Speech Acts and Rationality

Speech Acts and Rationality Philip R. Cohen Artificial Intelligence Center SRI International and Center for the Study of Language and Information Stanford University Hector J. Levesque Department of Computer Science University of Toronto" 1 Abstract This pallet derives the ha.sis of a theory, of communication from a formal theov,.' of rational interaction. The major result is a <h, mon~t fallen t hat. ilh,c,tionary acts need not I)e primitive, and .ee, I uot he reco~'nized..\s a t,'st case. we derive Searle's con- dit ions on reqt,est in~ from pri,ciples of ralionality coupled with a ~;ric~,an theory of iml~erativ,.s. The theory is shown to dis- tingui.~h insincere or nonserious imperatives from tr~le requests. ['~xlensions to indirect .~peech acts. and ramifications for natural language ~ystcms are also brieily discussed. 2 Introduction ']'he tlnifyin~ tilt'me of m,wh c-trent pragmatics antl discourse re~earrh is that the c.herence .f dialogue is to he folnnd in tile iuleraclinn of the cottver~alll'~' 1~61rI.I. Thal is, a speaker is re- garded a~s planning his ,lllcrance,~ re achieve his goals, which n,ay involve in{h..lwing a hean'r by the ,,se of comm,micative or "speech" acts. (-)u receiving an lltler~tnce realizing such an action, the hearer altempls Io infer the ~peaker's goal(s) anti to qndeffland how the 11llerat|rv fnrthcrs them. The hearer then adopts new goals (e.~.. to re-pond to a reqllest, to clarify the pre- vious ~peaker'~ lllll'r~ince or ~.:f,al) and plan~ his r~wn utterances to acl,ie:'e those. :\ cotl,cel'?~alion enslle~, I This view of language a.~ p.rposefid art ion has pervaded ('om- putational I,inzui-~ics re~carch, and ha.~ re~,lted in numerous protoCyl~e systems [I, 2, 3..',. 9. 25, 27]. llowever, the formal foundations underlying 01n... %v~l.ems haw" heen unspecified or .nder~peril'ied. In this ,.late ,~[' affairs, one cannot characterize what a ~,y.',tem .~llould ih~ independently from what it does. This paper hl,gins to rectify this sit-ation by presenting a fl~rmalizalinn of rational interaction. ~pon which is erected tile he~itmin~'- r,f a theory of rein m~miralion attd ~peech acts. Inter- ;wtion is d~.riv~,d fr~,m prmcil~h,.~ of rational action for indivi,h,al a~enas. ~.. well as lwinciph's -[ helief and goal adoption among a~enls. The h~sis of a theory nf purposefi,l communication thus "F, ll~,w ,,I' th~ Canadian lr, sti~,~t~- f~)r A,'.wanc~d R-search. ~This re~,.areh was mad- W,~sdde ;n part hy a gilt from ~he Systems Dew.l- opm~.n~ ["~.md:~ti,,n. and in part t,y suFport fr-m ti~e r)efens~ Advanced R~.se~rrh ['roje.rts .Ag,ncy un.h'r C,~n~ra.ct Nf~I)t)3D.8.I-K-0078 wilh the .N~v:~| ['~lec~ronic Systems C,,mm~nd. The views and om¢lusions eon- tain~'d in thls document ~re ~hos~" of the ~uthor~ and should not be inter- preted ;~ representa, tive of the. omci~.| policies, ~ither expre~ed or implied, oi" the Defense ~dvanced Research Projects Agency or the United States (Jovernment. Mu~h nf this rrsearrh was done when the second a.uthor wa~ employed at the Falrehild ('~m,r~ and Instrument Corp. emerges as a consequence of principles of action. 2.1 Speech Act Theory Speech act theory was originally conceived a~s part of action the- ory. Many of Austin's [.l] insights about the nature …

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