philosophy and computer science - timothy r. colburn

7/23/2019 Philosophy and Computer Science - Timothy R. Colburn

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Phi losophy

and

Compute r

Science


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E X P L O R A T I O N S IN P H I L O S O P H Y

J am e s H.

Fetzer,

Ser ies

Editor

Aesthetics

James

W .

M a n n s

S o c i a l

Philosophy

Gera ld F. Gaus

Modern Political Philosophy

Richard

Hude lson

Philosophy

a n d Computer

S c ienc e

Timothy R. Colburn


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\ \ - T C

E

X

P

L

0

R

A

T

I

0

N

s

i n p h i I o s o p h y

Phi losophy

and

Compute r Science

Timothy

R .

Colburn

James

H . Fetzer, Series Editor

9 \ / L E . Sharpe

Armonk, New

York

L o n d o n ,

Eng l and


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Copyr igh t

2000

by M .

E. Sharpe,

Inc.

All rights

reserved.

N o part of this book m a y be reproduced in a ny form

wi thou t wr it ten

permission

from th e publisher,

M .

E. Sharpe, Inc. ,

8 0 B us in es s P a rk D r iv e , A rm o n k , N e w Y o rk 10504.

Library

of Congress

Ca ta loging-in -Pub l i ca t ion Da ta

Colburn, Timothy

R.,

1 9 5 2 -

Phi losophy and computer

science

/T imothy

R.

Colbtun.

p. cm .

- ~

(Explorat ions

in

ph i losophy)

Inc ludes bibl iographical references and index.

I S B N l -56324-990-1 (h e :

alk.

paper).

ISBN

1-56324-991-X (pbk. :

alk.

paper)

1 .

Computer

s c ie n c e P h i lo s o p h y .

2 . Art i f ic ia l intell igence.

I. Title. I I . Series

QA76. l67.C65

1999

0 0 4 D C 2 l

99-28936

CIP

Printed in

the

United

S t a t e s of

Amer ica

The

paper

used

in

this

publ icat ion

m eets the

min imum

requirements

of

Amer ican

Nat iona l Standard

fo r

Informat ion

Sciences

Pennanence of

Paper

fo r Printed Library Materia ls,

A N SI Z

39 .48- I984 .

BMc)098765432

BMp)1098765432


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T o Car r i e , for

l ead ing

m e b ack to th e a c a d em y ,

a n d

to

J i m , fo r

lighting

th e

way.


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Contents

Series Preface ix

Acknowledgments

xi

1 Introduction

3

Part I Philosophical Foundations

of

Artificial

Intelligence 1 1

2 The Definition and

S c o p e

of

AI

1 3

3 AI and the History of

Philosophy

1 9

4

AI

and the Rise of Contemporary Science and Philosophy 4 1

Part

II

The New Encounter of

S c i e n c e and

Philosophy 5 1

5 AI and Logic 53

6

Models of the

Mind

6 8

7

Models of Reasoning 87

8 The Naturalization of Epistemology 1 0 5

vii


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Part

III The Philosophy

of Computer S c i e n c e

1 2 7

9 Computer Science and Mathematics

1 0 Two Views of Computer Science

1 1

Abstraction in

Computer

Science

1 2

Software,

Abstraction,

and Ontology

Notes

Bibliography

Index

1 2 9

1 5 3

1 7 4

1 9 s

2 1 1

2 2 1

233


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Series

Preface

T h e

series, Exp lo ra t ions

in

Ph i l osophy, is

i n t e nde d

to p ro v id e u n d e rgra d -

uates

a n d

o the r readers

with quality introductions

n o t o n ly

to th e

princi-

p a l

areas

of

ph i l os ophy ,

including

traditional

t op ics o f

investigation~

epis temology,

eth ics,

a n d

so c ia l a nd political p h i l o s o p h y b u t also to

c o n t e m p o r a r y subjec ts of impor tance--such

as

c o m p u t e r science, f em-

inist s tu die s, a n d

th e

eth ics

o f re p ro d u c tio n .

In each case, th e ed i to rs

h a v e chosen au t h o rs w h o co u ld n o t

o n ly e xp la in

th e cen t r a l p rob l em s

encoun tered within their re s pe c tiv e d o m a in s but w h o cou ld

also

propose

p r omis i n g

so lu t ions

to those prob lems, i n c lu d ing n o v e l a pp r oa c hes a n d

original

ana lyses .

T h e

present

v o l um e, P h i l os ophy

a n d

C o m p u t e r

Science,

p ro v i de s

a

lu -

c id

a n d

stimulating introduction to s om e

of th e

m o s t

f a sc i n a t i n g i deas ex-

p lo red in

c o n t e m p o r a r y

p h i l o so p h y a n d science, w h i ch

co nce r n

th e scope

a n d

limits

of c om pu t e rs a n d their

powers .

T h e a u t h o r , Timothy C olb u rn ,

w h o

is both

a

ph i losopher

a n d

a

c o m p u t e r s c ie n t is t, supp l ies

a

f r a m e w o r k

that is historical

a n d

ana l y t i ca l ,

exp la i n i n g

th e p h ilo s o p h ic a l o rig in s of

m a n y p ro ble m s

that a re raised

by

m o d e r n

c o m p u t i n g

mach i ne s . A n y o n e

with a n i n te res t

in artificial

in t e llig en c e , rea s on in g

by

mach i ne s , a n d th e

t heo r e t i ca l

f o u n d a t i o n s of c o m p u t e r science will

find

it re w ard i ng .

J a m es

H .

Fetzer

ix


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A c k n o w l e d g m e n t s

Th is b o o k w o u l d not

h a v e

been possible without th e support a n d en -

c ou ra g em en t of m y

brilliant

m e n t o r a n d

f r iend ,

Jim Fetzer. H e

p r ov i d ed

m e with th e

s em i n a l

i deas

that

first began to un i te

m y

distinct i n te l lec-

tual

l i ves in p h i l o so p h y a n d c o m p u t e r science, a n d he offered m e myriad

opportunities to

express

mysel f . I c a n n o t

thank

h im enough .

I w o u l d

also

l ike to thank Kluwer A c a d e m ic P u b lis h e rs

for

permiss ion

to use

pa r t s

of m y p ap e r s a p p e a r i n g in th e journal

M i n d s

a n d M a ch in es ,

a n d

fo r

permiss ion

to use

part

of

m y contribution

to

th e v o lu m e

Program

Ver ifica t ion :

F u n d a m e n t a l

Issues

in C o m p u t e r

Sc ience

(1993) .

T h a n k s

a re a lso d ue th e e d ito rs of The Monist: An

International

Qu ar te r l y of

G e ne r a l

P h i l o so p h i ca l

Inquiry,

for permiss ion to i nc lude part of

m y c on -

tribution

to th e J a n u a r y , 1 9 99 , is su e

o n

p h i l o so p h y of c o m p u t e r sc ience.

xi


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Philosophy

and

Computer

Science


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. _ . _ ]_ ..._

Introduction

P h i l o s o p h y

a n d

c o m p u t e r

science isnt

that

a rather

o dd c o m bin a-

tion? Such

is th e typical cocktail-party

response

w h e n

l ea r n i n g

of m y

acade mi c training

in

th e d is c ip lin e Socra tes

ca l led

the

l ove

of w i s d o m

a n d

m y

s ubs eq uen t

i m m e r s a l

in

th e wor ld of bytes,

p ro g ram s ,

sys tems

ana l ys i s ,

a n d g o v e r n m e n t cont rac ts . A n d such might be th e reac t ion to

th e title o f

this

book. B u t despite it s

cloistered

reputat ion and it s lit-

erary ,

as

oppos ed

to

techno log ica l ,

image,

th e

tradition

of

ph i l osoph i ca l

i n v es t ig a t i on ,

as

a ll of

us

w h o ha ve been sed uced

by it k n o w ,

ha s n o turf

limits. While fe w

but

th e truly p repa red ve n t u re into

ph i1osophy s

h a r d -

core inner ci rc le of ep is temo logy,

m et a phy s i c s , (meta)e th ics , a n d logic,

literally anything is fair ph i l osoph i ca l

g a m e

in

th e ou te r circ le

in

w h i c h

m o s t

of

us

exis t . And so

we

h a v e th e ph i l osophy ofs : ph i l osophy of

sci-

ence, p h i l o so p h y of

art,

of l anguage, ed uc a t i on . S om e of th e ph i l osophy

o fs

even

ha ve

n a m e s

befitting their integration into

vital

areas of m o d -

e rn

socie ty,

for

e xa m ple , m e d ica l e th ics a nd

e n v i r o n m e n t a l

eth ics ,

w h i ch

we ca n say a re sho r te r namesfor th e ph i l osoph ies of

e th i ca l dec is ions in

m e d ic in e a nd ecology. O n e o f th e a i ms of this b o o k is to m a k e a n ear ly

contribution to

a

n a s c en t p h i l o so p h y of c o m p u t e r science.

Which is

n o t

to say that there ha s

n o t been

a v a s t a m o u n t of work

d o n e

w h i ch

ca n

be descr ibed

as

th e cross-d isc ip l i na ry en c oun t e r of ph i l osophy

with c o m p u t e r science. Desp i te th e

typical

cocktail-party

reac t ion

to

this

c o m b i n a t i o n , th e

so lu t ions

to

m a n y

p rob l em s in c o m pu te r sc ience

ha ve benefi ted f rom

what

we might

ca l l appl ied

ph i l os ophy .

Fo r

exa m p l e ,

h a r d w a re lo gic

gate design

wou ld n o t

be

possib le

without

b o o le a n a lg eb ra ,

deve loped

by

th e n in e teen th -cen tu r y

m a t h e m a t i c i a n

George

B oo l e ,

whose

w o r k

he lped

la y th e f o u n d a t i o n

fo r

m o d e r n

logic. Later work

in logic,

particularly

th e d e v e l o p m e n t of pred ica te

ca lcu lus by

Gottlob Fre ge , h as

been

d ra w n u p on e x te n s iv e ly by

researchers in

sof tware

eng ineer ing

w h o

desire

a formal

l anguage for c o m p ute r p ro gra m semant i cs . Pr ed i ca te


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4

CHAPTER

1

calcu lus is

also

th e formal m o d e l used

by

m a n y of

those

w h o

i m p l e m e n t

a u t o m a t e d reason ing systems for

m e c h a n i c a l t heorem

p r ov i n g . These

t heorem

p r o v i n g techn iques ha ve even

fo rm ed th e

basis fo r

a sty le

of

genera l -purpose

c o m p u te r p ro g ra m m i n g cal led logic p rog ra m m i n g .

Fur the r mor e , th e app l i ca t i on of ph i l osoph i ca l m e t h o d s to c o m p u t e r

s cie nc e is not limited to

those in

logic. T h e s t u d y of eth ics , for

e x a m -

ple,

has fo un d bro ad

a pp l i ca t i on to compu te r - r e l a ted

issues

of

p r i vacy ,

secur i ty , a nd la w. While these issues a re

n o t

regarded a s ge r mane to

th e

science

of c o m p u t i n g

p e r

s e ,

t he y h a v e

ar isen

directly a s a

resu l t of

th e

dras t i c

changes

socie ty

has

u nde r go ne

d ue

to

th e

ubiquity

a nd po w er

of

c om pu t e rs .

In 1990,

a

major U.S.

sof tware v e n d o r

a t t e m p t e d to o p e n l y

m a r k e t a large mailing

list

c om p i l ed f rom public sources, but wa s forced

to withdraw it w h e n th e pub l ic outcry

o v e r

i n vas ion of privacy bec a m e

to o

great . While th e

sca l i ng

b ack of th e

U.S.

Strategic

Defense Initiative

in th e 19 8 0s cou ld

be seen

a s a

response

to t e ch n i ca l feasibility ques-

t i ons , a

major

u nde r l y i ng

m o r a l co nce r n i w as

w h e t h e r

a

nation

ought

to

en t r us t

its secur i ty , to such

a

large ex ten t , to m a c h in es . And n o w ,

with

th e p erv a d in g i nfluence of th e Wor ld Wide Web,

socie ty

ha s

been

forced

to c o n f r o n t issues re ga rd i ng free do m a nd

decency

in

th e digital

wor l d .

Within

th e

field of la w, m a n y s tic k y e th ic a l ques t i ons re la ted to

c o m -

puters h a v e

ar isen: Is

un a u tho r i zed use of a c o m p u t e r f rom th e p r i v a c y

of ones o w n h o m e , without d a m a g i n g a ny files o r

p ro g ram s (i.e.,

h a c k -

i ng ) ,

th e same a s b re ak i ng a n d enter ing? C a n a u tho r s of p ro g ram s that

a re exper t s

in m ed ic in e o r la w be sued

fo r

m al p rac t i ce ? S hou l d

c o m -

puter

p ro g ram s be

copyr igh tab le , o r s ho uld they

be

f ree, l ike a ir? S h ou ld

p r o g r a m m e d trading be a l lowed

o n

th e s tock

exchange? A nsw e r s

to th e

l as t tw o

ques t i ons ,

a nd o th ers

l ike

it,

w o u l d

ha ve

s ig n ifica n t

effects

o n

th e c on d uc t of o u r ec on om y .

N o n e

of

these

ques t i ons

cou ld

h a v e

been

pred ic ted

a

m ere fe w decades

ago. T o d a y , it

wou ld be

difficult

to find

a

college

curriculum that

d id

n o t

inc lude ,

in

e i the r th e

c o m p u t e r

sc ience o r

th e

p h i l o so p h y d e p a r t m e n t ,

a course

entitled

C o m p u t e r s

a n d S o c ie ty ,

Values a n d T ec hn o lo gy , o r

th e

l ike.

But o u r inquiry

in

this b o o k goes bey on d th e application of philo-

soph ica l m e t h o d to specific issues l ike those just

m e n t i o n e d .

Our

inquiry

a t t e m p t s to seek

a

n ew en c oun t e r between p h i l o so p h y

a n d

sc ience

by

e x a m i n i n g

th e

ways t hey ca n

cha nge one a n o t h e r

in th e

c o n t e x t of one

of sciences

newes t

d isc ip l ines. Th is t ype of

inquiry

is

in

addition to

th e traditional concern of p h i l o so p h y of science, w h i ch ,

in its

ana lyses of

concep ts

lik e e x p la n a tio n , t heory , a n d th e on to log ica l

s ta tus

of in fer red

ent i t ies, is typically unaf fec ted

by

th e c o n t e n t of particular sc ient ific d is-

cover ies .

This

in s u la r n a t u re

of p h i lo s o p h i c a l c o n t e n t a n d

m e t h o d

is

be ing


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INTRODUCTION 5

c h a lle n ge d b y w o r k

in

th e area of c o m p u t e r science k n o w n as artificial in-

te l l igence (AI),

particularly

in

th e traditional

ph i l osoph i ca l areas of logic,

ph i l osophy of m i n d , a n d e p is te m o lo gy .

Although even th e definition of th e fie ld of AI is fraught with philo-

s oph i c a l debate ,

genuine

ph i l osoph i ca l ques t i ons

c o m e

to th e fore a s re -

searchers

attempt to

m od e l h u m a n

i n te l l igence

in c om p ute r

p ro g ram s :

What is

th e

structure of

h u m a n knowledge

(so that we m a y represen t

it

in c o m pu te r

m e m o r y ) ? What is th e

process of

h u m a n

thought

(so

that we

m a y

m o d e l reason ing, l ea rn ing, a n d

creativity

in c om p u te r

p r o -

grams)?

I n te res t ing ly ,

whi le

AI

researchers

m u s t

ask

th e

s a m e

sor ts

of

cogn i t i ve ques t i ons

as ph i l osophers

d o , th e y u s ua lly agree with th e

per-

vas i ve

a ssu m ptio n, s ta te d by

Hobbes in

th e seventeenth centu ry ,

that

cognition is

computation,

a point

of

v iew

certainly n o t shared

by

a ll

ph i l osophers .

O n e

of th e f asc ina t ing

aspec ts

of AI is

its

co nce r n for both

c o m p u t e r

s c ie n tis ts a n d p h ilo s o p he rs .

A s

a subfield

of c o m p u t e r science,

it is a y o u n g d isc ip l i ne , but th e ques t i ons it

ra ises h av e been

th e o bje cts

of ph i l osoph i ca l

in v e s t ig a tio n fo r

centur ies . Th e re

is n o d ea r th of writing

o n this co nfl u e nce of concerns f rom

seeming l y

d i s p a ra t e d i sc ip lin e s , but

Part

I of

this

b o o k , Ph i l osoph i ca l

F o u n d a t i o n s

of Artificial I n te l l igence ,

p rov i d es a f resh treatment of their re l a t i onsh ip

by returning

to histori-

ca l ph i l osoph i ca l prob lems a n d

l ook i n g

a t th e m

in

th e

light

of h o w they

w o u l d

set th e stage

for

a n age

w h e n peop le w o u l d begin

p r o n o u n c i n g

c e rta in c o m p u te r

p r o g r a m s intelligent.

Th is retro-treatment of h is to r i ca l p h i l o so p h y is a n i n te res t ing exercise,

because it a l l ows us to

imag ine

a n

e p o ch a l sweep of ph i l osoph i ca l musings

t h rou gh th e ages,

in

w h i ch

concepts

of m i n d a n d re a so n in g a re first roo ted

in

th e

formal

o r

th e

d i v i n e , t hen

be co m e p o w ers

of

h u m a n i t y s

o w n

indi-

viduality, a n d finally a re

m an i fe s t

in

h u m a n i t y i s o w n ar t i f ac ts .

H o w e v e r

one

feels

a b o u t th e

inexorability

of this

sweep,

one thing

is

c lear : T h e

cons t ru c t i on of mo de l s of

m i n d

a n d reason ing ha ve today forced m a n y

ph i l osophers out of th e c lo is tered confines of their a

priori

w o r l ds .

O n e re as on

fo r th is emergence

is

cons is ten t with th e traditional role of

p h i l o so p h y as

a

gu id ing beacon ,

a

give r rather than rece i ve r of w i sdo m

in

its e n c o u n t e r with science. AI u n d e r w e n t

a

resurgence in th e

19 8 0s that

was primarily

th e resu l t

of

its s w itc h in g focus

f rom

sys tems

for d o i n g

mere ly

a u t o m a t e d

reason ing

to so-cal led

knowledge-based sys tems.

Prior

to this th e m o s t important

t heo r e t i ca l

tool for th e AI researcher

was

lo gic , a n d it wa s thought that

by

a u t o m a t i n g formal a n d wel l u n d e r s t o o d

pa t te r n s

of

i n ference, on e

cou ld

em u l a t e

h u m a n

intelligent b e h a v i o r

in

a c o m p u t e r p ro gra m . In so fa r as logic h a d been th e p ro v in c e of ph i loso-

phers

a n d m a t h e m a t i c i a n s , it wa s obv ious that p re v i o u s work

by

them


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6

CHAPTER

1

h a d a bear ing

on

AI. However , m a n y AI

researchers began

to

bel ieve

that

th e role of reason ing in m a c h i n e i n te l l igence h a d

been

overemphas ized

a t

th e

expense

of know ledge . Early AI p rog ra m s

were

ve ry good at p r o v i n g

t h e o r e ms

in

first-order

pred ica te

logic,

but

such

p ro g ram s

p r o v e d

hugely

inef f ic ien t w h e n used to i m p l e m e n t nontrivial

sys tems fo r

r ea s on i n g in

specific

areas. It

became

obv i ous

that

m ore ef for t

s p e n t on acqu i r i ng

a n d

digitally represen t i ng know ledge in a specific

a rea ,

c om b i n ed with

even

a

minimal

reason ing m e c h a n i s m , wou ld p a y off with p ro g ram s m o r e accu-

rately

e m u l a t i n g h u m a n e xp e rtis e

in

that area, a n d th e

first

truly success-

ful

a p p lic a tio n s in

AI

became

k n o w n

as

exper t

systems. Such

p ro g ram s

were

sa id

to

be

know ledge-based because

m u c h

of

th e i n tense

ef for t

in

their d e v e l o p m e n t centered a ro u n d th e re p re s en ta tio n a n d

manipulation

of s p e c ific k n o w le d g e, a s oppos ed to th e

effic ient

m o d e l i n g of me ch an i sms

of pure reason .

T h u s AI

researchers

became

i n terested

in

th e c o n c e p t of k n ow l ed g e

as

wel l as logic, a n d it

seemed reasonab le

to

suppose

that t he y c ou ld le a rn

so m e t h i ng

f rom

p h ilo s o ph e rs , w h o

ha ve been

thinking

a b o u t

knowledge

for

a l ong

tim e . T h e

m o s t

important area of

AI directly

re la ted to epis-

t e m o l o gy became

k n o w n as

knowledge

represen ta t i on . But it

wa s c lear

that,

to truly emula te intelligent b e h av i o r , not o n l y mo de l s of knowledge

rep resenta t ion

but

also

mode ls of c om in g to kn ow were necessary . In o t h e r

w o r ds , AI

p ro g ram s

h a d to be

able

to l ea rn . So t he re a re severa l impor-

tant aspects of know ledge with w h i ch AI researchers a n d practitioners

m u s t be

c on c e r n ed .

This ques t ion of h o w

p h i l o so p h y

ca n

help us

d o

AI is

c ouc hed

in

th e

language of

interdisciplinary cooperation, in which o n e discipline per-

ha ps

serend ip i tous ly

benefits

a n o t h e r b y o ffe rin g re l e van t

work

a l r e a d y

d o n e o r a n insightful outlook

p r ev ious l y

unseen . That this re l a t i onsh ip

is ev en p o s s ib le b etw e e n AI a n d p h i l o so p h y is d ue to-the o ve r l ap of sub-

ject

matter: p h i l o so p h y is concerned

with

issues of

h u m a n knowledge

a n d

reason ing,

a n d AI is concerned with

mode l i ng

h u m a n k n ow le d ge a n d

reason ing .

But ph i l os ophy , in

its

genera l

role of

critically

ev a lua t i n g bel iefs, is

mo r e t h a n m ere l y

a

potential partner with AI. P e r h ap s th e

m o s t

v is ib le

role p h i l o so p h y

ha s

p layed

in

this re la t ionsh ip is that of

w at ch do g , in

w h i ch

it

del ineates

th e

limits,

a n d s om e tim e s

even

attempts to

des t roy

th e f o u nda t i o ns , of AI.

These cr i t iques

proceed by taking

to ta s k th e c la im

that

computation

is even

a n

appropr i a te m o d e l

fo r

h u m a n thought o r

consc iousness

in th e

first

p lace .

Their primary

focus

is

n o t

logic o r knowledge, but of m i n d .

Here th e

primary

ques t ion

is w h e th e r p h ilo s o p h y

ca n

tell AI

what

it

ca n


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INTRODUCTION 7

d o. M a n y

ph i l osophers bel ieve th e

a n s w er to th is

ques t ion

is yes,

but

t he y

a re

la rgely

i gnored

by

AI

researchers

a n d

practitioners, because

th e

latters

focus

is

n o t

m i n d but lo gic a nd know ledge .

While

this ignor ing

is

d o n e

a t their per i l ,

it is

bec om i n g c lear

that a

s w i n g

in

th e

oppos i te

d i rec t ion ha s oc c u r red , to th e

point

where it is

c l a i m e d

that t echno log-

i ca l advances ,

espec ia l l y

those in c o m pu te r

science,

ca n shed

light

o n

traditional

ph i l osoph i ca l

prob lems.

To cla im this was

un th i n ka b le

within m a n y ph i l osoph i ca l

ci rc les

just

tw o

decades

ago,

and there

a re still those w h o will s tead fas t l y

resist

c o u n t e n a n c i n g th e possib i l i ty .

But

s ince

cer ta in

ques t i ons

traditionally

thought to be

p h i l o so p h i ca l su ch

as:

H o w

d o

we

c o m e

to k n o w

th ings?

What is th e structure of know ledge? What is th e

n a tu r e

of th e mind?-

a re n o w be ing asked

by

AI a n d cogn i t i ve science researchers

as

wel l , it is

i nev i tab le that

th e s e r es e a rc h e rs

will offer

answers

in

th e

techn i ca l t e rm s

with w h i ch

t hey a re familiar.

In shor t ,

th e

rapid

growth

in

th e

speed

a n d

comp le x i t y

of

c o m p u t i n g m a c h in es is tempting

peop le to put forth

mode ls of th e h u m a n m i n d

in

t e rm s of c o m p u t e r science. But w h y a re

c o m p u t e r science

mode ls so

t emp t i n g ? T o a n s w er th i s ,

it

he lps to discuss

so m e t h i ng a b o u t th e

relation

between

science

a n d

p h i l o so p h y

in

genera l .

Science

a n d

p h i l o so p h y a re

of ten

d is t i ngu ished

by pointing out that

sc ience seeks exp la n a t i on w h ile p h ilo s op h y seeks justification. T o a sk

what

causes th e t ides is a sc ient ific ques t ion ,

whi le

to

a sk what wou ld

cons t i tu te ade qu a te

grounds- fo r

be l iev ing

that

I s e e th e m o o n is

a

philo-

s oph i c a l

one .

What

rea so n d o yo u

ha ve fo r

b elie v in g X ?

is a typical

ques t ion

asked by

p h ilo s o p he rs , a n d th e

n a tu r e

of X d e t e rm i n es th e kind

of p h i l o so p h y

u nde r t ak e n .

For e x amp l e ,

What

rea son d o

yo u

h a v e for

be l iev ing

that

m e r c y

killing

is

w ro ng?

is a

ques t ion

for

n o r m a t i v e

eth ics ,

What reason

d o

yo u ha ve

fo r

be l iev ing in th e ex is tence of

d i se m b o d i e d

m i n d s ? is a

ques t ion for p h i l o so p h y of m i n d ,

a n d What

rea son d o

yo u

ha ve fo r b elie v in g that this

a r g u m e n t is

v a l i d ?

is a ques t ion

for

ph i l osoph i ca l logic. So p h i l o so p h y ha s been charac ter i zed as th e

critical

ev a lua t i on of

beliefs

t h rou gh th e

ana l ys i s

of concep ts

in a

given

area

of

i nqu i r y .

Of

course,

s cie nc e is also concerned with critically

ev a lua t i n g

bel iefs

a n d a n a l yz i n g

concepts .

But w h e n one l ooks a t th e k in d s of th ings X is

in

th e

ques t ions

a bo v e, o ne

not ices

that

n o n e

of

them

lend

themse l ves

to

e mp i r i ca l s tudy .

O n e

need n o t wi tness a c t u a l cases of

m e r c y

killing to

c o m e to

a conc lus ion

a b o u t

w h e t h e r it

o u g h t to

be

d o n e . By definition,

a

d i s em bod i ed m i n d is on e that c a n n o t

be subs ta n t i a ted

through p h ys i ca l

obs e r v a t i on . And th e

validity

o f a n

a r g u m e n t

form is n o t de t e rm i ne d

by

lo o kin g fo r

i ns tances of th e form

in

th e wor l d . So p h i l o so p h y ha s

also


20/256

8 CHAPTER 1

been charac ter i zed

as a

n on emp i r i ca l , o r a priori, d isc ip l i ne ,

in

distinct

c o n t r a s t

with science.

C o m p u t e r

science, be ing a sc ien ce,

wou ld

seem to

be d is t ingu ished

f rom

p h i l o so p h y just as a n y

o t h e r

science. But

c o m p u t e r sc ience

is u n i q u e

a m o n g th e sc iences

in

th e types of models it creates. In

seek ing

e x p l a n a -

t i ons, sc ience o fte n c o n stru c ts mo de l s to tes t hypo theses

fo r

e xp la i n i ng

p h e n o m e n a .

Fo r e xa m p le ,

it might

be

hypothes ized that th e p h e n o m e n o n

of th e northern

l ights

is caused by th e interaction of so la r

a t o m s

with th e

ear th s

m a g n etic fie ld .

To

test

this hypothes is ,

a

m o d e l of th e ear th

a n d

its

m agne t i c field cou ld

be

crea ted

in

a

l ab ora to ry ,

comp le te

with

a p p r o p r i a t e

magne ts

a n d

gaseous e lements .

T h e n ,

if,

u n d e r

th e

right

co nd i t i o ns , luminosity is

observed ,

th e hypothes is m a y

be

said to

be c on -

fir med .

This m o d e l , in th e

form

of

e x p e r i m e n t a l

a p p a r a t u s , is of

course

a p h ys i ca l

o b je c t, lik e

m a n y mode ls

built

a n d m a n i p u l a t e d in a n y of th e

natural

sc iences.

T h e mode ls

built

a n d

m a n ip u la te d in c om p u te r science,

however ,

a re n o t

p h ys i ca l

a t

al l .

C o m p u t e r

s cie nc e is

a

science concerned

with

th e

s t u d y of c o m p u t a -

tional processes. A c o m p u t a t i o n a l process

is

d is t i ngu ished f r om, say, a

c hem i c a l

o r e le c tr ic a l process,

in

that

it

is s tud ied in w a y s that ignore

its

p h ys i ca l

nature.1 Fo r e x amp l e , th e process

by

wh ich

a

ca rd p la ye r

ar ranges

ca rds in

h er h a nd , a n d

th e

process

by

w h i c h

a

c o m p u t e r sor ts

n a m e s

in

a c us t om er list, though t he y

share

nothing

in

c o m m o n p h ys i -

c ally , m a y

never the less

e m b o d y th e s a m e c o m p u t a t i o n a l

process .

T h e y

m a y , for e x amp l e , both

proceed by s c a n n i n g th e

i t ems to be

a r range d

one by one ,

d e t e r m i n i n g

th e p r o p e r place of each s c a n n ed item re la t i ve

to th e i t ems a l rea d y

scanned ,

a n d i nse r t ing it into that p lace , perha ps

n ec es s i ta t in g the

m o v i n g

of

p r ev ious l y

scanned

i t ems

to

m a k e

r o o m .

This

process

( k n o w n as

a n

insertion sor t

in

c o m p u t e r sc ience t e r ms)

ca n be

prec ise ly descr ibed

in a

f o r m a l l anguage

without talking

a b o u t

p l a y i n g

ca rds o r

se m i co ndu c t i ng

e lements .

W h e n so

descr ibed, on e

has a

c om pu-

tational

m o d e l

of th e

process

in th e form of a c o m p ute r p ro gra m . This

m o d e l ca n be

tes ted,

in a w a y

ana logous

to h o w

a hypo thes is

is tes ted

in

th e natural

sc iences,

b y e xe cu tin g th e program a n d o b se rv i ng

it s

be-

h av i o r . It

ca n a lso be rea son ed a b o u t a b s tra c tly , so

that we m a y

a n s w er

ques t i ons a b o u t

it,

such as,

a re

there o the r

processes w h i ch will ha ve

th e

same

effect

but

d o

it

m ore

effic ient ly?

Building

computational

mo de l s

a n d

a n s wer i n g these k i nds of ques t i ons form

a

large part of

what c o m p u t e r

scient is ts d o .

T h e exp los i ve

growth in

th e

n u m b e r

of c o m p u te r a p p lic a tio n s

in th e

las t severa l deca des has

s how n

that th e k in ds of rea l wor ld processes

ame nab l e to m o de lin g by c om p ute r a re l im i t less. Not o n l y

h a v e

tradi-


21/256

INTRODUCTION 9

tional

activities,

l ike

record

keeping,

i nves t ing, pub l i sh ing ,

a n d

ba n k in g ,

been

s imp ly conver ted to

con t r o l

by

c o m p u t a t i o n a l

mo de l s , but

who l e

n ew k i nds of activity ha ve been c rea ted that wou ld not be possib le

with-

out

such

mo de l s . These a re th e by-now-familiar virtual activities we

descr ibe in th e l anguage of

cyberspace:

e -m a i l, c h a t r o o m s , Web surfing,

on- l i ne s hopp i n g , Internet g a m i n g , a n d so on . But l o ng before

co m p u t e rs

c a m e to d o m i n a t e ev e ry d a y

l i fe,

c o m p u t a t i o n a l mo de l s were

em p l oy ed

to

descr ibe processes of a spec ia l s o rt, w h ic h h a v e exis ted a s l o ng a s

m o d e r n

H o m o sap iens

has

ex i s ted .

These

a re th e

processes

assoc ia ted with h u-

m a n re aso n in g

a nd kn ow le dge

organ iza t ion ,

a n d

computational

mo de l s

of

them

a re

th e concern

of

AI.

T h e s t u d y of th e na tu re of h u m a n

r e aso n i ng

a n d kn o wle dge ,

in

th e

form of

logic a n d e p is te m o lo gy ,

has , of c ou rs e, be en

a

focus of weste rn

p h i l o so p h y

s ince

Plato a n d Aristotle. However , not

until

th e

latter

part

of th e twentieth cen tu r y a n d th e a d ve nt of th e

digital

c o m p u t e r did

it

be-

come

possible to actually bui ld mode ls of reason ing that co n t a i ne d al leged

rep resenta t ions

of h u m a n k n ow le d ge . B e fo re that t ime ,

if yo u w an te d

to

s t u d y

h u m a n

rea so n in g o r th e

structure of

h u m a n

kn o wle dge , y ou

re -

m a i n e d for th e

m o s t

part

in

th e a priori wor ld of

ph i losophy,

utilizing

perha ps

a

d a t u m o r

tw o

f rom psycho logy . With co m p u t e rs , however ,

it

became possible to test ones

ep is temo log ica l

theory

if th e

theory

was

real izable

in

a

c o m p u t e r mo de l .

It therefore became reasonab le

to at

l east ask: C a n AI, a s a n

emp i r i ca l

d isc ip l i ne concerned with building a n d

obs e r v i n g mo de l s of h u m a n c o gn itiv e b eh a v io r, help us d o p h i l o so p h y?

If we

t ake

ser ious ly th e

charac ter iza t ion

of p h i l o so p h y given a bove ,

name l y , that it is

by

definition a

n o n e m p i r i c a l

d isc ip l i ne , t hen we m a y

re ga rd th e

ask ing

of

this

ques t ion

a s

a

ca tegory

mis take.

R od er i ck

Chis -

ho lm

is a

primary p r o p o n e n t

of this

v i ew:

Contemporary interest

in

th e nature

of

k n o w l e d g e pertains

not

only to

that

b r a n c h

of

p h i l o s o p h y

ca l led theory of know ledge o r

ep is temo logy ,

but

also

to th e fields of

information

t heo r y ,

artificial i n te l l igence, a n d

c o gn i t i ve sc ience. T h e

latter

d isc ip l ines

a re

not

alternatives

to th e

traditional theory

of

k n o w l e d g e

because they a re branc h e s of empirical sc ience a n d not of

p h i l o s o p h y .

Fo r

th e

m o s t

part,

th e

f ac ts

with

which

they

a re

c o n c e r n e d a re not

r e l e v a n t

to th e traditional p h i l o s o p h i c a l

ques t i ons .

However , m a n y c o n t e m p o r a r y researchers, both p h ilo so p he rs a n d c o m -

puter sc ient is ts , wou ld

t ake

issue with

th is

v i ew , finding it a m e t h o d o l o g -

i ca l d o g m a that m a y

h a v e

seemed

reasonab le

in

a n ear l ie r time

w h e n it

wa s

n o t

possib le to build digital mo de l s of

h u m a n

re a so n in g a n d

k n o w l -


22/256

1 0

CHAPTER

1

edge,

but

w h i ch

is

q ue stio n able a n d n a iv e

in th e

Information

Age.

This

is

a

genuine d ispu te , a n d m a y

ex t en d

to

what

s om e wou ld regard as

th e

v e ry fo un d a tio n s of ph i l osophy . But it is th e

case, fo r better

o r worse,

that

c o m p u t e r

s cie nc e is b e g i nn i ng to

a ffe ct h ow

we

d o

ph i losophy, a n d

Part II of th is book , The N ew E n c o u n t e r of Science

a n d

Ph i l osophy ,

descr ibes this reverse effect

in

deeper

deta i l , suggest ing

a

con t i nu ing

n ew

symbios is

in

th e fu ture.

While it is a n ew reve la t ion

fo r

some ph i l osoph i ca l thinking to be a f-

fected

by

th e running of c o m p u t e r p rog ra m s , i n d e p e n d e n t

ph i losophers

a re

by

n o m e a n s out of business. AI

is but a

subfield of c o m p u t e r sc ience,

a n d th e

cons ide ra t ion

of m i n d

a n d

reason notwithstanding, c o m p u t e r sci-

ence is r ipe

fo r

th e good o ld - fash ioned

ana l ys i s

that ph i l osophy p rov i d es .

T h u s , Part

III of

th is

b o o k , The P h i l o so p h y of C o m p u t e r Science,

a t-

temp ts

to

place

c o m p u t e r science within th e bro ad s pe ctru m of inquiry

that const i tu tes

science.

T h e concern here

is

to

d e a l

with th e inevitable

identity crises that c ro p u p

in

th e sel f- image of a n y a d oles ce nt, w h i ch

c o m p u t e r

science

certainly

is .

We will ask ph i l osoph i ca l

ques t ions l ike:

What

is

th e

relation

between

m a t h e m a t i c s

a n d

c o m p u t e r

science? Is

there

a

sense

in

w h i ch c o m p u t e r science

is

exper imen ta l

science?

Is

a

c o m p u t e r

p r o g r a m m e r

m ere l y

a

d a t a

w i za rd , o r

ca n she also

engage in information

model i ng? What

is

th e n a tu r e of

a bs t r a c t i on

in

c o m p u t e r science? What

a re th e o n to lo gic a l imp l i ca t i ons of

c o m p u t e r sc ience concepts?

In shor t ,

th is

b o o k is a b o u t th e p h ilo s o p h ic a l fo u n d a t io n s of

artificial

i n te l l igence

in

particular a n d c o m p u t e r science

in

genera l , a n d it is

a b o u t

th e con t r ib u t i ons that p h i l o so p h y a n d c o m p u t e r science

ca n

m a k e to each

o ther . It asks

where

c o m p u t e r science fits

in as a

science, h o w ph i l osophy

can guide c o m p u t e r science, a n d

h o w w o rk in

c o m p u t e r sc ience

ca n

s ha pe

ones

ph i l osophy . I

d o a dv ise

th e

r e ade r

that chapters 7 a n d

8 on

mo de l s

of

re as on in g a n d

th e naturalization of e pis te m o lo gy m a y i mp o se m o r e

d e m a n d s

u p o n

readers t h a n d o th e o the r chap te rs .

Still,

by th e conc lus ion

of

th is

b o o k , I hope that readers will be

suf f ic ien t ly

en l igh tened to begin

to a n s w er these ques t i ons fo r themse lves .


23/256

Part

I

hilosophical

Foundations

of

Artificial

Intelligence


24/256


25/256

_ . _ . 2 _

The Definition

and

Scope

of

AI

Since th e

first

tw o p a rts

of this b o o k

use

AI a s their

focus fo r e xa m in in g

th e relation between p h i l o so p h y a n d c o m p u t e r sc ience, I will o p e n this

part with a descr ip t ion of

w h a t

A1 is, a n d a

s h o r t

survey of th e k i n d s of

th ings that

AI p ro g ram s

do .

T h e

lure

a n d p rom i s e of c o m p u t e r science has a lways

been

th e abi l -

ity to m o d e l

digitally th e o bje c ts a n d processes w h i ch

o c c u r

in e v e r y d a y

l i fe.

W h e t h e r

it

be

b a n k

acco u n ts ,

baske tba l l

games,

o r s h op p in g m a l ls ,

th e digital m o d e l i n g of a n y entity is possible d ue to ever m o r e soph i s -

t i ca ted m e d i u m s of descr ip t ion ava i l ab le to

p r o g r a m m e r s

in th e form of

p r o g r a m m i n g languages a n d s o ftw a re d e v elo p m e n t e n v i r o n m e n t s . A s I

will

show

in ch ap t e r

1 1 , p r og ra m m e rs m o d e lin g

p o w e r

increases as their

ability to rep resent rea l -wor ld ent i t ies

in

so f tware

is facilitated,

a n d this

is

a c c om p l i s hed with ab s t rac t i on too ls .

T h e

less t he y

need

to

be

co nce r ne d

with

c o m p u te r-s p ec ific d e ta ils lik e m e m o ry m a n a g e m e n t

a n d

m a c h i n e

a d -

dress

manipulation,

th e

m o r e

t he y

ca n

co nce n t ra t e

on

rep resent ing

a n d

m a n a g i n g

rea l -wor ld

information a n d

objec ts .

At th e d a w n of th e digital age, a group of v i sio n a r y th in k e r s specu la ted

that

th e

r ea l world objects capab le of be in g m o d ele d in c lu d e th e intel-

l igent

r ea s on i n g processes

exh ib i ted

by

h u m a n s .

At

a

s m a l l confe rence

a t Dartmouth

in 1 9 5 6

these

th inkers

gathered

to

discuss th e

following

t h e me :

Eve ry aspect of l ea rn ing or a n y o th e r fe a tu re of i n te l l igence

can

in principle

b e

so

prec ise ly descr ibed t h a t a m a c h i n e can b e

m a d e

to

s i m -

ulate it.1 J o h n M c C a r t h y , one of th e at tendees,

c a m e

u p with th e term

artificial

i n te l l igence

to

descr ibe

th e field

c o m m i t t e d

to this

th em e, a n d

this

l a be l has s tuck . O n e w a y to

prec ise ly

desc r ibe i n te l l igence

is

by

c a r e fu lly c h a r a c te riz in g

it as a kind of s y m b o l p ro c es s in g go v e rn e d

by

strict ru les of s y m b o l manipulation. McCarthy real ized

that

in o r d e r to

tes t this

s ym bo l s ys te m hypothes is

he

needed

a p r o g r a m m i n g tool that

w o u l d a l low him to think

in

t e rms of

s ym b ols a n d

l ists of s y m bo l s ,

rather


26/256

1 4 CHAPTER

2

t h a n in t e rm s of bytes, r eg is te rs , a n d m e m o r y addresses . So he c rea ted

th e

list

p ro c e s sin g la n g u a ge

ca l led

Lisp

that con t i nues

as

th e

d o m i n a n t

AI research l anguage t od a y .

Marvin

M i n s k y ,

a n o t h e r of th e Dartmouth

con ference a t te nde e s , has

de fi ne d

AI as the sc ience of

m a k i n g m a ch in es d o th ings

that w o u l d re -

qu i re in t e llige nce if

d o n e

by men. 2

This definition

does not

presuppose

a

t he ory of h u m a n i n te l l igence such a s th e s ym bo l sys tem

hypo thes is ,

but

charac ter izes AI as be ing concerned

on l y

with m a c h i n e

behav io r

i n so fa r

as it m i m i c s h u m a n intelligent be ha v io r. T hu s we

ca n descr ibe tw o

dif-

fe ren t

a pp r oa c hes

to

AI,

one

that

a t t e m p t s

to

m a ke m a ch in es

think

l ike

h u m a n s ,

a n d

on e

that a t t e m p t s to

m a ke m a ch in es

a c t

l ike hum a n s . 3 T h e

f o r m e r

a p p r o a c h is t o d a y p laced within th e

interdisciplinary

field of cog-

nitive science,

in

w hic h th e o bje c ts of s t u d y a re th e

cogn i t i ve

processes

of a c t u a l h u m a n s

a n d

a n im a ls . T o tes t theor ies a b o u t these processes,

it

is of ten

e x p e d i e n t

to write p ro g ram s that

m o d e l

h u m a n

o r

a n i m a l

cog-

nitive arch i tec ture , a n d t hen to observe w h e t h e r th e p ro gra m s beha ve

(cogn i t i ve ly )

in th e

w a y

that

h u m a n s

a n d an i m a l s

do . T h e

latter

a p -

p r o a c h a ls o o bs erv e s th e cogn i t i ve b e h a v i o r of

p ro g ram s ,

but

ignores

th e

issue

of

w h e t h e r

AI faithfully

emula tes

th e

a c t u a l

structure

a n d

process

of

h u m a n reason ing, m ea s ur i n g

its

success

solely aga i ns t

th e b eh a v io r

of

a c o m p u t i n g artifact. This a p p r o a c h

ha s

th e

a d v a n t a g e

of

a v o i d i n g

both

con t rovers ies

o v e r

h o w h um an s think a n d

cr i t i c i sms

that mach i ne s will

ne v e r

be able

to

think l ike

h u m a n s .

But

there is a n o t h e r d im e n s io n a lo n g w h i ch

a pp r oa c hes

to AI

ca n be

d is t i ngu ished.

W h e t h e r

it is

thought o r b e h a v i o r that

is e m u l a t e d ,

s om e

a pp r oa c hes

to AI

d o

not use

h u m a n s

as their mo de l s , opting i n s t e ad for

th e

notion

of

a n

i d ea l

rational

agent .

Real iz ing

that

h u m a n

thought

a n d

b e h a v i o r a re both

myste r i ous l y

c o m ple x a nd

a t

t imes

unre l iab le , these

ap p r o ach e s m o d e l i n te l l igence

o n

a no t i on of i d ea l rationality.

T h e

re -

sulting sys tems

a re

j udged to be n o t h u m a n l i k e

in

their

b e h av i o r , but

agent l ike,

where

a n a g en t

is nothing m ore than a sys tem

that perce ives

a n d acts . O n e t ype of age n t that ha s

received

large a m o u n t s of

research

attention

in th e 1990s

is

th e sof tware agent, o r softbot.

Motivated by

th e

need to filter usefu l

knowledge

f rom e no r mo u s a m o u n t s of

information

ava i l ab le by

e lec t ron ic

mail a n d th e Wor ld Wide

Web, so f tware

agents

ha ve

s in ce been

app l ied in m a n y o the r

areas

including

e lec t ron ic

c o m -

merce

a n d

spacecra f t con t ro l .

W h a t e v e r

their a pp roa c h , AI practitioners a re taking a d v a n t a g e of

four decades

of research to p rod uc e sys tems within

a

wide

variety

of

a pp l i ca t i on s . These a pp l i ca t i on s

ha ve f o u nd their

w a y

into all

corners

of soc iety that a re

d e p e n d e n t u p o n t echno logy ,

including th e

military,

U


27/256

THE

DEFINITION

AND S C O P E

O F

AI

1 5

m ed i c i n e ,

science,

m a n u f a c t u r i n g ,

co mme r ce ,

a n d

fi nance .

T he k in d s

of

th ings that

AI

s ys te m s d o

mirror th e k in d s

o f ac t ions that

h u m a n s t ake in

their ca pa c i t y a s reasoners a n d d ec is io n m a ke rs

in

specific areas requiring

intellection. These areas

i nc lude

p l a n n i n g ,

schedu l i ng ,

r ecog n i t i on , c las-

s ifica t ion ,

d iagnos i s , pre d i c t i on ,

a n d

m a i n t en a n c e . T h e r ea s on i n g e m u -

l a ted

by

a

m a c h i n e

ca n

be

e ith e r in

con ju nc t i on

with h u m a n s ,

in

w h i c h

th e m a c h i n e acts

as

a n ass i s tan t , o r a lone,

in

w hic h th e m a c h i n e acts as

an a u t o n o m o u s intelligent agent .

T h e AI areas just m e nt i o ne d a re v ery bro ad , a n d t hus t echn iques d e-

v o t ed

to

t hem

a re

app l i cab le

to

multiple

ac t i v i t ies .

Fo r

exa m p l e ,

ef f ic ient

p l a n n i n g a n d s ch e du lin g a re

vital

to th e productivity a n d

profitability

of

large

m a n u f a c t u r i n g

co mp an i e s ,

so

th e

des ign,

cons t ru c t i on ,

a n d d ep lo y-

m e n t of c o m p u t e r p ro g ram s to

per fo rm

a u to m a t ed jo b -s h o p schedu l i ng

is a

focus of m a n y co mp an i e s , i n c lu d ing a u t o m o b ile m a n u fa c tu re rs .

But

p l a n n i n g a nd sc he du lin g a re

also

espec ia l l y important

within military

e n v i r o n m e n t s ,

in

wh i ch th e

ability

to generate l og is t i ca l p l a n s for , say,

th e rapid

mobilization

of c o m b a t forces

a t a n air

base

in

th e

face

of u n -

pred ic tab le ,

ambiguous ,

a n d

rapidly

c ha n g i n g

e n v i r o n m e n t s ,

is

critical

to national secur i ty . In f ac t , th e Defense A d v a n c e d Research Pro jec ts

A g e n c y (DARPA) work s with th e U.S. Air Force to f un d

AI

pro jec ts

in

force p l a n n i n g a n d aircraft d e p l o y m e n t , a m o n g others .

O n e of th e l a rgest areas of AI research

in

recogn i t ion

is

natural l an -

guage

process ing, of w h i ch there a re

m a n y

subareas.

A m o n g th e e a rly

hopes

for AI wa s th e ability to

per f o r m

natural

l anguage

translation,

say

f rom Russ ian to Engl ish . Th is p rov ed

no to r i ou s l y

difficult, a n d

po in ted

out

th e need

for knowledge of

c o n t e x t

w h e n dea l i ng with m a ch in e re p-

resen ta t i ons

of natural

l anguage.

(AI

fo lk lore

tel ls th e

story

of

a n

ear ly

sys tem

that a t t e m p t e d

to t r a n s l a te s imp le

sentences

f rom Engl ish to Rus-

s ian

a n d

then b ack to

En glis h. Wh en

th e sys tem was

given

The

spirit

is

willing but

th e fiesh is weak ,

it

r e sp o nde d with The

v o d k a is

good

but

th e m e a t

is rotten.)

But successes

ha ve

emerged ,

to

th e

point n o w

where t he re

a re u sa ble

front ends to da tab ase

sys tems supporting

natu-

ral l anguage quer ies .

Th e re is

also

n o w limited

v o c a b u l a r y

c o m m e r c i a l

dictation s o ftw a r e a v a ila b le ,

in

w hic h th e spoken

w o r d

is

c on v e r t ed

to

text.

In

th e area

of

d ia g n o s is , p e rh a p s

what first comes to

m i n d

is m ed i c i n e .

I n d eed , s om e of th e

m o s t

dramatically

successful

AI p ro gra m s ta k e a s in -

put

descr ip t ions

of th e

s y m p t o m s

a n d b ack gro u nd of a n af f l ic ted patient,

sa y

on e

suf fer ing

from lymph n o d e p ro ble m s , a n d

p ro du ce

as

output

a

co r re c t

d iagnos i s ,

a l on g with a de ta i led e x p l a n a t i o n

of th e fa c to rs used

in th e

p r og r a ms reason ing.5

But th e

m e t h o d s used

to create such

a

p r o -


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16

. CHAPTER2

gram

a re e qu a l l y

app l i cab le

to o t h e r

areas in

w h i ch

co r re c t

d iagnos i s

is

requ i red , both within med ic ine

a n d

in areas

n o t even r emo te l y s im i la r .

Th i s is because AI p ro g ram m e rs h a v e l ea rned that th e

bes t

w a y to de-

sign p ro g ram s is

by distinctly

se p a ra t i ng

th e p ro gra m s knowledge f rom

its contro l . In th e s a m e

w a y

that th e c o n t r o l m ec ha n i s m of a c o m p a c t

d isk p la ye r ca n a ccep t a nd

read

m a n y d i f fe ren t

d isks,

a wel l -des igned

AI p ro g ram s c o n t r o l me ch an i sm

ca n

acce p t a n d

process

knowledge f rom

m a n y d i f fe ren t areas. T h u s th e lymph n o d e programs c o n t r o l m ec ha n i s m

might be app l ied to know ledge o f, say, card io log ica l d isorders , to

p ro du ce

a

n ew

p r og r a m fo r

d iagnos ing

diseases

of

th e h ea rt.

But

bey on d

that,

th e

p ro g ram s c o n t r o l me ch an i sm might

just a s wel l be app l ied

to

n o n m e d i -

ca l d o m a i n s ,

f rom

th e t r ou b le shoo t i ng

of c o m p l e x

m a c h i n e r y

to even

th e

debugging

( u nco ve r i ng

p r o g r a m m i n g

mis takes ) of c o m p u t e r p ro g ram s .

P r o g r a m s that a re

able

to

per f o r m d iagnoses

o r o therw ise ana lyze

in

a n a rea normally

regarded as

re qu i r i ng h u m a n e xp e rtis e a re examp les of

exper t systems m e n t io n e d e a rlie r. T h e y first became

widespread

in

th e

19 8 0s a n d

n o w

there a re t hous a n d s

in

e v e r y d a y

use. T o giv e

just a

tas te

of th e

types

of exper t sys tem a pp l i ca t i on s b e in g c re a te d t o d a y , h ere a re

s om e re c e n tly re p o rte d

in

a n international journal o n

e x p e r t sys tems:

0 Evaluating a n d monitoring th e l eve l of

air

pollution.

0

Aiding probation off icers in

sentence

r e c o m m e n d a t i o n .

o

Predicting p a y m e n t

p e r fo rm ance

on c o n s u m e r l oans .

0 Auditing

tasks in a

large public acco u n t i ng firm.

0 D i agno s i ng equ ine

cough.

0 Ass is t ing

in

acco u n t i ng

ed uc a t i on .

0

Process s ele ctio n a n d cos t i ng of th e h o le -m a k in g ope ra t i on

in m a n u fa c tu rin g .

T h e focus

in e xp ert sys tems is on e m u l a t i n g

h u m a n e x pe rtis e

by

repre-

sen t i ng

e x p e r t

knowledge

in

a

l anguage

that

both

mach i ne s

a n d

h u m a n s

ca n

u n d e r s t a n d . Th is l anguage

is of ten

symbo l i c logic,

but it

ca n

also

be one of

a va r ie ty

of

o t h e r

w e ll-s p e cifie d a n d

u n a m b i g u o u s languages

fo r

rep resent ing

th e fa c ts

a n d

ru les that

ca n

be

el ic i ted

f rom

h u m a n

sub-

jec ts . Currently, there is ev en

a n

ef for t a t S ta n fo rd University to

create

a knowledge i n te r l ingua, o r u n i v e r s a l l anguage for r ep r es e n tin g fa c ts a n d

ru les.

T h e use

of

these languages

is

cen t r a l

to

what ha s c om e

to

be


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THE

DEFINITION

AND

S C O P E O F

AI

1 7

regarded as

th e c lass ica l

a pp roa c h to AI,

in w hic h

th e

symbo l i c

repre-

senta t ion of fa cts a nd ru le s, a lo n g with their manipulation via logic o r

logic- l ike

c o n t r o l me ch an i sms , is p a r a m o u n t .

N o w h e r e

in th e c lass i ca l a p p r o a c h

is

there

a n y

concern with th e w a y

in

w h ic h th e brain

phys io logica l ly goes

a b o u t th e

process

of

thinking

a n d

reason ing .

Th e re wa s a

tim e , in

th e

i n f a n cy of

m o d e r n

AI,

w h e n brain

ne u ro p h ys i o l o gy wa s cons ide red a s a m o d e l of computational thought,

but

fo r

va r ious

reasons

it wa s la rgely a b a n d o n e d

in

f a v o r of th e c lass i ca l

approach .7 In th e 1990s,

how eve r ,

a

resurgence

of th e

brain m o d e l

for

AI

o ccu r re d ,

d ue

la rgely

to

th e

success

of

artificial

n e u r a l

ne tworks ,

o r

p ro g ram s

that opera t e on th e principle of pa ra l l e l distributed process-

in g PDP . In P D P , c o m p u t a t i o n is

accompl i shed

through th e

work

of

m a n y

s m a l l

process ing e lements

taking

input f rom

a n d emitting

output

to

on e

a n o t h e r in m u c h th e

same

w a y

that

ne u r o ns

c o m m u n i c a t e

with

on e a n o t h e r

in a

bio log ica l

b r a i n .

Because of th e m a s s i ve connectivity

exh ib i ted

a m o n g

ne u r o ns in

th e

b ra in , th is

a p p r o a c h

to

AI is

somet imes

cal led

connec t ion i sm.

It turns out that

artificial n e u ra l n e tw o rk s

( A N N s )

a re g ood a t on e

thing that bra ins d o ve ry

w ell, a nd

that is

co m p l e x pattern

r ecog n i t i on ,

w h e t h e r th e

pattern

be a n image of

a

face, t yped charac ters ,

a

vo ice print,

o r quantitative

proper t ies of

c he m ic a l c om p o un d s. ANNs

ca n be m a d e

to recognize these pa t te r n s t h rou gh training techn iques that a re partially

b o r ro w e d f rom

w h a t

we k n o w

a b o u t

brain phys io logy . T h u s A N N s cons t i -

tute on e f ace t within

a large

area of AI

concerned

with m a c h in e le a rn in g .

Although

A N N s a re n o t th e on l y m o d e l fo r

m a c h i n e

l ea rn ing,

t he y

h a v e

p rov ed

successful enough a t l ow- leve l

tasks

to warrant a n exp los ion of

cu r r en t

research.

A m o n g th e

m a n y

c u r re n t a p p lic a tio n s

of this

research

are:

0

Class ifica t ion of bio log ica l part ic les f rom e l e c t ro n - m i c ro sco p y

images .

0

Class ifica t ion of seismic events .

0

Lea r n i n g

to fa c to r p o ly n o m ia l equa t ions .

0

Detec t i n g

c re d i t card

f r a ud .

T h e

success

of

A N N s

a n d o t h e r m a c h i n e

l ea r n i n g

t echn iques

in

th e

process ing

a n d

a ss im i l a t i n g of large a m o u n t s of d a t a

in

th e

training

p r o -

cess ha s

spur red

c u r r e n t i n te res t in a n a rea of

AI

k n o w n

as

knowledge

d i scovery

in

databases

(KDD;

also cal led

data mining). KDD

t r ies to

a u t o m a t e th e

process

of extracting f rom th e large a m o u n t s of d a t a ,

typ-

ically p r o d u c e d by sc ient ific a n d

bus iness

en d ea vo r s , u se fu l k no w le d ge


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1 8

CHAPTER 2

that

wa s

p r ev ious l y

u n k n o w n .

Potential a pp l i ca t i on s i n c l u de a n a l yz i n g

purchases to de t e rm i ne c u sto m e r p ro file s , d is c o v e rin g

pa t te r n s

in

hea l th

care, o r even d iscover ing galax ies.

Th e re a re m a n y o t h e r areas of AI that I

h a v e

not m e n t i o n e d

here,

a m o n g

t hem

c o m p ute r v is io n a n d robot i cs , but I h o p e this sect ion has

descr ibed th e field a d eq ua t e l y enough

so

that

we m a y

n o w return to o u r

fo cus o n

th e relation of p h i l o so p h y to c o m p u t e r

science.

While

c o m p u t e r

sc ience

is a y o u n g

field

even within th e m o de rn

era,

it

turns

out that

through

AI

p h i l o so p h y

ha s

fo r t hous a n d s of years

been

p o n d e r i n g ques-

t i ons

that

m a n y c o m p u t e r

scient is ts

a re

concerned

with

n o w .

In

th e n e x t

ch ap t e r we will

lo o k a t

AI

t h rou gh

th e

ages in

th e history

of

ph i losophy .


31/256

_. 3 _ _ .

AI and the History of Philosophy

W h e t h e r

AI

is

concerned

with c re a tin g c o m p u t e r sys tems that think

a n d

a ct like h u m a n s ,

o r that think

a n d a c t

rationally, it

m u s t

address th e

m o d e l i n g of

reason ing

in

c o m p u t e r p rog ra m s . T h e p r o g r a m m i n g part of

this e n de a vo r, h ow ev er, is

se co nda r y

to th e p ro ble m of

con cep tua l i z i n g

a m o d e l of reason ing

in

th e first

p lace.

T h e availability of digital c o m -

pu te rs in th e twentieth cen tu r y

has

o n l y

a l l owed

th e

test ing

of

h u m a n

reason ing

mo de l s ;

th e c on c ep tu a l

creat ion

of

such

mo de l s

has been

th e

topic of ph i l osoph i ca l

invest iga t ion

for centur ies ,

in

th e form of logic.

In a

r ea l sense,

t hen , l og ic ians

h av e sin ce

antiquity

been

laying s om e of

th e

f o u n d a t i o n s

of AI,

a l t houg h

without a n y fo reknowledge of elect ron ics

they n e v e r

cou ld

h a v e

i m ag i ne d

th e

purposes to w h i c h

their

work wou ld

ultimately

be put

in

m a c h in es .

T h e

historical

f oun d a t i on s

of AI

la y

not o n l y

in

th e work of those

i n terested

in

formalizing r e aso n i ng through logic. J u s t as

important

to

AI

a re

tw o

u n d e r l y i n g

ph i l osoph i ca l

theor ies c on c e rn i n g

th e

mind

a n d

its thought

processes,

name l y ,

that t he y

a re

u n d e r s t a n d a b l e

within both

a

phy s i c a l

a n d

a c o m p u t a t i o n a l

m od e l .

T h e

first theory

i n vo l ves

taking

a

s t a n d o n th e traditional p h ilo s o p h ic a l p r o ble m of th e re l a t i onsh ip be-

tween m i n d a n d bo d y . Fo r

if ,

as

in

th e t he ory of mind/body d u a l i s m ,

th e m e n ta l events m a k i n g up consc ious thought

a n d

rea s on i n g a re n o t

necessar i l y d e p e n d e n t u p o n

cer ta in

p h ys i ca l

events

fo r

both

their

ex is-

tence

a n d co n t e n t , t hen to pursue th e

artificial

crea t ion of thought a n d

r ea s on i n g processes

in

a phy s i c a l m e d iu m (lik e

a

c o m p u t e r )

m a y

not be

easy

to

justify.

It

shou ld

be

n o t ed ,

however ,

that

a success fu l defense

of

a

phys ica l i s t i c

v iew

of th e

h u m a n mind

does

not

necessar i l y

imply

that

it is possib le to artificially p rod uc e thought a n d re as on in g processes

in a .

c o m p u t e r . It is possib le to be

a n

antidualist regard ing

th e

mind/body

re l a t i onsh ip , y e t still d e n y th e possibility of

so m e t h i ng

l ike thought o r

consc iousness

in

such nonb io log ica l

matter

as what m a k es u p

co m p u t e rs .


32/256

20

CHAPTER

3

T h e

second

t he ory

i nvo l ves

a

c o m m i t m e n t

to

th e

m a n n e r in w h i ch

m e n t a l even ts

respons ib le

fo r thought

a n d re a so n in g

t ake p lace , w h e t h e r

their m e d i u m is

p h ys i ca l

o r n o t . If

these

ev en ts a re not computational

in

n a tu r e , with their process ing ach ieved through

ru le l i ke ,

algorithmic

con t r o l ,

then to

attempt

to real ize th e n a tu r e of

h u m a n

r ea s on i n g

in a

c o m p u t a t i o n a l e n v i r o n m e n t ( l ike

a

c o m p ute r p ro gra m )

m a y

be

similarly

misgu ided . A full u n d e r s t a n d i n g of th e ph i l osoph i ca l

f o u n d a t i o n s

of AI

requi res

s om e

knowledge

of th e c o n te x t p ro v id e d

by

both logic

a n d

phi-

l o s ophy of m i n d .

It

is

i n te res t ing

that

theor ies

o n

logic

a n d

ph i l osophy

of

mind

hos -

p i tab le to th e m o d ern AI project

ca n

be

seen a s flourishing

in Greek

antiquity, th en e ith er re legated to se co nda r y

s ta tus

o r re v ile d through

m e d i e v a l t imes, a n d finally res tored to respec tab i l i t y

in

m o d ern tim e s in

pre pa ra t i on

fo r

th e grea t sc ient ific a n d techno log ica l a d v a n c e m e n t s of th e

twentieth

cen tury .

Ancient

Views

of the Mind

With

respec t

to

th e

re la t ionsh ip

of

m i n d

to matter,

it

is

accep ted

that

th e

first

major figure to

fra m e th e

prob lem

ph i l osoph ica l l y

was Plato

(c . 427347 b.c.). That a person cou ld

be

regarded s i m p l y as a

b o d y

was

r e p u g n a n t

to P l a t o n i s m ,

as illustrated

in th e f o l l ow ing

d ia logue

between

Socrates

a n d Alc ib iades:

Soc: [T]he user a n d th e

thing

he uses a re

d i f ferent ,

a re they

not?

A lc : H o w d o yo u

m e a n ?

Soc: Fo r i ns tance, I

suppose

a sh o e mak e r

uses

a

r o u n d

tool,

a n d a

square one ,

a nd o th ers , w hen he

cu ts .

Alc: Y e s .

Soc: A n d th e

cutter

a n d user is

q u ite d iffe re n t

from

what

he

uses

in cu t t ing?

A lc : Of

course.

Soc: And

in th e s a m e

w a y what th e h a r p e r uses

in

harping

will be

d i f fe ren t f rom th e h a r p e r

h imsel f?

A lc :

Yes.

Soc: Well

t h e n ,

that

is

what

I

was

ask ing just

n ow w het he r

th e user a n d

what

he

uses

a re a lways ,

in y o u r o p in io n , tw o

d i f fe ren t

t h ings .

Alc : T h e y are.

Soc:

A n d

m a n

uses

h is whole

b o d y

too?

A lc : T o be

sure.


33/256

AI AND THE HISTORY O F PHILOSOPHY

21

Soc: A n d

we said that

th e user a n d w h a t

he

uses a re di f ferent?

Alc: Ye s .

Soc: So m a n

is

d iffe re n t fr o m h is o w n bo dy ?

A lc :

It

seems so.

Soc:

T he n w h ate ve r is

m a n ?

Alc : I c a n n o t say.

Soc: O h , but yo u c an th at h e

is

th e user of th e bod y .

Alc :

Yes.

Soc: And th e user of

it m u s t

be

th e

soul?

Alc :

It

m us t .

S o c : And ruler?

Alc :

Yes.1

By th e

us e r a nd

ruler of th e b o dy ,

we

ca n

t ake

S o cra te s s ou l to be

th e reason ing

m i n d

with w h i ch we

a re c on ce rn e d.

T h e strict separa t ion

of h u m a n s

essences

f rom their bodies is cons is ten t with

th e

celebra ted

Platonic T h e o r y of Forms, w h i ch st ra t ifies

reality into

th e m u t a b l e

objects

of

ordinary

exper ience a n d th e

i m m u t a b l e ,

tim e le ss , a n d t r a n s c e n d a n t

rea lm of

th e

Forms, l ike jus t ice, equa l i ty , o r un i ty , with w hic h th e mind is

c on c ern e d w h en it reasons o r ph i losoph izes.

Cer ta i n l y ,

th e mind o r sou l

has

knowledge

of ordinary

objects

l ike p e o p le , tre e s ,

a n d

stones, through

th e de l i ve rances of

sight,

hear ing ,

t ouch ,

a n d

so

on . But n e i t he r th e m i n d

n o r th e concepts

it

reasons a b o u t a re th em s elv e s part of this

co rp o re a l

wor l d . It wou ld h a v e

been

imposs ib le

fo r

Plato to

conce ive

of

a n

artifically

created

m i n d ,

fo r

anything

so

f abr ica ted cou ld

ex is t

o n l y

in

th e

imper f ec t

material

wor l d ,

whi le r e aso n i ng

occurs in

th e re a lm of th e

F o r ms .

That

th e w o rk in g s

of

th e m i n d

a re

n o t

to

be

couched

in phys ica l ,

cor-

p o re a l te rm s is

also

b orn out by

Pla to s

v iew that l ea rn ing, a primary

activity of th e m i n d , is rea l ly th e reco l lect ion of

knowledge acqu i re d

out-

s ide th e

p h ys i ca l

l ife of h u m a n beings

a n d within th e re a lm

of

th e Forms.

A s Socra tes r em a rk s to M e n o :

T h u s th e sou l , s ince it is immortal a n d ha s

been

b o rn

m a n y

t im es , a n d ha s seen

a ll

th ings

both

here a n d in

the

other world,

ha s

l e a r n e d everything that is. So we

need n o t be su r p r i sed if

it

ca n

reca l l th e

k n o w l e d g e

o f

virtue

o r

anything

else

w h i c h ,

as

we

see, it o nc e

possessed.

All nature is

a k i n ,

a n d th e s o u l ha s

l ea r ned

everything, so that w h e n a m a n h a s reca l led a single piece

of

k n o w l e d g e l e a r n e d it, in ordinary l anguaget her e

is n o reason

why he s h o u l d

not find out

all th e rest , if he keeps a stout heart

and d o e s

not grow weary of the

search, for seeking

and learning

a re

nothing

but recollection?


34/256

22 CHAPTER

3

Intimations of

r e i n ca r n a t i on i sm

in

P l a t o n i s m

notwithstanding,

th e

c o m -

m o na l i t i e s between P la ton i sm a n d l a te r Christian doc t r i ne regard ing

th e

re la t ionsh ip of m i n d a n d b o d y a re c lear ,

in

that mate r i a l i sm, o r a n y asso-

c ia te d v ie w that

al lows thought o r r e aso n i ng to be p re d i ca t e d of material

th ings,

is to

be re jected.

But whi le Christian th e o lo g y w o u ld d o m i n a t e m e d i e v a l ph i l osophy for

centur ies , it is important to point out

that antiquity

h a d its materialists

a n d s ke ptic s with

regard

to th e m i n d . H i p p o c ra t e s (c . 4 6 0 - 3 5 7 b.c.) was

b orn before

Plato a n d is

bes t kn ow n fo r

th e m e d ica l o a th .

H e wa s fasc i -

n a t ed

by

epi lepsy,

w h i ch a t

th e

time

wa s

given

th e

n a m e

sacred

d isease.

Hippoc r a tes

u nde rs t o o d that

th e disease

wa s gran ted a

divine origin d ue

both to its

st range m an i fe s t a t i o ns a n d

to genera l

public

i g n o ra n c e c on -

c e rn i n g its cause, but he a lso u n d ers to o d th e primary ro le p la y ed

in

th e

disease

by th e bra in . M o s t

importantly, he ex t en d ed

th e b ra in s role

f rom a

mere causer

of cer ta in d isorders to a cen t r a l f ac to r in all aspects

of m e n t a l l i fe:

M e n

o u g h t to k n o w

that from the brain, a n d from th e brain on l y ,

ar ise

o u r

pleasures,

j oys ,

l au gh te r

a n d je s ts ,

as

w el l

as

o u r

so r rows , p a i n s , griefs

a n d

tears .

Through

it,

in particular,

w e

think,

see,

hear , a n d distinguish th e ugly from th e beautiful, the

ba d from th e g o o d , th e p l e a s a n t from th e u n p le a sa n t . . . 3

B e y o n d

u n d e r s t a n d i n g th e c en tra l role

p layed

by th e b ra in , Hippoc r a tes

even

ve n t u re d phys ica l , causa l e x p l ana t i o ns of

m a d n e s s

a n d i n te l l igence:

M a d n e s s c o m e s from its mois tness . When th e brain

is abnormally

m o i s t ,

of

necess i ty it m o v e s , a n d w he n it m o v e s neither

s igh t

nor

hea r i ng

a re

still, but

we

s e e

o r h e a r n o w

on e

thing

a n d n o w

a n o t h e r , a n d th e t ongue speaks

in

ac c o rdanc e with th e things

seen a nd h ea rd o n a n y occas ion . But all

th e time th e

brain

is

still

a m a n is in te l l igent /1

Although

v iews of

th e

m in d o r

sou l a s

i n co r po r ea l

in

n a t u r e pers is ted

t h rou gh

th e c lass ica l

ages in th e

Platonist a n d Sto ic schools , t he re were

also

wel l deve loped sys tems of materialist p h i l o so p h y p o s t - P l a t o , partic-

ularly in

th e Ep ic ure a n schoo l . Epicurus ( 3 4 1 2 7 O

b.c.) ,

a n a d v o c a t e of

a t o m i s m ,

env i s ioned

th e

sou l

a s

be ing

c om pos ed

of

th e

s a m e

a t o m s

that

m a k e u p air, w i n d ,

a nd h ea t, as

wel l

as a

fourth

kind

of a t o m m a d e sen-

sua l l y

unde tec tab le

d ue to its m i n u t e size. O n e s s o ul, w h i c h

is

th e cente r

of th e

self,

is therefore

a n e m p i ric a l o b je c t be ca us e o n es

b o d y is . T h e

sou l is

intertwined with b o d y a n d

c a n n ot e xis t without it.

Although

m o s t

of Epicurus writings

h a v e

been

los t , tenets

of

th e

Ep i cu re an

schoo l

su rv i ve

in th e

writings of

l a te r devotees

a n d fo llo w e rs .


35/256

AI AND THE

HISTORY

O F PHILOSOPHY 23

O n e of t h e m ,

bor n

o v e r one h u n d r e d a n d

seven ty

years

a f te r

E picu ru s

d ea t h ,

was

th e R o m a n p o e t Lucre t ius

(c .

99-55

b.c.) ,

whose didactic

p o e m O n

th e N a t u r e of Things

wa s

a ce lebra t ion of

Ep i cu re an i sm . It

is

descr ibed

as

the fu l lest surviving expos i t i on of th e

m o s t c ohe ren t

a n d influential sys tem of

materialistic

p h ilo s o p hy p ro d u ce d in c lass i ca l

antiquity.5

It

is materialist

in

that

it

a t t e m p t s to lo c a te th e mind within

a p h ys i ca l

s u b s t r a t u m :

N o w I asser t

that

th e mind

a n d

the s o u l

a re

k e p t to g eth e r in

close

union a n d m a ke

u p

a

single n a t u r e , but

that

th e

directing

principle

w h ic h

we

ca l l

mind

a n d

u n d e r s t a n d i n g ,

is

th e

h e ad

so

to

s p e ak a n d re ign s paramount in the

w ho le

b o d y . It ha s a fixed

sea t

in th e

middle region

of

th e breas t :

here throb

fe a r a n d

a p p r e h e n s i o n , about

these

s p o ts d w e ll s o o th in g jo y s ; th e re fo r e

here is th e

understanding o r

mind.

While m o d e r n mate r i a l i sm w o u l d find th e

m i n d

m i s p l a c ed in th e breast ,

th e message is c lear that th e

facu l t ies

of u n d e r s t a n d i n g

a re

not to be

d i s em bod i ed , but to

fin d

their

seat

in matter. W he n c on fro n te d

with

e xp la i n i ng

th e

re la t ionsh ip

of

th e

mind

a n d

b o d y

as

t he y

interact

to

w a k e a m a n f rom sleep, for i ns tance,

Lucre t ius

refuses to c oun t en a n c e th e

possibility of

a

co nne c t i o n

between th ings

co rp o re a l a n d n o n c o r p o r e a l in

n a tu r e , ch o o s i ng

i ns tead a

materialist s tance:

[T]he nature of

th e

mind

a nd s o u l is bodily; for w h e n it

is seen to

p u s h

th e

l im bs , rouse th e body from

sleep,

a n d alter

th e

c o un te na nc e a nd gu id e a nd turn about

th e

w ho le m a n, a n d

w h e n

we

s e e

that

n o n e of

th e s e e ffe c ts ca n

t ake p lace

without

touch n o r

touch

without

b o d y ,

m u s t

we

not

admit that

th e

mind

a n d

the

sou l a re of a bodily nature?

So here

is a

repudiation of th e

strict

Platonic du a l i sm that wou ld

c o m e

to

d o m i n a t e both

p h i l o so p h y a n d t heo logy

in

th e

m i d d l e ages

a n d

l a te r

find its fu l lest m e t a p h y sic a l fl ow e r in g in C a rte sia n d u a lis m . It serves to

r e m i n d

us that AIs materialist intuition,

fa r

f rom be ing a product of th e

m o d e r n analytical a p p r o a c h to p h i l o so p h y

b uttre s s ed b y n e u ro p h y sio lo g-

i ca l

s cie n ce , is f o u n d

in

diverse ages a n d intellectual e n v i r o n m e n t s .

The Age

of Modern Philosophy

T h e fo u n d a tio n s of th e

m o d e r n

a p p r o a c h to AI were laid

b y p h ilo s o p he rs

w h o were concerned with

genera l

charac te r iza t ions of h u m a n u n d e r s t a n d -

ing. These ph i l osophers

regarded

as f u n d a m e n t a l th e ques t ion of

w h a t

is

th e n a tu r e of consc iousness,

including h o w

h u m a n s think

a n d

perce ive,

philosophy and computer science - timothy r. colburn

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