Grades of Explanation in Cognitive Science

RICHARD MONTGOMERY

GRADES OF EXPLANATION IN COGNITIVE SCIENCE

ABSTRACT. I sketch an explanatory framework that fits a variety of contemporary re-search programs in cognitive science. I then investigate the scope and the implications ofthis framework. The framework emphasizes (a) the explanatory role played by the semanticcontent of cognitive representations, and (b) the important “mechanistic”, non-intentionaldimension of cognitive explanations. I show how both of these features are present simul-taneously in certain varieties of cognitive explanation. I also consider the explanatory roleplayed bygroundedrepresentational content, that is, content evaluated by appeal to itstruth, falsity, accuracy, inaccuracy and other relational properties.

1. INTRODUCTION

What follows is an account of the structure of certain explanatory modelsin the cognitive sciences. At a minimum, I will show, this account describesthe explanatory structure of both connectionist models and more traditionalcomputational models, though it is clear that at least some aspects of theaccount apply much more broadly. The explanatory framework sketchedhere serves to highlight several key aspects of cognitive explanation, someof them neglected in other discussions. One broad philosophical goal itserves is to make ample room for cognitive explanations that are genuinelycontent sensitive, that is, cognitive explanations within which represen-tational or semantic contents play integral explanatory roles. I offer thisaccount as an antidote to the fairly prevalent syndrome ofcontent neglectthat characterizes many recent attempts to describe the nature of psycho-logical explanation. I define this syndrome asthe failure to adequatelyappreciate or to thoroughly investigate all the varieties of content-sensitiveexplanation that there are.Even philosophers of mind who have been atpains to accommodate the explanatory role of content (e.g. Burge 1986)have not yet fully recognized or investigated all the ways in which contentis implicated in explanatory practices either within cognitive science or inneighboring sociological disciplines.

I should emphasize at the outset that my aim in this paper is primarily todescribecertain explanatory practices in the cognitive sciences rather thanto legislatethem. I simply hope to show how it is that certain prevailing

Synthese114: 463–495, 1998.© 1998Kluwer Academic Publishers. Printed in the Netherlands.

464 RICHARD MONTGOMERY

explanatory practices manage to help us understand mind and cognition.I am tempted to think that, within a broadly physicalist world-view, therecanbeno other successful varieties of cognitive explanation, at least nonethat give representational content a genuine explanatory role, but I will notattempt to argue that here.

2. THREE GRADES OF EXPLANATION

In this section I use a well-known connectionist simulation as the vehiclefor introducing an account of how multiple varieties of cognitive expla-nation are sometimes integrated into a closely-knit series of explanatorygrades. I then consider how widely this model of graded explanationsapplies within psychology and cognitive science. I conclude this sectionby comparing the graded-explanations model of cognitive theorizing withDavid Marr’s widely known proposal to divide cognitive theorizing intocomputational, algorithmic and implementational levels.

2.1. Grades of Explanation in Connectionist Modeling

As folk wisdom would have it, we are often capable of learning from ourmistakes. Cognitive scientists have sometimes incorporated this folk wis-dom into elegant models of error-driven learning. One striking demonstra-tion of a learning process that permits inaccuracy to breed accuracy in thisfashion is provided by the connectionist simulation NETtalk designed bySejnowski and Rosenberg (1988) that learns to pronounce written Englishwords. In a typical version, NETtalk consists of three layers of neuron-likeprocessing units: an input layer, a hidden layer and an output layer. Patternsof activation across processing units at the input layer serve as alphabeticrepresentations of English letters, while patterns of activation at the out-put layer represent phonemes (characterized in terms of their articulatoryfeatures). Patterns of activation at any one layer produce patterns of acti-vation at successive layers by virtue of the existence of feedforward linksconnecting each unit at the lower layer with each unit at the next higherlayer. Each link between a pair of units at adjacent layers carries aweightthat determines the extent to which activation of the unit at the lower layerproduces activation of the unit at the adjacent layer. Initially, all weights areassigned randomly and, as a consequence, NETtalk babbles. However, thesimulation also incorporates a routine calledback propagationfor (i) com-paring the incorrect phonemic representations of English words with thecorrect pronunciations, and (ii) making incremental adjustments in weightsthroughout the network so as to gradually decrease the degree of error

GRADES OF EXPLANATION IN COGNITIVE SCIENCE 465

on subsequent trials. This process ultimately yields a striking percentageof correct pronunciations. NETtalk’s ability to produce correct phonemicrepresentations is explained jointly by its proclivity to make errors and bythe ability of theback propagationlearning algorithm to use informationabout the direction of the errors in order to incrementally correct futureperformance. In this fashion, initialinaccuracyplays a crucial role in pro-ducing and explainingaccuracyin the limit. In this respect, NETtalk learnsfrom its mistakes.

A fairly straightforward dissection of the NETtalk model shows it tocontain three distinct but interwoven varieties of the dynamic dependency,corresponding to three explanatory strands or styles of explanation. Thestyles are clearly related, but each has its own distinct explananda andexplanatia. Peel off all the features that make this model cognitive, the talkof representations, their representational content, and their accuracy or in-accuracy, and what remains is a model of neural or quasi-neural processesthat is both non-intentional and, broadly speaking, mechanistic.1 I willsay that such a model, characterized in terms of its mechanistic, non-intentional features providesgrade1 explanations.Within NETtalk we canisolate the following examples of grade1 explanation: (1a) patterns of acti-vation at the output layer in a trained network2 are explained by appeal topatterns of activation at the input layer and the weights attached to connect-ing links throughout the network, and (1b) weight changes after successivetrials (and similarly, changes in the relationship between input-layer acti-vation patterns and the output-layer activation patterns) are explained byappeal to back propagation.

In addition to its grade1 explanations, NETtalk also harbors two dis-tinctly cognitivetypes of explanation in which representations and repre-sentational contents play a role. What I will refer to asgrade2 explana-tionsare explanations that result from specifying, as integral componentsof explanans and explanandum, therepresentational contentsof certaingrade1 states and events, while, at the same time, systematicallyexclud-ing all assessments of the truth, falsity, accuracy or inaccuracy of thoserepresentations.3 In NETtalk we can isolate the following examples ofgrade2 explanations: (2a) The fact thatphoneme P is representedat the out-put layer is explained by citing the fact that activity at the inputrepresents acertain sequence of lettersL1, . . . ,Ln, and the fact that the weight settingsthroughout the network (implicitly) represent a certain set of linguisticrules R1, . . .Rm, which map letters to sounds. (2b) The fact that input-output mappings fromrepresented letters to represented phonemeschangeover time is explained by citing previous mappings between representedletters represented phonemes and the operation of back propagation. If


we don’t put too fine a point on it (cf. Cummins 1983) we can say thatgrade2 explanations areintentionalin character, and I will sometimes referto them asintentional explanationsor intentional-grade explanations.

Intentional-grade explanations aren’t the whole story where NETtalkis concerned, however. They aren’t even the main focus of research ef-forts such as that of Rosenberg and Sejnowski. Still speaking loosely,we might say that the focus of such research efforts isepistemological:It is, in this case, to show how a connectionist network can learn toac-curately represent appropriate English pronunciations, and to investigatethe independent variables that systematically affect this ability. To com-plete the story, to accommodate what I will callgrade3 explanations, wemust readmit, as integral components of explanans and explanandum, theassessments of truth, falsity, accuracy and inaccuracy that we earlier ex-cluded from NETtalk. Once we do so, we make available the followingexplanations: (3a) The fact that, in the trained network, output activitymanages to provideaccuratephonemic representations is explained byciting the fact that input activityaccuratelyrepresents certain letters of thealphabet, and the fact that weight settings (implicitly) representaccuratelinguistic rules for relating letters and sounds. (3b) The fact that, dur-ing training, output activity encodes increasinglymore accuratephonemicrepresentations is explained by appeal to the earlierinaccuraciesand theoperation of the back propagation algorithm. I will say that the assessmentsof truth, falsity, accuracy and inaccuracy that play a role in explanationsat grade3 serve toground the cognitive contents they describe. I will saythat explanations in which such assessments play an explanatory role aregrounded-content explanations.I will assume that, when a content is as-sessed as true, false, accurate or inaccurate it is effectively related to someother complex structure or states of affairs, and I will, as a general matter,say thatgroundingconsists in specifying such a relationship.4 It turns outthat grounded-content explanations are a rather large and motley collec-tion. I will survey some of the other varieties of explanatory groundingrelations in a subsequent section.

In the examples described here, there is aninclusiverelationship be-tween grade1, grade2 and grade3 explanations. Grade1 explanations arecontained withingrade2 explanations orexplicitly presupposedby them,and grade1 and grade2 explanations arecontained within, or explicitlypresupposedby grade3 explanations.5 Thus NETtalk is layered like anonion, and, at least in the examples described here, the onion is made out ofexplanations all the way down.6 The intentional (grade2) explanations thatpartly constitute the grounded-content (grade3) explanations in these casesare revealed by peeling away the layer that contains assessments of repre-


sentational accuracy and inaccuracy. The neural (grade1) explanations atthe heart of this onion are exposed by successively peeling away first theassessments of truth-value or degree of accuracy and then the ascriptionsof representational content.

2.2. The Scope of the Tri-grade Model

Let us now consider the extent to which the tri-grade model of cogni-tive explanation that has been sketched above is found within cognitivescience. It is, of course, already clear that manyconnectionistaccountsof learning fit the tri-grade model. It is also clear that many accounts ofcognition of the sort that John Haugeland (1986) has called Good Old-Fashioned Artificial Intelligence (GOFAI) fit the model. Let us consider,as a classic in the GOFAI genre, Terry Winograd’s (1972) well-knownwork on language understanding. Winograd’s model of language under-standing is embodied in SHRDLU, a computer program whose formalrepresentations, and whose processing operations over those formal rep-resentations, constitute dynamic processes at grade1. The formal symbolsutilized by SHRDLU represent such things as English language syntax andsemantics, the program’s BLOCKS world environment, and SHRDLU’svarious plans for interacting with that environment – though, at grade1,these facts about SHRDLU’s representational contents have not yet en-tered the picture. In addition to grade1 explanations, however, Winograd’smodel includes grade2 (intentional) and grade3 (grounded-content) expla-nations within which both representational contents and assessments oftruth-value, respectively, do become integral components of the explanansand explanandum. The inclusion of both grade2 and grade3 explanationsis apparent in Winograd’s accounts of howaccurateinformation about thecognizer’s linguistic and non-linguistic environment plays a role in permit-ting hearers to constructaccuraterepresentations of a speaker’s linguisticmeaning. The following example typifies Winograd’s concerns along theselines:

If we say “The city councilmen refused the demonstrators a permit because they feared vio-lence”, the pronoun “they” will have a different [correct] interpretation than if we said “Thecity councilmen refused the demonstrators a permit because they advocated revolution”.We understand this because of our sophisticated knowledge of councilmen, demonstrators,and politics – no set of syntactic or semantic rules could [correctly] interpret this pronounreference without using knowledge of the world. (Winograd 1972, 33)

Grounded content appears in Winograd’s account, in part, in his use ofsuch verbs of success(Ryle 1949) as “to understand” and “to know”,each of which implies that its object provides an accurate portrayal of theworld. In Winograd’s example, anaccuraterepresentation of the referent


of the pronoun “they” clearly depends upon, and is explained by,accuratereal world information about the subjects under discussion – city councilmembers, demonstrators, and so on – as well as byaccuratesyntactic andsemantic information. In a similar fashion, accurate information about theBLOCKS world environment supplements accurate syntactic and semanticinformation in a way that enables SHRDLU to provide accurate semanticinterpretations. Moreover, it is clear that genuine intentional-grade expla-nations underly these grounded-content explanations. When such featuresof Winograd’s model are added to the grade1 formal processes that themodel also contains, his theory of language understanding spans grade1,grade2 and grade3 explanations.

The tri-grade framework found in Winograd’s model is actually quitewidespread in GOFAI. Consider, for instance, that the rationale for con-structing an expert system is to createsymbol manipulating softwarethatcanreliably solve the kinds of problems that call for special expertise. Notethat the method of achieving that goal is to incorporate into the expert sys-tem a human expert’s generalknowledgein such a way that accurate inputdata can make possiblecorrect solutionsto such problems. All three gradesof explanation are implicit in this description, from grade1 formal explana-tions to intentional-grade and grounded-content explanations. It is unfor-tunate that the inherent interest of formal symbol manipulation in GOFAIhas sometimes blinded philosophers of mind (e.g. Jerry Fodor 1980) tothe fact that GOFAI models often traffic in formal operations, intentionalexplanations and grounded-content explanations simultaneously.

2.3. Extending the Scope of the Tri-Grade Model

The fact that research programs in cognitive science as apparently diver-gent as connectionism and GOFAI both fit the tri-grade model should beenough to convince us that the tri-grade model bears investigating. How-ever, it is also worth considering whether and how this model’s reach mightbe extended. Significantly, there are other research programs in cognitivescience that contain both intentional-grade and grounded-content explana-tions but that donot contain any explicit grade1 explanatory component.Such research programs may show us one way in which the tri-gradeexplanatory model that I have sketched here is less than universal. Con-sider, for instance, the research of Tversky and Kahneman (e.g. 1974) andsubsequent research influenced by it. Tversky and Kahneman and theircolleagues have sought to explain how cognizers arrive at systematicallyinaccurateconclusions about cause-and-effect relationships, probabilitiesand relative frequencies, and so on, and have attempted to do so by ap-pealing to (a) cognizers’accurateinitial data, and (b) their subsequent use


of faulty inferential heuristics. Grounded-content explanations are clearlypresent in this work, and these grounded-content explanations clearly con-tain intentional-grade explanatory components. No explicit grade1 expla-nations are present here, however.

Even so, there are at least three ways in which the full tri-grade explana-tory framework might at least be implicit in this work. First, explanationssuch as those offered by Tversky and Kahneman might effectivelyreduceto connectionist accounts, or to GOFAI models, or to other cognitive mod-els that, like these, do contain an explicit grade1 component. It is true, ofcourse, that such reductions would be somewhat different than the reduc-tions often contemplated in the philosophical literature: Both the reducedand the reducing theories would contain grounded contents, while, by con-trast, the varieties of reduction more commonly scouted by philosophers ofmind exclude grounded contents from both the reduced and the reducingtheory, and even have the unfortunate tendency to exclude all contentswhatsoever from the reducing theory. However, even though the reductionof one full-fledged cognitive theory to another, grounded-contents and all,is a somewhat different prospect than that often considered by philoso-phers, it is also susceptible to an alleged problem that has plagued moretraditional reductionist proposals in the philosophy of mind: the problemof themultiple realizabilityof the bearers of representational content andgrounded content by non-content bearing states and events at grade1. Forthis reason, I offer two additional proposals designed to accommodatemultiple realizability.

One such strategy for accommodating grade1 explanations within re-search programs such as that of Tversky and Kahneman is to supposethat the explanations provided within these research programs are bestconstrued asexplanation sketcheswhose grade1 components have simplynot been explicitly provided. Multiple realizability is allowed for by thisproposal because the incomplete explanation sketch can be completed byany number ofdifferentgrade1 processes that support the same groundedcontent on different occasions. In other words, the explanation sketch needhave noonecorrect completion.

If we assume that the missing grade1 component of the explanation-sketch is an explicitly neurophysiological component, the explanation-sketch proposal does not seem far-fetched. After all, given token physi-calism (Fodor 1974), explanations such as those offered by Tversky andKahneman already makeimplicit reference to neural events; they simplyfail to specify the neural properties under which these events are causallyefficacious. Moreover, for the purposes of cognitive psychology, we willsometimes prefer to leave such explanation sketches incomplete if no type-


type correspondences can be found between representational contents andunderlying non-intentional grade1 properties, since, by doing so, we willcapture important generalizations that would be missed if the grade1 com-ponent were always included (cf. Fodor 1974). Of course such explanationsketches sacrificecomplete explanationfor perspicuous generalization,but nature provides no guarantees that complete explanation and perspicu-ous generalization are always one-and-the-same.7

A third proposal also extends the tri-grade framework to research pro-grams such as that of Tversky and Kahneman. According to this proposal,cognitive explanations can sometimes include reference to grade1 causalprocesses as what can be calledexplanatory presuppositions, while onlyactually serving to explain why the terminal events in those presupposedsequences have the content and/or the content-grounding that they do.Suppose, for instance, one seeks to explain the representational accuracyof the neural outputs of perception, rather than the occurrence of neuraloutputs that are accurate perceptual representations. In this case one pre-supposesand does not seek to explain the occurrence ofany grade1 events.Instead, one merely seeks to explain why such events have representationalcontents that are accurate. On this presuppositional approach, it is not es-sential that a complete explanation actually provide a full description of thegrade1 process that terminates in the perceptual output in question, sincedoing so does not help satisfy the request for explanation but only morefully describes the explanatory presupposition. Like the explanation-sketchproposal, the presuppositional proposal provides for multiple realizability:The grade1 process that is presupposed but not explicitly described may bea different grade1 process on different occasions. And once again, one mayprefer to simply presuppose some grade1 process without incorporating itas an explicit component of one’s explanation because, by presupposing itin this way, one makes it possible to capture certain generalizations thatwould otherwise be missed.

I will not argue here for either the reductionist proposal, the explanation-sketch proposal or the presuppositional proposal beyond suggesting that,because they incorporate grade1 explanations, they share a common virtue:They extend the scope of one plausible solution to “the problem of mentalcausation” (see, e.g., Heil and Mele, eds., 1993) that the tri-grade accountof cognitive explanation makes attractive. The problem of mental causationhas recently dogged attempts to provide a robust account of psychologicalexplanation at the intentional grade that is fully compatible with physi-calism and, in the following section, I will show how the tri-grade modelavoids it.


Before I take up other issues, I would like to add one caveat aboutthe explanation-sketch and presuppositional proposals. It has been noted(e.g. by P. S. Churchland 1986) that successful intertheoretic reductionsgenerally do not leave the reduced theory intact but lead to at least somemodifications of it. Something similar may be true where the explanation-sketch and the presuppositional proposals are concerned: These proposalsmay not fit the relevant cognitive explanations without requiring revisionin the structure of those explanations. Like reductionist proposals, the ex-planation sketch and presuppositional proposals should not be accepted orrejected based on an assessment of whether they are adequateanalysesof the current structure of the cognitive explanations in question, but onlybased on whether they are adequatereconstructionsof those explanations.8

2.4. Reconstructing Marr’s Explanatory Levels

The tri-grade explanatory account developed here, along with the propos-als just sketched for broadening the scope of that account, can be used tohelp reconstruct David Marr’s (1982) widely known proposal concerningthe explanatory levels appropriate in cognitive science. Marr proposes thatresearch in cognitive science must proceed at three levels: computational,algorithmic and implementational. While these three levels do not map1 : 1 onto the three explanatory grades I have described above, I believe thatMarr’s account and the tri-grade account are consistent with each other,and that the tri-grade account can be used to illuminate certain featuresof Marr’s account. I will begin by sketching a way of mapping Marr’sproposedlevelsonto my explanatorygrades.

First, Marr’s computationallevel is plausibly viewed as constitutedby certain grounded-content explanations within which intentional-gradeexplanations are nested. In Marr’s account, the grounded-content explana-tions supplied at the computational level describe, in appropriately generalterms, the information processing operations that the cognitive system inquestion is designed to perform, and the aspects of the environment thatpermit it to perform in that way. Consider, for instance, how Marr describesthe nature of computational level theorizing where vision is concerned:

In the theory of visual processes, the underlying task is toreliably derive properties of theworld from images of it; the business of isolating constraints that are both powerful enoughto allow a process to be defined and generally true of the world is a central theme of ourinquiry. (Marr 1982, 23, italics added)

Burge (1986) has noted Marr’s grounded-content explanandum, but it isworth stressing that Marr’s explanans also seems to appeal to groundedcontent: the occurrence of reliably accurate perceptual outputs is explained,within Marr’s account by appeal to the occurrence of reliably accurate


representations at each of the earlier information processing stages. In-deed, Marr’s discussion of the computational level seems to imply that,whether computational level theorizing concerns the operations of the vi-sual nervous system or the operations of a cash register, the processes heis concerned with at the computational level are those which proceed fromaccurate representations to accurate representations.

Second, Marr’salgorithmic level, is plausibly viewed as consisting ofa set of formal, algorithmic processes defined over a set of formally (i.e.non-semantically) specified representational structures, and thus as occu-pying grade1 within the present scheme. For, as Marr makes clear, thealgorithmic level is the level at whichrepresentationsenter the picture (e.g.Marr 1982, 23), and, as he also indicates, representations are canonicallydescribed as formal symbol systems (pp. 20–21).

Finally, on the present construal of Marr’s views, hisimplementationallevel provides the physical underpinnings (possibly via intertheoretic re-duction) for the formal structures and formally specified processes of thealgorithmic level. It should be noted that, while the implementational levelis not provided for within the tri-grade model, its existence is clearly con-sistent with that model.

What does the tri-grade model that I have sketched hereadd to Marr’saccount? A number of things, I think. First, from the perspective of thetri-grade model, it seems apparent that, when Marr segregates the compu-tational level from the algorithmic level, he is simply singling out for sepa-rate attention certain important ingredients that, in nature, combine to forma single, integral explanatory whole consisting of grade3 grounded-contentexplanations within which grade1 and grade2 explanations are simulta-neously nested. Indeed, when we consider how Marr’s grounded-contentexplanations integrate with the rest of his account, we see that they mustfit either theexplanation-sketchproposal or thepresuppositionalproposaldiscussed above. Only these proposals will serve to account for the factthat Marr intends the grounded contents, described at the computationallevel, to fit and cohere with the formal representational structures at thealgorithmic level, and to do soby virtue of the fact that grounded-contentsat the computational level attach to explicit formal representational struc-tures at the algorithmic level.The tri-grade model described here supple-ments Marr’s account by characterizing the integrated whole into whichhis explanatory “levels” fit, and, specifically, by describing its compo-nent structure ofnestedexplanatory grades.9 In general, I would suggest,Marr’s theorizing shows, by example, that it can be advantageous to ab-stract certain grounded-content explanations from the integrated whole,while my proposal describes the whole and shows how Marr’s explanations


are to be integrated into that whole. Marr’s account does not help us fullyappreciate this nested whole, however, and, as we shall see, in the nextsection, nesting marks an important departure from certain accounts ofthe relationship between intentional and non-intentional explanations inpsychology.

As a final point of comparison, it might be noted that, while Marr fo-cuses on those grounded-content processes for which the cognitive systemsin question aredesigned, and in accord with which representational accu-racy begets additional representational accuracy, we have already begunto see that grounded-content explanations are a more diverse lot, and wewill see even more of their diversity below. Marr’s account of cognitiveexplanation hardly begins to capture the diversity that exists in this regard.

I need to add a caveat at this point. My proposal for mapping Marr’saccount onto my own assumes a certain construal of the nature of Marr’saccount, specifically, the construal endorsed by Kitcher (1988) whose dis-cussion of Marr’s explanatory level has served as my guide in the preced-ing paragraphs. While I think that construal makes good sense of Marr’sgeneral description of the three explanatory levels, I am less certain that itmakes good sense of his actual explanatory practice. Both when it comes todescribing the nature of the representational primitives at the algorithmiclevel in the visual system, and also when it comes to describing the relevantalgorithms, Marr (1982) seems to appeal to semantic content and (espe-cially when characterizing algorithms) to grounded content, rather than toany substantive non-semantic properties. This suggests that we can con-strue not only the computational level, but the algorithmic level as well, ascontaining grounded-content explanations within which intentional gradeexplanations are embedded. It also suggests that, for Marr, the implemen-tal level is the only real home of substantive non-semantic descriptions,and thus the only place at which Marr’s account adverts to grade1 expla-nations. On this construal, the computational level serves to isolate andidentify certain broad generalizations that characterize grounded-contentexplanations, generalizations that would be hidden if the same processeswere described only at the algorithmic level.

3. CONTENT-SENSITIVE CAUSAL EXPLANATION

This section serves two related goals. My primary goal is to show how thegrades-of-explanation framework provides for genuinelycontent-sensitiveexplanations at grade2 and grade3, that is, explanations in which contentactually has explanatory power. A related, secondary goal is to compare thegrades-of-explanation framework with a certain conception of explanatory


levelsthat has been common in philosophy. In this section I will restrictthe discussion to those tri-grade explanatory models whose grade1 expla-nations are explicitly neurophysiological. I invite the interested reader toconsider the extension of these remarks to other tri-grade models.

3.1. Grades of Explanation vs. Levels of Explanation

Suppose, then, that grade1 explanations are explicitly neurophysiological,as they purport to be in the case of NETtalk. It follows that grade2 andgrade3 explanations, which contain grade1 explanations as components,harbor both psychological content-properties and non-intentional neuro-physiological properties. Until fairly recently, philosophers seem not tohave realized that such properties might appear together in either the ex-planantia or the explananda of any single explanatory theory, and manystill seem not to appreciate this fact.10 Instead, these two kinds of prop-erties have often been relegated to two different explanatorylevels.Theexplanatory significance of the multigrade strategy for relating representa-tional contents to neurophysiological facts can be seen by comparing it tothe levels-strategy for accomplishing the same result.

Theparadigm exampleof the levelsstrategy is provided by the thesisthat intertheoretic reductiondescribes the relationship between an inten-tional psychology and a non-intentional neurophysiology.11 Within thisframework, thereducingneurophysiological theory occupies alower ex-planatory level and thereducedpsychological theory occupies thehigherexplanatory level. A non-reductionist example of the levels strategy is pro-vided by certain philosophical critics of that reductionist thesis. While re-jecting reductionism, these anti-reductionists (e.g. Fodor 1974) have con-tinued to require, as had reductionists, that the explanatory generaliza-tions of neurophysiology-in-the-limit serve, in some non-causal sense, toexplain, or account for the truth of, the explanatory generalizations ofpsychology-in-the-limit. This requirement is to be met by virtue of the factthat the psychological events over which the higher level psychologicaltheory quantifies are mereological sums of events over which the lowerlevel theory neurophysiological theory quantifies. Given this relationshipbetween psychological and neurophysiological events, it follows that eachinstanceof a true higher-level psychological generalization is constitutedfrom an instanceof a true lower-level neurophysiological generalization,specifically, the lower-level generalization instantiated when higher-levelevent-tokens are replaced by their lower-level constituents. Of course, ifreduction fails, these will not always be the same lower-level constituents,and thus the underlying lower-level generalization will not be the same ineach case either.


The two key assumptions that anti-reductionists such as Fodor havecontinued to share with reductionists will serve to define the levels ap-proach: (1) the assumption that psychology and neuroscience will both, inthe limit, formulate true theories with essentially non-overlapping theoret-ical vocabularies, and (2) the assumption that each instance of a correcthigher-level psychological explanatory generalization is true by virtue ofthe fact it is an instance of some lower level neurophysiological gener-alization, where the event tokens or state tokens over which the higherlevel theory quantifies are mereological sums of the event or state tokensover which the lower level theory quantifies.In light of Assumption (2),as suggested above, it might be said that higher level generalizations areexplained by appeal to lower level generalizations.12

It is clear that the relationship between lower and higher grades of ex-planation fails to satisfyeitherof these conditions. First, higher grade andlower grade explanations clearly do not belong to separate explanatorytheories with largely non-overlapping vocabularies. Second, lower gradeexplanations cannot, in general, serve to explain the truth of higher gradegeneralizations or in any way instantiate those higher grade explanations,for lower grade explanations often fitwithin higher grade generalizationsas a proper part and, I take it, nothing helps to explain itself

3.2. Mental Causation

I will now use the contrast between the grades-of-explanation frameworkand the levels-of-explanation framework to draw attention to the nature ofthe explanatory role exhibited by content-properties at grade2 and grade3within the former framework.

Within the grades framework, there is a clear division of explanatorylabor among the different explanatory grades. Ironically, the division ofthe labor is much clearer than the division of labor among different ex-planatory levels within the levels framework. At grade1, prior neural events(and neurophysiological standing conditions) serve to explain the occur-rence of subsequent neural events. At grade2,complexesconsisting ofneural-events-with-representational-contents play a role in explaining theoccurrence of other such complexes. And finally, at grade3, neural-events-with-grounded-contents play a role in explaining other neural-events-with-grounded-contents. Thus, although grade1, grade2 and grade3 events arenested within each other, there are distinct explanantia and explananda ateach grade. Moreover, within the three-grades framework, neural proper-ties, content-properties, and grounded-content-properties all play uniquesupporting roles in the resulting explanations: Prior neural properties havea unique explanatory link to subsequent neural properties, as do prior


content-properties to subsequent content properties and prior grounded-content properties to subsequent grounded-content properties.

By contrast, within the multi-level account endorsed by Fodor and oth-ers, the following conditions obtain: (i) psychological events at a higherlevel are explained by appeal to the psychological properties of antecedentpsychological events (including their content properties), while (ii)thevery same events(or the sums of their merelogical constituents) are alsoexplained at the neurophysiological level by appeal to the neurophysiolog-ical properties of prior neurophysiological events. Moreover, it is typicallyassumed that (iii) psychological properties have the causal/explanatorypotential they do solely by virtue of the causal/explanatory potential pos-sessed by the underlying neurophysiological properties. These coincidingexplanatory roles are just what would be expected if intertheoretic reduc-tion obtained. But intertheoretic reduction is typically not assumed (andclearly content-properties cannot reduce to non-intentional neural prop-erties). Under these conditions, thecoincidence, or near coincidence, ofexplanatory roles at the two levels fuels the quite legitimate and quitewidespread concern in the philosophy of mind that content-properties andnonintentional neurophysiological properties are actually in a direct ex-planatorycompetitionwith each other rather than being closely allied.If these properties actuallyare in competition, it has often seemed that,inevitably, neurophysiological properties must win.13 The clear divisionof explanatory roles that is available within the multi-grade frameworkprovides one way to circumvent worries that content-properties may haveno explanatory role to play.

But are the explanations within which representational contents playan explanatory rolecausalexplanations? Let me answer cautiously as fol-lows: At grade2 and grade3, the explanations that appeal to content-properties are at leastquasi-causalbecause they incorporate grade1 causalexplanations. However, one might think that the integral role played bycontents at grade2, and grounded-contents at grade3, somehow preventsthose explanations from being wholly causal.14 It should be noted, though,that the dynamic relationships that constitute grade2 and grade3 explana-tions do exhibit some importanthallmarksof (wholly) causal explanation:(1) They involve asymmetrical dependence relationships among distinctevents that are separated in time. (For instance, in the case of NETtalk, (a)any of a number of different initialerror patterns will all eventually con-verge on theright pronunciations and, (b) while back propagation system-atically permitsaccuracyto emerge frominaccuracy, it doesn’t systemat-ically permit inaccuracyto emerge fromaccuracy.) (2) These asymmetricdependence relationships do not result from the presence of a third, inde-


pendent factor on which the events in question also individually depend(i.e., there is no analog of a “common cause”). (3) Some grounded-contentexplanations areprobabilistic (as when thetruth of a cognizer’s induc-tive conclusion is explained by thetruth of the cognizer’s premises). (4)Some grounded-content explanations also serve to explain the occurrenceof low probability events(as when a false conclusion, drawn on the basisof overwhelming inductive evidence, is attributed to “inductive error”). (5)Furthermore, a distinction can be drawn betweenprocessesandpseudo-processeswhere both intentional-grade and grounded-content explanationsare concerned.15 (In particular, certain sequences of cognitive events con-stitute pseudo-processesprecisely because they contain sequences of rep-resentational contents – or sequences of grounded-contents – that are notrelated in a way that makes for higher grade explanations, even though theunderlying neurophysiological events constitute genuine causal processes.Such cases are discussed in Section 4.)

I should stress that these hallmarks of causality are not just a reflectionof underlying grade1 causal connections. Instead, they are ajoint productof grade1 causal relationships, relationships of dependency among grade2contents and relationships of dependency among grade3 grounded con-tents. I will not suppose the considerations summarized in (1)–(5)entailthat grade2 and grade3 content-sensitive explanations are wholely causal.But, for the time being, I suggest, a causal account seems at least plausibleon these grounds. That may change as we examine additional featuresof such explanations. At the end of the paper I will briefly return to thequestion of whether content-sensitive explanations are causal explanationsor non-causal explanations.

4. THE INDEPENDENCE OF GROUNDED-CONTENT EXPLANATIONS

Having attempted to show how explanations within the multi-grade frame-work can be genuinely content-sensitive, I would now like to explore thefeatures of this explanatory framework, focusing in this section on therelationship between the two content-sensitive explanatory grades I havedescribed, intentional-grade explanations and grounded-content explana-tions. As closely intertwined as they are, I will show that these two gradesof explanation retain an interesting kind of independence: First,one cannottake an intentional explanation, add a characterization of truth valuesor degrees of representational accuracy for the pertinent contents, andthereby be assured of having produced a grounded-content explanationSecond,one cannot take a grounded-content explanation, subtract talk oftruth-values or degrees of accuracy, and thereby be assured of having an


intentional explanation.I will use an example from folk psychology toprovide support for this first thesis. I will cite NETtalk as an example ofthe second thesis.

4.1. Intentional Explanations Without Grounded-Content Explanations

Let us begin by considering the following case, framed in the language offolk psychology: Suppose the question under discussion by two individu-als, Juan and Evita, is the question, “Did Adolph Hitler have any friends?”Juan decides, wrongly, that Joseph Stalin and Hitler were friends and, onthat basis, concludes, accurately as it happens, that Hitler had at least onefriend. Evita notes, correctly I will suppose, that Eva Braun was Hitler’sfriend even if no one else was, and, on that basis concludes that Hitler hadat least one friend.

Now let us consider what can be explained where the beliefs of Juanand Evita are concerned, and what cannot be explained. In both cases, ofcourse,intentional gradeexplanations can be provided for the conclusionsthat are drawn. These explanations cite the premises believed by Juan andEvita, and their use of existential generalization. But it appears that, whilethe result of adding truth values to the cognitive contents (and inferencerules) involved in Evita’s inference is a grounded-contentexplanation, nosuch explanation can be produced in Juan’s case.

In order to see how this is so, it will be useful to begin with a clearcharacterization of theexplanandain these cases. Both Juan and Evita, as ithappens, arrive at the same correct belief that Hitler had at least one friend,a correct belief for which we can request a grounded-content explanation.Such a request, I suggest, is equivalent to asking the following question:

Why did X conclude, correctly, that Adolph Hitler had at leastone friendrather than drawing a different, incorrect conclusion(perhaps the incorrect conclusion that Hitler had no friends)?

(Q1)

The truth of the proposition that Hitler had at least one friend is pre-supposed, or held fixed, in this case; it does not vary between the tar-get of the explanation and the contrast class. Thus, when requesting agrounded-content explanation in this case we are not asking the followingquestion:

Why did X conclude, correctly, that Adolph Hitler had at leastone friendrather than concluding, incorrectly, that Hitler hadat least one friend?

(Q2)

Question (Q2) would not be a request for a grounded-content explanationthat cited the grounded causal antecedents of the cognizer’s conclusion.


Instead, it would call for an explanation of how it was that Hitler managedto have any friends at all (rather than being friendless).

If we want an answer to (Q1), then we get it where Evita’s inference isconcerned:

Evita reasoned by valid deductive inference (using inferencerule EG) from the true premise that Eva Braun was AdolphHitler’s friend.

(A1E)

By citing belief in a true premise and the use of a deductively valid infer-ence rule, we provide an explanation for the truth of Evita’s conclusion,given the contrast class described in (Q1). But now consider what happenswhen, by adding information about truth values to the relevant intentional-grade explanation, we attempt to provide a grounded-content explanationfor Juan’s true belief that Adolph Hitler had at least one friend.

Juan reasoned by valid deductive inference (using inferencerule EG) from the false premise that Joseph Stalin and AdolphHitler were friends.

(A1J)

As an explanation, this is a complete non-starter. You might say that, whilethe addition of content-groundings in the case of Evita still left us with agenuineprocess, we have only a kind ofpseudo-processin this case. Whatis the difference between the two cases? Surely it is something like this:The general rules of inference in accord with which belief in a deductiveargument’s premises leads to belief in the argument’s conclusion are rulesaccording to which true premises yield a true conclusion. However, thosegeneral rules are not ones in virtue of which false premises yield true con-clusions – or even false conclusions. The rules are also not ones in virtue ofwhich false premises yield true conclusionswith some probability or other.If, by sheer good luck, we could actually determine the probability withwhich false premisesdo yield true conclusions in deductive arguments,that fact would be “accidental” and not lawlike, and would thus not helpus provide an explanation for the truth of the conclusion. Given the contrastclass supplied by (Q1), there simply is no explanation for the accuracy ofJuan’s conclusion. It issui generis.We would normally say that Juan wasright by accidentor by sheer luck.16

The example just cited makes clear that one cannot, as a general rule,add truth values to the contents of an intentional grade explanation and beguaranteed of having created a grounded-content explanation. In that re-spect, intentional grade explanations can occur independently of grounded-content explanations. However, this variety of independence doesn’t pre-clude the possibility that intentional explanations are dependent upon


grounded-content explanations in a different, more general way. A numberof philosophers, including Donald Davidson (e.g., 1970), Daniel Dennett(e.g., 1971), John Haugeland (e.g., 1981), and Christopher Cherniak (e.g.,1981) have held that no cognizer can reason, or even instantiate propo-sitional attitudes, unless s/he can at least sometimes reasonsuccessfully,i.e., from true premises to true conclusions using reliable rules of infer-ence. Let us call this commonly held thesis therationality constraint.Astraightforward corollary of the rationality constraint is the following the-sis about the relationship between intentional-grade and grounded-contentexplanations: No cognizer is capable of instantiating intentional-grade ex-planations which employ propositional attitudes unless s/he can at leastsometimes instantiate grounded-content explanations in which belief intrue premises, and the application of reliable rules of inference, serve toexplain the attainment of true conclusions.17 According to this corollary,the occurrence of intentional-grade explanations is still, in an important re-spect, dependent upon the occurrence of grounded-content explanations.18

4.2. Grounded-Content Explanations Without Intentional Explanations

The preceding example was used to argue for the conclusion that one can-not take an intentional explanation, add a characterization of truth values ordegrees of representational accuracy for the pertinent contents, and therebybe assured of having produced a grounded-content explanation. I will nowprovide some reason to believe that one cannot take grounded-content ex-planations, subtract talk of truth-values or degrees of accuracy, and therebybe assured of having produced an intentional explanation.

Consider NETtalk once again. On NETtalk’s first trial, letters of the al-phabet are represented at the input layer and a phonemic representation is,in consequence, activated at the output layer. This happens because activityat the input layer causes activity at the output layer in a way that is deter-mined by the activation levels at the input layer and the arbitrary weightsettings with which the program begins. But the attendant relationship be-tween represented letters and represented sounds is completely arbitrary;earlier representational contents and later representational contents are not,in this case, related in a way that establishes the semantic or inferentialrelevance of the former to the latter. Consequently, I suggest,one cannotsay that the actual content of the phonemic pattern that is represented atthe output layer is explained, even partly, in terms of the letters representedat the input layer. Onecanmake this claim after training has progressed tosome point, for, at some point, it seems to make sense to say that the mod-ified weights have encoded linguistic generalizations that characterize therelationships between letters and sounds.19 However, as long as we under-


stand the network to contain no such generalizations at the outset, but onlyarbitrary weight settings at grade1, we have no explanatory relationshipbetween the contents of input representations and the contents of outputrepresentations at the intentional level. The relationship is, to be sure, fullydetermined, thanks to the operation of causal mechanisms at grade1, butit is, nonetheless,arbitrary in a sense that seems to preclude explanatoryconnections between contents. We might, with some justification, say thatwhat we have here is a certain kind ofpseudo-process.Indeed, this caseprovides us with an isolated example of the kind of explanatory inert-ness of cognitive content whose prospect has fueled recent discussionsof mental causation. It is worth noting, though, that this inertness is notuniversal, as “epiphobes”20 have feared, but is created by a special set ofcircumstances.21

The explanatory inertness of intentional contents at grade2 in this casedoes not seem to preclude genuine grounded-content explanation at grade3.Add assessments of representational accuracy to the very contents that atgrade2 exhibitno explanatory engagement, and the result is a bonafidegrade3 explanation: Specifically, at grade3 we are able to explain why,before training, the output layer contains such wildlyinaccuratephonemicrepresentations of input words. The explanation is as follows: The grade1causal relationships between input and output layers yield a correlation be-tween the letters represented in the network’s input layer and the phonemicinformation represented within the output layer that,given the accuracy ofthe input representations, is simply inconsistent with what is required foraccurate representation of phonemic structure.

This grounded-content explanation results from grounding the very con-tents that, at grade2, exhibit in no explanatory relationship. The grounded-content explanation in this case requires only that there are certaincorrela-tionsin effect between representational contents at input and output layers.It does not require the existence of explanatory links between the semanticcontents at the input layer and the semantic contents at the output layer.Note, however, that we do provide a genuine grounded-content explanationin this case: Appeal to theaccuracyof input representations is essential inexplaining theinaccuracyof output representations. For suppose the inputrepresentations had been inaccurate representations of the input letters. Inthat case, further inaccurate correlations between alphabetic representa-tions and represented sounds could conceivably have served to compensatefor the errors in input representation in a way that would have yieldedaccurate phonetic representations. Sometimes two wrongsdomake a right.

The NETtalk example just cited serves to make a plausible case forthe following negative conclusion: While some grounded-content expla-


nations contain intentional grade explanations as nested components, onecannot, as a general rule, take a grounded-content explanation, subtractcontent-groundings, and be guaranteed that an intentional-grade explana-tion will be the result. This negative conclusion makes grounded-contentexplanations independent of intentional-grade explanations in an importantrespect. However, nothing said so far precludes the possibility that, in amore indirect way, the presence of grounded-content explanations still re-mains dependent upon the presence of intentional-grade explanations. Thefollowing considerations serve to make this point: Recall therationalityconstraintwhose consequences were briefly considered above. That con-straint says, in part, that an individual can possess propositional attitudesonly if that individual at least sometimes reasons from true premises totrue conclusions using reliable rules of inference. Now note that thosegrounded-content explanations in which true premises lead, via reliablerules of inference, to true conclusions, contain intentional-grade explana-tions as components. Indeed, the process of reaching a conclusion frompremises via a rule of inference provides aparadigm caseof intentional-grade explanation. It follows that, for any individual who possesses propo-sitional attitudes, there will be at least some grounded-content explanationswhich contain intentional-grade explanations as components.22 Accord-ingly, if the rationality constraint is correct, the existence of grounded-content explanations still depends in an important way on the existence ofintentional-grade explanations.

5. NATURAL KINDS AND GROUNDED-CONTENT EXPLANATIONS

In this section and the following one, I focus attention exclusively ongrounded-content explanations. Such explanations have received relativelylittle systematic attention from philosophers compared to the amount ofattention that intentional-grade explanations have received.23 But, if I amright, such explanations are actually quite widespread, and so an attempt tounderstand their workings should be of interest in its own right. Moreover,the existence of such explanations has important consequences for the na-ture of psychological explanation generally, as I am about to show by con-sidering the relationship between so-callednatural kindsand grounded-content explanations.

There are, no doubt, scientific domains within which the distinctionbetweennatural kinds, categories and properties, on the one hand, andunnatural(or artificial or anthropocentric, or merely heuristic) kinds, cat-egories, and properties, on the other hand, has great significance. Withinthose domains, one might suppose, both natural and unnatural kinds, etc.


are successfully instantiated, butonly the instantiations of genuine naturalkinds, categories and properties ever play an integral role in explanations.Psychology is arguably not one of those domains, however. In particular,it appears thatthe successful instantiation of any kind, category or prop-erty (“natural” or “unnatural”) is eligible to play an explanatory role ingrounded-content explanations.24 Let me begin by considering, as a foilfor my thesis, a dilemma that Jerry Fodor (1980) has posed for what helabelsnaturalistic psychology.

Fodor understandsnaturalistic psychologyto be a scientific researchprogram that, broadly speaking, concerns itself with organism-environmentrelationships. Fodor argues that any such psychology impales itself on thehorns of a dilemma when it attempts to characterize the environment in away that is suitable for scientific purposes: Either the environment must bedescribed in the way in which the individual cognizer thinks about it, or itmust be described in a way that is appropriate to the natural sciences, andboth proposals are unsatisfactory.25 If the environment is described in theterms in which human cognizers think about it, then it will be described ina way that doesn’t make for good science, because we often think aboutthe environment in ways that, even while accurate, don’t carve nature atits joints, that is, don’t provide us with natural kinds, natural categoriesor natural properties. The properties in terms of which we think aboutthe environment include such non-natural properties asbeing a pencilandbeing what Granny likes with her herring(Fodor’s examples) out of which,Fodor claims, no science that seeks lawlike explanatory principles can befashioned. But now suppose that we attempt to grasp the other horn ofFodor’s dilemma. Suppose we opt to describe the environment in a waythat appeals only to natural kinds and categories. Under those circum-stances, according to Fodor, the science of psychology is held hostage tofindings in other sciences and, in effect, psychology is no longer aspecialscience, but a science ofeverything.

Fodor’s own response to the dilemma is to renounce naturalistic psy-chology. But the viability of grounded-content explanations in cognitivescience suggests the plausibility of a different response to Fodor’s dilemma.I will propose that, at least for the purpose of providing grounded-contentexplanations, we simply grasp the dilemma’s first horn, making scientificuse of any accurate descriptions by which the cognizer knows the environ-ment, whether or not they designate so-called natural kinds. That responseto the dilemma becomes plausible, given the following consideration:Ina grounded-content explanation, if the explanans contains X’s true beliefthat p, then both the belief that p and the fact that p play an integralrole in the explanans.Now, with that consideration in mind, let the fact


thatp contain the instantiation of a putatively non-natural propertyQ –any putatively non-natural property – and the instantiation of that propertyplays an explanatory role in explanations that appeal to grounded content.For supposep is a premise in a sound deductive argument that cognizerC uses in order to arrive at belief in the argument’s conclusion. Then thefact thatp, and hence the instantiation ofQ, will play an integral role inexplaining howC’s belief in the conclusion manages to be true.

One might object as follows to this line of reasoning: The propositionthatX’s belief thatp is true is to be understood by appeal to a correspon-dence theory of truth, a theory according to which the following definitionholds:X’s belief that p is true= df X’s belief that p corresponds(in a sensespecified) to an actual state of affairs.While the analysans here containsa characterization of the nature of the correspondence in question, andperhapsentails that p, it needn’t actually say this, and hence it needn’tactuallysaythat anything has the non-natural propertyQ. Of course, thepropositionp (which says that propertyQ is instantiated) may well been-tailedby the claim thatX’s belief thatp is true, but it is not, in general, truethat the entailments of explanatory claims are also part of the explanatoryapparatus. For instance, letr serve as an explanans, then, throughr entails[r or s], the proposition [r or s] is a proposition that will typically not haveexplanatory value.

There are a number of ways to respond to this objection. Here are threesuggestions: First, one may argue that the proposition thatp (the propo-sition which says thatQ is instantiated) is not just any old entailment ofthe proposition thatX’s belief that p is true, but is a factin virtue of whichthe latter holds. Such facts, it might be insisted,are full-fledged parts ofthe explanation, even if not all entailments are. Second, one might simplydecline to endorse a correspondence theory of truth, opting instead for adeflationary theory according to which the proposition thatX’s belief thatp is trueis strictly equivalent to the proposition thatX believes that p andp. Such an account provides an unquestionable explanatory role for thefact thatp. Moreover, deflationists such as Horwich (1990) have argued,plausibly I think, that no explanatory power is sacrificed by such defla-tionary accounts. Third, while declining to endorse a deflationary accountof truth, one might note that, without sacrificing explanatory power, wecould introducea predicate for use in grounded-content explanations, callit a schmuthpredicate, whose semantic function we defined in accord withthe proposals of some deflationary theory. The result would be sufficientto show that there are indeed grounded-content explanations in which thefact thatp, and hence the fact thatQ is instantiated, plays an explanatoryrole even thoughQ is not a natural kind.


In one way or another, it thus appears that grounded-content explana-tions open the way for a variety of no-holds-barred explanations in whichthe instantiation ofany property whatsoevercan play an integral explana-tory role. This feature of grounded-content explanation, and hence of psy-chological explanation, is surely unique.

6. THE VARIETIES OF GROUNDED-CONTENT EXPLANATION

The most obvious way togroundcognitive contents is to relate them tothe states of affairs that render those contents true or false, accurate orinaccurate. I will refer to this assemantic grounding.But there are otherways of grounding cognitive contents that also have genuine explanatorypower. In this section I broaden the discussion to consider some othervarieties of grounded-content explanation and the questions they raise.Even philosophers who are “friends of content” and who have paid someattention to the role of semantic grounding in cognitive explanations (e.g.,Burge 1986) have not appreciated the wide range of grounding relationsthat have explanatory relevance either in cognitive science or in related dis-ciplines. I offer no more than a partial, preliminary survey of non-semanticgrounding relations and their explanatory roles.

6.1. Coordinate Content-Grounding

Non-semantic content-grounding plays an explanatory role, for instance,in David Hull’s (1988) account of what motivates scientists, and how theyproduce the kinds of cognitive products that are most likely to get themwhat they want. I begin by sketching a few of his central proposals.

Hull observes that, while scientists are typically motivated by curiosityabout the corner of the world they choose to study, they are also quitestrongly motivated by the desire to receive recognition for their scientificcontributions. What they most want in the way of recognition, Hull claims,is the approval of those who work in the same subfield. Scientists gainapproval primarily when other researchers use their work with appropriatecitation. Other things being equal, Hull suggests, scientists have the bestchance of having their work cited in this way if they produce and publishcognitive products thatinnovate but within significant limits.While onlyoriginal work wins citations, Hull stresses that sharp limits to originalityare dictated by the need to cite the work of others in support of one’s ownviews in order to maximize the chance that one’s innovations will be ac-cepted and used by others.26 Hull thus seeks to explain a scientist’s successat gaining the kind of credit they crave by appealing (in part) to what can


be called theoriginality indexof those ideas. Thisoriginality indexis justa measure of the extent to which a scientist’s work incorporates, or reliesupon, or presupposes the views of others, and in the extent to which itdeparts from those views.27

Notice that, if we tag a set of scientific proposals with an originalityindex, weground certain cognitive contents, though we do not therebyassess the truth or falsity, accuracy or inaccuracy of those contents. Instead,we merely relate them to the cognitive contents of others. I will refer tothis variety of grounding ascoordinate groundingin order to distinguish itfrom thesemanticgrounding discussed above which involves assessmentsof the truth, falsity, accuracy or inaccuracy of cognitive contents.

It is, in general, not surprising to discover that the relationship betweenthe cognitive contents of different individuals can play an integral rolein explanations. Such ideas are familiar to sociologists and anthropolo-gists, especially those who are interested in understanding the causes andeffects ofshared ideologies(e.g., Geertz 1973) and, indeed, Hull offershis proposals as part of an explicitlysociologicaltheory of the scientificprocess. But it is worth noting that at least some explicitlypsychologi-cal theories also make use of coordinate grounding. Consider, as a casein point, the psychological study of creativity. There seems to be someconsensus among psychologists who work in this area that creative ideasare: (a) unique or uncommon or original, as measured against the ideas ofsome reference class of individuals, and (b) generally valued by individualsin some reference class. But both (a) and (b) are varieties of coordinategrounding. Thus the attempt to explain the production of creative ideas is,at least in part, the attempt to explain the production ofideas that exhibitcoordinate grounding.However, psychological theories of creativity, inspite of the fact that they involve coordinate grounding, have a characterthat seems to mark them as distinctly psychological rather sociological.They address such questions as the following:

(1) Does extended unconscious thinking play a role in creativity?(2) What role does memory retrieval play in enabling, and in blocking,

creative solutions?(3) How does ‘incubation’ (i.e., temporarily laying a problem aside) aid

creative processes?(4) What kinds of goals do highly creative individuals set, and how do

they manage the extended creative projects on which they work?(5) How important to creative activity is the reliance on analogies between

diverse subject matters?(6) What is the relationship between successful creation and the extensive

revision of one’s preliminary products?28


These research questions make it clear that successful psychological ex-planations for creativity – as opposed to successful sociological ones –are expected to contain substantial commitments about the character ofintentional-gradepsychological processes. That is no doubt, at least inpart, what marks them aspsychologicalexplanations, rather than socio-logical explanations.

It is instructive to contrast such psychological explanations with the ex-planation for creativity in science that Hull’s theory contains. On Hull’s ac-count, scientists tend to exhibit the level of creativity they do because theyare curious about the world (or the corner of it they have chosen to study)and they want to receive validation from their scientific peers.29 Consis-tent with Hull’s account, scientific creativity might also be explained asa selection effect: Individuals who are unable to exhibit appropriate lev-els of scientific creativity either tend not to enter scientific disciplines,or tend not to stay in them. Explanations for scientific creativity suchas these, while not inconsistent with the explanations sought by cogni-tive psychologists, say little or nothing about intentional-grade processesgoing on in the heads of scientists. But what they do say seems to suitthem to play a role in sociological theorizing, where the main action isinterpersonal rather than intrapersonal, and where, as a consequence, in-trapersonal intentional-grade processes are unlikely need, or to receive,detailed description.

6.2. Serious vs. Frivolous Content-Grounding

There is actually an embarrassing wealth of different styles of grounded-content explanation. The following example, deliberately somewhatbaroque in character, will perhaps serve to make the point. Imagine apossible worldWi (not ours) in which, as matter of lawlike contingentfact, a proposition is true if and only if it is, in the long run, believed by aconsensus of the individuals existing in that world. Now suppose we wishto explain why someone in theactual world holds a certain belief that isgrounded by virtue of the following fact: It expresses a propositionthatwould be the object of long-run consensus among the cognizers inWi .Suppose, in addition, the belief in question was arrived at as the result of amodus ponens argument whose premises are also beliefs thatwould be theobjects of long-run consensus inWi . We can explainwhy the individualdraws a conclusion that would be the object of long-run consensus inWi

by making reference to (a) the fact that the premises of the argument aregrounded in just the same way as the conclusion is, and (b) the fact thatmodus ponens preserves this grounding relationship. That this explanation


seems frivolous does not detract from the fact that it is, nonetheless, anexplanation.

The preceding example serves to suggest that a wide variety of strate-gies for grounding cognitive contents are likely to yield correct grounded-content explanations. You can invent your own baroque examples. Suchexamples also make it clear that different varieties of correct grounded-content explanation are not all created equal. How, then, can we distinguishfrivolousgrounded-content explanations such as that just offered fromse-rious grounded-content explanations of the sort that were discussed ear-lier? One suggestion is that a certain kind of “fit” with broader theoreticalcontexts typifies serious grounded-content explanations but not frivolousones. For instance, the varieties of coordinate grounding and semanticgrounding that we are prepared to take seriously – at least those varietiesdiscussed above – relate cognizers to aspects of the actual world, both so-cial and non-social, with which they also systematically causally interact.By virtue of that fact, these grounded-content explanations fit perspicu-ously into broader scientific theorizing about human cognizers and theirenvironmental and social interactions. And ultimately, of course, at leastsome serious grounded-content explanations, presumably involving bothsemantic content and coordinate content, serve to mesh with evolutionarybiology, where explanations are provided for the very origins of cognitiveactivity.

But perspicuous “fit” with broader theoretical contexts apparentlydoesn’t require causal interaction with those states of affairs that provideeffective grounding. Suppose we were convinced that a social contracttheory of justice such as that proposed by John Rawls’ (1971) was correct.We might then find it useful, for purposes of providing grounded-contentexplanations, to ground moral and political beliefs by appeal to whether ornot they matchedwhat would be agreed upon by individuals in the originalposition making decisions from behind the veil of ignorance.

The loose concept of “perspicuous fit” to which I have just helpedmyself needs a kind of analysis that I am not prepared to offer here. Mean-while, however, it is surely safe to suppose that, as a very general matter,the varieties of grounded-content explanation that we are willing to regardas seriousrather thanfrivolous are determined by our various interests.The thesis of interest-relativity accommodates those scientific and othertheoretical interests that determine what counts as “perspicuous fit” in thecases discussed above, but it also accommodates the role of broader humaninterests as well. Thus the fact that truth, falsity, accuracy and inaccuracycan have both instrumental and intrinsic value and disvalue for humancognizers, independently of any scientific interests they may have in cogni-


tive science, can help explain why cognitive scientists take seriously thoseexplanations that ground cognitive contents by appeal to their truth, falsity,accuracy and inaccuracy. The point generalizes beyond explanations thatinvolve semantic grounding to those that involve coordinate grounding aswell: The fact that we care about what others around us think and what theyvalue, and whether they think and value the same things as we do, mayhelp explain why we take seriously at least certain kinds of explanationsthat appeal to coordinate grounding.

Note that the broad interests in truth, falsity, accuracy and inaccuracy towhich I have just alluded are presumably among the importantepistemicvaluesthat philosophers have in mind when they describe epistemologyas an explicitlynormativediscipline (e.g., Goldman 1986). The possibilitythat these broad interests shape the kinds of explanations that cognitivescientists attempt to provide gives us an interesting perspective on the re-lationship between “fact” and “value” in cognitive science: Whether or notcognitive concepts or cognitive explanations are themselves value-laden, itmay still be true that broad epistemic interests in truth and falsity, accuracyand inaccuracy play a role in shaping the field of cognitive science byencouraging the pursuit of grounded-content explanations and by helpingto determine thekindsof grounded-content explanations that are pursued– typically, those that trade in truth and falsity, accuracy and inaccuracy.30

7. CONCLUDING REMARKS

I have been exploring the explanatory framework constituted by the tri-grade model of cognitive explanation described at the outset of this paper. Ihave attempted to show how this framework gives representational contenta genuine explanatory function, and I have marshalled preliminary evi-dence on the question of whether the content-sensitive grade2 and grade3explanations provided for within this framework are genuinely causal. Ihave also argued for some claims about the nature and the scope of thisexplanatory framework and of the varieties of cognitive explanation thatit encompasses. I would now like to loosely and speculatively knit a fewof these threads together. In Section 3, while endorsing the view that in-tentional explanations and grounded-content explanations are genuinelycontent-sensitive, I offered only qualified endorsement of the thesis thatsuch explanations are causal. A pair of more recent developments maylead one to wonder whether even that qualified endorsement should bewithdrawn. First, I have argued that the instantiation of any old prop-erty, natural or unnatural, can play a role in grounded-content explana-tions. Second, I have introduced the promiscuous category offrivolous


grounded-content explanations. In the final analysis, these and other as-pects of content-sensitive explanations may make them seem so differentfrom standard cases of causal explanation that we will prefer to call themnon-causal.

A final observation. I have argued that, within the three-grades frame-work, representational content plays a genuine explanatory role both inintentional-grade explanations and in grounded-content explanations,whether or not that role is causal. Grounded-content explanations havebeen largely neglected by philosophers of mind/cognitive science whohave, nonetheless, been extremely interested in how and whether contenthas a genuine explanatory role to play within a physicalist world view. Anassessment of the explanatory role of representational content is arguablyincomplete, however, until the nature of grounded-content explanations, inall their variety, is better understood.31

NOTES

1 Of course NETtalk neurons are not at all like living, breathing neurons – and they aren’tsupposed to be. Construed as neural networks, NETtalk and other connectionist modelsembody deep and systematic heuristic inaccuracies. Indeed, Smolensky (1988) has arguedthat it iswrong to construe connectionist networks as neural networks. I ignore these con-cerns for the purposes of the present discussion.2 For reasons that will emerge in Section 4 I am only considering the fully trained networkhere.3 Or at least all those assessments thatcanbe excluded. See Note 4.4 A concept of grounding that is useful for present purposes needs additional qualifica-tions. One qualification is needed to accommodate the proposals of Putnam (1975) andBurge (1979; 1986), who have argued that content ascriptions either presuppose or areconstituted by facts about the individual’s natural and social environment. Presumablythose presuppositions or constituent facts already provide part of the explanatory role ofcontent ascriptions in intentional-grade explanations. If so, then in order to preserve theexplanatory division of labor between content ascriptions and grounded-contents that wasdescribed above, we should say that grounded contents include only those relationships tocontent that can be (as I put it above) “peeled off”, leaving untouched the content attributionitself and its explanatory power.5 Specifically, in the NETtalk examples described above, explanation (1a) is containedwithin explanation (2a), which is contained within explanation (3a), and explanation (1b)is contained within (2b), which is contained within (3b).6 In Section 4, I will show that there are principled limits to this inclusive relationship,in particular, that there are both (a) grounded-content explanations without underlyingintentional-grade explanations and (b) intentional-grade explanations without overlyinggrounded-content explanations.7 For instance, generalizations that describe relationships between parental phenotypesand offspring phenotypes (e.g. blue eyes in parents and blue eyes in offspring) are not


explanatory at all, since they leave out the causal mechanism, the genotype, and yet theymay nevertheless be true and even lawlike generalizations (Segal and Sober 1991).8 There are two issues here: (i) Does the tri-grade account that is used to provide the recon-struction in question actually receive scientific confirmation? (ii) Does that trigrade accountconstitute a revision of the unreconstructed psychological theory, or merely a change ofsubject? One might think that the fewer changes one makes in the unreconstructed theorythe safer it is to suppose one has simply reconstructed the original (cf. Churchland 1986 onreduction). By that standard, the strategies for reconstruction sketched here surely do not,simply by virtue of adding grade1 explanations, change the subject.9 In the following section, I will say more about just how those explanatory componentsare integrated.10 The anti-reductionist argument in Hardcastle (1992) capitalizes on the fact that theneurosciences employ characterizations of semantic content. She cites P. S. Churchland(1986) as another philosopher who has emphasized this point.11 There is a lot of “levels” talk going around. I am certainly not trying to capture all ofit here. Talk of levels of explanation in connection with Marr’s work clearly doesn’t fit thepresent conception of explanatory levels, as indicated above.12 Where reductionism holds, it makes sense to suppose that what has been secured in thisway is a non-causal explanation of each higher level generalization by appeal to somelower-level generalization. Where reductionism fails to hold, I think we can plausiblyconclude that eachinstanceof a higher level generalization is explained by aninstanceof some lower-level generalization, However, in this second case, I realize that one maybe unhappy about endorsing the more universal claim that the higher level generalizationitself, rather than each of its instances, receives an explanation.13 There is a rather large literature on this issue to which I cannot do justice here. Auseful collection of recent articles on the issue is found in Heil and Mele (1993). See alsoreferences cited there. I address these issues more fully in a paper in progress entitled‘How Minds Make Things Happen’. In that paper I argue that, while there are content-sensitive explanations for the occurrence of content-bearing events, and for the occurrenceof grounded-content bearing events, there are no content-sensitive explanations for theoccurrence of behaviors, physically described.14 Fodor (1987), for instance, offers interesting grounds for doubt on this score. Afternoting that “intentional properties essentially involve relations between mental states andmerely possible contingencies”, he proposes the following metaphysical principle:

. . . the causal powers of a thing are not affected by its relations to merely possible entities;only relations toactualentities affect causal powers. (Fodor 1987, 141)

15 In drawing this distinction I rely on theintuitive distinction to which Salmon (1994)refers, rather than to histheoreticalaccount of the distinction.16 The same element of luck or accident has often seemed to be present in those cases ofjustified true beliefs that fail to constitute knowledge in Gettier’s examples (Gettier 1963)and in other Gettier-like cases (e.g. Feldman 1974). (Note that Juan, in the example I haveoffered here, also provides us with a Gettier-like case if we stipulate that he is justifiedin believing that Hitler and Stalin are friends, as well as in his subsequent applicationof existential generalization.) In fact, Peter Unger (1968) has proposed that knowledge isdistinguished from merely true belief by its “non-accidental” character. While there is notroom here to consider these issues in the detail that they demand, I suggest that the elementof luck or accident that philosophers have detected in Gettier and Gettier-like cases simplyinvolves the absence of a grounded-content explanation for the true beliefs in question


and that knowledge requires, among other things, the presence of such a grounded-contentexplanation. I take up this issue at length in a work in progress.17 The rationality constraint places conditions on the occurrence of propositional attitudes,attitudes which are grounded by assessments of their truth values. It has sometimes beensupposed that there are, in addition, non-propositional attitudes and representations whichare not grounded by assessment of their truth values, but, instead, by assessments of theirdegree of accuracy. If one holds such a view, one might wish to formulate a principlelike the rationality constraint for non-propositional attitudes and representations, althoughI have not done so here. Armed with such a principle, one could presumably formulate acorollary that is also comparable to the corollary formulated here.18 I wish to thank John Haugeland and Alvin Goldman for a conversation which helped meto see the usefulness of addressing the issues contained in this paragraph. See below foradditional discussion of the rationality constraint and its implications. I take no positionhere on the truth of the rationality constraint.19 It is fair to ask when during training such general rules make their appearance – as longas one doesn’t expect a fully determinate answer to that question. There need be no precisepoint at which rules kick in.20 This term was coined by Fodor 1990.21 Smolensky (e.g. 1988,1991) sometimes makes claims that seem to imply the widespreadinertness of representational content within connectionist models at grade2, but, while Icannot discuss these matters in detail here, I believe that appearances are misleading. Inparticular, Smolensky (1988) concedes that weights encode implicit knowledge, and I havebeen supposing that such a condition is sufficient for the explanatory relevance of inputlayer contents. In addition, while apparently offering grounds to doubt thecausalrelevanceof content, Smolensky (1991) also offers grounds for supposing itsexplanatoryrelevance.Finally, Smolensky’s (1988) distinction between theconceptualandsubconceptuallevelmakes it possible to suppose the explanatory irrelevance of contents at the conceptual levelwhile admitting their explanatory relevance at the subconceptual level.22 As above, I assume that one could formulate a version of the rationality constraintthat applies to non-propositional representations and that one also could derive from it acorollary that is comparable to this one.23 Scattered references to grounded-content explanations can be found in a variety ofplaces, including Putnam (1978), Burge (1986), Horwich (1990), and Nozick (1993), butno systematic, sustained investigations exist. I have discussed grounded-content explana-tions in Montgomery (1989; 1995a; 1995b).24 If this thesis is true, then the class of natural kinds may suffer one of three possible fates.First, that class may be effectivelyenlargedbecause kinds which werethoughtto be non-natural are natural after all, since they appear in grounded-content explanations. Second, itmay be thatthere are no natural kindsbecause their existence depends on the assumptionthat natural kinds and unnatural kinds are both non-empty categories. Third, it may be thatboth natural kinds and unnatural kinds still exist, but the distinction simply fails to havethe same significance in psychology as it has elsewhere. I do not wish to make a choiceamong these options.25 Fodor dismisses the possibility, explicitly considered by Gibson (1979), that the envi-ronment might be described by using a vocabulary of natural kinds and categories that issuited specifically to a science of organism-environment causal interactions.26 Limited originality not only helps guarantee evidential support for one’s work but also,even more obviously, helps insure therelevanceof one scientist’s work to that of another.


Unless I missed something, Hull doesn’t actually make this last point (though he mayimplyit).27 How is an originality index actually determined? Hull offers only a negative suggestion.The amount of originality in a scientific proposal isnotdetermined by whether or not somespecific set of cherished scientific principles, guarded by a protective belt (cf. Lakatos1979), is denied. There is no such set of principles, according to Hull.28 For surveys of the research on these questions, see Perkins (1981) and Finke et al.(1992).29 Notice that these conditions do not have to be sufficientin generalfor the exercise oflimited originality as long as they tend to be sufficient forscientists.30 In Montgomery (1995b) I explore a somewhat different connection between fact andvalue in cognitive science, a connection that also depends on the existence of grounded-content explanations.31 I wish to thank Alvin Goldman for his comments and his encouragement on this project.I also wish to thank the twoSynthesereferees for their help. During the summer of 1994,my research on this project was supported by a Radiological Consultants AssociationSummer Research Fellowship at West Virginia University, for which I wish to expressmy gratitude to the WVU Foundation, Inc. and to the WVU Office of Academic Affairs. Iam also grateful to the Center for the Philosophy of Science at the University of Pittsburghfor the opportunity to present a draft of this paper as part of a symposium on Cognition andExplanation at the Center’s Third In-House Conference in the fall of 1994. Final revisionsof the paper were completed in the fall of 1997 during a very enjoyable, and very profitable,period spent as a Visiting Fellow at the Center, while I was on sabbatical from West VirginiaUniversity.

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Department of PhilosophyWest Virginia UniversityP.O. Box 6312Morgantown, WV 26505U.S.A.E-mail: [email protected]

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Grades of Explanation in Cognitive Science