.require "memo.pub[let,jmc]" source
.double space
.once center
%4Comments on Searle's "Minds, Brains and Programs"%1

	John Searle's refutation of the Berkeley answer that the system
understands Chinese proposes that a person (call him Mr. Hyde) carry
out in his head a process (call it Dr. Jekyll) for carrying out
a written conversation in Chinese.  Everyone will agree with Searle
that Mr. Hyde does not understand Chinese, but I would contend, and
I suppose his Berkeley interlocutors would also, that provided certain
other conditions for understanding are met, Dr. Jekyll understands
Chinese.  In Stevenson's story, it seems assumed that Dr. Jekyll and Mr.
Hyde time-share the body, while in Searle's case, one interprets a
program specifying the other.

	Searle's dismissal of the idea that thermostats
may be ascribed belief
is based on a misunderstanding.  It is not a pantheistic
notion that all machinery including telephones, light switches
and calculators believe.
Belief may usefully be ascribed only to systems about which someone's
knowledge can best be expressed by ascribing beliefs that satisfy
axioms such as those in (McCarthy 1979).  Thermostats are sometimes
such systems.  Telling a child, %2"If
you hold the candle under the thermostat, you will fool it
into thinking the room is too hot, and it will turn off the furnace"%1
makes proper use of the child's repertoire of intentional concepts.

	Formalizing belief requires treating
simple cases as well as more interesting ones.  Ascribing beliefs
to thermostats is analogous to including 0 and 1 in the number
system even though we would not need a number system to treat
the null set or sets with just one element; indeed we wouldn't even
need the concept of set.

	However, a program that understands should not be regarded
as a theory of understanding any more than a man who
understands is a theory.  A program can only be an illustration
of a theory, and a useful theory will contain much more than an
assertion that "the following program understands about restaurants".
I can't decide whether this last complaint applies to Searle
or just to some of the AI researchers he criticizes.

%3McCarthy, John (1979)%1:
"Ascribing Mental Qualities to Machines" in %2Philosophical Perspectives 
in Artificial Intelligence%1, Martin Ringle (ed.), Harvester Press.