Patrick Suppes. The limits of rationality.pdf

7/27/2019 Patrick Suppes. The limits of rationality.pdf

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THE LIMITS OF RATIONALITY*Patrick SUPPES

Stanford UniversityIn this lecture I survey a number of approaches to rationality, butemphasize throughout the expected-utility or Bayesian model as themost mportant and developed theoryof rationality proposed inrecent years. Because the problems of group rationality as reflectedin our laws and customs have an importance equal to problems ofindividual rationality, I move back and forth from the individual tosociety, and I begin with one of my favorite historical examples ofbureaucracy out of control.

The passion forbureaucratic egulationofhuman activity isnowhere better exemplified, than in the sumptuary laws repeatedlylaid down andpartiallyenforced in ancientRome and later inEurope from medieval to early modern times. The Didean law of 143B.C. of the Roman Republic limited the number of guests and theamount of food that could be served in a private residence. In 1294,Philippe le Bel of France restricted family meals to two dishes plussoup for dinner. In the 14th century,dward III of England imposedsumptuary legislation on the food that was to be given servants. In15 h-centuryFlorence, three courses was the maximum permitted atprivate dinners; two at supper. Police had the right of inspection ofbanqueting halls at any time to be certain that the sumptuary lawswere being obeyed.

In 16thcentury Venice,pheasant,peacock, guinea fowl, black-cock, and woodcock were all banned, along with trout and otherfreshwater fish. Repeated edicts in the 16th century all imposed re-straint on Parisian eating habits,so that even at festive occasions onlythree courses were supposed to be served. A host who violated the

*An earlier draft of this lecture was first given as the Howison Lecture in Phi-loso phy, University of California, Berkeley, February 22, 1979

Grazer Philosophische Studien, 12/13, 1981, pp. 85-101.


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8edicts was liable to fine; hisguests and the cook as well could be


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87selves are for the purp osef achieving an end n view. This Aristotelianview might b e charac terized as a kind of qualitative dynamics of ra-tio na lity . T he good reasons play th e role of causes or of forces inmech anics. There is an amb iguity in this view as to whether goodreasons can be given for ultim ate ends, bu t th is rather delicate pointneed not concern us now . Indeed, my objective is not to refine or tobring together these two approaches to rationality but rather toargue th a t we have n ot recognized sufficiently the ex ten t to whicheither is subjec t t o severe limitation s. Exc ept in th e most limited andusually trivial situations is it possible to say that an act ion s perfect-ly ration al or th at a man has acted in a perfectly rational way. Wecan, with Thomas Aquinas, speak of the perfection of God but notof man.O the r philosophical senses of being ratio nal are set aside as no trelevant t o th e present focus. F o r exam ple, rationalism as the viewthat reaso n rathe r than the senses provides the proper foundation ofknowledge is irrelevant. Thus, historically what has been known ast h e rational school of physicians being rationalists in th e sensejust defined would in th e sense of interest here be regarded as irra-tional because of their refusal t o use em pirical evidence. In a similarway I a m n o t here concerned w ith th e cntrast between rational anddivine theology. Nor am I concerned with rational as a form of ab-straction as in tha t glorious subject of 18th-century natural philos-ophy , rationa l mechanics.I. The Mar k e t ModelReturning t o th e formsofrationalityof nteresthere,one mportantresponse to th e sump tuary laws of th e past is that the rational ap-proach would have been to give free play to market forces to deter-mine t h e distributionof ood. Fo rm an y economists, the perfectionof G od is nearly matched b y th e perfection of markets, which oftenseem to be thoughtof as an instrum ent of God. n thebroader philo-sophical tradition of analyzing t h e con cep t of rationality, it mayseem strange to speak of markets as amodel of rationality, bu t,especially no w , strong claims are m ade, either mplicit or explicit, fo rth e use of m arket mechanisms as a rational approach o problems ofdistribution and herefore as th e appropriate rational approach t odistributive justice.Although the analysis is,I thin k, obvious, it may be useful to


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ed as a mechanism fo r dealing with limited rationality on the pa rt ofbuy ers and sellers. T h e complete exchange of information necessaryfor explicitrationalcalculation, tmay be argued, is afantasyofrationa lity th a t in its worst extrem es is widely recognized. Even int h e m ost rigid Com munist countries, fo r example, some kind of con-sumer m ark et exists in th e sense th a t cen tralized decisions are notm ade o n precisely w hat is to b e ssued in term s of foo d, lothing, andshelter to each consumer. T h e necessity f or some pocket mo neyhas been recognized from time imm emorial, even b y th e most regi-m en ted an d egalitarian of armies.Th e imp ortant feature of the m arket m odel is that it provides apractical alternative to any attem pts at com plete rationality in thedistribution of goodsand services by a state or corporate bureau-cracy.II Expec t edUt i l i t yMo d e lT he th eo ry of mark ets as developed by A dam Sm ith, David Ricardo,and others was the greatest early intellectual accomplishment of thesocial sciences. An explicit con cep t of utility o n which to build aqu antitativ e demand theory of t h e marke t cam e somewhat later inth e 1 9 th ce ntu ry in the work of Gossen, Jevons, Walras, and others,bu t the y m ad e the verly strong assumption ha t util ity was additive,in the Same way that height or weight is. At the next stage this as-sum ption w as weakened by Edgew orth, An tonelli, and I. Fisher tot h e c oncep t of an indifference surface fo r comm odity bundles.Earlyin hiscentury,Pareto to ok he s tepof proposing a heory ofdemand in terms of the behavioristic concept of purely ordinal pref-erences for com mo ditybundles.Co ntem porary expected util i ty theory goes beyond the ideas ofPareto in two essential respects. First, preferences are not restrictedt o com m od ity bu nd les, bu t to any field of choice about which deci-sions are to be m ade . A nd , seco nd , the theo ry s set up explicitly todeal w ith unc ertainty. Ordina l prefere nce s are sufficient in generalonly in situations of essentially com plete knowledge of th e relevantpossible state s of affairs. These extensions beyo nd Pareto actuallyhave an indepe nden t h is tory thatoes back t o t h e 8th century.)Th e in tui t ion back of th e expected utility mode is on e tha t isw idely accep ted. W hen, as individuals, we are forced t o make deci-sions, especially consequential ones, we m ust deal with two m ain fac-


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90tors: first, our beliefs about what isgoing to happen and, second, t

e the ideas in soa decision abou


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91tant to us in almost all circumstances than what happens during thecoming year. Thus, whatever the patients decision, we can in a parti-cular case apply the expected utility model to give an analysis thatshows that the patients choices were in the particular instance ra-tional under some plausible set of assumptions.

As the last remark hints at, there are various ways of applying theexpected utility model. I want to say something about each of theseways, which I describe as the biological, the psychological, and thenormative model.

iological ModelThe biological approach is to regard the model as part of the compu-tational machinery of the organism. Instantaneously, the model isalways satisfied in the actions taken by the individual, and withoutdifficulty the model could beextended o he behavior ofothermammals and even lower in the phylogenetic scale if desired. Thisbiological model has consequences that can be investigated, but itsuse in the theory of rationality s limited, because if we only requireinstantaneous satisfiability, then enough parameters can be adjustedto fit the dataof any momentary choice.Psychological ModelA more interesting approach, and one that has a fairly substantialempirical history by now, is the application of the expected utilitymodel to the actual behavior of individuals in avariety of situations.In this case, the model is tested by assuming some constancy overtime and thus reducing the parameters that can be adjusted. An indi-vidual who is too inconstant in his behavior will, under this standardset of assumptions, not satisfy the model and will be said not to be-have in accordance with this rational canon. There is a problem thathas been repeatedly faced in the application of the model to actualbehavior. It is that some theory of error is required, just as a theoryof error is required even for the best physical theories of atomic orastronomical bodies. Introduction of this theory of error is a rathercomplicated affair but seems essential to any serious application toreal behavior. It should be obvious, of course, that the introductionof a theory of error itself represents a limit on the egree to which apurely rational account can be given of an individuals behavior. Infact, in ,our conceptual thinking about these matters there is not a


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itly b y the individual but are partcious evaluation s his beliefs and


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9consistency of computations required by the expected utility modeldoes not guarantee the exercise of judgment and wisdom in the tradi-tional sense. The Aristotelian view that the rational man acts in ac-cordance with good reasons is not a necessary part of the normativemodel of expected utility, and it is far from clear how these two con-cepts can be put together n satisfactory form.

There is still another fundamental difficulty with the normativemodel as a complete theory of rationality. When we attempt to ex-tend it from individual to social decision processes, we do not knowhow to aggregate the individual utility models to make a rationaldecision among alternatives for the group. The literature on thesematters is large, and the results are mainly negative. But a central factabout most of the studies makes the situation morenegative than thenegative results themselves seem to . This is that almost all studies,from Arrows classical impossibility theorem onward, ignore con-flicts of interest and strategic moves to reflect those conflicts. Theanalysis of social decision procedures is ordinarily based on the as-sumption hat he problem is to assess in straightforward fashioneach plain mans desires and to choose a social policy in a mannerthat best reflects differing individual preferences. But the politics ofthe real world cast skepticism on this assumption. It seems to methat there is good ground for thinking that when serious conflicts ofinterest exist, the political negotiations that follow are both neces-sary and, at the same time, follow no obvious model of rationality.Negotiations between industry and labor, government and farmerschoose whatever conflicting groups you want end up with deci-sions that are based on compromise, but the details of the compro-mise are shaped by idiosyncratic features of negotiators, yesterdaysweather, and other random happenings. There is not, and in my viewnever will be, anycomplete model of rationality that is at all satisfac-tory for accounting for the esults.III. The Legal ModelOnce problems of conflict are brought o the urface, it might be sug-gested that the proper place to look for a model of rationality is inthe practice of the law. The judge,weighing justice in the balance, isoften houghtof as the very model of the rational deliberatorreaching an impartial ,and objective judgment of the rights and in-terests of the parties in conflict. It might even be claimed that the


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95Before arriving where I can observe the freeway and make a decision,I estimate the probability as about a half that the freeway is crowded.If it is crowded I will take the parallel regular street; if it is not, I willtake the freeway.I arrive on the cene, make an observation hat thefreeway is crowded, and thus take the parallel regular street. In theBayesian view, it is natural to say that my observation that the free-way is crowded is certain, and therefore that I assign a probability ofone tohis observational evidence.

Although there are clear differences, this desirability of evidencebeing certain is in the grand tradition of the theoryf demonstrationin Aristotles Posterior Analytics Descartes Discourse on M eth odand Kants Critique of Pure Reason all elaborate fantasies, in myjudgment. No harm seems to be done by sticking with a simple ac-count of certain events in the example of deciding which road to tra-vel, and I would agree that there is much ordinary talk that uses in anatural and easy way the notion of being certain about not only pres-ent observed events but also future ones. For example, it does notseem at all strange or strained to say that it is certain I will not begoing to New York this week and therefore cannot meet someonewho calls about a conference to beheld there.

Nonetheless, for either the theory or practice of complex deci-sions, the search for certainty is one of the disastrous romantic fea-tures of both ancient and modern thought. Whether we are decidingwhat measures to take to control inflation, what the effects of low-level radiation are, or what political alliances to make for tomorrowssecurity, we operate in an uncertain world, which cannot be broughtto a point of certainty, and moreover, much of the evidence that wedeal in is equally far from certain and is dubious in character. Tosome, it sounds like an alliance with the devil to speak of using du-bious evidence, but dubiety has an honored place in the repertoire ofany realistic decision maker. The technical ways of conditioning onuncertain evidence are important if for neo-Bayesians, but I will notpursue the matter further here.Criticism o CompletenessImplicit claims of completeness are very much a part of he standardBayesian or expected utility model of rationality. The conceptualmachinery is there to deal with any problem, and t satisfies a canonof completeness in the sense that it gives an answer in principle,


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97must be made. There is no serious evidence that this set of decisionscan be reduced to an explicit theory of rationality. Many practicaland conceptually inexplicit decisions must be made in every area ofexperimentation, or indeed of empirical inquiry, ranging from high-energy physics to thepsychology of auditory judgments.

The second point is that it is relatively straightforward to thinkabout applying a criterion of rationality o decisions formulated in atheoretical framework. This reflects aeneral scientific fact of life. Inevery branch of science, the theoretical language is relatively simpleand easy to learn compared with the complex, arcane, and esotericlanguage used to express the lore of experimental procedures, fromthe calibration of instruments to the collection of data. I will nothere attempt to document this thesis. I, in fact, consider it obviousto anyone acquainted with actual scientific practice in some devel-oped branch of investigation. Decisions taken in the framework ofsuch highly empirical language and thought routinely seem toohighly context-dependent obe assessed in terms of any generalcriterion of rationality.

The hird point is that he fantasy of explicit formality, withelimination of all need for intuitive judgment, is recognized as anoutmoded concept, even in mathematics. Hilberts program of for-malism was upset years ago by Gdels incompleteness theorems, andthe gap between formal theories of proof, for example, and actualmathematicalpractice, requiring judgments of all kinds, isnowwidely acknowledged. I emphasize the essential place of judgment inscience and mathematics, because this is the area of thought and ex-perience that seems most amenable to regimentation by models of ra-tionality.The essential place of judgment in decision making has been rec-ognized by various people, including de Finetti, for some time. Butthere has been a countertendency, generated by the thicketof tech-nical results about decision making in modern mathematical statis-tics, that tends to uggest that judgment can be eliminated in favor ofthe application, in a routine nd objective and possibly even algorith-mic way, of technical results. There has also been a pernicious trendof long standing in classical philosophy of both ancient and moderntimes that reenforces this view perhaps the best example s thefoolish attempt to construct our knowledge of the world from indu-bitable sense data. What I have said about the essential role of intui-


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98tive judgment in assessing evidence in scientific experiments extends


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99practice and in most cases explicit teaching by an experiencedcoach. We are, for a variety of reasons, much more romantic andunsystematic about learning mental skills.

To a considerable extent, however, the area of agreement appearsto be greater than that of difference. A more important point is onethat cuts across the division between mental and physical skills. Thisis whether or not there is a simple and agreed-upon objective crite-rion of performance. If we are training a marathon runner or a om-petitor for the 1000-meter race, we can, by measuring his runningtime each day, have an excellent simple and objective criterion ofperformance and improvement in performance. In the case of com-petitive games, the criterion is more complicated but still in the endrather simple because of our ability to tabulate who won and wholost when real play starts. Thesame can be said for mental skills thatinvolve objective tasks like those of arithmetical computation. In thecase of physical skills like that of mountain limbing, or mental skillssuch as those of judging the qualities of complex objects, for ex-ample, paintings, horses, or beautiful people, there is absent agreed-upon, simple, and easily applicable criteria of performance. All thesame, the absence of such simplicity does not prohibit highly success-ful training and teaching; this general observation applies whether weare talking about physical skills like mountain climbing or mentalskills like judging works of art of a given category.

I emphasize also my optimism about developing a proper psychol-ogy of such skills, in particular, a proper educational psychology forteaching such skills. The important reservation to this optimism isthat the teaching will not be verbally explicit; it will not be algorith-mic in the sense of providing the student an algorithm for reachingthe intended result. Rather, it will depend upon the kinds of compli-cated indirect and subtle methods already familiar in the training ofmany different physical and mental skills. The long tradition of ap-prenticeship in training craftsmen is one of the inest examples. Thistradition, it should benoted, has flourished in modern scientificlaboratories.

It is my own view that, because of the overly rationalistic and lin-guistically oriented approach to intuitive judgment in the past, wehave not developed in anyadequate way the kinds of effectiveteaching regimes that are possible. The first step isto understand thenature of intuitive judgment hat it is a skill more like running


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101there is n o t even a theoretical exact value to be measured and thusthere is n o h op e even theoretically of refining th e approximations toan ex act value, which was one of t h e mistaken concepts of classicalphysics.Th e utility or loss fun ctio ns of t h e statisticians, which are

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Patrick Suppes. The limits of rationality.pdf