
shown that this belief is false.

Of course, the management of hierarchical complexity isn't all there
is to intelligent systems.

Aaron Sloman,
School of Cognitive and Computing Sciences,
Univ of Sussex, Brighton, BN1 9QH, England
    EMAIL   aarons@cogs.sussex.ac.uk
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