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Computationalism New Directions edited by Matthias Scheutz A Bradford Book The MIT Press Cambridge, Massachusetts London, England  2002MassachusettsInstituteofTechnology Allrightsreserved.Nopartofthisbookmaybereproducedinanyformbyany electronicormechanicalmeans(includingphotocopying,recording,orinforma- tionstorageandretrieval)without permissioninwriting fromthepublisher. This book was set in Sabon by Achorn Graphic Services, Inc., on the Miles 33 system andwasprintedandboundinthe UnitedStates ofAmerica. LibraryofCongressCataloging-in-PublicationData Computationalism:newdirections / editedbyMatthiasScheutz. p. cm. “ABradfordbook.” Includesbibliographicalreferencesandindex. ISBN0-262-19478-3(hc:alk.paper) 1.Computerscience. 2.Artificialintelligence. I.Scheutz,Matthias. QA76.C54747 2002 004—dc21 2002019570 Contents Authors vii Preface ix 1 Computationalism—The Next Generation 1 Matthias Scheutz 2 The Foundations of Computing 23 Brian Cantwell Smith 3 Narrow versus Wide Mechanism 59 B. Jack Copeland 4 The Irrelevance of Turing Machines to Artificial Intelligence 87 Aaron Sloman 5 The Practical Logic of Computer Work 129 Philip E. Agre 6 Symbol Grounding and the Origin of Language 143 Stevan Harnad 7 Authentic Intentionality 159 John Haugeland Epilogue 175 References 187 Index 199 Authors PhilipE.Agre,DepartmentofInformationStudies,UniversityofCalifornia, LosAngeles,LosAngeles,CA90095–1520,USA [email protected] http://dlis.gseis.ucla.edu/pagre/ B.JackCopeland,PhilosophyDepartment,UniversityofCanterbury, Christchurch,NewZealand [email protected] http://www.phil.canterbury.ac.nz/jack_copeland/ StevanHarnad, CognitiveSciencesCenter,ECS,SouthamptonUniversity, Highfield,SouthamptonSO171BJ,UnitedKingdom [email protected] http://cogsci.soton.ac.uk/harnad/ JohnHaugeland,DepartmentofPhilosophy, UniversityofChicago,Chicago, IL60637,USA [email protected] MatthiasScheutz, DepartmentofComputer ScienceandEngineering, UniversityofNotreDame,NotreDame,IN46556,USA [email protected] http://www.nd.edu/(cid:1)mscheutz/ AaronSloman, SchoolofComputerScience,TheUniversityofBirmingham, BirminghamB152TT,UK [email protected] http://www.bham.ac.uk/(cid:1)axs BrianCantwellSmith, DepartmentsofPhilosophyandComputerScience, DukeUniversity,Durham, NC27708–0402,USA [email protected] http://www.ageofsig.org/people/bcsmith/ Preface Are minds computers? Or, to put it in more philosophical jargon, are mentalstatescomputationalstates?Andifso,canhumancognitionthen beunderstood interms ofprograms? Computationalism—theview that mental states are computational states—is based on the conviction that there are program descriptions of mental processes and that, at least in principle, it is possible for computers, that is, machines of a particular kind, to possess mentality. Initsearlydayscognitivescienceralliedaroundcomputationalism,but in recent times this paradigmatic computational view of mind has come increasingly under attack. Connectionists and dynamicists have tried to replaceitwithalternativemodels.Biologistsandneuroscientistshaveat- tempted to understand the mind directly at the level of the brain, thus skippingthe“computationallevel.”Socialtheoristsandroboticistshave argued that the essence of intelligence is to be found in situated interaction with the external world, rather than in a purely internal world of symbol manipulation. Philosophers have argued that traditional con- ceptions of computationalism (and more generally functionalism) are at best conceptually inadequate, if not vacuous (e.g., leading to the ab- surd view that any physical system can be viewed as implementing any computation). Manyofthese critiques sharea commontheme. Computation failsas an explanatorynotion for mind,the critics claim,because computation, assumed to be defined solely in abstract syntactic terms, necessarily ne- glectsthe real-time,embodied,real-worldconstraints withwhichcogni- tive systems intrinsically cope. Although these views have led some researchers to abandon computationalism altogether, an increasing number is willing to reconsider x Preface the very notion of computation, motivated in part by the recognition that real-world computers, like minds, must also deal with issues of embodiment, interaction, physical implementation, and semantics. This recognition raises the possibility that classical computationalism failed not because computing is irrelevant to mind, but because purely “logical” or “abstract” theories of computation fail to deal with issues thatarevitaltobothreal-worldcomputersandminds.Perhapstheprob- lemisnotwithcomputingperse,butwithourpresentunderstandingof computing, in which case the situation can be repaired by develop- ingasuccessornotionofcomputationthatnotonlyrespectstheclassical (and critical) limiting results about algorithms, grammars, complexity bounds, and so on, but also does justice to real-world concerns of daily computational practice. Such a notion that takes computing to be not abstract, syntactic, disembodied, isolated, or nonintentional, but concrete, semantic, embodied, interactive, and intentional offers a much better chance of serving as a possible foundation for a realistic theory of mind. Computationalism: New Directions is a first attempt to stake out the territoryforcomputationalismbasedona“successor”notionofcompu- tation.Itcoversabroadintellectualterritory,fromhistoricdevelopments of the notions of computation and mechanism in the computationalist paradigm,toquestionsabouttheroleofTuringmachinesandcomputa- tionalpracticeinartificialintelligenceresearch;fromdifferentconstruals of computation and their role in the computational theory of mind, to the nature of intentionality and the origin of language. Thefirst chapterservesbothas historicoverviewof thecomputation- alist thinking and as introduction to the later chapters. It attempts to extractahistorictrajectorythattiesthemechanistviewsofpastcenturies topresentperspectivesoncomputation.Variousreferencestolaterchap- ters point to places where the arguments are developed in more detail. In the second chapter, Brian Smith examines various attempts to an- swer the question “what is computation?” Focusing on formal symbol manipulationandeffectivecomputability—twooutofaboutadozendif- ferentwaysofconstruing“computation”—heshowsthatneitherofthem candojusticetothethreeconceptualcriteriahesetsforth.Hisinvestiga- tionleadstotheclaimthat“computation”isnotsubjectmatterandeven- tually to the demand for a new metaphysics. Preface xi B. Jack Copeland also points to a crucial distinction in chapter three, thatbetweenanarrowandawideconstrualof“mechanism.”Thewide conception countenances the possibility of information-processing ma- chinesthatcannotbemimickedbyauniversalTuringmachine,allowing in particular the mind to be such a machine. Copeland shows that arguments for a narrow mechanism—the view that the mind is a ma- chineequivalenttoaTuringmachine—arevitiatedbyvariouscloselyre- lated fallacies, including the “equivalence fallacy” and the “simulation fallacy.” Chapter 4 takes on the issue of whether minds are computational in theTuring-machinesensefromaquitedifferentperspective.Here,Aaron Slomancriticizesthecommonviewthat thenotionofa Turingmachine isdirectlyrelevanttoartificialintelligence.Heshowsthatcomputersare the result of a convergence of two strands of historic developments of machinesanddiscussestheirrelevancetoartificialintelligenceaswellas their similarity to various aspects of the brain. Although these historic developmentshavenothingtodowithTuringmachinesorthemathemat- icaltheoryofcomputation,heclaimstheyhaveeverythingtodowiththe taskofunderstanding,modeling,orreplicatinghumanaswellasanimal intelligence. In chapter5 Phil Agre revealsfive “dissociations,” thatis, intellectual tensionsbetweentwoopposingconceptionssuchas“mindversusbody,” that have accompanied artificial intelligence (and computationalism) fromitsverybeginning.Heshowsthatalthoughitisrecognizedthatthe twoconceptsunderwritingeachoppositionaredistinct,theyareuninten- tionallyconflatedinthewritingsofthefield.Toovercomethesedifficul- ties, Agre advocates a “critical” technical practice that may be able to listen to and learn from reality by building systems and understanding the ways in which they do and do not work. Inchapter6StevanHarnad,advocatinganarrowconceptionofmean- ing,showshowpersemeaninglesssymbolsforcategoriesareconnected to what they mean: they are grounded in the capacity to sort, label, and interact with the proximal sensorimotor projections of their distal category-membersinawaythatcoheressystematicallywiththeirseman- tic interpretations. He points out that not all categories need to be grounded this way and that language allows us to “steal” categories quickly and effortlessly through hearsay instead of having to earn them xii Preface throughriskyandtime-consumingsensorimotortrial-and-errorlearning. Itisthroughlanguagethatanagent(e.g.,arobot)canacquirecategories it could not have acquired through its sensors. JohnHaugeland,then,broadensthediscussionaboutmeaningandin- tentionality in chapter 7 by providing a positive account of what is re- quired for a “system” to have original intentionality, which he takes to be essential to genuine cognition. His main conclusion is that original intentionalitypresupposes anabilityto accept responsibility.Thus,con- trarytotheassumptionsofmanyresearchers,responsibilityisanessential topicofcognitivescience,andthenotionsofintentionalityandcomputa- tionmaybothbeexplanatorilydependentonthenotionofresponsibility. Allsevenchaptersarecompletelyself-containedandcan,therefore,be read in any order. Common to all of them is the intention to initiate a discussioninanattempttoexplicate,distill,andassessthefoundationsof cognitivescience, ratherthanquicklyandprematurelyacceptordismiss computationalism as a viable theory of the mind for whatever reason. For each chapter (except the first) a preceding editor’s note provides a briefoverviewofwhattoexpect.Theepilogue,finally,reflectsinamore speculative way on what the next steps may be in the development of a successornotionofcomputationinanattempttoisolatepromisingdirec- tions and topics for future research. It ismy hopethat Computationalism: New Directionswill contribute to the development and study of a “successor notion” of computation and the range of its possible applications in the computationalist paradigm. Such a notion will have to take into account issues such as the program-processdistinction,thenotionofimplementationandquestions ofphysicalrealization,real-timeconstraintsandreal-worldinteractions, the use and limitations of models, relations between concrete and abstract, the proper interpretation of complexity results, the relation between computation and intentionality, notions of “wide content” and “wide mechanism,” notions of locality and causation, virtual machines and architecture-based concepts, and many more. By addressing these andotherquestionssocrucialto afirmfoundationforcognitivescience inthisnewcentury,thisbookismeanttobeaninvitationtophilosophers and scientists alike to engage in and further this discussion. Finally,Idonotwanttomisstheopportunitytoexpressmygratitude to the many without whom the book would not have become a reality. Preface xiii I would especially like to mention and thank the authors of the various chaptersfortheircontributions,theparticipantsoftheNTCS’99confer- ence in Vienna, “Computationalism: The Next Generation,” for all the stimulating discussions, Leopold Stubenberg, Markus Peschl, my wife Colleen Ryan-Scheutz and many others for their critical comments on the various drafts of my contributions, Thomas Mayer for casting the topicsofthisbookincolorfulpixelsforthebookcover,andRobertPrior andJudyFeldmannfromMITPressfortheireditorialsupport.Thebook would not have been the book it is without them.