realism, ramsey sentences and the pessimistic meta-induction

Studies in History and Philosophy of Science 41 (2010) 375–385

Contents lists available at ScienceDirect

Studies in History and Philosophy of Science

journal homepage: www.elsevier .com/ locate/shpsa

Realism, Ramsey sentences and the pessimistic meta-induction

David PapineauDepartment of Philosophy, King’s College London, Strand, London WC2R 2LS, UK

a r t i c l e i n f o a b s t r a c t

Keywords:ScienceRealismRamsey sentencesApproximate truthReference

0039-3681/$ - see front matter � 2010 Elsevier Ltd. Adoi:10.1016/j.shpsa.2010.10.002

E-mail address: [email protected]

This paper defends scientific realism from the pessimistic meta-induction from past reference failure. Itallows that a descriptive theory of reference implies that scientific terms characteristically fail of deter-minate reference. But it argues that a descriptive theory of reference also implies an equivalence betweenscientific theories and quantificational claims in the style of Ramsey. Since these quantificational claimsdo not use any of the referentially suspect scientific terms, they can be approximately true even whenthose terms fail to refer determinately.

� 2010 Elsevier Ltd. All rights reserved.

When citing this paper, please use the full journal title Studies in History and Philosophy of Science

1. Realism under threat

1.1. Introduction

The empirical evidence often justifies belief in scientific theo-ries. For instance, the great wealth of chemical and other relevantdata leaves us with no real alternative to believing that matter ismade of atoms. Similarly, the natural history of past and presentorganisms makes it irrational to deny that life on earth has evolvedfrom a common ancestry. Again, the character and epidemiology ofinfectious diseases effectively establishes that they are caused bymicrobes. Peter Lipton did much to illuminate the logic of theseand many similar inferences. Often the observed facts admit ofonly one good theoretical explanation. Rationality therefore dic-tates that we infer the truth of this explanation. (Lipton, 1991/2004.)

In this paper I shall assume that abductive inferences of thiskind can be legitimate. Of course, the observed facts will neverforce a theoretical conclusion by logic alone. Since theories saymore than their observable implications, there is always the logicalpossibility of alternatives to even the very best explanation. Per-haps the chemical facts appear as they do, not because there areatoms, but because tiny green men are constantly labouring tomake it seem as if there are atoms. But this kind of purely in-principle ‘underdetermination of theory by the evidence’ cannot

ll rights reserved.

by itself discredit abductive inferences. To suppose that the merelogical possibility of error discredits a form of inference is to setthe standards too high. Apart from anything else, this would ruleout any knowledge of the future, let alone of the unobservableworld.

So I shall take it that we are entitled to believe a theory whenthe only other options consistent with the evidence are cooked-up alternatives with no serious pretensions to truth. Of course,scientists aren’t always in the happy circumstance where thedata rule out all but one substantial explanation. Often they willbe faced with a number of real options, not just silly cooked-upconstructions. But science is extremely ingenious at uncoveringor engineering new evidence that can eliminate serious candi-dates from such competitions, and often enough this process ofelimination proceeds until only one real explanation is leftstanding, and the only other alternatives still consistent withthe data are mere logical possibilities unworthy of seriouscredence.

1.2. The pessimistic meta-induction

So the ‘underdetermination of theory by evidence’ is no reasonto reject the realist contention that we can know our best scientifictheories to be accurate descriptions of reality. My focus inthis paper will rather be on a different threat to scientific

http://dx.doi.org/10.1016/j.shpsa.2010.10.002

mailto:[email protected]

http://dx.doi.org/10.1016/j.shpsa.2010.10.002

http://www.sciencedirect.com/science/journal/00393681

http://www.elsevier.com/locate/shpsa

376 D. Papineau / Studies in History and Philosophy of Science 41 (2010) 375–385

realism—namely, the ‘pessimistic meta-induction’ from past theo-retical failures. If we look back at the history of science, we findthat many previously accepted theories are now discarded. Nodoubt the scientists of the time thought that their favouredtheories were the only possible explanations of the data. But withhindsight we can see that they were wrong. The ‘pessimistic meta-induction’ draws the obvious moral. Science characteristicallyoverextends itself when it judges that the empirical evidencefirmly establishes some theory. So it would be a mistake to viewthe theories currently favoured by contemporary science as estab-lished knowledge. (Laudan, 1981.)

A first response to this argument is that it paints with too broada brush. It lumps theories of very different kinds into one referenceclass. In particular it does not discriminate between theories sup-ported by a great deal of evidence and those supported by very lit-tle. Many of the theories accepted in the history of science had nosubstantial empirical support. There was very little evidence forhumoural medicine, alchemical theories of matter, or the miasmatheory of disease. So there is no reason to suppose that the failureof theories like these discredits the far more strongly evidencedtheories of modern science.

However, this response only takes us so far. For not all past the-oretical failures can be attributed to poor evidence. Many theoriesthat we now reject once claimed a significant amount of empiricalsupport. It would be silly to say that there was little evidence forclassical mechanics, say, or the caloric theory of heat, or theaether-based theory of electromagnetic radiation. And so the fail-ure of these theories really does cast serious doubt on our pres-ent-day theories. If even well-supported theories like these canturn out to be false, then who is to say that some of our most fa-voured current theories may not fail too?

At this point it is natural to appeal to a different strategy. Maybea number of well-evidenced past theories have since been dis-carded. But none of these theories was completely mistaken. Theymay have involved some false assumptions, which is why we nolonger uphold them. But nevertheless they can be deemed to havebeen approximately true. And this then suggests that we can re-spond to the pessimistic meta-induction by maintaining that ourcurrent theories are no doubt approximately true too. Of course,this is less than holding our present-day theories to be fully true.But it would be very ambitious indeed to claim that our currenttheories are true in every last respect—especially given the evi-dence that many highly-evidenced past theories have containedat least some mistakes. If we are to uphold some version of scien-tific realism, it would seem sensible to settle for the lesser claimthat our current theories are approximately true, not true in everydetail.

As is well-known, the notion of approximate truth is notstraightforward. However, I shall say little in this paper aboutalternative ways of regimenting this notion. I take one lesson ofthe last few decades of research into this topic to be that there isno good notion of approximate truth tout court. If we are to speakof approximate truth, we need to specify the respects in which weare comparing our theory with the truth. For example, in thinkingabout classical mechanics, how much weight do we put on accu-racy with respect to bodies moving at relatively low speeds in cer-tain privileged reference frames, and how much on other cases?Clearly there is no ‘objective’ answer to such questions. It is simplya matter of which areas of application we place most weight on.Still, even if the notion of approximate truth needs to be relativizedin this way, this does not empty it of interest. In particular, it canstill play a role in responding to the pessimistic meta-induction.Suppose that past theories have at least proved approximately truein certain specific respects. Then it is open to us to argue that thehistory of science gives us reason to suppose that present-day the-ories are also approximately true in these same respects.

1.3. Questions of reference

However, as I said, I do not want to dwell on the knotty notionof approximate truth in this paper. Rather my main concern will bewith something that is generally supposed to be a precondition forapproximate truth, however the latter is understood—namely, suc-cessful reference. In general, claims made using non-referringterms are either false or truth-valueless. In order to speak truly,you must first make contact with reality. So it looks as if a theorymust make successful reference to real-world entities if it is to beso much as a candidate for approximate truth. If its terms don’t re-fer to anything, then there doesn’t seem to be any question of howfar the theory describes its subject matter accurately.

However, if this point is granted, then it looks as if realism is introuble once more. For many past theories were not only false, buthad central terms that failed to refer. Nor can this objection beblocked by claiming that it is only poorly evidenced past theoriesthat so failed to refer. For non-referring terms are not peculiar tosuch groundless theories as humoural medicine or the miasmatheory of disease. Along with humours and miasmas, we now alsoreject gravitational forces, caloric fluid, and the aether. But, as ob-served above, Newtonian gravitational theory, the caloric theory ofheat, and nineteenth-century electromagnetism were highly con-firmed theories, if any are. So it seems that even highly confirmedtheories can fail to be approximately true, for want of successfulreference.

One popular realist response to this objection is to querywhether the central terms of such highly confirmed theories reallyfailed to refer. Advocates of this line typically argue that wide-spread attributions of reference failure stem from an excessivelydescriptivist approach to reference, and can be avoided if we adopta more sophisticated causal theory of reference. Where descriptivetheories of reference are ‘stingy’, in the sense that they are quick toattribute non-reference to past theories, causal theories are more‘generous’, and imply that far more past terms succeeded in refer-ring to real entities.

To see why this is so, note that descriptive theories of referencemaintain that any referring term latches onto that entity that sat-isfies some set of associated descriptions accepted by users of theterm. Now, there are familiar issues about exactly which descrip-tions are relevant to so fixing reference. But without trying to de-cide this issue here—it will figure prominently in what follows—we can see how the descriptive theory will be relatively quick toimply that old terms failed to refer. Thus suppose that the term‘aether’ referred to that entity, if any, that satisfies such descrip-tions as ‘medium for the propagation of electromagnetic radiationin accord with Maxwell’s equations’, ‘elastic solid’, and ‘at rest inabsolute space’. Since in reality there is no entity that satisfies allthese descriptions, it would then follow that ‘aether’ does not refer.

And more generally the descriptive theory will tend to implythat the entities posited by past theories do not exist, for want ofanything that satisfies all the relevant descriptive demands. Grav-itational forces do not exist, since there are no dynamic agents thatsatisfy the classical law of universal gravitation. Caloric fluid doesnot exist, since there is no fluid that is responsible for the phenom-ena of heat. And so on.

By contrast, causal theories of reference theories will tend touphold the referential success of past theories. On the causal view,reference is not fixed descriptively, but via some kind of initialdubbing or ostension. The relevant term then spreads causallythrough the community and continues to refer to the originalbearer. (Kripke, 1980.) In the case of theoretical terms in science,we can think of scientists as initially pointing to some observablephenomenon (gravitational motion, heat transfer, light) and thencoining a term for its unobservable basis. (Putnam, 1973.) On thiscausal account, then, the scientists’ theories about the nature of

D. Papineau / Studies in History and Philosophy of Science 41 (2010) 375–385 377

these entities play no role in fixing the reference of their terms, andso their theoretical mistakes threaten no reference failure. Insteadtheir terms simply refer to the actual entities underlying the rele-vant phenomena. So ‘gravitational force’ comes out as referring tospace-time curvature, ‘aether’ as referring to the electromagneticfield, and ‘caloric’ as referring to kinetic energy. The scientistswho coined these terms may have had mistaken theories aboutthese entities, but they were referring to them for all that.

The causal theory of reference thus promises to block the threatof reference failure. However, the trouble is that the causal theorylooks too good to be true. After all, it is by no means intuitivelyobvious that we want to count ‘gravitational force’, ‘caloric’ and‘aether’ as genuinely referring terms. Even worse, the causal theorythreatens to attribute reference in yet more dubious cases. If point-ing to some observable effect can secure reference to an underlyingcause, then why shouldn’t ‘miasma’ refer to infectious microbesand ‘phlogiston’ to an absence of oxygen? But something hasclearly gone wrong if our theory of reference ends up attributingreference to paradigm non-referring terms like these.

1.4. Descriptive realism

In response to this worry, some defenders of realism have soughtto elaborate ‘hybrid’ theories of reference. Their aim is to devisesome mix of causal and descriptive requirements which will begenerous enough to attribute reference to terms in well-supportedmature theories, while not being so open-handed as to do the samefor ‘miasma’ and ‘phlogiston’ (for example, Newton-Smith, 1981;Hardin & Rosenberg, 1982; Kitcher, 1993; Psillos, 1999). But by thisstage the argument is starting to look somewhat strained. Does thesuccess of scientific realism really depend on whether some fine-tuned theory of reference can discern enough (but not too much)referential success in past scientific theories? If we are to be realists,we need to be able to maintain that successful past theories are byand large approximately true. But it seems odd to suppose that thisissue hinges crucially on delicate semantic issues about the preciseline between referring and non-referring terms.

My aim in what follows will be to back up this suggestion byshowing how we can uphold the approximate truth of past theo-ries even if we embrace a purely descriptive theory of referencethat implies that the central terms in those theories failed to refer.So I will be questioning the widely-held assumption that successfulreference is a precondition for approximate truth. Against this, Ishall argue that a descriptive theory of reference offers a way ofunderstanding scientific theories on which reference is irrelevantto approximate truth. On this construal of scientific theories, atheory can be approximately true even if none of its central termsrefer successfully.

In arguing this, however, I shall not be attempting to defend thedescriptive theory of reference against the causal theory. Thatwould take me far beyond the scope of this paper. Even so, I do in-tend the argument of this paper as a defence of scientific realism.You can think of me as arguing in the alternative. Either thedescriptive theory of reference is right, in which case we can haveapproximate truth without successful reference, as I shall show be-low. Or alternatively the causal theory of reference is right, inwhich case approximate truth isn’t threatened by reference failurein the first place. So either way scientific realism will be all right.

For what it is worth, though, I do think that there are good argu-ments for viewing many scientific terms descriptively. For mosteveryday terms, there seems no doubt that the descriptive theoryof reference is mistaken. Names of people, places, and many natu-ral kinds lock onto to their referents in a way that owes little ornothing to our possibly mistaken ideas about their distinctive fea-tures. Any kind of initial contact is often enough to fix reference forterms of this sort. But in the special case of theoretical terms in

science, we often aim to refer to quite unfamiliar kinds of thing,and we may need to appeal to theoretical descriptions to specifywhat sort of entity we are aiming to attach our term to (cf Papi-neau, 1979, ch. 5.7). Moreover, there may be no opportunity forany ‘initial contact’ in the absence of our theoretical descriptions,since the putative referent may not yet have displayed any distinc-tive observable manifestations which may serve as the basis forsome ostensive identification. (The Higgs boson at the time of writ-ing would be a case in point.) For both these reasons, it looks as iftheoretical descriptions often play an essential role in fixing thereferents of scientific terms, and moreover that they do so in sucha way that the terms will fail to refer if nothing in reality satisfiesthese descriptions.

Of course, there is much more to say about this topic. There aremany dimensions to the debate between causal and descriptivetheories of reference, and these brief remarks leave many issuesunaddressed. I offer them only as some motivation for my concernin this paper with the consistency of scientific realism with thedescriptive theory of reference. Still, as I said, my overall defenceof realism does not depend on the descriptive theory. For thosewho remain unpersuaded that the descriptive theory offers theright account of scientific terms, I can retreat to my argument inthe alternative—it doesn’t matter to realism whether the causalor descriptive theory is right, since realism will be fine either way.

2. Theories and descriptions

2.1. Quine’s verificationism

In this second part of this paper I shall temporarily turn awayfrom issues of scientific realism, and instead concentrate on thedescriptive approach to reference for scientific terms. My aim willbe to show how a descriptive theory can best be developed in theface of some familiar difficulties. In the third and final section Ishall then return to realism, and show how it can be defended inthe context of the resulting descriptive theory.

An initial difficulty facing any descriptive theory of reference isQuine’s attack on the analytic-synthetic distinction (Quine, 1951,1960). Quine argued that we cannot separate the descriptiveassumptions in a scientific theory into those that play a role in con-stituting the meanings of theoretical terms and those that do not. Ifwe combine this with the assumption that the meanings of theo-retical terms must somehow be constituted by the theoreticalassumptions they enter into, then it is difficult to avoid the holistconclusion that all theoretical assumptions together play a role infixing the meanings of theoretical terms. And this then threatensan extreme degree of stinginess on the part of descriptive theoriesof reference, for now it is hard to avoid the unhappy consequencethat any scientific term will fail of reference as soon as any of theassumptions in the surrounding theory turns out to be false. Thislooks bad, not just for scientific realism, but for the whole idea thatthe reference of scientific terms is determined descriptively.

To assess Quine’s attack on the analytic-synthetic distinction,we need to disentangle two distinct strands in his thinking—hisholism and his verificationism. I shall be arguing that there is sometruth in Quine’s holism, but that we can only appreciate its signif-icance once we disassociate it from his misguided verificationism.

Quine’s holism consists in the view that all theoreticalassumptions alike play a role in breathing meaning into theoret-ical terms. His verificationism then lies in the further thoughtthat meaning is use—that is, that attaching a meaning to a termis a matter of being disposed to use the term a certain way, byasserting sentences involving it on the basis of sensory stimulior other information, and in turn inferring further claims fromsentences involving it.

‘the U such that (E!X , . . . , X )(T(U, X , . . . , X )’


It is not difficult to show that Quine’s verificationism is prob-lematic, whatever we think of his holism. Note how his verifica-tionist view of meaning implies a particular kind of connectionbetween theories and the meanings of scientific terms. The mean-ings you attach to a scientific term will depend on what theoriesyou accept. This is because the theories you accept influence theway you use scientific terms. For example, if you accept the phlo-giston theory of chemistry, then you will hold that burning causesair to become saturated with ‘phlogiston’, that ‘dephlogisticated’air is easily breathable, and so on. Similarly, if you accept the atom-ic theory of matter, you will deem water to be made of hydrogenand oxygen ‘atoms’, hold that different elements are each madeof a distinctive kind of ‘atom’, and so forth. So, from the verifica-tionist perspective, your commitment to these theories will deter-mine the meanings you attach to ‘phlogiston’ and ‘atom’. Since thetheories affect your dispositions to apply these terms, they affectthe meanings you attach to these terms.

There are many objections to this verificationist account of theconnection between theories and meanings. Most immediately, itimplies that people who accept different theories involving someterm will automatically attach different meanings to that term.This then leads to the doctrine of ‘incommensurability’, accordingto which the adherents of different theories are unable to commu-nicate, for lack of any terms with common meanings. One particu-larly graphic consequence of this doctrine is that it becomesimpossible to use the terms of some theory to reject the entitiesposited by that theory. For example, we can’t express our disbeliefin the ontology of the phlogiston theory by saying ‘there is no phlo-giston’. Since we non-believers use the term ‘phogiston’ differentlyfrom those who embrace the phlogiston theory, this denial won’tmean the same to them as it does to us.

Note that these unfortunate consequences of the verificationistapproach are largely independent of the holist doctrine that alltheoretical assumptions make a difference to meanings. For similarresults follow as soon as the acceptance of any substantial set ofassumptions with synthetic consequences are deemed to affectmeanings. This alone will imply that those who disagree about thisset of assumptions will attach ‘incommensurable’ meanings to therelevant terms, that we cannot use the terms embedded in theseassumptions to reject the entities they posit, and so on.

The real source of these problems is nothing to do with hol-ism, but rather lies in the verificationist view that meaning canbe influenced by synthetic commitments. Once we allow thatuse determines meaning, and therewith that the adoption ofempirical claims affects meanings by affecting the way we useterms, then there is no avoiding the conclusion that people whoembrace different synthetic claims will attach different meaningsto their terms.

2.2. Non-verificationist descriptivism

There is a quite different non-verificationist way of thinking ofthe connection between theories and meanings that avoids theseproblems. On this alternative conception—I shall call it the‘descriptivist’ account—the meanings we attach to our terms donot depend on what theories we accept, but simply on what theo-ries we understand. We grasp the meaning of a theoretical term byappreciating the descriptive content associated with the relevanttheory. And it is perfectly possible to appreciate this content with-out actually accepting the theory.

To see in more detail how this works, suppose that therelevanttheory involving some term ‘F’ is ‘T(F)’. Then it is open tous to regard the term ‘F’ as having its reference fixed via thedescription ‘the U such that T(U)’. That is, ‘F’ can be understood asreferring to the unique U that satisfies the assumptions in ‘T’, if thereis one such thing, and to fail of reference otherwise. In this spirit, we

might regard ‘atom’ as referring to a category of entities, if there isone, of which there is one type for each element, which combine insimple whole number ratios, which cannot be destroyed by chemicalmeans, and so on. Again, we might regard ‘phlogiston’ as referring tothe substance, if there is one, that is emitted in combustion, absorbedduring chemical reduction; and so on.

On this descriptivist account, there is still a close connection be-tween meanings and theories. But the meanings of your terms nolonger depend on which theories you accept. Which theories you ac-cept will of course affect your dispositions to apply terms. But fornon-verificationists this won’t make a difference to the meaningsof the terms themselves. Even though I reject the phlogiston theory,and so use the term ‘phlogiston’ quite differently from the eigh-teenth-century chemists who endorsed the theory, this doesn’t stopme meaning the same by the term as they did (and so being able todeny what they think simply by saying ‘there is no phlogiston’). Forwe can all understand the term ‘phlogiston’ as equivalent to the rel-evant description—the putative substance that is emitted duringcombustion and absorbed during reduction – independently ofour divergent views as to whether this description is satisfied.

In line with this, note that on the descriptivist account themeaning you attach to a term is independent of your syntheticcommitments. Somebody who understands a term ‘F’ in terms ofsome theory ‘T’ will be committed to the ‘Carnap sentence’ of thetheory—‘if (E!(U)(T(U)), then T(F)’—but this claim will be analyticnot synthetic. For example, your understanding of the term ‘phlo-giston’ will commit you to the relevant analytic claim, that ‘if thereis a specific substance emitted during combustion and absorbedduring reduction, then it is phlogiston’. But you needn’t therebybe committed to the synthetic commitments of the phlogiston the-ory itself.

From the descriptivist perspective, the original theory ‘T(F)’ canbe decomposed into the analytic Carnap sentence and the syn-thetic ‘Ramsey sentence’ of the theory—‘(E!(U)(T(U))’. The Ramseysentence expresses the substantial commitments of the theory—there is a specific entity which . . .—while the Carnap sentence ex-presses the definitional commitment to dubbing that entity ‘F’. Theoriginal theory framed using the term ‘F’ is thus equivalent to theconjunction of the Ramsey and Carnap sentences. Using the term‘F’ commits you to the definitional Carnap sentence (‘if there is aspecific substance emitted during combustion . . . , then it is phlo-giston’) but not to the substantial Ramsey sentence (‘there is sucha substance’).

So far I have been considering how a single term ‘F’ can be de-fined in terms by some set of theoretical assumptions ‘T(F)’. But ofcourse any scientific theory will contain a number of theoreticalterms all of which will call for a similar definition, and whosemeaning cannot therefore be presupposed if we are aiming for ageneral explanation of how descriptive definitions of theoreticalterms work. The solution is to quantify into the position of theseother terms when defining any given term. That is, we can defineany given such term as equivalent to ‘the entity such that thereare some other entities which are related to each other and tothe first entity in the way specified by the theory’.

More formally, suppose ‘F1’, ‘F2’, . . . , ‘Fn’are the relevant terms in‘T(F1, F2, . . . , Fn)’. Then we can define ‘F1’ as

2 n 2 n

and similarly for the other ‘F’s.However, I shall simplify what follows by assuming, as before,

that we are only defining one theoretical term at a time. This ispurely for expository convenience. As just explained, there is noproblem in extending the technique to allow the coordinateddescriptive definition of a number of terms. (Cf Lewis, 1970;Papineau, 1996.)


Of course, If we are going to define a number of theoreticalterms by what some theory says about them, then there had betterbe some other terms in the theory that are not so descriptively de-fined. We will need some non-logical terms whose meaning issomehow non-descriptively given, if we are to succeed in explain-ing the meaning of other terms in terms of them. However, I shallnot pause to discuss the availability of such independently mean-ingful terms at this stage. In section 3.2 below I shall explain howto think about this issue in the context of the pessimistic meta-inductive threat to realism. Until then let us simply assume thatthe theories at issue contain enough terms with non-descriptivecontents for the meanings of the other terms to be fixeddescriptively.

2.3. Indeterminacy of theoretical reference

In what follows I shall assume the descriptivist account of theconnection between theories and meanings in place of Quine’s ver-ificationist perspective. Still, this may not seem to make a greatdeal of difference to the viability of a descriptive theory of refer-ence for scientific terms. For we are still left with Quine’s holism,and this threatens comprehensive reference failure within thedescriptivist framework just as much as within the verificationistone.

Thus suppose that all the assumptions of the atomic theory con-tribute to the description that fixes the reference of the term‘atom’. Then the term ‘atom’ will fail of reference as soon as anyof those assumptions is erroneous. For example, suppose that thetheory has the mass of carbon atoms marginally wrong. Then therewill be no category of entities, one sort for each element, and soforth, and with the carbon sort of entity each of mass such-and-such. And so, according to the descriptive account as elabo-rated so far, the term ‘atom’ will fail of reference. And, in general,if all the assumptions of a scientific theory are packed into thedescriptions that fix the meanings of its terms, then those termswill fail of reference except in the unlikely event that the theoryis accurate in every last particular.

Still, perhaps we can embrace the spirit of Quine’s holism with-out being driven to this extreme ascription of reference failure. It isnot clear that Quine’s arguments really establish that all theassumptions in a theory play a definitional role. I think we canaccommodate Quine’s thinking just as well if we say that it is oftenindeterminate which assumptions play a definitional role.

The basic truth behind Quine’s arguments is that there is oftenno fact of the matter whether or not some assumption is part of themeaning of some term. Is it part of the meaning of ‘virus’ thatviruses have a protein coat? Is it part of the meaning of ‘photon’that photons have integer spin? Is it part of the meaning of ‘energy’that energy is conserved? With these and many other similar ques-tions there seems no good reason to answer one way or the other.Nothing in scientific practice seems to hang on whether or notthese assumptions are built into meanings of the relevant terms.

At the same time there are plausible limits to this Quinean inde-terminacy. Some assumptions look as if they definitely don’t con-tribute to meanings. For example, there is surely somethingimplausible in the supposition, floated a couple of paragraphs back,that a precise value for the mass of carbon atoms might be builtinto the meaning of ‘atom’. On the other side, it is arguable thatsome assumptions definitely do play a role in fixing meaning. Thusit would be hard to deny that it is part of the modern meaning of‘atom’ that there is one kind of atom for each element.

I have argued in previous papers (see especially Papineau, 1996)that the best way to accommodate Quine’s holist insights is to rec-ognize that many theoretical terms in science display a certainkind of semantic indeterminacy. While their reference may befixed by association with theoretical descriptions, there is no

precise answer as to exactly which descriptions enter into this ref-erence-fixing role. No doubt we can rule out some descriptions(carbon atoms have such-and-such mass) as definitely not makinga semantic contribution. And there are no doubt some otherdescriptions (atoms come in one kind for each element) that domake such a contribution. But in between there will be a widerange of descriptions where it is simply indeterminate whetherthey are part of the meaning of the relevant term or not.

We can see why scientific practice is in general happy to toler-ate such indeterminacy. Suppose you have some fully detailed the-ory ‘T(F)’. Since the theory contains a lot of detail, you doubt thatthere is any category satisfying every last thing the theory saysabout F. Still, you are confident that some minimal core set of cen-tral assumptions suffices to identify a unique referent for ‘F’. More-over, you are confident that this referent also satisfies a lot of theother claims made by the theory. In this typical kind of case, youwill be indifferent between a wide range of different ways of defin-ing ‘F’. For all these alternative definitions will serve to fix exactlythe same reference for ‘F’.

To see clearly how this will work, let us divide the assumptionsin ‘T(F)’ into

(i) ‘Ty(F)’—those minimal core assumptions that are needed toidentify a unique referent for ‘F’

(ii) ‘Tp(F)’—those further assumptions that can reasonably beassumed also to be true of F

(iii) ‘Tn(F)’—the remaining assumptions including more detailedclaims that are unlikely all to be true of F.

Using this symbolism, we can see that any set of descriptionswhich includes ‘Ty((F)’ (‘y’ for yes) and excludes ‘Tn(F)’ (‘n’ for no)can be expected to identify just the same identity, however manyof the assumptions in ‘Tp(F)’ (‘p’ for perhaps) are or are notincluded.

This is why we get no definite answer when we ask such ques-tions as: is it part of the meaning of ‘virus’ that viruses have a proteincoat? Microbiologists have never bothered to answer this questionbecause they know it doesn’t matter. You might define ‘virus’ viathe description ‘infectious agent that is smaller than bacteria andcan only reproduce within host cells’. Or you might define it as ‘infec-tious agent that is smaller than bacteria and can only reproducewithin host cells and has a protein coat’. But nobody is going to loseany sleep wondering which of these is the ‘right’ definition. Exactlythe same category is going to be picked out either way.

The point generalizes. No scientists agonize abut whether it ispart of the meaning of ‘photon’ that photons have integer spin,or of ‘energy’ that energy is conserved, or so on, for the simple rea-son that they are confident that however they decide the issue itwill make no difference to what the terms refers to.

Of course, in some special cases the scientists turn out to bewrong to suppose that such definitional issues do not matter,and then they will need to make a decision in order to ensure thattheir term has a definite referential value. These will be caseswhere there is in fact no entity that satisfies all of ‘Ty(F) & Tp(F)’.Then it will indeed matter how much of ‘Tp(F)’ is included in thedefinition. If all of ‘Tp(F)’ is included, then ‘F’ will fail of reference,but a less specific definition may well deem ‘F’ to refer. For in-stance, take the Newtonian term ‘mass’. Suppose that ‘Ty(F)’ con-sists of ‘proportional to amount of matter, inversely proportionalto acceleration’. But what about ‘independent of velocity’? Wasthat part of the definition or not? Of course Newtonian physiciststook no view on this, since they thought the same quantity wouldbe picked out either way. But they were wrong, since there is noactual quantity that satisfies all of ‘proportional to amount of mat-ter, inversely proportional to acceleration and independent ofvelocity’. If the term ‘mass’ has this inclusive definition, then it


does not refer to anything. On the other hand, if ‘independent ofvelocity’ is not part of the definition, then the term ‘mass’ does re-fer to a real quantity, relativistic mass.

In this kind of case there is no fact of the matter about what theold term actually referred to. Since the users of the term never sawthe need to be specific about their definition, their term was inde-terminate in reference. On one way of refining ‘mass’’s meaning, itrefers to nothing. On another way of refining the meaning, it refersto relativistic mass. (Cf. Field, 1973).

Once we realize that this is the situation, then of course we willsee that we need refine the definition of the term one way or theother in order to secure a definite content. I take it that in the caseof ‘mass’ our current understanding does not require independenceof velocity and so has it referring to relativistic mass. But weshould not therefore suppose that something in the pre-relativisticunderstanding of the term made this the right way to go. It wouldhave been equally consistent with the indeterminate original New-tonian usage to deem velocity-independence to have been part ofthe meaning and thus to conclude that ‘mass’ lacks any reference.

This kind of case—where a supposedly harmless indeterminacyof descriptive definition turns out to generate a real indeterminacyof actual-world reference—is not uncommon. Was it part of thepre-relativistic meaning of ‘straight line’ that parallel straight linescan never meet? Was it part of the nineteenth-century meaning ofthe word ‘atom’ that the atoms for each element are all absolutelyidentical? Questions of this kind are easily multiplied. If in suchcases the extra assumptions come to be viewed as part of the def-inition, then the term will be deemed to lack reference. If not, thenthe term will be deemed to refer successfully. Once it is seen tomatter, precision is added to the definition in one way or the other.But this choice of whether or not to deem ‘mass’ to refer (and sim-ilarly with ‘straight line’, ‘atom’, ‘caloric’, ‘aether’, . . . ) should notbe thought of as determined by prior usage, but rather as a freedecision to refine our language in one way rather than another.

If there is any pattern to the way such choices are made, it is likelyto be sociological rather than semantic. Sometimes the proponentsof a new theoretical idea will wish to present themselves as makinga radical break with their predecessors. In such a case they will have amotive to portray the old theory as essentially mistaken, and its cen-tral terms as essaying referring to mythical entities. ‘Caloric’, ‘aether’and ‘miasma’ might well be cases of this kind. In other cases, by con-trast, theoretical innovators will wish to represent themselves ascarrying on the work of their teachers, preserving their findingswhile augmenting them. In this latter kind of case the innovators willwant to interpret the old theory as essentially correct, referring toreal entities all right even if not accurate about every last detail oftheir behaviour. Perhaps this is what happened with ‘straight line’,‘atom’, ‘mass’ and ‘electricity’.

In any case, even if these simple sociological suggestions are mis-taken, the underlying point stands. There is no need to suppose thatchoices between replacing or preserving the old terms are rationallydictated by old meanings plus new facts. It is far more plausible tosuppose that prior usage often fails to dictate how the new factsshould be described, and so leaves it open how our terms shouldbe refined when such further precision proves necessary.

3. Quantificational realism

3.1. Ramsey sentences and approximate truth

The last section explained how to think of the connection be-tween scientific descriptions and the meanings of theoretical

1 Much of this section draws on an earlier paper written jointly with Pierre Cruse (Crusequeried by Hardin & Rosenberg, 1982.

terms. It might still be unclear how any of this helps with scientificrealism. The threat to realism, remember, was that the centralterms in past theories characteristically seemed to fail to refer.One option was to resort to a causal theory of reference in the hopethat this would show that such reference failure was not prevalentin the history of science. But I promised to defend scientific realismeven on the assumption that theoretical terms have their referentsfixed descriptively.

My clarifications of the descriptive approach may not seem tohelp. For one thing, it is still open to the opponent of realism to ar-gue that, even given my analysis, many past terms definitely failedto refer, on the grounds that, contrary to the confident opinion ofpast scientists, there have turned out to be no entities that satisfyeven the minimal core assumptions (‘Ty(F)’) that they assumedwould suffice to identify a unique referent. (What is phlogiston,if not a substance emitted during combustion? What is the aether,if not a medium at rest in absolute space? And so on.)

Moreover, even in the case of past terms that did not so defi-nitely fail to refer, it can be queried whether my analysis gives real-ists what they need. My analysis may imply that such past termswill refer on some admissible readings, and fail to refer on others.But it looks as if any respectable realism would want scientific the-ories to come out approximately true for sure, not just approxi-mately true on some readings.

My strategy at this point will be to question the assumptionthat the approximate truth of a theory depends on its terms suc-cessfully referring. This assumption is widely taken for granted inthe debate about scientific realism. Thus we find Putnam arguing,in defence of the approximate truth of theories about electrons,curved space time, and DNA molecules, that:

‘‘If there are such things, then a natural explanation of the suc-cess of these theories is that they are partially true accounts ofhow they behave . . . But if these objects don’t really exist at all,then it is a miracle that [these theories] successfully predict[s]phenomena . . . ’’ (1978, p.19)

And Laudan claims, even more directly, that:

‘‘ . . . a realist would never want to say that a theory is approxi-mately true if its central terms fail to refer’’ (1981, p. 33).

However, there is a way to have approximate truth without ref-erence.1 In the last section we saw how quantification into term po-sition transforms a scientific theory ‘T(F)’ into its Ramsey sentence—‘(E!(U)(T(U))’. Now, it is arguable that all the substantial commit-ments of the original theory about F are contained in its Ramsey sen-tence—there is a specific entity satisfying such-and-suchrequirements—and that nothing of substance is lost by switchingfrom the original formulation to the latter. But note now that the lat-ter Ramsey formulation does not itself use the term ‘F’. So issuesabout the referential success or failure of ‘F’ cannot make any differ-ence to the approximate truth of this Ramsey sentence.

We can take it that the Ramsey sentence of any serious scien-tific theory will not be fully true—there will be no specific entitysatisfying all of the open sentence ‘T(U)’. But clearly this referencefailure does not stop the Ramsey sentence ‘(E!(U)(T(U))’ beingapproximately true—as it would be if some entity satisfies nearlyall of ‘T(U)’ even if not absolutely all of it.

To take an example, suppose that a Ramsified nineteenth-century atomic theory says inter alia that there is a category ofmicroscopic entities of which there is one kind for each element,which combine in simple whole number ratios, which cannot befragmented by chemical means, and whose masses are all exactintegral multiples of the mass of the particles for hydrogen. We

& Papineau, 2002). The assumption that approximate truth requires reference is also


now know there is nothing satisfying all of this description, sinceatomic masses are not exact integral multiples of the atomic massof hydrogen (instead they are mostly close to integral multiples).But even so it is certainly true that there are entities which satisfynearly all of that description, since there are indeed entities whichcome in one kind for each element, combine in simple whole num-ber ratios, cannot be fragmented by chemical means, and whosemasses are close to integral multiples of the atomic mass of hydro-gen. And since the original Ramsey sentence implies this weakerexistential claim, this means that many of the consequences ofthe relevant Ramsey sentence are true. And so, to this extent, theRamsified atomic theory will have a high degree of approximatetruth. And it is clearly irrelevant to this whether or not the term‘atom’ successfully refers—since the Ramsified theory does makeany use of this term.

Again, suppose that a Ramsified aether-based theory of electro-magnetic radiation asserts that there is an entity which is the seatof electromagnetic phenomena, which displays transverse radia-tion satisfying Maxwell’s equations, and consists of an elastic solid.As before, nothing satisfies all these requirements. Even so, there isstill something which is the seat of electromagnetic phenomenaand involves transverse radiation satisfying Maxwell’s equa-tions—namely, the electromagnetic field—even if it is not an elasticsolid. And this means that many of the implications of the Ramsi-fied electromagnetic theory will be true, even if ‘aether’ fails of ref-erence. Once more, we see how a Ramsified theory can beapproximately true even if the original theory suffers referencefailure.

Switching from theories formulated using referring terms totheir Ramsey sentences thus allows us to by-pass issues of refer-ence failure when assessing the theories for approximate truth.Maybe the characteristic fate of scientific terms is indeed to failof reference. But it by no means follows that the Ramsey sentencesof the theories they were used to state did not have a high degreeof approximate truth.

Of course, switching attention to the approximate truth of Ram-sey sentences does not by itself insulate realism against any pessi-mistic appeals to the historical record. The Ramseyan turn maysucceed in by-passing issues of reference failure, but it still remainsa substantial question whether the Ramsey sentences for the gen-eral run of well-evidenced past theories are even so much asapproximately true. I have just suggested that the Ramsey sen-tence of nineteenth-century atomic and electromagnetic theoriesare indeed so approximately true. Still, even if this is right for theseparticular theories, nothing guarantees that this is the patternrather than the exception across the history of science. However,having noted this point, I shall have nothing more to say about itin this essay. There is no question of my here undertaking the kindof survey of the history of science that would be required for a fulldefence of scientific realism along the lines indicated. So for thepurposes of this paper I shall content myself with the point thatreference failure per se leaves it open that the Ramsey sentencesof past theories may generally be approximately true. Whetherthey actually are is a further issue.

3.2. Different reasons for Ramsification and Newman’s objection

I suggested in the last subsection that by Ramsifying we can by-pass questions of reference and attend to approximate truth di-rectly. But of course Ramsification does not allow us to do awaywith referring terms altogether, for the reasons flagged at theend of subsection 2.2 above. If we eliminated all the non-logicalterms in a scientific theory in the Ramsey style, we would be leftwith nothing but a specification of pure logical structure, and thiswould allow any number of unintended satisfiers. So if the Ramseysentence of a theory is to have any pretensions to capture the con-

tent of the original theory, then there must be some restrictions onwhich non-logical referring terms are to be replaced by quantifica-tional surrogates.

This issue is often discussed without due attention to the sur-rounding philosophical context. This is unfortunate, because theappropriate restrictions on which terms should be eliminated byRamsification depend on the philosophical motivations for appeal-ing to Ramsey sentences.

Since Ramsey first introduced the device of Ramsey sentences,different philosophers have used it for a range of different pur-poses. The logical positivists, and Ramsey himself, viewed Ramsifi-ciation as a way of explaining how theories can make claims aboutunobservable entities, in the face of the empiricist principle thatnon-logical terms need to be directly associated with senseimpressions in order to be meaningful. (Ramsey, 1931.) Function-alist philosophers of mind appeal to Ramsey sentences to explainhow mental terminology can commit us to the existence of brainstates that play certain causal roles, even though we are ignorantof the nature of those brain states, and even though different suchbrain states may play a given role in different individuals. (See forexample Lewis, 1972.) And in this paper I am suggesting that wecan appeal to Ramsification to avoid the threat to scientific realismposed by the pessimistic meta-induction on past reference failure.

Now, these different motivations for Ramsifying will imposedifferent requirements on which non-logical terms need to be re-placed by quantificational surrogates. The logical positivists’ pro-gramme required them to replace all non-observational termsthat were not directly associated with sense experience. Function-alists in the philosophy of mind want to replace terms for mentalstates by quantifications over brain states, but this implies norequirement that they replace all terms that are non-observationalin the positivists’ sense. And for the purposes of this paper we wantto quantify away those terms which the history of science indicatesare threatened with reference failure, which again need not includeall the positivists’ non-observational terms. After all, my reason forappealing to Ramsey sentences is simply to show how scientifictheories can be construed as making approximately true claimseven though some of their central terms fail to refer—and thereis nothing in this appeal to Ramsey sentences to require the elim-ination of all terms which are in some sense non-observational, asopposed to those which seem likely to fail of reference.

There is a well-known argument querying the ability of Ramseysentences to capture the content of their original theories. As wasfirst observed by Newman (1928), if the only non-logical terms leftare observational in positivist sense, then the Ramsey sentence willdo no more than impose a cardinality requirement on the unob-servable realm, and there will thus be many unintended ways inwhich it can be satisfied. (After all, if the Ramsey sentence just saysthat there are some unobservable entities and some relations thatlink those entities to each other and observable entities in specifiedways, then any appropriately sized collection of abstract objectswill satisfy this claim.)

One response to Newman’s challenge is to restrict the range ofthe relevant variables by requiring that they range over naturalproperties and relations, rather than over any entities whatsoever.It is a nice question whether this suffices to stop positivist-styleRamsey sentences from being trivially satisfied. However, we neednot pursue this issue here, as there is another response available inthe context of our present anti-meta-inductive appeal to Ramseysentences. Given the use to which we are putting Ramsey sen-tences, there is no reason why terms like ‘cause’ and ‘spatiotempo-rally contiguous’ should not remain unRamsified. After all, there isnothing in the history of science to suggest that these terms arethreatened with reference failure. (And a similar point can be madeabout the functionalist appeals to Ramsification in the philosophyof mind.)


The Newman worry immediately disappears once terms forrelations like causation and spatiotemporal contiguity are allowedto remain unRamsified,. (Cf Cruse, 2005. See also Russell, 1968, p.176 quoted by Ainsworth, 2009.) To take a simple example, it isone thing to say that there are some entities that bear somemany-one relation to chickenpox attacks—and certainly plenty ofcollections of abstract objects like numbers will make this true. Itis another thing to say that there are some entities that cause chic-kenpox attacks by entering the sufferer’s body—and it is clear en-ough only chickenpox viruses will verify this more specific claim.

Maybe the original positivist motivation for Ramsification re-quires that terms for relations like causation and spatiotemporalcontiguity must be replaced by quantificational surrogates. Theseare ‘mixed predicates’ that can have both observable and unob-servable relata, and to that extent might be argued not to satisfythe strict positivist requirement on observational meaningfulness.Still, as I have observed, there is nothing in the anti-meta-inductiveappeal to Ramsey sentences to require a similar elimination ofthese mixed predicates. They may not be strictly observational,but this in itself is no reason to think that they may fail of refer-ence. So in the context of the argument of this paper it is perfectlylegitimate to leave these terms unRamsified and so able to tiedown the interpretation of the rest of our theories.

3.3. Theories and their Ramsey sentences

I have suggested that we can by-pass questions of reference byswitching attention from term-using scientific theories of the form‘T(F)’ to their quantificational Ramsey sentences ‘(E!(U)(T(U))’. Butthis will only vindicate the approximate truth of the original theo-ries themselves to the extent that the substantial content of thesetheories is indeed the same as that of their Ramsey sentences. Sofar I have not paused to examine this assumption. However, it isnot hard to see that it can by no means be taken for granted. Thereare two obvious ways in which theories may fail to be equivalentto their Ramsey sentences. First, the terms that are Ramsified awaymay not have their references fixed by description to start with,but via some kind of causal contact. Second, even if they do havetheir references fixed by description, not all the assumptions con-tained in the original theory may play a role in defining the rele-vant terms. Either of these possibilities will drive a wedgebetween the claims made by the original theory and those madeby its Ramsey sentence. I shall address these two points in turn,the first in this section and the second in the section after next.2

In effect the first point has already been dealt with. Recall thedialectic of this paper. I am arguing in the alternative. Either scien-tific terms have their reference fixed causally, in which case thereis no pessimistic meta-induction from past reference failure; orthey have their reference fixed descriptively, in which case I amaiming to explain how theories framed using these terms can beapproximately true whether or not those terms refer. So I canby-pass the worry that causal determination of reference maycause theories to diverge from their Ramsey sentences—since ifthat’s how the reference of central terms is determined, then real-ism is in good shape anyway.

Still, it will be illuminating briefly to consider how causal deter-mination of reference can separate theories from their Ramsey sen-tences. Let me illustrate the possibility by a baby example. Supposethat I have the theory that ‘Jill Smith lives in Leverton Street, hasred hair, and drives a Ford’. The Ramsey sentence of this theory

2 It may occur to some readers that there is a yet further reason for differentiating thereferents fixed descriptively by all the assumptions in the surrounding theory. If theoreticalin the same way as their quantificational surrogates. However, we can ignore this point forthe arguments of this paper. And even if they mean that theories and their Ramsey sentenctruth value in the actual world. (For further discussion of this issue see Papineau, 1996, e

is that ‘there is a unique woman who lives in Leverton Street,has red hair, and drives a Ford’. Now suppose that there is indeedone red haired-woman who lives in Leverton Street and drives aFord, but that this isn’t Jill Smith. In fact I’m largely wrong aboutJill Smith—she lives in the next street and drives a Toyota, thoughshe does have red hair. In this case, the content of my original the-ory is manifestly different from that of its Ramsey sentence. Afterall, the Ramsey sentence is entirely true, but my original theorymostly false.

This dissociation can occur because the reference of the term‘Jill Smith’ isn’t fixed descriptively but causally. I take it to beuncontroversial that ordinary proper names refer to the causal ori-gin of their use, not to whichever entity satisfies the descriptionsassociated with them. So claims made using ‘Jill Smith’ say some-thing quite different from claims about whatever satisfies the asso-ciated descriptions I associate with this name.

If scientific terms similarly referred to the causal origin of theiruse, then there would be room for an analogous dissociation. Thescientific terms would refer to the underlying causes of the phe-nomena that prompted their introduction, not to whatever hap-pens to satisfy descriptive assumptions associated with them.And to some extent a theory framed using such terms would makedifferent claims from the Ramsey sentence of that theory.

Now, this kind of possibility raises a number of issues. A naturalquery is whether this kind of dissociation is a genuine possibilityfor scientific theories. It would seem odd to end up concluding thata scientific theory is largely mistaken about some category eventhough its assumptions correctly characterize some different cate-gory. And this could be taken to argue in favour of a descriptivetheory for scientific terms over a causal one. But I shall not attemptto add to the points I have already made in favour of a descriptiveapproach to scientific terms in section 1.4 above. At this stage letme simply rest content once more with the dialectical consider-ation that realism is in good shape anyway, if the descriptive the-ory is wrong.

3.4. Structural realism

I still need to address the worry that, even if reference is fixeddescriptively, theories may still diverge from their Ramsey sen-tences because not all the assumptions in the theory play a rolein fixing reference. But first I would like to digress briefly andsay something about ‘structural realism’.

The points made in the last section might have made somereaders think of John Worrall’s epistemic ‘structural realist’ re-sponse to the pessimistic meta-induction (Worrall, 1989). The cen-tral idea of this response is to distinguish scientific claims about‘structures’ from those about ‘natures’, and to argue that whilethe history of science displays a pattern of mistaken scientificclaims about the nature of scientific entities, it does not discreditclaims about their structure. So, for example, Worrall’s argues that,even though nineteenth-century electromagnetic theory waswrong about the nature of the ‘aether’, it was quite right aboutthe structural equations governing electromagnetism. More gener-ally, he suggests that new theories tend to preserve the structuralclaims of their predecessors, even if they discard their assumptionsabout natures. Structural realism thus implies that we believewhat our current theories say about structures but not natures.

At first sight, this might sound as if it draws on a distinction be-tween term-using metaphysical formulations of scientific theories

ories from their Ramsey sentences, which arises even if theoretical terms have theirterms are genuinely referring terms, then they will not interact with modal operatorspresent purposes. The relevant modal niceties are in themselves of no importance to

es are not fully semantically equivalent, it will still be a priori that they have the samespecially section 5.)


and their quantificational Ramsey versions, advocating belief in thelatter but not the former. As we have just seen, these two versionscan well say different things, if the relevant referring terms aregoverned by the causal theory of reference. The referring-term ver-sion will make claims about the specific entities involved in theorigins of the relevant terms’ use, while the Ramsey sentence ver-sion will content itself with saying that there are entities satisfyingsuch-and-such a descriptive structure. This might seem very likethe structural realist’s contrast between claims about the natureof some reality and claims solely about its structure.

However, on closer examination it seems doubtful that this is auseful way to understand structural realism. Structural realists areaiming to defend scientific realism against the pessimistic meta-induction via a ‘divide and rule’ strategy. The idea is to distinguishthe ‘good’ structural parts of theories from the ‘bad’ commitmentsto natures. The former are upheld by the history of science, whilethe latter are discredited, and so we should restrict our scientificcommitments to structural claims. But then it looks wrong to sug-gest that the ‘bad’ commitments to natures depend on the causaltheory of reference. After all, the causal theory of reference doesnot render the history of science a threat to realism—on the con-trary, as we have seen, the causal theory tends to imply that allpast scientific terms were referentially successful. If structuralrealists think that terms conveying commitments to natures, like‘aether’, are characteristically non-referring, then it looks as if theyare taking the reference of such terms to be fixed descriptively, notcausally, and to fail of reference because of the falsity of assump-tions built into them. And indeed this is just how structural realistscharacteristically argue—‘aether’ failed to refer because it turnedout that nineteenth century thinkers were wrong to assume thatthe medium of electromagnetic radiation is an elastic solid at restwith respect to absolute space.

Given this, it does not seem helpful to think of structural realistsas somehow divorcing the metaphysical content of scientific theo-ries themselves from the structural content of those theories’purely descriptive Ramsey sentences. Rather, it looks as if weshould interpret structural realists as understanding all theoreticalclaims in a descriptivist Ramseyan manner from the start, with the‘metaphysical’ parts of the theory (‘there is an elastic solid at restwith respect to absolute space’) being understood descriptivelyjust us much as the structural parts. On this reading, the structuralrealist strategy is then simply to distinguish the good mathemati-cal parts of such descriptively understood theories from the badmetaphysical parts. The full Ramsey sentences of scientific theoriesare characteristically false, but in general the fault lies with thetheory’s claims about ‘natures’ rather than ‘structures’. So in gen-eral we can avoid commitment to falsehood by restricting our-selves to ‘structural’ claims and distancing ourselves from claimsabout ‘natures’.

So understood, structural realism would be consonant with theapproach to realism adopted here. I have observed that the pessi-mistic meta-induction does not stop us upholding the approximatetruth of our theories’ Ramsey sentences. However in itself thisobservation is little more than a general framework for a realiststance. As I observed earlier, ‘approximate truth’ is an open-endedterm, and to fill out a commitment to approximate truth we needto specify the respects in which we expect our theories to beapproximately true. Perhaps we can see structural realism as offer-ing one way of fulfilling this obligation. We should expect our the-ories to be approximately true in their claims about ‘structures’,but not about ‘natures’.

So viewed, however, structural realism clearly stands in need ofsome further explanation of the distinction between the ‘struc-tural’ and ‘natural’ parts of scientific theories. Now, it is sometimessuggested that this can be provided by ‘Ramsification’ itself—thatis, that the Ramsey sentence will give us the structural content

of scientific theories shorn of any metaphysical commitments tonatures. But in the light of the above remarks this makes littlesense. A scientific theory will only carry metaphysical commit-ments beyond those of its Ramsey sentence if some of its terms re-fer non-descriptively, yet the arguments of structural realists seemto commit them to a descriptive theory of reference for claimsabout ‘natures’ as well as ‘structures’.

This is not to say that there may not be other good ways ofdistinguishing the structural from the natural claims of scientifictheories. For example, perhaps we can make something of thecontrast between the ‘mathematical’ and ‘metaphysical’ commit-ments of scientific theories. Still, the point remains that struc-tural realism owes us an explanation of such a distinction, andthat mere mention of ‘Ramsification’ is not enough (cf. Psillos,1999.)

3.5. Non-Ramseyan quantifications

Finally, let me return to the other worry about equating scien-tific theories of the form ‘T(F)’ with their quantificational Ramseysentences ‘(E!(U)(T(U))’—namely, the worry occasioned by thefact that not all the descriptions in a scientific theory will playan equal role in defining its terms. As we saw in my discussionof Quine earlier, even if there is often no fact of the matterwhether some assumption contributes to the meanings of theterms it involves, it would be a mistake to draw the extreme hol-ist conclusion that every theoretical assumption is meaning-constituting.

However, as I shall explain in a moment, this means that we can-not equate the synthetic content of a theory ‘T(F)’ with that of itsRamsey sentence ‘(E!(U)(T(U))’, even on the assumption that thereference of ‘F’ is fixed descriptively. And this implies in turn thatwe cannot infer the approximate truth of a scientific theory directlyfrom the approximate truth of its Ramsey sentence. Still, the prob-lem is not serious. We can easily enough avoid any commitment toextreme holism, yet still retain the idea of by-passing issues of ref-erence when assessing the approximate truth of theories.

To see how this can work, let us first assume that the meaningof ‘F’ is fixed descriptively by some definite subset of ‘T(F)’’sassumptions which I shall symbolize as ‘Tr(F)’ (’r’ for restricted). Ishall revert to the more realistic assumption that it is often inde-terminate what goes into ‘Tr(F)’ in a moment.

Now, it is certainly true that, if the meaning of ‘F’ is so fixed bysome restricted subtheory of ‘Tr(F)’, then the content of ‘T(F)’comes apart from that of its Ramsey sentence ‘(E!(U)(T(U))’.

To see why, first consider the general case of any claim ‘C(F)’employing the so-defined term ‘F’. Since ‘F’ is defined in terms ofthe restricted ‘Tr(F)’ rather that the whole ‘T(F)’, the claim ‘C(F)’ willno longer imply or presuppose that there is some unique entitysatisfying the whole of ‘T(F)’, but only that there is one satisfying‘Tr(F)’. That is, ‘C(F)’ should not now be equated with

‘ðEUÞððTðUÞ & ðWÞðTðWÞ ! U ¼ WÞÞ & CðUÞÞ’

but rather with the analogous formula employing Tr(U) in place ofT(U)—namely

‘ðEUÞððTrðUÞ & ðWÞðTrðWÞ ! U ¼ WÞÞ & CðUÞÞ’:

Applying this to ‘T(F)’ itself, this overall theory then comes out asequivalent, not to the simple Ramsey sentence, ‘(E!U)(T(U)’, whichunpacks as

‘ðEUÞðTðUÞ & ðWÞðTðWÞ ! U ¼ WÞÞ’

but to the more complex claim:

‘ðEUÞððTrðUÞ & ðWÞðTrðWÞ ! U ¼ WÞÞ & TðUÞÞ’:


Note how this latter claim says more than the simple Ramsey sen-tence. It says that there is a unique U satisfying the restricted ‘Tr(U)’,not just that the whole of ‘T(U)’ identifies a unique entity. This claimcould be false even if the Ramsey sentence is true, if the assump-tions in ‘Tr(U)’ are not strong enough by themselves to pick outsomething unique but those in ‘T(U)’ are.

Some readers might wonder to what extent this is a real danger.It is easy enough to think of cases where the full ‘T(U)’ contains toomany claims (for example, claims about the precise mass of carbonatoms) to allow any satisfiers. But it is not so obvious that there arereal cases where some plausible reference-fixing ‘Tr(U)’ allows aplurality of entities yet the extra assumptions in the full ‘T(U)’prune these down to one. So could we not simply put such casesto one side, and argue that in practice the content of theories‘T(F)’ is close enough to that of their simple Ramsey sentencesfor the approximate truth of the latter to vindicate that of the the-ories themselves? (cf. Cruse & Papineau, 2002.)

However, there is no need to resort to this somewhat unsatis-factory line of argument. Recall the basic point of our appeal toRamsey sentences. It allowed us to by-pass questions of reference,and focus on the approximate truth of the non-term-using Ramseysentence. The important point here was not that we could equatetheories with their Ramsey sentences as such, but that we couldequate them with some non-term-using quantificational claim.This allowed us to assess the approximate truth of the latter with-out any threat from reference failure. Now, there is nothing in theidea that a theory is equivalent to the more complex claim ‘(EU)((-Tr(U) & (W)(Tr(W) ? U = W)) & T(U))’ rather than to its simpleRamsey sentence to stop us pulling this trick. This claim is stillequivalent to a non-term-using quantificational claim, and so wecan still by-pass questions of reference and assess the approximatetruth of the theory simply by asking how far this quantificationalclaim is true.

So, to adapt our earlier example, suppose that the reference ofthe nineteenth-century term ‘atom’ was fixed by the restrictedset of claims (‘Tr(F)’) that there is one kind of atom for each ele-ment, that they combine in simple whole number ratios, and thatthey cannot be fragmented by chemical means. The nineteenth-century atomic theory (‘T(F)’) then went on to say a lot more,which means that, even given this descriptive fixing of referencefor ‘atom’, the theory is equivalent not to its Ramsey sentencebut to the more complex ‘(EU)((Tr(U) & (W)(Tr(W) ? U = W)) &T(U))’. But clearly there is nothing to stop us asking about theapproximate truth of just this more complex claim, and concludingthat while it is not fully true—the category satisfying ‘Tr(U)’ doesn’tsatisfy all the further assumptions in ‘T(U)’ including the assump-tion that their masses are exact integral multiples of the hydrogenatom’s mass, say—it still has a high degree of approximate truth—the category satisfying ‘Tr(U)’ does have masses that are generallyclose to integral multiples of the hydrogen atom’s mass.

Let me now bring in the point that it is often indeterminatewhich assumptions in a theory fix the reference of its terms. Aswe saw earlier, it is unrealistic to suppose that there is a sharp-cut off point between the set of assumptions that play such a rolein defining some term ‘F’ and those that do not. In reality there willbe a large penumbra of uncertainty. Some assumptions (‘Ty(F)’)may definitely play a definitional role, and some may definitelyplay no role (‘Tn(F)’), but there will be a wide range of assumptions(‘Tp(F)’) where it is simply undecided whether they enter into ‘F’’sdefinition or not. As I observed earlier, it is unsurprising that scien-tists will often happily leave this issue open, since they are oftenconfident that just the same entity will be picked out howevermuch of ‘Tp(F)’ is included in the definition.

Well, insofar as it is indeterminate which assumptions from‘Tp(F)’ go in to the definition of ‘F’, then it will be indeterminate ex-actly what is said by claims made using ‘F’. We will have a range of

ways of defining ‘F’ between which usage does not decide—that is,a range of admissible ‘Tr(F)’s in the above terminology, each con-structed by adding some part of ‘Tp(F)’ to ‘Ty(F)’. And so our originaltheory ‘T(F)’ will be indeterminate in meaning between all thedifferent quantificational claims we get by plugging these differentadmissible ‘Tr(F)’s into the formula ‘(EU)((Tr(U) &(W)(Tr(W)?U = W)) & T(U))’.

But now we can evaluate our theory as we might evaluate anyclaim that is vague or indeterminate in content. We consider thedifferent possible ways of making the claim precise, and see whattruth values it has under these different admissible ‘precisifica-tions’. Sometimes claims involving indeterminate terms have thesame truth value on all such precisifications. That is why ‘JohnMalkovich is bald’ is definitely true, and ‘David Beckham is bald’is definitely false, even though ‘bald’ is a vague term.

In the same way, we can assess our scientific theories by consid-ering the truth value of ‘(EU)((Tr(U) & (W)(Tr(W) ? U = W)) & T(U))’on all the different admissible ways of determining ‘Tr(U)’. Or morefruitfully, since any complex scientific theory will no doubt containsome definite falsity on all its readings, we can ask about theapproximate truth of this formula across all admissible readings.

Given the points made so far, we can see that the approximatetruth of this formula may well vary across different choices of‘Tr(U)’. The less that’s put into ‘Tr(U)’, the stronger the claim madeby this formula, since it claims that there is a unique entity satis-fying ‘Tr(U)’. So the stronger formulas will have a greater amountof approximate truth than the weaker ones, if there is such a un-ique entity, and may well have a lesser degree, if there isn’t. Butthis is fine-tuning. A good theory can be expected to achieve a rea-sonable degree of approximate truth across all admissible readings.

Of course, as I said earlier, it is a historical matter, not to be set-tled by abstract analysis, whether the general run of well-evidenced past theories have a certain degree of approximate truth.And as before there is no question of trying to defend this historicalclaim here. It will be enough if our abstract analysis shows that thesemantic indeterminacy of scientific theories does not precludefrom being approximately true on all admissible readings.

3.6. Summing up

The descriptive theory of reference implies that scientific termsoften fail to refer, and so suggests that scientific theories are inca-pable of approximate truth. But if the descriptive theory of refer-ence is correct, then scientific theories will be equivalent toquantificational claims that do not use the troublesome non-refer-ring terms. Given this, the approximate truth of these theories willbe independent of whether those terms refer.

Acknowledgments

Peter Lipton was my friend and colleague. Our careers over-lapped in a number of ways. I was one of the examiners for hisPhD. Then he visited Cambridge for a year when I was a lecturerin History and Philosophy of Science. Some time later I left for Lon-don, and Peter was appointed to the vacant post, taking over myoffice and telephone number. He made such a difference to theDepartment that it is hard to believe he is not still there. He wasa wonderful person and is very much missed. I am glad to dedicatethis paper to his memory.

References

Ainsworth, P. (2009). Newman’s Objection. The British Journal for the Philosophy ofScience, 60, 135–171.

Cruse, P. (2005). Ramsey sentences, structural realism and trivial realization. Studiesin the History and Philosophy of Science, 36, 557–576.


Cruse, P., & Papineau, D. (2002). Scientific realism without reference. In M. Marsonet(Ed.), The problem of realism. Aldershot: Ashgate.

Field, H. (1973). Theory change and the indeterminacy of reference. Journal ofPhilosophy, 70, 462–481.

Hardin, C., & Rosenberg, A. (1982). In defence of convergent realism. Philosophy ofScience, 49, 604–615.

Kitcher, P. (1993). The advancement of science. New York: Oxford University Press.Kripke, S. (1980). Naming and Necessity. Oxford: Blackwell.Laudan, L. (1981). A confutation of convergent realism. Philosophy of Science, 48,

19–49.Lewis, D. (1970). How to define theoretical terms. Journal of Philosophy, 67, 427–446.Lewis, D. (1972). Psychophysical and theoretical identifications. Australasian Journal

of Philosophy, 50, 249–258.Lipton, P. 1991/2004. Inference to the best explanation. London: Routledge. First

edition 1991, expanded second edition 2004.Newman, M. (1928). Mr. Russell’s ‘‘causal theory of perception’’. Mind, 37, 137–148.

Newton-Smith, W. (1981). The rationality of science. London: Routledge and KeganPaul.

Papineau, D. (1979). Theory and meaning. Oxford: Oxford University Press.Papineau, D. (1996). Theory-dependent terms. Philosophy of Science, 63.Psillos, S. (1999). Scientific realism: How science tracks truth. London: Routledge.Putnam, H. (1973). Explanation and reference. In G. Pearce & P. Maynard (Eds.),

Conceptual change. Dordrecht: Reidel.Putnam, H. (1978). Meaning and the Moral Sciences. London: Routledge and Kegan

Paul.Quine, W. (1951). Two dogmas of empiricism. Philosophical Review, 60, 20–43.Quine, W. (1960). Word and object. Cambridge Mass: MIT Press.Ramsey, F. (1931). Theories. In R. Braithwaite (Ed.), Foundations of Mathematics and

Other Essays. London: Routledge and Kegan Paul.Russell, B. (1968). The autobiography of Bertrand Russell, II. London: Allen & Unwin.Worrall, J. (1989). Structural realism: The best of both worlds? Dialectica, 43,

99–124.

realism, ramsey sentences and the pessimistic meta-induction

Documents