According to metaphysical realism, the world is as it is independentof how humans or other inquiring agents take it to be. The objects theworld contains, together with their properties and the relations theyenter into, fix the world’s nature and these objects [togetherwith the properties they have and the relations they enter into] existindependently of our ability to discover they do. Unless this is so,metaphysical realists argue, none of our beliefs about our world couldbe objectively true since true beliefs tell us how things are andbeliefs are objective when true or false independently of what anyonemight think.

Many philosophers believe metaphysical realism is just plain commonsense. Others believe it to be a direct implication of modern science,which paints humans as fallible creatures adrift in an inhospitableworld not of their making. Nonetheless, metaphysical realism iscontroversial. Besides the analytic question of what it means toassert that objects exist independently of the mind, metaphysicalrealism also raises epistemological problems: how can we obtainknowledge of a mind-independent world? There are also prior semanticproblems, such as how links are set up between our beliefs and themind-independent states of affairs they allegedly represent. This isthe Representation Problem.

Anti-realists deny the world is mind-independent. Believing theepistemological and semantic problems to be insoluble, they concluderealism must be false. The first anti-realist arguments based onexplicitly semantic considerations were advanced by Michael Dummettand Hilary Putnam. These are:

1. Dummett’s Manifestation Argument: the cognitive andlinguistic behaviour of an agent provides no evidence that realistmind/world links exist;
2. Dummett’s Language Acquisition Argument: if such links wereto exist language learning would be impossible;
3. Putnam’s Brain-in-a-Vat Argument: realism entails both thatwe could be massively deluded (‘brains in a vat’) and thatif we were we could not even form the belief that we were;
4. Putnam’s Conceptual Relativity Argument: it is senseless toask what the world contains independently of how we conceive of it,since the objects that exist depend on the conceptual scheme used toclassify them;
5. Putnam’s Model-Theoretic Argument: realists must either holdthat an ideal theory passing every conceivable test could be false orthat perfectly determinate terms like ‘cat’ are massivelyindeterminate, and both alternatives are absurd.

We’ll proceed by first defining metaphysical realism,illustrating its distinctive mind-independence claim with someexamples and distinguishing it from other doctrines with which it isoften confused, in particular factualism. We’ll then outline theRepresentation Problem in the course of presenting the anti-realistchallenges to metaphysical realism that are based on it. We discussmetaphysical realist responses to these challenges, indicating how thedebates have proceeded, suggesting various alternatives andcountenancing anti-realist replies. We finish with a brief review ofrecent realist/anti-realist debates in meta-ontology.

• 1. What is Metaphysical Realism?
• 2. Mind-Independent Existence
• 3. The Anti-Realist Challenges to Metaphysical Realism
  • 3.1 Language Use and Understanding
  • 3.2 Language Acquisition
  • 3.3 Radical Skepticism
  • 3.4 Models and Reality
  • 3.5 Conceptual Schemes and Pluralism
• 4. Realism and Anti-Realism in Meta-Ontology
• 5. Summary
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

1. What is Metaphysical Realism?

Metaphysical realism is the thesis that the objects, properties andrelations the world contains, collectively: the structure of the world[Sider 2011], exists independently of our thoughts about it or ourperceptions of it. Anti-realists either doubt or deny the existence ofthe structure the metaphysical realist believes in or else doubt ordeny its independence from our conceptions of it. Realists aboutnumbers, for example, hold that numbers exist mind-independently. Thisview is opposed by Nominalists who deny the existence of abstractobjects and Intuitionists who agree numbers exist, but as mentalconstructions, denying their mind-independence. Some realists aboutlaws of nature, to take an empirical example, hold that laws arerelations between universals [Armstrong 1983], others that laws areontologically primitive entities [Maudlin 2007]. Anti-realists aboutlaws of nature, on the other hand, either deny there are any laws atall [Cartwright 1983; van Fraassen 1989] or else discern a dependenceon human concepts in the nature of these laws, interpreting them asexpressing certain expectations we have about regularities that weunconsciously project onto the world [Blackburn 1986].

Metaphysical realism is not the same as scientific realism. That theworld’s constituents exist mind-independently does not entailthat its constituents are as science portrays them. One could adopt aninstrumentalist attitude toward the theoretical entities posited byscience, continuing to believe that whatever entities the worldactually does contain exist independently of our conceptions andperceptions of them. For the same reason, metaphysical realists neednot accept that the entities and structures ontologists posit existmind-independently.

Henceforth, we shall often just use the term ‘realism’ tomean metaphysical realism. Opposition to realism can take many formsso there is no single theoretical view denoted by the term‘anti-realism’. In particular, anti-realism is notIdealism, even though Idealism is its most recognised form. Oneapproach, popular in Continental Philosophy, rejects realism on thegrounds that words can only acquire their meaningintra-linguistically, through their semantic relations withother words, where these relations are grounded in our linguistic andcultural practices, rather than through referential relations to theworld outside of language. This view, Anti-Representationalism as itis sometimes called, has gained traction in analytic philosophy also[See Price 2009].

Within the ranks of Analytic Philosophy, Verificationists andPragmatists also reject realism, though for different reasons. Weshall mainly focus in this entry on the types of criticism voiced bythese two groups of Analytic philosophers with Michael Dummettadvocating a certain kind of Verificationism and Hilary Putnam acertain kind of Pragmatism. While accepting Representationalism, bothDummett and Putnam rejected realism by deploying semanticconsiderations in arguments designed to show that realism isuntenable. The main goal of this entry is to outline these‘semantic’ challenges to realism and to criticallyappraise them.

The characterization of realism in terms of mind-independence above isnot universally accepted. Some object that mind-independence isobscure [e.g. Chalmers 2009; for relevant discussion, see the entryontological dependence]. Others maintain that realism is committed, in addition, to adistinctive (and tendentious) conception of truth [Putnam 1981, 1985,1992; Wright 1993; Button 2013; Taylor 2006] or, more radically, thatrealism just is a thesis about the nature of truth—that truthcan transcend the possibility of verification, ruling statements forwhich we can gather no evidence one way or the other to bedeterminately either true or false. An example would be “JuliusCaesar’s heart skipped a beat as he crossed the Rubicon.”Thus the realist on this view is one who believes the law of bivalence(every statement is either true or false) holds for all meaningful(non-vague) statements [Dummett 1978, 1991, 1993].

In the same vein, Crispin Wright [1992a, 2003] presents a nuancedalethic analysis according to which discourses may be more or lessrealist depending on which distinctive ‘marks of truth’they satisfy.

These semantic formulations of metaphysical realism are unacceptableto realists who are deflationists about truth, denying that truth is asubstantive notion that can be used to characterise alternativemetaphysical views [see the entry on thedeflationary theory of truth]. Realists collectively complain, with some justice, that theanti-realist arguments are really arguments against the correspondence(or other substantive) theory of truth rather than realism [Devitt1983, 1991; Millikan 1986]. This is an important reason for preferringan ontological construal of realism rather than a semantic one.

There is, in fact, an obvious worry about using the notion ofmind-independence to characterise realism: it appears to consignmental states and events to irreality. Surely your savouring the tasteof espresso, say, is dependent on your mind if anything is? Moreover,just as certainly the nature and content of the experience of tastingespresso depends upon one’s beliefs and expectations. Indeed,but this is not what the ‘mind-independence’characterisation of realism means to exclude. Rather, it is theexistence of conscious events that is deemed to beindependent of the particular opinions or theories we might hold abouttheir existence —given conscious events do exist, were ourdescendants to uniformly dismiss them as illusory, they would bemistaken. The ‘mind-independence’ at issue is epistemicrather than ontological.

On this understanding of realism, it is an error to identify realismwith factualism, the view that sentences in some discourse or theoryare to be construed literally as fact-stating ones. The anti-realistviews discussed below are factualist about discourse describingcertain contentious domains. Adopting a non-factualist orerror-theoretic interpretation of some domain of discourse commits oneto anti-realism about its entities. Factualism is thus a necessarycondition for realism. But it is not sufficient. Verificationists suchas Dummett reject the idea that something might exist without ourbeing able to recognize its existence. They can be factualists aboutentities such as numbers and quarks while anti-realists about theirnature since they deny any entities can exist mind-independently.

To elaborate the notion of mind-independent existence, consider Petervan Inwagen’s argument for the existence of numbers [van Inwagen2016], which he describes as “a typical neo-Quineanargument”. The argument rests on two Quinean theses, van Inwagentells us. Firstly, that there is only one kind of variable, a variablethat occupies nominal position, the range of which is unrestricted.Secondly, that the meanings of the quantifiers are univocal.^[1]

Given these two background assumptions, the argument he gives isthis:

1. There are objects that have both mass and volume.
2. The average density of an object that has both mass and volume isthe ratio of its mass to its volume.
3. So, there is at least one thing that is a ratio.
4. Anything that is a ratio is a number.
5. Hence, there are numbers.

(3) follows from (1) and (2), with the conclusion (5) deducible from(1), (2) and (4). Moreover, both (2) and (4) are, if not analyticallytrue, simple mathematical truths. (1), on the other hand, is anempirical fact, van Inwagen notes. The argument is clearly valid andthe three premises that support the conclusion are all highlyplausible. Should we not just accept that numbers exist? Manyphilosophers think so but some philosophers demur. Amongst the latterare those who think that the meaning of ‘there exists’varies from context to context [Hilary Putnam and Eli Hirsch are twoprominent advocates whose ideas we review]. There are others who thinkthat the existential quantifier carries no ontological import[Azzouni, J. 1997]. If one accepts Quine’s two assumptions aboutthe existential quantifier, however, and regards the argument assound, hasn’t one thereby accepted realism about numbers?

No. For, while the argument establishes the existence of numbers, ifit is indeed sound, it leaves their nature unspecified. Hence, it doesnot prove that numbers exist independently of human (or other) minds.Moreover, since the inferences are intuitionistically valid,anti-realists can accept it. The argument gives Intuitionists whobelieve numbers are mental constructs just as much as Platonists whobelieve they are eternal abstract objects a reason to believe numbersexist.

2. Mind-Independent Existence

Why do some find the notion of mind-independent existence inadequatefor the task of formulating metaphysical realism? The most commoncomplaint is that the notion is either obscure, or, more strongly,incoherent or cognitively meaningless. An eloquent spokesman for thisstrong view was Rudolf Carnap: “My friends and I have maintainedthe following theses,” Carnap announces [Carnap 1963,p.868]:

1. The statement asserting the reality of the external world(realism) as well as its negation in various forms, e.g., solipsismand several forms of idealism, in the traditional controversy arepseudo-statements, i.e., devoid of cognitive content.
2. The same holds for the statements about the reality or irrealityofother minds.
3. For the statements of the reality or irreality ofabstractentities (realism of universals or Platonism, vs.nominalism).

In spite of his finding these disputes meaningless, Carnap indicateshow he thinks we could reconstruct them (sic.) so as to make somesense of them: if we were to “replace the ontological thesesabout the reality or irreality of certain entities, theses which weregard as pseudo-theses, by proposals or decisions concerning the useof certain languages. Thus realism is replaced by the practicaldecision to use the reistic language”.

Carnap does not have in mind a factualist reformulation ofmetaphysical realism here—his “reistic” language isstrictly limited to the description of “intersubjectivelyobservable, spatio-temporally localized things or events”.

What matters here is not Carnap’s sense of a commensurabilitybetween a metaphysical thesis about reality and a practical decisionto speak only about observable things, but rather that he thinks hecan explain how the illusion of meaningfulness arises for themetaphysical theses he declares “devoid of cognitivecontent”. His explanation has to do with a distinction betweentwo types of questions —internal andexternalquestions:

An existential statement which asserts that there are entities of aspecified kind can be formulated as a simple existential statement ina language containing variables for these entities. I have calledexistential statements of this kind, formulatedwithin agiven language,internal existential statements. [Carnap1963, p. 871]

Whereas internal questions about the existence of physical objects areto be answered by observations that confirm or disconfirm sentencesasserting their existence, existential statements about abstractobjects are analytic, Carnap contends:

Just because internal statements are usually analytic and trivial, wemay presume that the theses involved in the traditional philosophicalcontroversies are not meant as internal statements, but rather asexternal existential statements; they purport to assert theexistence of entities of the kind in question not merely within agiven language, but, so to speak, before a language has beenconstructed. [1963, p. 871]

Having dismissed all external existential questions as devoid ofcognitive content, Carnap decides that both realism which asserts theontological reality of abstract entities and nominalism which assertstheir irreality are “pseudo-statements if they claim to betheoretical statements” (ibid).

Where Carnap could make no sense of the notion of mind-independentreality, Albert Einstein had no such difficulty. For, together withPodolsky and Rosen, Einstein famously proposed a test for elements ofreality in their EPR paper [Einstein, Podolsky and Rosen 1935:777–8]:

If, without in any way disturbing a system, we can predict withcertainty (i.e. with probability equal to unity) the value of aphysical quantity, then there exists an element of physical realitycorresponding to this physical quantity.

Tim Maudlin [2014, p.7] explains the significance of the EPR criterionthus:

Suppose … I canwithout in any way disturbing a systempredict with certainty the value of a physical quantity … thenthe relevant element of reality obtained …independently ofthe determination being made. Because, as we have said, the meansof determination did not (by hypothesis) disturb the system.

Realists might wish to endorse the EPR criterion as an idealized testfor the mind-independent reality of (macro-)physical quantities— even if we rarely (if at all) are able to “predict withcertainty” the outcome of an experiment, we can, some wouldargue, approach near-certainty in a significant class of cases withoutdisturbing the system.

3. The Anti-Realist Challenges to Metaphysical Realism

3.1 Language Use and Understanding

The first anti-realist challenge to consider focuses on the use wemake of our words and sentences. The challenge is simply this: whataspect of our linguistic use could provide the necessary evidence forthe realist’s correlation between sentences and mind-independentstates of affairs? Which aspects of our semantic behaviour manifestour grasp of these correlations, assuming they do hold?

For your representations of the world to be reliable, there must be acorrelation between these representations and the states of affairsthey portray. So the cosmologist who utters the statement “theentropy of the Big Bang was remarkably low” has uttered a truthif and only if the entropy of the Big Bang was remarkably low.

A natural question to ask is how the correlation between the statementand the mind-independent state of affairs which makes it true issupposed to be set up. One suggestive answer is that the link iseffected by the use speakers make of their words, the statements theyendorse and the statements they dissent from, the rationalizationsthey provide for their beliefs and actions and so forth; cognitively,it will be the functional role of mental symbols in thought,perception and language learning etc. that effects these links.

However, when we look at how speakers actually do use their sentences,anti-realists argue, we see them responding not to states of affairsthat they cannot in general detect but rather to agreed uponconditions for asserting these sentences. Scientists assert “theentropy of the Big Bang was remarkably low” because they allconcur that the conditions justifying this assertion have beenmet.

What prompts us to use our sentences in the way that we do are thepublic justification conditions associated with those sentences,justification conditions forged in linguistic practices which imbuethese sentences with meaning, anti-realists aver.

The realist believes we are able to mentally representmind-independent states of affairs. But consider those cases whereeverything that we know about the world leaves it unsettled whether arelevant state of affairs obtains. Did Socrates sneeze in his sleepthe night before he took the hemlock or did he not? How could wepossibly find out? Yet realists hold that the sentence “Socratessneezed in his sleep the night before he took the hemlock” willbe true if Socrates did sneeze then and false if he did not.

The Manifestation challenge to realism is to isolate some feature ofthe use agents make of their words, or their mental symbols, whichforges the link between mind-independent states of affairs and thethoughts and sentences that represent them. Nothing in thethinker’s linguistic behaviour, according to the anti-realist,provides evidence that this link has been forged—linguistic useis keyed to public assertibility conditions, not undetectabletruth-conditions. In those cases, such as the Socrates one, where wecannot find out whether the truth-condition is satisfied or not, it issimply gratuitous to believe that there is anything we can think orsay or do which could provide evidence that the link has been set upin the first place. So the anti-realist claims [Dummett 1978, 1991,1993; Tennant 1987, 1997; Wright 1993].

Why should we expect the evidence to be behavioural rather than, say,neurophysiological? The reason anti-realists give is that the meaningsof our words and (derivatively for them) the contents of our thoughtsare essentially communicable and thus must be open for all speakersand thinkers to see [Dummett 1978, 1993].

Anti-realists contend there is nothing in cognitive or linguisticbehaviour that could provide evidence that people grasp what it is fora sentence to be true in the realist’s sense of‘true’. How can you manifest a grasp of a notion which canapply or fail to apply without you being able to tell which? How couldyou ever learn to use such a concept?

One possible realist response is that the concept of truth is actuallyvery simple, and it is spurious to demand that one always be able todetermine whether a concept applies. As to the first part, it is oftenargued that all there is to the notion of truth is what is given bythe formula “‘p’ is true if and only ifp”. The function of the truth-predicate is to disquotesentences in the sense of undoing the effects of quotation—thusall that one is saying in calling the sentence “Yeti arevicious”true is that Yeti are vicious.

It is not clear that this response really addresses theanti-realist’s worry, however. It may well be that there is asimple algorithm for learning the meaning of ‘true’ andthat, consequently, there is no special difficulty in learning toapply the concept. But that by itself does not tell us whether thepredicate ‘true’ applies to cases where we cannotascertain that it does. All the algorithm tells us, in effect, is thatif it is legitimate to assertp it is legitimate to assertthat ‘p’ is true. So are we entitled to assert‘either Socrates did or did not sneeze in his sleep the nightbefore he took the hemlock’ or are we not? Presumably that willdepend on what we mean by the sentence, whether we mean to beadverting to two states of affairs neither of which we have anyprospect of ever confirming.

Anti-realists follow verificationists in rejecting the intelligibilityof states of affairs that we cannot detect and tend to base theirrules for assertion on intuitionistic logic, which rejects theuniversal applicability of the Law of Bivalence (the principle thatevery statement is either true or false). This law is thought to be afoundational semantic principle for classical logic. However, somequestion whether classical logic requires bivalence [e.g. Sandqvist2009]. Others dispute the idea that acceptance or rejection ofbivalence has anymetaphysical (rather thanmeaning-theoretic) consequences [Edgington, 1981; McDowell 1976; Pagin1998; Gaiffman 1996]. There is, in addition, a question as to whetherthe anti-realist’s preferred substitute for realisttruth-conditions in verification-conditions (or proof-conditions)satisfies the requirement of exhaustive manifestability [Pagin2009].

Perhaps anti-realists are right. But if so, they need to explain how apractice based on a pervasive illusion can be as successful as modernscience. Anti-realists perturbed by the manifestability of realisttruth are revisionists not just about parts of our linguisticpractice, they are revisionists about our understanding of the world.The consequence of this revisionist stance is that mathematics andscience require extensive and non-trivial revision. The debate aboutwhether classical logic should (or can) be rejected onmeaning-theoretic grounds is ongoing: Burgess 1984, Hellman 1989,Michael 1999 and Read 2000 are critical of Dummett’s case forrejecting classical logic, whereas Cogburn 2005, Cozzo 1994, Prawitz1977, 1987, 1994 and Tennant 1997 are, in varying degrees,supportive.

Perhaps the most persuasive realist reply to Dummett’smanifestation challenge questions the need for epistemic access to‘verification-transcendent’ states of affairs tounderstand a sentence. How do we understand a sentence like“Socrates sneezed in his sleep the night before he took thehemlock”? By understanding the sentence’s component wordsand their mode of composition. No epistemic confrontation with aninaccessible past state of affairs is required given that we haveepistemic access to the semantic values of the sentence’scomponents and their mode of composition. That we do indeed understandthe truth-conditions associated with the Socrates sentence in therealist way, as verification-transcendent ones, is manifest in ouracceptance of statements such as “Socrates either sneezed in hissleep the night before he took the hemlock or he did not,independently of what anyone believes”. Call this theCompositionality Reply.

Anti-realists respond to the Compositionality Reply by arguing thatall we make manifest by asserting things like “Socrates eithersneezed in his sleep the night before he took the hemlock or he didnot, independently of what anyone believes” is our pervasivemisunderstanding of the notion of truth. They apply the same diagnosisto the realist’s belief in the mind-independence of entities inthe world and to counterfactuals which express this belief. Weovergeneralize the notion of truth, believing that it applies in caseswhere it does not, they contend [Tennant 1987, 1997; Wright 1993].

An apparent consequence of their view is that reality is indeterminatein surprising ways—we have no grounds for asserting thatSocrates did sneeze in his sleep the night before he took the hemlockand no grounds for asserting that he did not and no prospect of everfinding out which. Does this mean that for anti-realists the worldcontains no such fact as the fact that Socrates did one or the otherof these two things? No. For anti-realists who subscribe tointuitionistic principles of reasoning, the most that can be said isthat there is no present warrant to assert \(S \lor \neg S\): thatSocrates either did or did not sneeze in his sleep the night before hetook the hemlock. Realists who endorse the Compositionality Reply maycounter that classical disjunction is the simplest projection fromconcrete cases: we understand the disjunction by projecting from ourown case, for example: “I am sneezing now or I am not sneezing now”[thanks, again, to the reviewer]. We return to this issue below in§3.2.

Dummett contends that a speaker’s understanding of meaning isexhaustively manifested by certain recognitional abilities —those that are exercised when determining whether the truth-conditionsof sentences are satisfied. Recent research, however, has cast doubton his claim, unearthing crucial semantic recognitional abilities thatarenot manifest in use. Psychologists have testedpeople’s understanding of logical rules using universitystudents as their subjects for the last sixty years or so. Recently,they have compared subjects’ responses to ‘Control’syllogisms such asAll vehicles have wheels; Bikes are vehicles.So, bikes have wheels [De Neys 2014] with responses to‘Conflict’ syllogisms likeAll vehicles have wheels;Boats are vehicles. So, boats have wheels. The consistent findingacross hundreds of such studies has been that while mostuniversity-educated subjects accept the Control syllogisms theyreject the Conflict ones, judging that the conclusion‘boats have wheels’ doesnot follow from thepremises thatall vehicles have wheels andboats arevehicles. The studies seem to show that even highly educatedpeople are unaware of basic logical rules, particularly so whensubjects make no reference to these rules when quizzed about theirresponses. Yet, Wim de Neys (2012) persuasively argued that a range ofmore sophisticated measures suggest this may not be so. The measuresincluded ones for skin conductance showing increased autonomic arousalwhen solving Conflict syllogisms; eye-tracking, showing increasedsaccades to Conflict syllogism premises and conclusions compared tothose for Control syllogisms; higher activation of the anteriorcingulate cortex (an area known to be active in conflict detection)for Conflict syllogisms; longer response latencies and decreasedresponse confidence when solving Conflict syllogisms as compared toControl ones. De Neys concludes from these findings that whilesubjects do indeed recognise logical rules, in most cases thisrecognition is not sufficient to counter a strong bias to reject anyreasoning that leads to an obviously false conclusion: “Hence,although solving conflict problems might require abundant executiveresources, detecting the conflict is successful even for the mostbiased reasoners.” [ibid, p.31]

3.2 Language Acquisition

The second anti-realist challenge to realism concerns our acquisitionof language. The challenge is for realists to explain how a childcould come to know the meanings of certain sentences within his/herlanguage: the ones which the realist contends have undetectabletruth-makers associated with them. How could the child learn themeanings of such sentences if these meanings are determined by statesof affairs not even competent speakers can detect? In short,competence in one’s language would be impossible to acquire ifrealism were true [Dummett 1978, 1993; Wright 1993]. This is theLanguage Acquisition challenge.

Consider the sentence (S) once more:

• (S) Socrates sneezedin his sleep the night before he took the hemlock.

Realists say (S) is either true or false even though we may (andalmost certainly will) never know which it is. The state of affairswhich satisfies (S)’s truth-condition when it is true, its‘truthmaker’, and the state of affairs which satisfies thetruth-condition of the negation of (S) when (S) is false are supposedto be able to hold even though competent speakers cannot detectwhether they do. How could the child ever learn about thisundetectable relation?

A straightforward realist reply is, again, the Compositionality Replyencountered in §3.1— that knowledge of the meanings ofsentences with undetectable truth-conditions like (S) is acquired inthe same way as knowledge of the meanings of sentences withrecognisable truth-conditions: namely, compositionally by acquiringknowledge of the lexicon and the relevant compositional principles[Pagin 2009].^[2] While anti-realists contest the interpretation of the compositionalprinciples that generate sentences with undetectable truth-conditions[where realists assert \(S \lor \neg S\) is true (S being theSocrates sentence), anti-realists maintain there is no ground forasserting this disjunction [e.g. Tennant 1987]], this does nothing toshow that the realist’s classical disjunction is unlearnable[thanks to a referee for emphasizing this point], and, as we saw in§3.1, there is a simple way in which it could be learned.

The Acquisition challenge is exacerbated by the anti-realist’sassumption that since the linguistic meaning of an expressionE is determined solely by competent speakers’ use ofE the child’s task in all cases is to infer or observethe meaning ofE from its use. Thus Dummett [1978 pp.216–217], in discussing the meaning of mathematical statements,proposes a thesis he argues holds for the meanings of every kind ofstatement:

The meaning of a mathematical statement determines and is exhaustivelydetermined by its use. The meaning of a mathematical statement cannotbe, or contain as an ingredient, anything which is not manifest in theuse made of it, lying solely in the mind of the individual whoapprehends that meaning: if two individual agree completely about theuse to be made of the statement, then they agree about its meaning.The reason is that the meaning of a statement consists solely in itsrole as an instrument of communication between individuals, just asthe powers of a chess-piece consist solely in its role in the gameaccording to the rules.

W.V.O. Quine is even more insistent on the public nature of linguisticmeaning. Displaying his unshakable faith in Skinnerian models oflanguage-learning he writes [1992, pp. 37–38]:

In psychology one may or may not be a behaviourist, but in linguisticsone has no choice … There is nothing in linguistic meaningbeyond what is to be gleaned from overt behaviour in observablecircumstances.

Some realists reject the publicity of meaning principle as it appliesto language learning. While many accept that the meaning of a word isdetermined by its use in a given language, not all do [e.g. Chomsky1986; Fodor and Lepore 2002]. Realists who think of semanticunderstanding as a mental state reject the idea that a speaker’sunderstanding of meaning is exhaustively manifest in its useas aninstrument of communication. They argue meaning is fixed by itsinternal role in expressing thought. If Dummett’s manifestationrequirement is a demand for a behaviouristic reduction of semanticknowledge, they argue, it should be rejected [Burgess 1984; Chomsky1986]. However, some sympathetic to the demand for fullmanifestability of semantic knowledge reject the behaviouristicconstrual and instead justify it on conceptual grounds [e.g. Shieh1998, McGee 2015].^[3]

The Acquisition Challenge is a vexed one for realists to respond tobecause Dummett shares little common ground with the many (realist)philosophers, linguists and cognitive scientists who believe languageacquisition is effected by a dedicated language module [Fodor 1975,1983, 2008; Chomsky 1986, 2006; Crain 2012; Pinker 1994] or even withthose who disavow modularity but agree that semantic knowledge ispartly unconscious. Thus, Dummett rejected Chomsky’s thesis thatspeakers have unconscious knowledge of the rules of Universal Grammaron the Wittgensteinian grounds that it was, at best “anexplanatory hypothesis, not a systematisation of facts open toview.” [Dummett 1981]. Dummett apparently took this“systemisation of facts” to be satisfied by an accountthat pairs knowledge of meaning with recognitional abilities.^[4]

Evidence from developmental psychology indicates some meaning ispre-linguistic and that some pre-linguistic meaning or conceptualcontent relate to situations that are not detectable by the child. Forexample, psychologists have discovered systems of core knowledgeactivated in infancy that govern the representation of,interalia concrete objects and human agents [see Spelke 2003; Spelkeand Kinzler 2007]. An interesting finding from preferential gazeexperiments suggests 4 month old infants represent occluded objects ascontinuing behind their barriers.^[5]

While these findings do not by themselves show that the meanings ofmental symbols is not determined by public use, they do provideevidence that ‘verification-transcendent’ conceptualcontent is laid down in the earliest stages of cognitivedevelopment.

It should be noted that the anti-realist’s model of disjunctionseems at odds with how we actually use disjunction. For it rules manyquite innocuous-looking disjunctions as unacceptable:

We say of a coin to be tossed that (C)The coin will either landHeads or Tails without having any idea which face it will land onor of a lottery with one ticket to be drawn from a million ticketsthat (L)One of these tickets will be the winning ticketwithout wishing to say of any one ticket that it will win. In fact, itis arguably the point of disjunction to allow speakers to conveyuseful information about the number of live possibilities when they donot know which of those possibilities does (or did or will) obtain.Indeed, even when we can never find out which alternative holds orheld or will hold. Consider (D)The number of dinosaurs on Earthwas either odd or even. Most people hear (D) as a trivial truth.Why? Presumably because if there were dinosaurs on earth, there musthave been a definite number of them, N say, where N is a positiveinteger. But as all positive integers are either odd or even, N iseither odd or even. Yet, it is utterly unlikely that we could everknow what positive integer N is. Hence, we’ll (almost certainly)never know whether the number N of dinosaurs that roamed our world wasan odd positive integer or an even one.

Whence, disjunction provides a plausible method for a language learnerto acquire the notion of verification-transcendent truth. Just becausethe disjunctions in (C) and (L) are assertible even though theirindividual disjuncts are not (at the time of utterance or ofentertaining the disjunction in thought) and the disjunction (D) isassertible even though we will never find out which disjunct holds, wecan come to grasp how a statement such as (O)There were an oddnumber of dinosaurs on earth could be true without our ever beingable to verify it is. For, as (D) is true, it must either be that (O)is true or else that (E)There were an even number of dinosaurs onearth is true instead. Thus, either (O) or (E) is true, thoughundetectably so.

3.3 Radical Skepticism

According to Hilary Putnam, the metaphysical realist subscribes notjust to the belief in a mind-independent world but also to the thesisthat truth consists in a correspondence relation between words (ormental symbols) and things in that mind-independent world. Call thisthesiscorrespondence truth (after Devitt 1991). Moreimportantly, metaphysical realists aver that an ideal theory of theworld could beradically false, Putnam contends:‘radical’ in the sense thatall (or almost all)of the theory’s theses could fail to hold. Such a global failurewould result if we were to be ‘brains-in-a-vat’, ourbrains manipulated by mad scientists (or machines, as in the movieThe Matrix) so as to dream of an external world that wemistake for reality. Call this thesisradical skepticism.

It is widely believed that states of affairs that are trulymind-independent do engender radical skepticism. The skeptic contendsthat for all we could tell we could be brains in a vat—brainskept alive in a bath of nutrients by mad alien scientists, or, inPutnam’s preferred version, by super-computers so that there areand never were any flesh and blood creatures as we imagine there tobe. All our thoughts, all our experience, all that passed for sciencewould be systematically mistaken if we were. We’d have no bodiesalthough we thought we did, the world would contain no physicalobjects, yet it would seem to us that it did, there’d be noEarth, no Sun, no vast universe, only the brain’s deludedrepresentations of such. At least this could be the case if ourrepresentations derived even part of their content from links withmind-independent objects and states of affairs. Since realism impliesthat such an absurd possibility could hold without our being able todetect it, it has to be rejected, according to anti-realists.

Putnam assays to prove that realism is not just false but internallyinconsistent. It is the goal of his Brain-In-A-Vat Argument to provenot only that we arenot brains in a vat but that wecould not be. When I talk of Putnam’s Brain-In-A-VatArgument,BIVA, I shall mean his argument for themodal thesis that wecould not be brains-in-a-vat. Mostdiscussions of Putnam’s Brain-In-A-Vat Argument focus instead onthe question of whether Putnam has shown that we are not BIVs. [I amindebted to a SEP reviewer for emphasizing the need to focus on themodal conclusion thatwe could not be brains-in-a-vat and forhelpful suggestions about arguments for this conclusion]. Thedifficulty we face is that the only clear argument Putnam gives forthe modal conclusion is very brief and, as we shall see, a littleperplexing.

A crucial assumption of theBIVA is semanticexternalism, the thesis that the reference of our words and mentalsymbols is partially determined by contingent relations betweenthinkers and the world. This is a semantic assumption many realistsendorse. To understand semantic externalism, it is useful to recallthe ‘Twin-Earth’ considerations used to support it: onTwin-Earth things are exactly as they are here on Earth except for onedifference—whereas for Earthly humans water has the chemicalcomposition H₂O, for our döppelgangers on Twin-Earth,twumans, water is instead composed of some substance unknown to us onEarth, XYZ. Now when you and your twuman counterpart say (or think)“‘Water’ refers to water” both of you utter(or think) truths. But which truth you both think or utter differs.For humans “‘Water’ refers to water” expressesthe truth that the term ‘water’ in English refers to thatsubstance whose chemical composition is H₂O. For our twumanTwin-Earth counterparts, however, their sentence“‘Water’ refers to water” expresses the truththat their term ‘water’ in Twenglish refers to thatsubstance whose chemical composition is XYZ.

Now, according to Putnam, while the realist’s mind-independencethesis entails that we could indeed be brains in a vat, Externalismentails that were we to be BIVs we could not even entertain this as apossibility (since a BIV’s thoughts are about virtual BIVs, notBIVs). Putnam concludes that (externalist) realism is incoherent[Putnam 1981]. For this argument to work, however, Putnam must beassuming a rather restrictive form of modal rationalism: we could bebrains in a vat only if in the circumstance that we were envatted, wecould conceive that we were envatted.

There is, in fact, nological incoherence in believing boththat (I) It is possible that one is a BIV and that (II) If one is aBIV one could never conceive that one was —as the figure belowillustrates.

Figure. Consider a universe of 4 worlds.If we arenot in fact brains-in-a-vat (so that the hypothesisv that we are brains in a vat is false, \(\neg v\) is true at\(w^*\), the actual world) we can nonetheless entertain \((E)\), thehypothesis that we are (so that \(Ev\) is true at \(w^*\)),recognizing as we do so that were we to inhabit a world such as \(w'\)in which we are brains-in-a-vat (v holds at \(w'\)), we wouldlack the semantic resources to articulate thoughts reflecting our ownenvatted state so that wecould not so much as entertain thethought that we were brains-in-a-vat (\(\neg Ev\) holds not only at\(w'\) but at all those worlds ( \(w''\), \(w'''\)) accessible from\(w'\)).

Putnam’s argument for realism being inconsistent does not seemcompelling. However, he offers another argument based upon Externalismthat seeks to prove we could not be brains-in-a-vat. This is hisBIVA. It rests upon the following reasoning: “So, ifwe are brains in a vat, then the sentence ‘We are brains in avat’ says something false (if it says anything). In short, if weare brains in a vat, then ‘We are brains in a vat’ isfalse. So, it is necessarily false.” [1981, p.15]. Putnam apparentlythought he had proved by means of Externalism that we could not bebrains-in-a-vat. Has he? Suppose I worry that I might be abrain-in-a-vat. Seeking reassurance that I could not be, I readPutnam’s words. I ponder the sentence “If I am a brain-in-a-vat,then the sentence ‘I am a brain-in-a-vat’ is false”. IfExternalism is true, I reason, then if I indeed am a brain-in-a-vat,the pronoun ‘I’ in my language (vat-English or v-English)refers not to me but tovirtual me,v-me, and theterm ‘brain-in-a vat’ or ‘BIV’ refers not toreal BIVs but tov-BIVs. That being so, the sentence ‘Iam a brain-in-a-vat’ in v-English will mean thatv-me is av-BIV. But that proposition is true, not false. I thenreconsider: perhaps the singular pronoun ‘I’ refers to mein every possible situation, whatever my nature? If so, then in thecircumstance that I am a BIV my utterance (or mental tokening) of‘I am a BIV’ will mean thatI am a v-BIV. Thatproposition is false. But it is not the proposition Putnam isdiscussing. The proposition Putnam thinks is necessarily false is theproposition thatI am a BIV.

Is there then no valid argument in the spirit of Putnam’sBIVA which could be used to show that we could not bebrains-in-a-vat?

Michael McKinsey has cleverly reworked Putnam’s argument to showagainst the sceptic that we are not (and we can know that we are not)brains-in-a-vat. [His anti-skeptical argument, AS, in section 9 of hisWinter 2024 archived entryskepticism and content externalism]. Here, I adapt McKinsey’s AS argument to formulate a revisedbrain-in-a-vat argument,BIVA*. Consider the set ofworlds U wherein I am a denizen with much the same cognitive abilitiesas I have now in the actual world @ such that in every world w of U, Ipossess at least a modicum of logical acumen. The BIV hypothesis isthat I could be a brain-in-a-vat (a lab-grown computer-controlledbrain dreaming it is a human denizen of an external world experiencingand thinking about that world in just the way that I experience andthink about it). Alternatively, I could be a computer simulation of ahuman imagining that it is a human. Then:

1. In any world w ∈ U, I understand that the proposition that Ihave a body entails I am not a BIV.
2. Thus, in any world w ∈ U, I have the concept of a BIV.
3. Suppose that there is a world w′ ∈ U in which I am aBIV.
4. Then, by (2), in w′ I have the concept of a BIV.
5. But, by Externalism, if I’m a BIV in w′, then inw′ I do not have the concept of a BIV.
6. Hence, in w′ I both have and do not have the concept of aBIV.
7. Therefore, there is no world w′ ∈ U in which I am aBIV.

BIVA* rests on the two assumptions of Minimal LogicalAcumen, and (Semantic) Externalism. Premise (2) seems correct: onecannot grasp the proposition that one is not a BIV unless one has theconcept of a BIV. The MLA assumption guarantees I can recognize basicentailments such as from the proposition that I have a body to theproposition that I am not a BIV. Premise (5) rests on Externalism:since BIVs are lab-grown computer-controlled brains or computersimulations of humans who inhabit a virtual world in thought, BIVscannot refer in thought or word to real world brains or computersimulations.Of course, the argument is only as good as its Externalistassumptions and prominent realists such as Frank Jackson and DavidLewis follow Robert Stalnaker in rejecting Externalism for an‘Internalist’ view of semantic content according to whichthe content of a sentence is the set of possible worlds in which it istrue. Those realists who do accept Externalism and are swayed by theMcKinsey-styled argumentBIVA*, on the other hand,still owe us an explanation of how we can so much as grasp theproposition that we are brains in a vat or virtual humans (if only toreject it). Their answer will be that while all our evidence cannotrule out this possibility, if Externalism is true there is no way theworld could have been wherein this possibility obtained. That is tosay, these realists believe that while it isepistemicallypossible that we are brains-in-vats or virtual humans, it is notmetaphysically possible (if Externalism is true).

3.4 Models and Reality

Putnam’s Model-Theoretic Argument is the most technical of thearguments we have so far considered. We shall not reproduce all thetechnicalities here. The central ideas can be conveyed informally,although some technical concepts will be mentioned where necessary.The argument purports to show that the Representation Problem—toexplain how our mental symbols and words get hooked up tomind-independent objects and how our sentences and thoughts targetmind-independent states of affairs—is insoluble.

According to the Model-Theoretic Argument, there are simply too manyways in which our mental symbols can be mapped onto items in theworld. The consequence of this is a dilemma for the realist. The firsthorn of the dilemma is that s/he must accept that what our symbolsrefer to is massively indeterminate. The second horn is that s/he mustinsist that even an ideal theory, whose terms and predicates candemonstrably be mapped veridically onto objects and properties in theworld might still be false, i.e., that such a mapping might not be theright one, the one ‘intended’.

Neither alternative can be defended, according to anti-realists.Concerning the first alternative, massive indeterminacy for perfectlydeterminate terms is absurd. As for the second, what can it mean for amapping to be the intended mapping if not that it satisfies everyconceivable operational and theoretical constraint? Yet Putnam’sModel-Theoretic Argument proves that there will invariably beinterpretations of an ideal theory on which all the theory’ssentences come out true which do satisfy any constraint we mightchoose to impose on them, anti-realists maintain.

Now, in logic theories are treated as sets of sentences and theobjects (if any) that sentences talk about appear as elements of thedomain of set-theoretic entities calledstructures.Associated with these structures areinterpretation functionsthat map individual constants onto individual objects of the domainand n-place predicates onto n-tuples of elements in the domain. When astructure makes all the sentences of a given theory true it is calledamodel of the theory. By demonstrating that there is a modelof T we show theory T is consistent. If T turns out to be true in itsintended model, then T is truesimpliciter.

For an informal illustration of the basic ideas of model theory, seethe supplementary document,Model Theory: Core Ideas.

Let us call structures whose domains consist of numbers‘numeric’ structures. The nub of Putnam’sModel-Theoretic Argument against realism is that the realist cannotdistinguish the intended model for his/her total theory of the worldfrom non-standard interlopers such as permuted models or ones derivedfrom numeric models, even when total theory is a rationally optimalone that consists, as it must do, of aninfinite set ofsentences and the realist is permitted to impose the most exactingconstraints to distinguish between models. This is a very surprisingresult if true! How does Putnam arrive at it?

Putnam uses several different arguments to establish the conclusionabove. The argument of prime concern to realists, as Taylor (2006)emphasises, is the argument based on Gödel’s CompletenessTheorem, GCT. For, following Lewis [Lewis, 1984], realists mightconcede to Putnam that they cannot single out the intended model ordistinguish it from various ersatz models, but argue that this is notnecessary since it suffices that an intended modelexists,even if we cannot specify it. This response does not answer the GCTargument, however. For this argument purports to prove directly thatan ideal theory of the world could not be false, a conclusion flatlyinconsistent with realism. See the supplementary documentThe Model-Theoretic Argument and the Completeness Theorem for an outline of this argument.

Putnam has another model-theoretic argument against realism, thePermutation Argument, also designed to guarantee we can find a trueinterpretation of an ideal theory:

Suppose that the realist is able to somehow specify the intendedmodel. Call this intended model \(W''\). Then nothing the realist cando can possibly distinguish \(W''\) from a permuted variant \(W^*\)which can be specified following Putnam 1994b, 356–357:

We define properties of being a cat* and being a mat* such that:

1. In the actual world cherries are cats* and trees are mats*.
2. In every possible world the two sentences “A cat is on amat” and “A cat* is on a mat*” have precisely thesame truth value.

Instead of considering two sentences “A cat is on a mat”and “A cat* is on a mat*” now consider only the one“A cat is on a mat”, allowing its interpretation to changeby first adopting the standard interpretation for it and then adoptingthe non-standard interpretation in which the set of cats* are assignedto ‘cat’ in every possible world and the set of mats* areassigned to ‘mat’ in every possible world. The result willbe the truth-value of “A cat is on a mat” will not changeand will be exactly the same as before in every possible world.Similar non-standard reference assignments could be constructed forall the predicates of a language. [See Putnam 1985, 1994b.]

Bas van Fraassen [1997] provides a concise informal sketch ofPutnam’s Model-Theoretic Argument:

LetT be a theory that contains all the sentences we insistare true, and that has all other qualities we desire in an idealtheory. Suppose moreover that there are infinitely many things, andthatT says so. Then there exist functions (interpretations)which assign to each term inT’s vocabulary anextension, and which satisfyT. So we conclude, to quotePutnam, “T comes out true, true of the world, providedwe just interpret ‘true’ as TRUE(SAT)”.

Here ‘TRUE(SAT)’ means “true relative to a mappingof the terms of the language ofT onto (sets of) items in theworld”.

Why should we interpret ‘true’ as TRUE(SAT)? Because truthis truth in an intended model and, Putnam argues, amongst all themodels ofT that make all its theses come out true there isguaranteed to be at least one that passes all conceivable constraintswe can reasonably impose on a model in order for it to be an intendedmodel ofT.

Realists have responded to the argument by rejecting the claim that amodelM of the hypothetical ideal theoryT passesevery theoretical constraint simply because all of the theory’stheses come out true in it. For there is no guarantee, they claim,that terms stand in the right relation of reference to the objects towhichM links them. To be sure, if we impose anothertheoretical constraint, say:

Right Reference Constraint (RRC): Termt refers to objectx if and only if \(Rtx\) whereR is the rightrelation of reference,

thenM (or some model based on it) can interpret this RRCconstraint in such a way as to make it come out true. But there is adifference between a model’s making some description of aconstraint come out true and its actually conforming to thatconstraint, metaphysical realists insist [Devitt 1983, 1991; Lewis1983, 1984].

Thus Devitt and Lewis claim that Putnam’s alternative modelM has not been shown to satisfyevery theoreticalconstraintmerely by making some description of eachtheoretical constraint true.

Skolem’s Paradox in set theory seems to present a strikingillustration of Lewis’s distinction between (re)interpreting aconstraint to make it come out true and genuinely satisfying thatconstraint. The Löwenheim-Skolem Theorem states that everyconsistent, countable set of first-order formulae has a denumerablemodel, in fact a model in the set of integers \(\mathbb{Z}\). Now inZF one can prove the existence of sets with a non-denumerable numberof elements such as the set \(\mathbb{R}\) of real numbers. Yet the ZFaxioms comprise a consistent, countable set of first-order formulaeand thus by the Löwenheim-Skolem Theorem has a model in\(\mathbb{Z}\). So ZF’s theorem \(\phi\) stating that\(\mathbb{R}\) is non-denumerable will come out true in a denumerablemodel \(\mu\) of ZF.

How can this be? One explanation is that \(\mu\) makes \(\phi\) trueonly at the cost of re-interpreting the term‘non-denumerable’ so that it no longer meansnon-denumerable. Thus \(\mu\) is not the intended model\(M^*\) of ZF. It looks as if the metaphysical realist has a clearillustration of Lewis’s distinction at hand in set theory.

Unfortunately for the realist, this is not the only explanation. Infact, Putnam used this very example in an early formulation of theMTA. Just because there are different models that satisfy \(\phi\) insome of which \(\mathbb{R}\) is non-denumerable but in others of which(such as \(\mu\)) \(\mathbb{R}\) is denumerable, Putnam argued, it isimpossible to pin down the intended interpretation of‘set’ via first-order axioms. Moreover, well beforePutnam, Skolem and his followers had taken the moral of Skolem’sParadox to be that set-theoretic notions are indeterminate [Forfurther discussion, see the entry onSkolem’s paradox].

The question of how to interpret Skolem’s Paradox merely raisesanew the question of what it is for a theory such as the hypothesizedideal theoryT to satisfy a right reference constraint,(RRC). Putnam [1985] regards it as simply question-begging for arealist to assume her notion of an intended model is determinate: i.e.that terms such as ‘satisfaction’ or‘correspondence’ refer to those relations to which shewishes them to refer. That her term ‘refers’ refers to herdesired reference relation is ‘just more theory’. Realistshave responded that Putnam is wilfully re-interpreting their semanticterms as he sees fit.^[6]

Is there some independent way to validate Lewis’s distinction?Michael Resnick thinks so [Resnick 1987]. Putnam maintained thatM, the model he constructs of the ideal theoryT, isan intended model because it passes every operational and theoreticalconstraint we could reasonably impose. It passes every theoreticalconstraint, he argues, simply because it makes every thesis ofT true. But unless the Reflection Principle(RP) below holds, Resnick argues, this inference isjust anon-sequitur:

• (RP)To any conditionf that a model of a theory satisfies, therecorresponds a conditionC expressible in the theory that thattheory satisfies.

However, this principle is false. The simplest counterexample to it,Resnick points out, is Tarskian truth. Suppose we impose onT’s modelM a condition \(f^*\) thatM makes all ofT’s theses come out true. Then,unlessT is either inconsistent or too weak to expresselementary arithmetic no truth predicate will be definable inT. Whence there will be no conditionC expressibleinT corresponding to this condition \(f^*\) onT’s model(s)M. Resnick concludes(ibid):

Any true interpretation ofT whatsoever—even one whichdoes not satisfyC—will make true every thesis ofT, including T’s assertion thatC issatisfied. Which suffices to block the ‘just more theory’gambit.

The philosophical consensus appears to be that Lewis and Resnick areright. Note that their argument, if sound, works against thePermutation Argument also. Apart from the authors already discussed,important criticisms of the MTA were advanced in Hale and Wright 1997,van Cleve 1992 and Bays 2008. However, some very sophisticatedanti-realist attempts to buttress the Model-Theoretic Argument againstLewis-styled criticisms have appeared. Igor Douven reconstructsPutnam’s argument, defending it against standard objections[Douven 1999]. Barry Taylor presents a detailed explication anddefence of Putnam’s Just More Theory reply [Taylor 2006], asdoes Tim Button [Button 2013]. Whether these newer formulations of theMTA succeed in answering the Lewis/Resnick objection is an open question.^[7]

3.5 Conceptual Schemes and Pluralism

According to conceptual pluralists, there can no more be an answer tothe question “What is the structure of the world?” outsideof some scheme for classifying entities than there can be an answer tothe question of whether two eventsA andB aresimultaneous outside of some inertial frame for dating those events.The objects that exist are the objects some conceptual scheme saysexists—‘mesons exist’ is true just because mesonsexist relative to the conceptual scheme of current physics.

Realists think there is a unitary sense of ‘object’,‘property’ etc., for which the question “whatobjects and properties does the world contain?” makes sense. Anyanswer which succeeded in listing all the objects, properties, eventsetc. which the world contains would comprise a privileged descriptionof that totality [Putnam 1981]. Anti-realists reject this. For them‘object’, ‘property’ etc., shift their sensesas we move from one conceptual scheme to another. Some anti-realistsargue that there cannot be a totality of all the objects the worldcontains since the notion of ‘object’ isindefinitelyextensible and so, trivially, there cannot be a privilegeddescription of any such totality. [For discussions of indefiniteextensibility see Dummett 1978, 1991; Linnebo 2018; Warren 2017].

How does Putnam defend conceptual relativity? One way is by arguingthat there can be two complete theories of the world which aredescriptively equivalent yet logically incompatible from therealist’s point of view. For example, theories of space-time canbe formulated in one of two mathematically equivalent ways: as anontology of points, with spatiotemporal regions being defined as setsof points; or as an ontology of regions, with points being defined asconvergent sets of regions. Such theories are descriptively equivalentsince mathematically equivalent and yet are logically incompatiblefrom the realist’s point of view, Putnam contends [Putnam 1985,1990]. Call the point based theory \(T_1\)and the region-based theory\(T_2\).

Anti-realists regard two theories as descriptively equivalent if eachtheory can be interpreted in the other and both theories explain thesame phenomena. This judges \(T_1\) and \(T_2\) as descriptivelyequivalent. Realists can accept the two theories are descriptivelyequivalent. What the realist cannot accept is that \(T_1\) and \(T_2\)are logically incompatible. Thomas William Barrett and Hans Halvorsonargue that the two theories “ … are simply convenientways of expressing the geometric facts that are more fully expressedby a comprehensive theory” that quantifies over both points andlines. \(T_1\) and \(T_2\) cannot be incompatible according to Barrettand Halvorson because they are in essence thesame theory[Barrett and Halvorson 2017]. This seems right: points exist in\(T_2\) just as they do in \(T_1\). The two theories differ only intheir choice of theoretical primitives, not in their ontology. Thegeometric case thus does not provide an instance of two theories thatare descriptively equivalent but logically incompatible (from therealist’s point of view). Realists deny the existence of suchtheories.

So, consider another Putnam-styled case [Putnam 2004]. Ernie looksinto his bag and sees there are 3 coins and nothing else and announces“There are exactly 3 objects in my bag.” Maxi looks intoErnie’s bag and shakes her head “No Ernie, there are 7objects in your bag!” she corrects him. The Carnapian pluralistfeels she can defuse the conflict and accommodate both points of viewby maintaining that whilst 3 objects exist-in-E (whereE is Ernie’s everyday framework), 7 objectsexist-in-M (withM Maxi’s mereologicalframework). But even if Maxi can endorse both of these claims (sincethe mereological objects include Ernie’s 3 coins), it is not atall certain Ernie can do so. If Ernie is unpersuaded that mereologicalfusions of objects are themselves objects, then he may rejectMaxi’s putative truthmaker for her framework-relative existenceclaim “7 objects exist-in-M”.

In this case, Maxi and Ernie do disagree about what exists. However,the pluralist’s suggestion that 3 objects exist-in-Ebut 7 objects exist-in-M is not clearly warranted. There aresimpler explanations: one is that by ‘object’ Ernie meansordinary object, by ‘object’ Maxi means mereologicalobject. Nothing deeper than that is required to explain theirdisagreement. Rather than existence or truth that is relativized, themeanings of their terms differ. On this account, pluralists havemistaken a plurality of meanings for a plurality of modes of being.However, other explanations are also possible: for instance, it may bethat Ernie and Maxi do mean the same thing by ‘object’ buthold incompatible theories about what counts as an object. Moreimportantly, as a reviewer noted, the debateneed not turn onthe notion of an object: it can proceed with quantifiers, for example.The disagreement then would arise from divergent interpretations ofthose quantifiers.

Putnam’s pluralism has provoked very different reactions fromrealists. Some argue that conceptual pluralism is consistent withrealism [Lynch 1998; Horgan and Timmons 2002; Sosa 2003], others takePutnam’s pluralism to amount to the claim that ontologicalexpressions are either indeterminate or that alternative ontologiesare equally good, both alternatives being problematic [Eklund 2008].Realists cannot make sense of the Carnapian idea that existence andtruth are relative to a conceptual scheme [Brueckner 1998]. Peter vanInwagen provides a trenchant criticism of Putnam’s claims (remarks in square brackets added for clarification):

I cannot grant that ‘Carnap’s’ [Ernie’s]and ‘The Polish logician’s’ [Maxi’s]descriptions are equally good or equivalent descriptions of thepopulation of a world [e.g., the contents of Ernie’sbag]—not at least if Carnap’s description is ‘aworld that contains three mereological simples and nothingelse’. I cannot grant that theycould be ‘equallygood or equivalent descriptions of the population of a world’since they are straightforwardly incompatible. (vanInwagen 2002)

Recently, however, some impressive neo-Carnapian defences ofconceptual pluralism have been proposed that bring new considerationsto bear on these debates. We briefly review some of these in section4.

4. Realism and Anti-Realism in Meta-Ontology

Debates in meta-ontology (analytic ontology) over the last twentyyears have sparked renewed interest in realism. They have also seen amarked shift in how realism, i.e. ontological realism, is understood.“The central question of metaontology”, Theodore Sider, aprominent ontological realist, contends, “is that of whetherthere are many equally good quantifier meanings, or whether there is asingle best quantifier meaning.” [Sider 2009, p.397]. WhereSider argues for a single best quantifier meaning, Eli Hirsch believesthere are a multiplicity of possible quantifier meanings that areequally good, a thesis he callsQuantifier Variance. Thismeaning-theoretic focus is something new.^[8]

It is no surprise, then, to find that the positions marked out as‘realist’ and ‘anti-realist’ by those engagedin ontological disputes do not always coincide with realism andanti-realism as we have explained these metaphysical views.^[9]

A more significant division is between metaontologists who accept arobust conception of ontology, anddeflationistsabout ontology who don’t. Sider defends robust ontology [Sider2009, 385–386]:

“ontological deflationists”… have said …when some particles are arranged tablewise, there is no“substantive” question of whether there also exists atable composed of those particles. There are simply different —and equally good — ways to talk. I, on the other hand, accept avery strong realism about ontology. I think that questions about theexistence of composite objects are substantive, just as substantive asthe question of whether there are extra-terrestrials.

Neo-Carnapians such as Putnam, Eli Hirsch, David Chalmers, AmieThomasson, and Huw Price are ontological deflationists who embraceconceptual pluralism about ontological matters. Hirsch, however,thinks conceptual pluralism is perfectly consistent with realism[Hirsch, E. 2002]. Matti Eklund understands Hirsch to mean that heconsiders the world to be an amorphous lump [Eklund, M., 2008] (citingMichael Dummett), a ‘lump’ that alternative and equallyfeasible conceptual schemes serve to make intelligible. For Sider, incontrast, rejecting an intrinsic structure to the world is to reject realism.^[10]

Competing views about temporal persistence do not seem to be semanticin nature. While Perdurantists believe that things persist throughtime by virtue of having temporal parts thatperdure,Endurantists reject the notion of temporal parts as incoherent—things persist byenduring: they are wholly presentwhenever they exist. As observed in the entry ontemporal parts:

This looks like a straightforward ontological disagreement, a disputeabout what exists.

Eli Hirsch is not convinced, however:

I claim that the dispute between Endurantists and Perdurantists isverbal … each party ought to agree the other party speaks atruth in his own language. [Hirsch 2011, 229]

How can this be? Endurantists think perdurantists are guilty ofspatializing time when they talk about temporal parts; perdurantiststhink enduring objects cannot explain change. How can there be arapprochement of the sort Hirsch has in mind?

Hirsch’s novel and intriguing idea is that what makes theendurantist/perdurantist temporal parts debate and thenihilist/universalist mereological debate merely verbal ones is thefact that the protagonists in these debates mean different things bytheir quantifiers, in particular their existential quantifiers, intheir ontological assertions. While both protagonists speak a commonlanguage, here English, in which certain ontological claims such as‘there are tables’ happen to come out true, this is asuperficial socio-linguistic fact about English that might not havebeen so: we and they could just as easily have spoken English* (anontological nihilist language) in which the sentence ‘there aretables’ came out false. Protagonists in these ontologicaldisputes are, unwittingly, engaged in a ‘merely verbal’debate and are thus talking past each other.^[11]

How does the deflationist tell that an ontological dispute is a‘merely verbal’ one? Hirsch thinks that when we interpretthe words of another, we assign truth-conditions to their sentences bymatching those sentences with sets of possible worlds, guided by themetasemantic maxim that the speaker’s assertion of thosesentences should come out true. The maxim applies to ontologicaldisputes such as the Ernie/Maxi dispute about mereology — thereare possible languages in which both speakers’ assertions comeout true. Where a ‘character’ of a sentence is a functionfrom contexts of utterance to truth-conditions, Hirsch contends:“speakers of either language should allow that speakers of theother language assert sentences that have the same characters and thesame truth-values as they themselves assert” [Hirsch 2009,p. 242].

In this way Ernie should attribute the same set of possible worlds(intensions) to Maxi’s sentence ‘There are seven objectsin your bag’ as he associates with his own sentence ‘Thereare three objects in my bag’ and Ernie should interpret Maxi asuttering a truth in so doing. Ernie and Maxi are asserting the verysame proposition but are using different words to express it. Theyare, as a result, simply talking past each other.

Hirsch’s doctrine of quantifier variance QV dominates currentmetaontological debate. Some have questioned whether interpreters onone side of an ontological dispute can admit that the language ofthose on the other side is possible. For to do so each interpretermust be able to provide a Tarskian semantics for the other’slanguage. But an Endurantist won’t be able to do this for thePerdurantist’s sentence such as ‘Alice_t is atemporal part of Alice’ since the predicate ‘is a temporalpart of’ has an empty extension in the Endurantist’slanguage [Hawthorne 2006; Eklund 2009]. Others suspect QV is aninternally unstable position: how can an Endurantist speaking herlanguage E allow that a sentence like ‘Alice_t is atemporal part of Alice’ is atrue sentence of thePerdurantist’s language P without admitting that there aretemporal parts [e.g. Hale and Wright 2009; Dorr 2014]? Warren 2015provides a convincing QV response to this ‘Collapse’argument. An important resource, containing papers by some of theauthors cited, is the collection of essays anthologised in Chalmers etal 2009 [For background on mereology see the entrymereology and for discussion of whether there are composite objects, see theentrymaterial constitution and the entryordinary objects].

The meaning-theoretic focus on Quantifier Variance in metaontologyrepresents a fascinating development. The implications for ontologicalrealism are as yet undecided.

5. Summary

We have considered a number of challenges to realism, the thesis thatthe objects and properties that the world contains, its nature andstructure, exist independently of our conception or perception ofthem. Historically, these challenges came from two camps: (1)neo-verificationists led by Dummett who assimilate belief inmind-independent world to a belief in a verification-transcendentconception of truth which they profess to find unintelligible, and (2)pragmatists and pluralists led by Putnam who also question theintelligibility of the realist’s mind-independent world but forreasons independent of any commitment to verificationism. Whileneo-verificationism today claims few adherents, within the ranks ofanalytic ontologists, pluralism and Carnap’s version of it inparticular, has enjoyed something of a revival. Today, perhaps themost active and engaging debates about realism are meta-ontologicalones that involve neo-Carnapian pluralists and their ontologicalrealist opponents.

Both the historical debate between realists and their anti-realistopponents and the meta-ontological debate are still very much open. Ifrealists could provide a plausible theory about how correspondencesbetween mental symbols and the items in the world to which they refermight be set up, many of these challenges could be met. Alternatively,if they could explain how, consistently with our knowledge of amind-independent world, no such correspondences are required to beginwith, many of the anti-realist objections would fall away asirrelevant. In the absence of such explanations it is still entirelyreasonable for realists to believe that the correspondences are inplace, however, and there can, indeed, be very good evidence forbelieving this. Ignorance of Nature’s reference-fixing mechanismis no reason for denying it exists.

Bibliography

• Armstrong, David, 1983,What is a Law of Nature?Cambridge: Cambridge University Press.
• Azzouni, Jody, 1997, “Applied Mathematics, ExistentialCommitment and the Quine-Putnam Indispensability Thesis,”Philosophia Mathematica, 5: 193–209.
• Bago, B. and W. De Neys, 2017, “Fast Logic?: Examining thetime course assumption of dual process theory.”Cognition, 158: 90–109.
• Barrett, Thomas William, and Hans Halvorson, 2017, “FromGeometry to Conceptual Relativity,”Erkenntnis, 82(5):1043–1063.
• Bays, Timothy, 2001, “On Hilary Putnam and hisModels,”Journal of Philosophy, 98: 331–50.
• –––, 2008, “Two Arguments AgainstRealism,”The Philosophical Quarterly, 58(231):193–213.
• Bennett, Karen, 2015, “‘Perfectly Understood,Unproblematic and Certain’: Lewis on Mereology,” in BarryLoewer and Jonathan Schaffer (eds.),A Companion to DavidLewis, Oxford and New York: Blackwell.
• Berger, A. (ed.), 2011,Saul Kripke, New York: CambridgeUniversity Press.
• Berger, A., 2011, “Kripke on the Incoherency of Adopting aLogic,” in Berger (ed.) 2011, 177–210.
• Blackburn, S., 1986, “Morals and Modals,” inFact,Science and Morality, G. Macdonald and C. Wright (eds.), Oxford:Basil Blackwell.
• Blackburn, S. and K. Simmons (eds.), 2000,Truth,Oxford: Oxford University Press.
• Boghossian, Paul, 1989, “The Rule FollowingConsiderations,”Mind, 93: 507–49.
• Bostrom, Nick, 2003, “Are you living in a ComputerSimulation?”The Philosophical Quarterly, 53(211):243–255.
• –––, 2005, “The Simulation Argument: Replyto Weatherson”Philosophical Quarterly, 55(218):90–97.
• Brandom, R. (ed.), 2000,Rorty and His Critics, Oxford:Blackwell.
• Brueckner, A., 1986, “Brains in a Vat,”Journal ofPhilosophy, 83(3): 148–167.
• –––, 1992, “If I’m a Brain in a Vatthen I’m Not a Brain in a Vat,”Mind, 101:123–28.
• –––, 1998, “Conceptual Relativism,”Pacific Philosophical Quarterly, 79(4): 295–301.
• –––, 2008, “Brains in a Vat”Journal of Philosophy, 83(3): 148–167.
• Burgess, John, 1984, “Dummett’s case forintuitionism,”History and Philosophy of Logic, 5(2):177–194.
• Button, T., 2013,The Limits of Realism, Oxford: OxfordUniversity Press.
• –––, 2015, “Brains in vats and modeltheory” in S. Goldberg (ed.) 2015, pp. 131–154.
• Carnap, R., 1950, “Empiricism, Semantics and Ontology”Revue Internationale de Philosophie, 4: 20–40.
• Carnap, R., 1963, “Replies and SystematicExpositions”in Schilpp, P. (ed.) 859–1013.
• Cartwright, Nancy, 1983,How the Laws of Physics Lie,Oxford: Oxford University Press.
• Chakravartty, Anjan, 2007,A Metaphysics for ScientificRealism: Knowing the Unknowable, Cambridge: Cambridge UniversityPress.
• Chalmers, David, 2009, “Ontological Anti-Realism” inD. Chalmers, D. Manley, and R. Wasserman (eds.) 2009,77–129.
• –––, 2010,The Character ofConsciousness, Oxford: Oxford University Press.
• Chalmers, D., D. Manley, and R. Wasserman (eds.), 2009,Metametaphysics: New Essays on the Foundations of Ontology.Oxford: Oxford University Press.
• Chomsky, Noam, 1986,Knowledge of Language, Westport, CT:Prager.
• –––, 2006,Language and Mind, 3rdedition, Cambridge: Cambridge University Press.
• Cogburn, Jon, 2005, “The Logic of Logical Revision:formalizing Dummett’s argument,”Australasian Journalof Philosophy, 83(1): 15–32.
• Cozzo, Cesare, 1994, “Are Dummett’s Requirements on aTheory of Meaning Sufficient for Rejecting Classical Logic?”Erkenntnis, 40(2): 243–263.
• Crain, Stephen, 2012,The Emergence of Meaning,Cambridge: Cambridge University Press.
• Crain, Stephen and D. Khlentzos, 2010, “The LogicInstinct,”Mind and Language, 25(1): 30–65.
• David, Marian, 1991, “Neither Mentioning ‘Brains in aVat’ nor Mentioning Brains in a Vat Will Prove That We Are NotBrains in a Vat,”Philosophy and PhenomenologicalResearch, 51(4): 891–896.
• Davidson, Donald, 1973, “On The Very Idea of a ConceptualScheme,”Proceedings and Addresses of the AmericanPhilosophical Association, 47: 5–20.
• –––, 1979, “The Inscrutability ofReference,”Southwestern Journal of Philosophy, 10(2):7–19.
• –––, 1999, “The Folly of Trying to DefineTruth,”Journal of Philosophy, 93(6):263–79.
• –––, 2000, “Truth Rehabilitated,” inBrandom (ed.) 2000, 65–73.
• De Neys, W., 2012, “Bias and Conflict: A Case For LogicalIntuitions,”Perspectives on Psychological Science,7(1): 28–38.
• De Neys, W., E. Moyens, and D. Vansteenwegen, 2010,“Feeling we’re biased: Autonomic arousal and reasoningconflict,”Cognitive, Affective & BehaviouralNeuroscience, 10(2): 208–216.
• De Neys, W., O. Vartanian, and V. Goel, 2008, “Smarterthan we think: when our brains detect that we are biased.”Psychological Science, 19(5): 483–489.
• Devitt, Michael, 1983, “Realism and the Renegade Putnam: ACritical Study ofMeaning and the Moral Sciences,”Noûs, 17(2): 291–301.
• –––, 1991,Realism and Truth, SecondEdition, Princeton: Princeton University Press.
• Dolev, Yuval, 2007,Time and Realism: Philosophical andAnti-Philosophical Perspectives, Cambridge, MA: MIT Press.
• Dorr, Cian, 2011, “Physical Geometry and FundamentalMetaphysics,”Proceedings of the Aristotelian Society,111(1): 135–179.
• –––, 2014, “Quantifier Variance and theCollapse Theorems,”The Monist, 97: 503–570.
• Douven, Igor, 1999, “Putnam’s Model-Theoretic ArgumentReconstructed,”Journal of Philosophy, 96(9):479–490.
• Dummett, Michael, 1978,Truth and Other Enigmas, London:Duckworth.
• –––, 1981, “Objections to Chomsky,”London Review of Books, 3(16), September 3, 1981 [Dummett 1981 available online].
• –––, 1993,The Seas of Language,Oxford: Oxford University Press.
• –––, 1991,The Logical Basis ofMetaphysics, Cambridge, MA: Harvard University Press.
• –––, 2000, “Is Time a Continuum ofInstants?,”Philosophy, 75: 497–515.
• –––, 2000, “Of What Kind of Thing is Trutha Property?” in Blackburn and Simmons 2000, 264–281.
• –––, 2002, “Victor’s Error,”Analysis, 62(2): 1–2.
• –––, 2004,Truth and the Past, NewYork: Columbia University Press.
• –––, 2006,Thought and Reality, Oxford:Clarendon Press.
• Ebbs, Gary, 1992, “Skepticism, Objectivity and Brains inVats,”Philosophical Topics, 20(1): 1–33.
• Edgington, Dorothy, 1981, “Meaning, Bivalence andRealism,”Proceedings of the Aristotelian Society,1980–1981, Vol. 81: 153–173.
• Einstein, A., B. Podolsky, and N. Rosen, 1935, “CanQuantum-Mechanical Description of Physical Reality Be ConsideredComplete?”Physical Review, 47(10): 777–780.
• Eklund, Matti, 2006, “Meta-Ontology”PhilosophyCompass, 3: 317–334.
• –––, 2008, “The Picture of Reality as anAmorphous Lump” in Theodore Sider, John Hawthorne and DeanZimmerman (eds.),Contemporary Debates in Metaphysics,Oxford: Blackwell, 382–396.
• –––, 2009, “Carnap and OntologicalPluralism” in D. Chalmers, D. Manley, and R. Wasserman (eds.)2009, pp. 130–156.
• Field, Hartry, 1978, “Mental Representation,”Erkenntnis, 13: 9–61.
• –––, 1998, “Some Thoughts on RadicalIndeterminacy,”The Monist, 81(2): 253–273.
• –––, 2001,Truth and The Absence ofFact, Oxford: Clarendon Press.
• Fodor, Jerry, 1975,The Language of Thought, HarvardUniversity Press, Cambridge, Massachusetts.
• –––, 1983,The Modularity of Mind,Cambridge, MA: MIT Press.
• –––, 2008,The Language of ThoughtRevisited, Oxford: Clarendon Press; New York: Oxford UniversityPress.
• Fodor, Jerry and Ernest Lepore, 2002,The CompositionalityPapers, Oxford: Clarendon Press.
• Forbes, Graeme, 1995, “Realism and Skepticism: Brains in aVat Revisited”Journal of Philosophy, 92(4), 205 –222.
• Gaiffman, Haim, 1996, “Is the ‘Bottom-Up’Approach from the Theory of Meaning to Metaphysics Possible?”Journal of Philosophy, 93(8): 373–407.
• George, Alexander, 1993, “How Not to Refute Realism,”Journal of Philosophy, 90(2): 53–72.
• Gödel, Kurt, 1949, “A Remark About the Relationshipbetween Relativity Theory and Idealistic Philosophy,” inAlbert Einstein: Philosopher-Scientist (The Library of LivingPhilosophers: Volume 7), P.A. Schilpp (ed.), Evanston, IL: Open Court,558.
• Goldberg, S. (ed.), 2015,The Brain in a Vat, Cambridge:Cambridge University Press.
• Hale, B. and C. Wright, 1997, “Putnam’sModel-Theoretic Argument against Metaphysical Realism,” inACompanion to the Philosophy of Language, B. Hale and C. Wright(eds.) Oxford: Blackwell, 427–457.
• –––, 2009, “The Metaontology ofAbstraction,” in D. Chalmers, D. Manley, and R. Wasserman (eds.)2009, pp. 178–212.
• Hand, Michael, 2003, “Knowability and Truth,”Australasian Journal of Philosophy, 81(2):216–228.
• Hauser, Kai, 2001, “Objectivity over Objects: A Case Studyin Theory Formation”Synthese, 128: 245–285.
• Hawthorne, John, 2006, “Plenitude, Convention andOntology,” in J. Hawthorne,Metaphysical Essays,Oxford: Oxford University Press, pp. 53–69.
• –––, 2009, “Superficialism inOntology,” in D. Chalmers, D. Manley, and R. Wasserman (eds.)2009, pp. 213–230.
• Hazen, Allen, 2012, “Intuitionism,” inTheRoutledge Companion to Philosophy of Language (Chapter 5.8),Gillian Russell and Delia Graff Farra (eds.), New York: Routledge,667–677.
• Hellman, Geoffrey, 1989, “Never Say ‘Never!’ Onthe Communication Problem between Intuitionism and Classicism,”Philosophical Topics, 17(2): 47–67.
• –––, 1992, “The Boxer and His Fists: TheConstructivist in the Arena of Quantum Physics,”Proceedingsof the Aristotelian Society (Supplementary Volume), 66:61–77.
• Huemer, Michael, 2016, “Serious Theories and SkepticalTheories: Why You Are Probably Not a Brain in a Vat,”Philosophical Studies, 173(4): 1031–1052.
• Hirsch, Eli, 1993,Dividing Reality, New York: OxfordUniversity Press.
• –––, 2002, “Quantifier Variance andRealism,”Philosophical Issues, 12: 51–73.
• –––, 2005, “Physical Object Ontology,Verbal Disputes and Common Sense,”Philosophy andPhenomenological Research, 70(1): 67–97.
• –––, 2009, “Ontology and AlternativeLanguages” in D. Chalmers, D. Manley, and R. Wasserman (eds.)2009, pp. 231–259.
• –––, 2011,Quantifier Variance and Realism:Essays in Meta-Ontology, New York, Oxford: Oxford UniversityPress.
• Horgan, T. and M. Timmons, 2002, “Conceptual Relativity andMetaphysical Realism,”Noûs, 36(1):74–96.
• Horwich, Paul, 1990,Truth, Oxford: Blackwell.
• Jackson, Alexander, 2015, “How You Know You Are Not a Brainin a Vat,”Philosophical Studies, 172(10):2799–2822.
• Jackson, Frank, 2000,From Metaphysics to Ethics: A Defence ofConceptual Analysis, Oxford: Clarendon Press.
• Jenkins, C.S., 2010, “What Is Ontological Realism?,”Philosophy Compass, 5/10:880–890.
• Khlentzos, Drew, 2004,Naturalistic Realism and theAntirealist Challenge, Cambridge, MA: Bradford Books, MITPress.
• –––, 2016, “Naturalism and the Question ofRealism” in K. J. Clark (ed.),The Blackwell Companion toNaturalism, Chichester: Wiley-Blackwell, pp. 150–67.
• –––, 2020, “Conceptual Schemes,” inThe Routledge Handbook of Philosophy of Relativism (Chapter48), M. Kusch (ed.), London, New York: Routledge, Taylor & FrancisGroup, pp. 457–467.
• Lewis, David, 1983, “New Work for a Theory ofUniversals,”Australasian Journal of Philosophy, 61:343–77.
• –––, 1984, “Putnam’s Paradox,”Australasian Journal of Philosophy, 62: 221–36.
• –––, 1991,Parts of Classes, Oxford:Blackwell.
• –––, 1994, “Reduction of Mind” in S.Guttenplan,Companion to the Philosophy of Mind, Oxford:Blackwell, pp. 412–31.
• Linnebo, O., 2018, “Dummett on IndefiniteExtensibility,”Philosophical Issues, 28(1):196–220.
• Lynch, Michael (ed.), 2001,The Nature of Truth: Classic andContemporary Perspectives, Cambridge, MA: MIT Press.
• Lynch, Michael, 1998,Truth in Context: An Essay on Pluralismand Objectivity, Cambridge, MA: MIT Press.
• Lowe, E. J. and A. Ramichandran (eds.), 2009,Truth andTruthmaking, Stockfield: Acumen.
• Michael, Michaelis, 1999, “Dummett’s Argument againstClassical Logic,”Philosophia, 27(3–4):359–382.
• Maudlin, Tim, 2007,The Metaphysics within Physics,Oxford: Clarendon Press.
• –––, 2014, “What Bell did,”Journal of Physics A: Mathematical and Theoretical, 47:1–24.
• McDowell, John, 1976, “Truth-conditions, Bivalance andVerificationism,” in G. Evans & J. McDowell (eds.),Truth and Meaning: Essays in Semantics, Oxford: ClarendonPress, 42–66.
• –––, 1994,Mind and World, Cambridge,MA: Harvard University Press.
• McGee, Vann, 2015, “Inscrutability and itsDiscontents,”Noûs, 39(3): 397–425.
• McGinn, Colin, 1976, “Truth and Use,” in M. Platts(ed.),Reference, Truth and Reality, London: Routledge &Kegan Paul, 19–40.
• –––, 1979, “An Apriori Argument forRealism,”Journal of Philosophy, 76: 113–33.
• –––, 1982, “Realist Semantics and ContentAscription,”Synthese, 52: 113–34.
• Millikan, Ruth, 1986, “Metaphysical Anti-Realism?”Mind, XCV: 417–431.
• Moretti, Luca, 2014, “Global Scepticism, Underdeterminationand Metaphysical Possibility”Erkenntnis, 79(2):381–403.
• Nagel, Thomas, 1986,The View from Nowhere, Oxford:Oxford University Press.
• –––, 1997,The Last Word, Oxford:Oxford University Press.
• Pagin, Peter, 1998, “Bivalence: meaning theory vsmetaphysics”Theoria, 64(2–3):157–186.
• –––, 2009, “Compositionality,Understanding and Proofs,”Mind, 118(471):713–737.
• Papineau, David (ed.), 1996,The Philosophy of Science,Oxford: Oxford University Press.
• Pinker, Steven, 1994,The Language Instinct, New York:Harper Perennial Modern Classics.
• Prawitz, Dag, 1977, “Meaning and Proofs: On the Conflictbetween Classical and Intuitionistic Logic,”Theoria,48: 2–40.
• –––, 1987, “Dummett on a theory of meaningand its impact on logic,” in B. Taylor (ed.),MichaelDummett: Contributions to Philosophy, Dordrecht: MartinusNijhoff.
• –––, 1994, “Meaning theory andanti-realism,” in B. McGuinness and G. Olivieri (eds.),ThePhilosophy of Michael Dummett, Dordrecht: Kluwer.
• Price, Huw, 2009, “Metaphysics after Carnap: the ghost whowalks?” in D. Chalmers, D. Manley, and R. Wasserman (eds.) 2009,pp. 320–346.
• Pryor, James, 2007, “What’s Wrong with McKinsey-styleReasoning?” in S. Goldberg (ed.),Internalism andExternalism in Semantics and Epistemology, Oxford: OxfordUniversity Press, pp. 177–200.
• Putnam, Hilary, 1981,Reason, Truth and History,Cambridge: Cambridge University Press.
• –––, 1985,Realism and Reason, volume 3ofPhilosophical Papers, Cambridge: Cambridge UniversityPress.
• –––, 1987, “Truth and Convention: OnDavidson’s Refutation of Conceptual Relativism,”Dialectica, 41: 69–77.
• –––, 1990,Realism with a Human Face,Cambridge, MA: Harvard University Press.
• –––, 1992,Renewing Philosophy,Cambridge, MA: Harvard University Press.
• –––, 1994a, “The Dewey Lectures,”Journal of Philosophy, 91: 445–517.
• –––, 1994b,Words and Life, Cambridge,MA: Harvard University Press.
• –––, 2000a,The Threefold Cord: Mind, Bodyand World, New York City: Columbia University Press.
• –––, 2000b, “Richard Rorty on Reality andJustification,” in Brandom (ed.) 2000, 81–87.
• –––, 2004,Ethics Without Ontology,Cambridge, MA: Harvard University Press.
• –––, 2012a, “Corresponding withReality,” in M. Caro and D. Macarthur (eds.),Philosophy inan Age of Science, Cambridge, MA: Harvard University Press,72–90.
• –––, 2012b, “How to be a Sophisticated‘Naïve Realist,” in M. Caro and D. Macarthur (eds.),Philosophy in an Age of Science, Cambridge, MA: HarvardUniversity Press, 624– 39.
• –––, 2015, “Naturalism, Realism, andNormativity,”Journal of the American PhilosophicalAssociation, Volume 1(2): 312–328.
• Quine, W.V.O., 1992,Pursuit of Truth, Cambridge, MA:Harvard University Press.
• –––, 1969, “Ontological Relativity,”in W. Quine,Ontological Relativity and Other Essays, NewYork: Columbia University Press, pp. 69–90.
• –––, 1964,Word and Object, Cambridge,Mass.: MIT Press.
• Read, Stephen, 2000, “Harmony and Autonomy in ClassicalLogic,”Journal of Philosophical Logic, 29(2):123–154.
• Resnick, Michael, 1987, “You Can’t Trust an IdealTheory to Tell the Truth,”Philosophical Studies, 52:151–160.
• –––, 1990, “Immanent Truth,”Mind, 99(395): 405–424.
• Sandqvist, Tor, 2009, “Classical Logic withoutBivalence,”Analysis, 69(2): 211–218.
• Schilpp, Paul (ed.), 1963,The Philosophy of RudolfCarnap, La Salle: Open Court.
• Shapiro, Stewart, 1998, “Proof and Truth: Through Thick andThin,”Journal of Philosophy, 95(10):493–521.
• –––, 2001, “Why Anti-Realists andClassical Mathematicians Cannot Get Along,”Topoi, 20(1): 53–63.
• Shapiro, Stewart and William Taschek, 1996, “Intuitionism,Pluralism and Cognitive Command,”Journal ofPhilosophy, 93(2): 74–88.
• Shieh, Sanford, 1998, “On The Conceptual Foundations ofAnti-Realism,”Synthese, 115(1): 33–70.
• Sider, Theodore, 2011,Writing the Book of the World,Oxford: Oxford University Press.
• –––, 2009, “Ontological Realism” inD. Chalmers, D. Manley, and R. Wasserman (eds.) 2009, pp.384–423
• Shoemaker, Sydney, 2011, “Kripke and Cartesianism,”inA. Berger (ed.) 2011, pp. 327–342.
• Soames, Scott, 2014, “The Place of Quine in AnalyticPhilosophy,” inA Companion to W.V.O. Quine (Chapter21), Gilbert Harman and Ernest Lepore (eds.), Oxford: Wiley-Blackwell,432–464.
• Sosa, Ernest, 2003, “Ontological and Conceptual Relativityand the Self,” in Michael J. Loux and Dean W. Zimmerman (eds.),The Oxford Handbook of Metaphysics, Oxford: Oxford UniversityPress.
• Spelke, E. S., 2003, “What Makes Us Smart? Core Knowledgeand Natural Language,” in E. Gentner and S. Goldin-Meadow(eds.),Language in Mind: Advances in the Study of Language andThought, Cambridge, MA: MIT Press, 277–311.
• Spelke, E. S. and K. D. Kinzler, 2007, “CoreKnowledge,”Developmental Science, 10:89–96.
• Stirton, William, 1998, “Anti-Realism, Truth Conditions andVerificationism,”Mind, 106(424): 697–716.
• Taylor, Barry, 2006,Models, Truth and Realism, Oxford:Oxford University Press.
• Tennant, Neil, 1987,Anti-Realism and Logic, Oxford:Clarendon Press.
• –––, 1997,The Taming of the True,Oxford: Clarendon Press.
• –––, 2002, “Victor Vanquished,”Analysis, 62(2): 135–142.
• Thomasson, A., 2015,Ontology made easy, Oxford: OxfordUniversity Press.
• Tymoczko, T., 1989, “In Defence of Putnam’sBrains,”Philosophical Studies, 57(3):281–297.
• van Cleve, J., 1992, “Semantic Supervenience and ReferentialIndeterminacy,”Journal of Philosophy, 89:341–361.
• Van Fraassen, B. C., 1980,The Scientific Image, Oxford:Oxford University Press.
• –––, 1989,Laws and Symmetry, Oxford:Clarendon Press.
• –––, 1997, “Putnam’s Paradox:Metaphysical Realism Revamped and Evaded,” in J. Tomberlin(ed.),Philosophical Perspectives, 11: 17–42.
• –––, 2002,The Empirical Stance, NewHaven: Yale University Press.
• van Inwagen, Peter, 2002, “‘Carnap’ and‘the Polish Logician’,”Acta Analytica,17(28): 7–17.
• –––, 2014, “Modes of Being andQuantification,”Disputatio, 6(38): 1–24.
• –––, 2020, “The neo-Carnapians,”Synthese, 197(1): 7–32.
• Wagner, Steven, 1993, “Why Realism Can’t BeNaturalized,” in S. Wagner and R. Warner (eds.),Naturalism:A Critical Appraisal, Notre Dame: University of Notre Dame Press,211–253.
• Walker, Ralph, 1995, “Verificationism, Anti-Realism andIdealism,”European Journal of Philosophy, 3(3):257–272.
• Warren, J., 2015, “Quantifier Variance and the CollapseArgument,”Philosophical Quarterly, 65(259):241–253.
• –––, 2017, “Quantifier Variance andIndefinite Extensibility,”Philosophical Review,126(1): 81–122.
• Weatherson, Brian, 2003, “Are You a Sim?”Philosophical Quarterly, 53(212): 425–431.
• Weiss, Bernard, 1996, “Anti-Realism, Truth-Value Links andTensed Truth Predicates,”Mind, 105(420):577–602.
• Williamson, Timothy, 2000, “Tennant on the Knowability ofTruth,”Ratio, 13(2): 99–114.
• –––, 2000,Knowledge and Its Limits,Oxford: Oxford University Press.
• Wright, Crispin, 1984, “Kripke’s Account of theArgument against Private Language,”Journal ofPhilosophy, 81: 759–78.
• –––, 1993,Realism, Meaning and Truth,Oxford: Blackwell.
• –––, 1992a,Truth and Objectivity,Cambridge, MA: Harvard University Press.
• –––, 1992b, “On Putnam’s Proof ThatWe Are Not Brains in a Vat,”Proceedings of the AristotelianSociety, 92(1): 67–94.
• –––, 2000, “Truth as Sort of Epistemic:Putnam’s Peregrinations,”Journal of Philosophy,97(6): 335–364.
• –––, 2000, “Truth: A Traditional DebateReviewed,” in Blackburn and Simmons (eds.) 2000,203–238.
• –––, 2001, “Minimalism, Deflationism,Pragmatism, Pluralism,” in Lynch (ed.) 2001, 751–787.
• –––, 2002, “(Anti-)Sceptics Simple andSubtle,”Philosophy and Phenomenological Research, 65(2): 330–348.
• –––, 2002a, “The Conceivability ofNaturalism” in T. Szabo Gendler and J. Hawthorne (eds.),Conceivability and Possibility, Oxford: Clarendon Press.
• –––, 2003,Saving the Differences: Essays onThemes fromTruth and Objectivity, Harvard UniversityPress, Cambridge, Massachusetts.
• Xu, F. and V. Garcia, 2008, “Intuitive statistics by8-month old infants,”,Proceedings of the National Academyof Sciences of the United States of America, 105:5012–5015.

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Acknowledgments

Thanks to a reviewer for many helpful criticisms and corrections.Thanks also to Marinus Ferreira, Jesse Alama and a subject editor fortheStanford Encyclopedia of Philosophy for their help inshaping earlier versions of this entry.