Unification, Reduction, and Non-Ideal Explanations

TODD JONES

UNIFICATION, REDUCTION, AND NON-IDEAL EXPLANATIONS

ABSTRACT. Kitcher’s unification theory of explanation seems to suggest that only themost reductive accounts can legitimately be termed explanatory. This is not what we findin actual scientific practice. In this paper, I attempt to reconcile these ideas. I claim thatKitcher’s theory picks out ideal explanations, but that our term “explanation” is used tocover other accounts that have a certain relationship with the ideal accounts. At times,“versions” and portions of ideal explanations can also be considered explanatory.

1. INTRODUCTION

Philip Kitcher’s “unification” theory of explanation (1983, 1989) hasemerged as a leading successor to the Hempelian hypothetico-deductivetheory of explanation. This theory holds that explanation is fundamentallya matter of showing how numerous disparate conclusions about the worldcan be derived from a small set of premises. Such a theory, which attemptsto provide a comprehensive theory of something as complex as expla-nation, is bound to be controversial. Unsurprisingly, critics have raisedquestions about numerous aspects of the unification theory (e.g. Salmon1984; Koertge 1989; Barnes 1992a, 1992b; Humphreys 1993).

My own concerns center around the fact that the unification theorycan easily appear to be committed to an extreme form of reductionismthat is unsupported by actual scientific practice. If our world is composedentirely of fundamental particles moving in arrangements dictated by asmall number of forces, then the most unifying descriptions should bethose that describe everything in terms of a small number of laws and“brute facts” of physics. But throughout science, accounts that do not takethis most reductive form are routinely thought of as explanatory – think,for example, of almost any branch of medicine.

In light of the hodgepodge of things routinely accepted as explanationsin the sciences and elsewhere, a temptation among many scholars has beento abandon the Hempelian project of searching for a general systematictheory of scientific explanation. My aim here is to show that such an aban-donment would be premature. Worries about the frequency of successfulreduction in science, need not imperil the unification theory of explanation.

Synthese 112: 75–96, 1997.c 1997 Kluwer Academic Publishers. Printed in the Netherlands.

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A closer look at our concept of explanation shows how scientific expla-nation can appear anarchic, while at the same time being fundamentallyconstrained by the principles of unification.

2. SKETCH OF THE UNIFICATION THEORY

On the unification view, explanations are deductive derivations which con-clude with a statement of the fact to be explained. What makes the unifi-cation theory’s view of explanation strikingly unique is its assertion thatthe ability of an account to explain something cannot be measured bylooking at that account alone. To qualify as an explanation, an accountmust be a particular instance of a general schematic “derivation pattern”.It must also be an instantiation of one of these derivations patterns thatbelongs to a larger group of derivations patterns that together constitutesomething called the “explanatory store”. The explanatory store is com-posed of the smallest set of derivation patterns that together can be used togenerate the largest amount of our total knowledge of the universe. Thus,ideally, to determine the right explanation of a particular phenomenon,one must first know which of the various possible systematizations of ourentire knowledge base is made up of the fewest schemas of derivation. Theright explanation is only that derivation taken from the sparsest possible“explanatory store” over our knowledge. An account of some phenomenonwhich is not taken from this store is not the correct scientific explanation.

One can see how this account of explanation works more clearly bylooking at an example. Suppose someone wants to explain why a compoundmade of two elements contains the element weight ratios it does. Accordingto the unification theory, one does this by showing how one can account forthis by using a unifying derivation pattern that one can use over and overagain to give conclusions of this sort. In explaining numerous differentconclusions with the same patterns, we minimize the brute facts we needto know and we unify our knowledge of the world. Thus, the (at leastpreliminary) explanation for the weight ratios in a given compound comesfrom showing how one derives this ratio from instantiating this derivationschema which tells us how such ratios are generally computed:

1. There is a compoundZ between X and Y that has the atomic formulaXpY q.

2. The atomic weight of X is x; the atomic weight of Y is y.3. The weight ration of X to Y in Z is p times x to p times y.

UNIFICATION, REDUCTION, AND NON-IDEAL EXPLANATIONS 77

One gives explanations of particular weight ratios by using this generalschema and replacing the X , Y , and Z “placeholder” variables with thenames of chemical substances. P and q are replaced by the number ofatoms of involved in the compound, and x and y are filled in with thenatural numbers representing the atomic weights of these elements (takenfrom Kitcher 1989, 446). Here, one explains by showing how a fact is notisolated and mysterious, but is one of many facts that can be derived usingone of a small number of general schemas which, together, enable us todeduce why most of the facts about the world must be as they are.

3. UNIFICATION AND MULTIPLE REALIZABILITY

As I alluded to earlier, I believe the central apparent weakness of the uni-fication theory is that scientists and others continually give what seemlike explanations using a high level, non-unifying idiosyncratic vocabu-lary. Imagine, for example, someone giving an account of the formation ofwater molecules by saying that the hydrogen atoms involved became pos-itively charged and were therefore attracted to negatively charged oxygenmolecules. It is hard to see how this could count as any kind of explanationfor the unification theory advocate. The “attraction” spoken about herecould certainly, alternatively, be discussed in terms of what happens at alower level – ionic bonding in the outer orbitals. This lower level accountenables one to explain the event in a very general vocabulary which canbe used to describe the vast array of various chemical combinations. Bythe unification theory’s criteria for explanatoriness, the lower level accountshould be considered to be the correct explanation of this phenomena. Butwhile the higher level account may be loose and informal, it is not clear thatit is not explanatory. Cases like this exist throughout science, and seem tobe counterexamples to the unification theory of explanation. If explanationis really based on providing a unified picture of our knowledge, why doscientific explanations so often refer to a hodgepodge of different highlevel entities and processes, even when more unifying low level accountsare readily available?

I believe there is one class of accounts which are non-reductive, butwhich nevertheless can be shown to fit the unification theory’s criteria forbeing an explanation in a fairly straightforward manner. In Jones (1995),I discuss how some types of accounts can be considered explanatory onthe unification theory, even when they are not reductive, because suchaccounts involve what can be called multiply realizable generalizations.Generalizations can be termed “multiply realizable”, when a particulargiven structural description at the high level can be instantiated in numerous

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different ways at the micro-level. A simple case of multiple realizabilitycan be found in this example first described by Hilary Putnam (1973):a square peg a certain length across cannot be put into a round hole thesame length across. While it may be true that in any particular case, onecan give a molecular description of what prevented the peg from passingthrough the bole, there is no low level molecular account that explains whythis generalization holds true. The reason one can’t give such a low levelderivation is straightforward. This generalization holds true regardless ofwhether the pegs and holes in question are huge or tiny, and holds true fora wide range of different materials. While there are high level geometricalfeatures that are the same in each situation, there are no low level featuresthat are common to each situation. At the micro-level, “round holes” canbe constructed out of an indefinite number of arrangements of molecules.

Now the unification perspective requires that explanations be drawnfrom the store of explanation schemas that provides the most sparse sys-tematization of our knowledge. However, this store must also be a sys-tematization that maximizes the number of conclusions we can generate. Ifwe want our explanatory store to approach giving us a complete catalogueof truths about the world, it must include all those patterns necessary togenerate these truths. It must also include, as axiomatic statements, thosetruths that are not derivable from any other statements. For the reasons justdescribed, many multiply realizable generalizations are not derivable fromlow level derivation schemas. If they are not derivable from descriptionsof lower-level entities, then the explanatory store must either include suchhigh level generalizations as axioms, or be capable of generating them withother high level patterns. Multiple realizability, along with the conclusionmaximization requirement, then, seems to necessitate that our explanatorystore include at least some high level non-reductive explanatory schemas.

4. OTHER HIGH LEVEL ACCOUNTS AND THE TEMPTATION NOT TO EXPLAINTHEM

More vexing for the unification perspective however, are cases like that ofwater molecule formation described above. Here, the “attraction” spokenabout is (unlike multiply realizable processes) something that is directlyreducible into a unique statement about what happens at a lower level –ionic bonding in the outer orbitals. As this lower level schema is usable innumerous cases, we should use it here, and systematize our knowledge bykeeping the high level non-general account out of our explanatory store.Indeed, in general, if explanation consists in unifying our knowledge,then unless multiple realizability is involved, explanations should derive


conclusions reductively, based on a small unifying set of shared constituentelements and processes.

But this is not what we find. In case after case, we see scientific expla-nations that are not constructed in the most general low-level vocabularypossible – even when we know how to derive the conclusions involvedusing a lower level vocabulary. “The snake secretes a poisonous venom inits bite which paralyzes the central nervous system”, is a perfectly accept-able explanation of how a rattlesnake bite can kill you, even though amore unifying description in terms of the underlying physiology can begiven. If explanation is really based on providing a unified picture of ourknowledge, why do scientific explanations so often make use of high levelentities and processes, even when more unifying low level accounts arereadily available?

There is a certain temptation to try to deal with cases like the watermolecule and the snake bite with a “quick fix” solution. We might try todeny that such cases were really true scientific explanations. This temp-tation, I believe, should be resisted. First, we routinely call these andthousands of other cases like them “explanations” all the time. In trying toclarify what a scientific explanation is, it seems quite backwards to beginby declaring that numerous accounts commonly accepted as explanatory(scientific or not) are really not explanations. Alternatively, we might grantthat such cases are explanatory, but claim that they are not scientific. This,however, presumes that we have some reliable means of demarcating thescientific from the non-scientific. At present, we have no such ability tomake this sorting – certainly not for the borderline cases of interest for thepresent concerns. And even if such a divide could be made, high level non-reductive vocabularies are certainly used throughout areas like biology andmedicine that are unproblematically judged to be scientific.1

Another reaction to these sorts of cases is not so easy to dismiss.Faced with a vast array of idiosyncratic vocabularies and different types ofaccounts in different sciences, numerous scholars have suggested that ourbest option is deny that there is a systematic account of explanation to begiven. The reason that so many accounts are non-reductive, and get awaywith breaking what the unification theory sees as the “rules” constitutingproper explanation, is that there is no single set of rules of proper expla-nation. Kuhn (1970) and Feyerabend (1970), for example, are notoriousfor claiming that different subdisciplines have different standards for whatconstitutes good research, and also, presumably, of what constitutes anexplanation of a phenomena in question. As far back as the late fifties andearly sixties, numerous linguistically-oriented philosophers such as Scriv-en (1959) Toulmin (1961) and Bromberger (1962) objected to Hempel’s

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D-N view of explanation, in part, because they believed that different sortsof questions demanded different types of explanations. Hanson’s 1958 dis-cussion of explanation remains a classic point of reference. Hanson wrotethat what would be regarded as an explanation of a man’s car crash fatal-ity was dependent on who was asking the question. The physician wouldexplain the death as being the result of a multiple hemorrhage. The lawyerwould explain it as a result of driver negligence. The auto-manufacturerwould see it as deriving from a deficiency in the car’s brake design, andthe civic planner would account for it in terms of foliage blocking terms ofvisibility on the road (Hanson 1958, 54). More recently both van Fraassen(1980) and Achinstein (1983, 1986) have denied that there is any accountthat can tell us what an explanation is, independent of the context and thepresuppositions under which a question was asked.

On these scholars’ views, the absence, in numerous scientific accounts,of the unifying low level entities and derivation patterns seemingly requiredby the unification theory is just a special case of a more general lack ofsystematicity in explanation. Non-reductive, non-unifying accounts cancount as explanations because nothing in the notion of explanation reallyrestricts them from so counting. Van Fraassen’s (1980) view that virtuallyanything can count as an explanation in the right context probably goes thefarthest, here.

While this “explanation is idiosyncratic” view certainly provides a sim-ple and straightforward way of dealing with the apparent counterexamplesto the unification view, I believe such a move is both highly prematureand inaccurate. In almost any domain, we are better off with a systematictheory if we can get one. Understanding explanation is no exception. Weshould not be willing to stop looking for a systematic theory unless thereis overwhelming evidence that such a theory cannot be found. We certain-ly don’t yet have any such overwhelming evidence. Indeed, we currentlyhave numerous reasons for thinking that the notion of explanation is farmore restrictive than van Fraassen or Achinstein allow (see Salmon 1989;Kitcher 1989; Kitcher and Salmon 1987). What I wish to argue here is thatthe unification view can still be seen as giving us the desirable systematictheory. A closer look at the notion of explanation shows how the seem-ingly idiosyncratic accounts we find in science are still governed by theprinciples of unification, extended in a particular way.

5. IDEAL AND NON-IDEAL EXPLANATIONS

In my view, the reason so many non-reductive accounts are deemed accept-able scientific explanations is because the term ‘explanation’ can refer to


two different things. It can refer to a detailed underlying “ideal” answer toa why-question, but also to a sparser answer that has a particular type ofrelation to this ideal one. In my view, we are willing to call many rough,non-reductive accounts “explanations” so long as they relate in the rightway to the ideal account. I claim that the unification theory is set up toidentify ideal explanations. The non-ideal accounts that can be consid-ered explanatory are the ones that are related in the right way to theseunification-based ideal accounts. In what follows, I will discuss how lessdetailed accounts are related to ideal ones in ways that enables them to beconsidered explanatory themselves.

One place where the idea that the term ‘explanation’ can refer to two dif-ferent types of account has been discussed is in Wesley Salmon’s ScientificExplanation and the Causal Structure of the World (1984). Salmon, echo-ing Peter Railton (1981), puts this idea this way: The term “explanation”is ambiguous. Sometimes the term refers to the complete extremely mul-tifaceted underlying network of causal relations behind any event. Thiscan be called the ideal explanation. At other times, the term ‘explana-tion’ refers to what he and Railton call explanatory information – sets ofstatement that merely give information about this complex underlying net-work. When anyone asks to be given a scientific explanation of something,Salmon contends, they nearly always want merely to be given explanatoryinformation. While the true answer to a given why-question is always aset of long causal chains, the appropriate answer to a why-question, inpractice, must be some subset of the complex underlying causal story.

While there is much to disagree with in Salmon’s causal theory ofexplanation (see Kitcher 1989), I believe that he and Railton are correctin distinguishing ideal explanations from other accounts that we are alsowilling to call ‘explanations’. What’s more, this distinction can easily beappropriated and used to clarify how the unification perspective allowsmany non-reductive accounts to be considered explanatory. Following theguiding principles of the unification perspective strictly and literally yieldsthe underlying ideal explanation of phenomena.2 Where the causal theorysupposes an ideal explanation to consist in a description of a complexcausal network, the unification approach would see an ideal explanation as ahierarchical interlinking set of derivation patterns which together allow oneto deduce why phenomena must be as they are. When multiple realizabilityis not involved, such ideal explanations will tend to be reductive. However,when people ask for explanations, they do not want this ideal underlyingtext. They usually want information about some part of it in which they areinterested. I claim that such partial accounts will be accepted as explanatoryas long as this information is related to the underlying account that the

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unification theory picks out as ideal in the right way. A non-reductivenon-multiply instantiable account, then, can still be termed “explanatory”on the unification theory, because of this second, weaker definition of“explanation”.

How must a non-ideal account be related to an ideal one in order tomerit the label “explanation”? While Salmon and Railton’s distinctionbetween actual and ideal explanations points us in the right direction forunderstanding how non-reductive accounts can be seen as explanations,I believe that their view goes wrong in its characterization of the natureof the relationship between the actual and the ideal. The Salmon–Railtontheory says that explanatory information that gives information about theunderlying account can also be termed explanatory. This is a more system-atic view of explanation than van Fraassen’s, but a closer look reveals thatour concept of information is actually still more systematic and restrictivethan they suggest. It’s simply not the case that all explanatory informationabout an ideal account is, itself, considered explanatory. Saying “the idealaccount of a wedged bicycle seat involves molecules” does give one infor-mation about the ideal account. But it is not an explanation in the way thatsomething even as minimal as “metal expands when heated” is. Somethingmore is clearly required of a non-ideal explanation than that it merelygives information about the ideal account. Neither Salmon nor Railton,however, propose any solution to overcome this limitation. Railton, notunaware of the problem, is content with saying that there is a continuum ofexplanatoriness, with sometimes infinitely large explanations at one end,and extremely minimal information about this ideal text at the other. Onthis view, even quite unexplanatory statements about ideal texts such as“the relevant ideal text contains more than 102 words of English” is mere-ly labeled as lying toward one end of the continuum of explanatoriness(Railton 1981, 246). Resorting to such continuum claims seems to me to beanother case of prematurely giving up on finding a more systematic accountof explanation. Railton is forced into this position by characterizing therelationship between actual and ideal explanations in terms of somethingas minimal as the actual “giving information about” the ideal. I suggest, bycontrast, that in order to count as an explanation, a non-ideal account mustbe related to the ideal account in a much more substantial way. To count asexplanatory, a non-ideal account must, in some sense be some “version”of the ideal account, perhaps very condensed and redescribed, or be someportion of some version. I suggest that when we look at non-ideal accountswhich we do and do not consider explanatory, we will find that the oneswe consider explanatory are accounts that we can think of as versions ofideal accounts. It is having this relationship with ideal accounts, rather than


merely talking about them, that enables numerous non-reductive accountsto count as explanatory.

6. VERSIONS OF IDEAL ACCOUNTS

The general idea behind the claim that non-ideal accounts count as explana-tory if they are versions of ideal accounts is fairly straightforward. A ver-sion of an ideal explanation, like a version of any account, is one whichitself “tells the same story” that some canonical account does. It does notmerely give information about that story. Versions of accounts are allowedto deviate to a considerable, but not unlimited degree from the canonicalmodels they are versions of. To be a version of an ideal explanation, anaccount must tell a story, using some terminology, that says how certainentities, processes and forces (described in detail in the ideal explanation)makes the state of affairs to be explained likely or inevitable. It must notuse terminology which names entities and processes that are not involved.3

An ideal scientific explanation of how its possible to make mayonnaise, forexample, might talk about the bonding properties of rod-shaped lecithinmolecules giving one end of the molecule an affinity to bond with the watermolecules, while the other end, which touches oil particles, is repulsed bywater, and how a lecithin coating enables oil molecules to float through-out the aqueous solution. It would go on to say and how the lecithinsacquire electric charges which repel the oil molecules from each other,keeping them from coalescing (Kurti and This-Benkhard 1994). One cangive what I’m terming a version of this explanation by saying only that thelecithins in the egg yolks can emulsify the oil, suspending it throughoutthe water. What would not count as a version, on the other hand, is sayingthat “lecithins enable the oil to dissolve in the water”, as this terminologydoes not tell the same story of what happens as the ideal explanation. Thisaccount, which can not be intuitively considered a condensed version ofthe ideal, can not be considered explanatory.

What I am claiming here can be summarized this way: Explanationseems to be a more a more idiosyncratic haphazard affair than the unifi-cation theory would indicate. One response to this would be to agree withthose who claim that there is no systematic theory of explanation to behad. Salmon and Railton’s response is to suggest that the term explanationcovers both an ideal account and accounts that give information about it.This is on the right track, but still incorrect. I am claiming that the unifi-cation theory enables us to identify which accounts are ideal explanations,and that other accounts intuitively considered explanatory are ones consid-ered to be versions or portions of these unification-based ideal ones. My

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evidence for this claim is that when we look at numerous cases of highlevel accounts we consider explanatory and at cases that we don’t, we findwhat we saw in the emulsification, water molecule, and bicycle seat casesdescribed above: Cases where the high level account could be describedas a version of some ideal account were considered explanatory, and casesthat could not were not. It is being able to be considered a version of theideal account, and not merely giving information about the ideal account,or meeting various pragmatic criterion which determines whether or notsomething will count as an explanation.

I believe that, in this context, the concept of a version has a clear enoughmeaning that for an overwhelming majority of cases, we can straightfor-wardly say when accountX is or isn’t a version of a certain ideal account.Possession of the ideal explanation and a familiarity with our ordinaryconcept of a version is usually all that’s needed to enable us to judge whichnon-ideal accounts will be intuitively considered explanatory. If intuitionsabout being a version play so central a role in determining which non-ideal accounts count as explanatory, it would certainly be advantageous tohave a systematic account of the principles which underlie our judgmentsof something’s being a version. Such a theory would certainly give us adeeper understanding of explanation. It would also give us some normativeguidance on what to say in various “borderline” cases of explanatoriness.4

Developing a precise detailed theory of what constitutes a version, how-ever, is clearly not a task that can be undertaken here. In what follows,though, I will say a few things about what ordinary usage suggests aboutwhat does and doesn’t count as a version, and point out some areas wherefurther philosophical reflection is needed to help clarify the boundaries ofwhat counts as a version of an explanation.

7. FINDING CONSTRAINTS ON BEING A VERSION – REFERENCE

In thinking about which non-ideal accounts count as versions of ideal ones,we must begin with the requirement that the rougher, non-ideal story mustnot contradict the story told in the ideal account if it is to count as a version.But we certainly need much more than this. A high level account of howphotographs are produced certainly does not in any way contradict an idealexplanation of how hydroelectric power is generated, but it does not countas a version of it. A non-ideal account, then, must not only not contradictthe ideal account, but it must also be talking about the same thing. Talkingabout the same thing, however, cannot mean that the high level descriptionhas “the same meaning” as an ideal low-level one. Terms like “water”,“oil”, and “emulsify”, can all be said to have had clear concrete meanings


before anyone had any notions of the molecular structures and processesinvolved in the underlying ideal explanations. If we want to more preciselyclarify our intuitive idea that a version “tells the same story” as the idealaccount, the central notion involved is not meaning but reference.

If we look closely at our intuitions about which explanations count asversions of other explanations, we will find that a central feature requiredfor one account to be considered a version of another is that the sec-ond account refer to the same entities, processes, and conditions as thefirst one. Consider the ideal explanation of the water molecule forma-tion case discussed above. The unification theory tells us how to pickout a list of schematic sentence patterns and their fill-in rules that can beused over and over again to explain various phenomena of this sort. Anideal account of a water molecule formation would consist of an instan-tiation of some very long and complex QM schema about orbitals etc.Let that be (S1; : : :; Sn). Any account that we could consider a version ofthat ideal account would instantiate some schema (S�

i; S�

j; : : :; S�

n) where

there is a coreferential map taking each S�

iand mapping it onto some

set of Si’s, preserving inferential relationships etc. from the full schema.In our everyday explanations of water molecule formation, speaking ofa process of “positively charged hydrogen atoms becoming attracted tothe negatively charged oxygen atom”, describes it in a way which mapsthis description, via common referents, to the ideal account’s QM entitieswith the loss of an outer electron entering into an ionic bond connection. Isuggest that the high level account is intuitively considered a version of thelower level one because the entities and processes referred to remain thesame, as do the overall inferential relations between descriptions referringto the same entities. In other words, a version is formed by picking outparts of the ideal explanation and formulating an account which refersto the same collection of entities, processes, and conditions in a differentlanguage.

I suggest that reference is the central notion governing which accountsare versions of others because it provides a way of giving, in some sense,“the same information” without having to explicitly spell out details. Whenone says that “lecithins in the egg yolks can emulsify the oil : : : ” one isnaming the complex electrostatic repulsion process involved here, as that’swhat ‘emulsify’ refers to. Because reference is a relation between wordsand actual states of the world, microstructural states are automaticallyreferred to, even when nobody is spelling out these details. One resultof this, as Putnam (1975) has pointed out, is that people can refer tomicrostructural processes even when only experts know what these are. Ibelieve this accounts for the intuition that some high level accounts can

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count as a version of an ideal explanation even when the speaker lacksknowledge about how the ideal explanation would go. Hence, part of aperfectly decent version of the ideal scientific account of how the humanbody uses food to produce motion is the phrase “food is digested in thestomach”. The ionic bonding involved in the stomach acid’s breaking downof food referred to in an ideal scientific account is also the referent of theterm ‘digestion’, even if only a few experts know this. Saying that thestomach “bakes” or “explodes” the food inside, on the other hand, cannotbe not a version of the ideal account, for although these terms are vague,they definitely refer to processes different from the chemical breaking downthat takes place in the stomach. Other cases work the same way. I suggestwe can explain the lubriciouness of graphite by saying it is composed ofplanes of atoms that “slip over one another”. Such terminology can clearlyrefer to structures referred to in an ideal scientific account – bonded planesof atoms that form layers because each atom is bonded to three other atomsbeside it, but not to any atoms in the layers below it. We can’t explain itby saying that “it is composed of carbon, a very soft material”, since thereis nothing in the ideal scientific account that “carbon’s softness” can referto. This feature of reference also accounts, as well, for the intuition that ifexperts came to believe that the something’s microstructure was differentthan previously thought, a high level account might no longer be considereda version of the ideal one, even if the teller knows nothing about the newthinking.

Reference is clearly an important notion in understanding what is meantby a version. But it is also a notion where much more philosophical workneeds to be done to clarify how the notion can be used to help solveproblems involving explanation. Answering questions about whether anaccount counts as a version of an ideal explanation will always involveseeing if the terms in the non-ideal account refer to events and processesin the ideal one. But, in some cases, our current theories are unable to tellus whether they do.

Consider what current philosophical theorizing says about the referenceof terms embedded in mistaken theories. On one leading account of thereference of theoretical terms, David Lewis’s, certain terms embedded inmistaken theories have no referent. Lewis makes this point in a story abouta detective speculating on a murder. In his story, the detective speculateson the activities of three unknown men he calls persons X , Y , and Z . Hegoes on to say,

[I]f we learned that no triple realized the [detective’s] story or even came close, we wouldhave to conclude that the story was false. We would also have to deny that the names ‘X’,


‘Y ’, ‘Z’ named anything; for they were introduced as names for the occupants of roles thatturned out to be unoccupied. (1980, 209)

For Lewis, the same point applies to scientific and other terms. In thecontext of our discussion, Lewis’s views on reference have the consequencethat high-level theoretical terms that have roles in theories that are mistaken(a presumably not uncommon occurrence in rough, high level theories)could not refer to entities and processes in ideal explanations. One difficultyhere is that Lewis never makes clear how wrong a theory has to be for itsterms to fail to refer (see Stich 1996). In Lewis’s detective story, ourintuitions tend to be that if the detective made one mistake about X’sactivities, ‘X’ could still refer. But what about 10 mistakes? What aboutthree or four? The rough high level theories whose terms are used in non-ideal accounts could well have various large and small mistakes withinthem. This theory of reference would often be unable to tell us whether anaccount’s terms refers to entities in the ideal account, and hence whetherit counted as a version and an explanation.

Even more problematic, however, is the fact that Lewis’s account seemsto be directly contradict another major theory of reference – the so calledcausal theory of Kripke (1972) and Putnam (1973). On the causal theory,a term’s reference is determined by its having the right sort of causalconnection with its usage by a chain of speakers, ultimately tracing back tothe causal circumstances in which the term was first introduced (see Devittand Sterelney 1987). On this theory, a person can still refer to things evenif he or she holds very mistaken beliefs about them. Even if the biblicalJonah had never actually been in the belly of a large fish, on this view,when we speak about Jonah, we are still speaking about a particular personwho was given the name “Jonah” by his parents – a person who rightlyor wrongly first had this story told about him (see Kripke 1972). Lycan(1988) has recently pointed out that if this theory is right, then Lewis’stheory must be quite wrong and we can not claim the entities of roughhigh level theories are non-referring simply because parts of the theoriesare mistaken. Using a causal theory of reference could allow us to countvarious accounts as versions that Lewis theory would not.

There has been a large philosophical literature debating the merits ofthese two theories. Stich (1992, 1993) for example, points out that ifLewis’s theory seems far too conservative, Kripke’s is far too liberal, forcausal chains that are not unlike those for terms like ‘water’ or ‘planet’ canbe found for terms like ‘witch’ that seem clearly not to refer. It is not myplace, here, to enter into a debate about the merits of various theories ofreference here. I bring up this debate as an example of an area where onefinds a central constraint on the notion of a version – reference – but where

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understanding the exact boundaries of that constraint will take a great dealmore philosophical work.

8. OTHER GUIDELINES ON BEING A VERSION – EXTRA FEATURES

Reference, with all of its problems, is clearly the central feature determiningwhich non-ideal explanations can count as versions of ideal ones. Butordinary linguistic practice reveals some other interesting constraints onand extensions of the concept of a version of an explanation as well. Oneinteresting thing found by looking carefully at ordinary linguistic practiceis that we are unwilling to count an account as a version of an ideal one ifit’s one whose terms are associated with prototypical features that are notpresent in the ideal account. This is true, regardless of what theory turns outto be the right theory of reference. Suppose, for example that an extremelyliberal variant of the causal theory of reference turns out to be the onewe ultimately accept. According to that variant, when Cavendish isolatedoxygen gas in the late eighteenth century, and labeled it “dephlogisticatedair” using the terminology of the prevailing chemical theory, he therebylicensed us to use “dephlogisticated air” for oxygen. Even if this did countas referring to oxygen, however, (which, in my view, it doesn’t, see alsoEnc 1976; Kitcher 1992) ordinary linguistic practice would still not countany account of animal respiration which talked about “dephlogisticatedair” as being a version of the ideal account. Some central characteristicsand features of phlogiston theory were that phlogiston was a substancethat existed in some materials and was released into the air when thesesubstances were burned. Whatever the term phlogiston does or doesn’t referto – these features have been regarded as central prototypical characteristicsof how phlogiston worked. If no entities and processes like these exist inthe underlying ideal account of something, ordinary linguistic practicedictates that a phlogiston-based account, which connotes the involvementof something with these features, could not be termed a version of anoxygen-based one. It could be no more a version of an account of respirationthan an account of the disappearance of dragons could be called a versionof an account of dinosaur extinction. If terminology typically causes usto think of certain features being present when they were not, ordinarylanguage dictates that such an account can’t be called a version of anexplanation. This provides another constraint determining which rougherhigh-level theories count as versions of ideal ones.5

While discussing how ordinary language puts some constraints on whatcan count as a version of an ideal account, we should note that ordinarylanguage is also structured in ways that make the notion of a version some-


what more liberal than a more regimented language might. One noteworthyfeature of our language that enables the notion of a version of to be con-siderably looser than the notion of an ideal account is that in versions wetolerate the use of terminology that can, but does not specifically, referto features not present in ideal accounts. We seem to be quite willing tocount accounts using terms which refer to a vague heterogeneous mixtureof entities and properties as versions of more ideal accounts, even if onlysome parts of that mixture play a role in the actual ideal explanation. Wecan give a decent account of a car’s breaking down, for example, by sayingthat the carburetor was not getting enough air, even though it was specifi-cally the lack of oxygen, a part of the air mixture, that caused the problem.Here, reference was made to a larger set of entities and processes than areactually involved in the ideal account. Why do we tend to be willing toaccept it as a version of an ideal account?

What’s behind this acceptance, I believe, is that we commonly allownames for a collection to be interpreted as also referring to one or more ofthe subparts within them. Thus, it is not regarded as erroneous to say “theman needs his tools for that” when he really needs only his hammer. In suchcases, claiming that a conglomerate or collection is involved or required isgenerally not taken to be in conflict with statements saying only a particularsub-part is involved. I believe our notion of a version of an account obeysthis convention. We do not consider accounts which refer to heterogeneousmixtures as necessarily being committed to the proposition that all partsof the mixture are involved in the process referred to. The only time anaccount referring to a mixture becomes unacceptable is when the languageused is structured such that uninvolved parts of the mixture are specificallyhighlighted as taking part in the process. An account becomes unacceptableas a version of an underlying account when the terms referring to a mixturearen’t just the general ones that can be interpreted as meaning “the mixtureor whatever the important subset of the mixture happens to be”. Thingsbecome problematic when the terminology specifically and unambiguouslytypically connotes the whole or specific parts of the whole. Hence, “iron’sexposure to air, eventually causes it to turn reddish” can be an acceptableversion of a longer underlying ideal story, as this statement can also mean“iron’s exposure to a part of the air causes it to turn reddish”. “Nitrogen,carbon dioxide, oxygen, (etc.) cause iron to turn reddish”, however, is notan accurate statement, because these things aren’t all involved in turningiron reddish. Such a statement is false, even though the statement “air turnsiron reddish” is true and air is nitrogen, carbon dioxide etc. Our linguisticconvention is such that we allow a vague term which refers to a mixture to

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connote a subpart, but we don’t allow a more detailed specification of themixture to do so.6

9. PORTIONS

When we ask for explanations, then, Salmon and Railton are correct inmaintaining that we are not interested in being given all the details of theunderlying ideal explanation. What I have been claiming, however, is thatwe want something more substantive than merely information about theideal account. What we want is some version of the ideal account. Above,I have been discussing how giving an account which differs from the idealbut refers to the same conditions enables us to give an account which wesee as a properly explanatory version which can, nevertheless, leave outa host of the details. At this point, we need to mention another way inwhich we tolerate accounts which depart still further from ideal unifyingones: our willingness to label portions (and portions of versions) of idealexplanations as explanatory.

A quick survey of the various types of accounts considered intuitivelyexplanatory reveals that we tend to be quite willing to count numerousdifferent parts of a lengthy ideal account, or even a rough version of thataccount, as an explanation of a phenomenon. Consider again Hanson’s caraccident case. The ideal explanation of the fatality might have descriptionsof multiple hemorrhaging, driver negligence, brake deficiency and poorroad planning all playing a factor in the derivation of the end result. Yetvarious people are willing to count naming any one of these factors as anexplanation in its own right.

Here is what I suggest is going on with such cases: Salmon and Railtonare entirely correct in their assertion that when people ordinarily ask foran explanation, what they really want is only some portion of an expla-nation. An entire ideal account rarely needs to be articulated to supplysomeone with the information they require for some task. Hence, peopleare quite used to receiving only part of an explanation when they ask foran explanation. The term ‘explanation’ is, thus, very naturally extendedto mean a portion of an explanation, as well as an ideal one. Here, then,we have another way, besides being a version, in which an account weterm an ‘explanation’ can vary considerably from an account which theunification theory would pick out as an ideal one. Furthermore, if versionsare considered explanatory, and if a part of an explanation can be consid-ered an explanation, we should not be surprised to find that portions of aversion can also be considered explanatory. We needn’t look at too many


cases to see that we routinely do consider such partial high level accountsexplanatory (as in the Hanson case).

In allowing portions of explanations to be considered explanatory, ouruse of the term “explanation” becomes considerably more liberal than itwould be if we reserved the term for ideal accounts only. Instead of havingto specify each and every detail of, say, what made the nuclear accidentat Chernoble inevitable, we will often accept very small portions of thestory as explanations of what happened. Our allowing not only portionsof ideal accounts, but portions of versions of ideal accounts makes thenotion of explanation still more liberal, enabling a host of vague, highlevel partial accounts to seem intuitively explanatory. But allowing suchliberality is no defect for a theory of explanation. Our intuitive notion ofexplanation is, indeed, a very broad and liberal one – and any adequatetheory of explanation must accommodate this fact. Such liberality in oureveryday use of the term ‘explanation’ is likely to be what tempts peoplelike van Fraassen or Achinstein to stop looking for a systematic underlyingtheory of explanation. It leads Salmon and Railton to claim that thereis merely a continuum of explanatoriness – with some information thatmerely talks about ideal accounts lying toward one end of the continuum.What I have been claiming is that such responses are both unnecessary andincorrect. The liberality of our notion of explanation, can be perfectly wellaccommodated within the systematic, restrictive account of explanationprovided by the unification theory. We need only widen the theory by notingthat our ordinary notion of explanation considers versions and portions ofideal explanations, as well as ideal ones as counting as explanatory. Nothingis an explanation unless these requirements are met.

One remaining concern is the issue of which portions of ideal or non-ideal explanations count as explanatory? Clearly not all portions do at alltimes. It is here, I suggest, that we likely really do have the anarchy thathas lead many to despair of finding a systematic account of explanation.Saying “clouds discharge their excess static electricity” may seem like aperfectly legitimate explanation of the appearance of lightning to a curiousteenager, but not to a meteorologist surprised by the sudden presence of astorm. What determines the difference?

I think we have no basis for being optimistic about philosophers ofscience finding anything systematically interesting about which portionsof explanation will count as explanatory to various people at various times.I believe this will always depend on idiosyncratic facts about why theasker wants to know the information and what background informationshe has. Again, the Hanson car wreck case illustrates this point nicely.Talking about a multiple hemorrhage will not count as an explanation of

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the man’s death for the lawyer (although it will for the doctor). People withdifferent interests and concerns will be interested in different portions of adetailed underlying text, and may consider only these portions “explanato-ry” answers to their questions. Which portions and how large any of theseportions needs to be for an account to be considered explanatory is like-ly to be determined by a host of additional pragmatic context-dependentconsiderations.

Our situation, then, is that part of what determines what people willcount as an explanation consists of a large host of pragmatic, context-sensitive, difficult to systematize considerations. It is little wonder thatmany have concluded that we should despair of trying to give a systematicunderlying account of explanation. What this attitude overlooks, however,is that these unruly anarchic considerations are ones that are additionalto systematic central ones determining what is and isn’t an explanation.It is true that different people are interested in different parts of a fullexplanation of a state of affairs. It is true that different people put differentadditional requirements on which pieces of information that they willcount as explanatory. But that is all perfectly consistent with there beingan underlying systematic theory about what sort of thing an explanation is.In my view, the unification theory provides the best theory to date of whatwe fundamentally consider explanations to be. Accounts which meet thecriteria laid out in the unification theory give us ideal explanations. I havebeen arguing that certain accounts which are related to these ideal accountsin particular ways can also be considered explanatory. The unificationaccount thus tells us what sort of thing an explanation is, and what minimalrequirements must be met to be considered one. Various people, in variouscircumstances, may place idiosyncratic difficult-to-systematize additionalconstraints determining which portions of a non-ideal account they willconsider explanatory. This makes it difficult to tell which sorts of accountspeople will consider explanatory when, but it in no way means that theunification theory cannot give us a systematic theory of what explanationsis.

10. CONCLUDING REMARKS

We began this paper with a puzzle for the unification theory. The unificationtheory of explanation seemed to be set up in such a way that only the mostreductive accounts could properly be termed explanatory. Yet this is notwhat we find in actual scientific practice. What I have suggested here isthat this predilection for reductionistic theories is not incorrect when weare discussing ideal scientific accounts (when multiple realizability is not


involved). But it is important to realize that we use the term “explanation”to also cover other, non-ideal accounts. In this paper I have attempted tosay something about which non-ideal accounts can be explanatory. Mysuggestion is that a minimal constraint on all accounts we tend to considerexplanatory is that such accounts be viewable as versions of the idealaccounts, or portions thereof. If a non-ideal account meets these minimalrequirements for explanatoriness, along with various additional context-dependent requirements, then it can be considered an explanation, evenif a more reductive, more unifying account is available. Our desire tohave a unified understanding of the world, where we reduce the numberof mysterious fundamental givens, and our pragmatic desires to efficientlyobtain relevant information do not conflict. What we term an “explanation”is often a result of their intricate combination.

NOTES

1 Another tempting “quick fix” is Hempel’s response to similar worries. Hempel (1964,427) merely declared that in actual practice, we are not required to give the full covering lawaccount – which is the real underlying explanation – when various parts of it are well known.However, this solution seems unavailable to Kitcher. The covering law model allowed allkinds of various and sundry high level laws to be part of the underlying explanation. Evenif we didn’t name them each time we gave an explanation, they were still a legitimate partof the underlying explanation. Kitcher’s view, on the other hand, looks like it doesn’t allownon-unifying terminology to be part of legitimate explanations at all – so the problem isnot just one of pragmatic curtailment.

In the solution I discuss here, I attempt both to say more about which actual pragmaticaccounts can be termed explanatory and about how pragmatic considerations can be madeto fit with Kitcher’s somewhat more restrictive view of explanation.2 Kitcher also recognizes a distinction between ideal and actual explanations (see 1989).Yet he seems to have a much narrower view of actual explanations than the view describedhere, and he does not use this point to address the issue of non-reductive explanations.3 With this definition, the high level theory has to have a narrower relationship to theideal account than merely being a true description of it to count as a version of it, and,consequently, as an explanation. At the same time this relationship is looser than the highlevel’s theory being “reducible” to the lower level account. (Though high level theories thatare strictly reducible are subsets of this larger set of versions). This looseness is surely avirtue, as there have been precious few cases in which the classical requirements for beingreducible have actually been met (see Feyerabend 1962; Churchland 1986; Maull 1978).4 It is possible, of course, that, ultimately, no systematic underlying theory detailing ourintuitions about versions will be found. It may be that our intuitions here are various,context sensitive and idiosyncratic. It is hard to know where to begin, for example, findinga systematic theory of what counts as a version of say, a fable. Does a version of LittleRed Riding need to mention a wolf, a grandmother, a walk through the woods? In morescholarly contexts it has often proved just as difficult to say when one theory is a versionof another. Consider the acrimonious debates in transformational linguistics about whether

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one theory should count merely as a “notational variant” of Chomsky’s standard theory(Chomsky 1980). Rorty (1979), and Stich (1996) have recently argued that we don’t evenhave systematic intuitions about when two terms have the same referent – a far clearernotion than that of version. Yet even if it turns out there is no systematic theory to be had,here, it is certainly worth the effort to look for one.5 Note, however, that in discussing this constraint, I, like Lewis with regards to reference,have said nothing about the degree to which the high level theory must be wrong aboutfactors present before it become impossible for it to count as a version of an ideal one.Exploring this question would be an example of a project for future philosophical researchin this realm.6 Similar considerations, I believe, apply to the famous hexed salt example. Explaining acase of dissolving by saying “hexed salt always dissolves in water” refers to a mixture ofproperties held by the salt, but specifically highlights one of the properties in that mixturethat does not actually play a role in the underlying explanation of the process in question.Indeed, saying it dissolves merely because “the salt in this shaker dissolves in water” wouldbe disqualified for the same reasons.

There is a second reason that referring to mixtures can also be explanatory. Some-times referring to the whole mixture tells you something about the means by which theparticular subpart was able to be involved. Hence, “the crops were destroyed by acid rain”,can be explanatory, even if it was the acid and not the rain that was responsible for thecrop damage. Mentioning rain, here tells you how the acid came into contact with the crops.

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Department of PhilosophyUniversity of Nevada, Las VegasLas Vegas, NV 89154U.S.A.E-mail: [email protected]

Unification, Reduction, and Non-Ideal Explanations

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