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C00006 00005	thomas[e87,jmc]		Position paper for Journal of Philosophical Logic
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\title{The Logic Approach to AI}

\noindent Abstract: The most straightforward approach to AI is to express
what the system needs to know in a first order language and have it
programmed to deduce what it should do to achieve its goals.  This
requires formalizations of common sense knowledge and reasoning.
Therefore, the approach has had to be modified to include non-monotonic
reasoning, and further modifications may be required involving the
formalization of context.  However, using logic as the basis for AI still
looks promising --- even after 30 years.

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\section{Introduction}

It is evident that Leibniz, Boole and Frege all hoped to include
common sense knowledge in the domain formalizable by mathematical
logic.  However, this has proved very difficult, and the difficulties
have not been easy to diagnose, let alone solve.  Since the successful
applications of mathematical logic have been to the foundations
of mathematics, some people have concluded that this is all it's good
for.

Since the late 1950s there have been proposals to use mathematical
logic to formalize common sense knowledge and reasoning for purposes
of artificial intelligence.  Success has been moderate, but nevertheless
logic is the main tool used today in AI systems.  Systems differ in
how much logic is used, and some use far less than the full first
order logic.  For example, many expert systems never infer new
general sentences, but only go from the general to the particular,
and this suffices for many applications.
\smallskip\centerline{Copyright \copyright\ \number\year\ by John McCarthy}
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thomas[e87,jmc]		Position paper for Journal of Philosophical Logic
special issue on AI and Philosophical Logic, due dec. 1
msg.msg[1,jmc]/165p
e87.in[let,jmc]/165p
THOMASON@C.CS.CMU.EDU


Wittgenstein


	The use of logic in artificial intelligence is controversial
in a variety of ways.  Sometimes it's simple ignorance.

	One moderately prominent AI researcher said, ``Why do you
have this prejudice in favor of this language invented by Russell?''

	Sometimes it's some kind of existential despair.

Problems in formalizaing common sense.
	1. ccntext
	2. non-monotonic reasoning
	3. arising from insufficient reification of ordinary kinds