Editing Willard Van Orman Quine (section)

=== Metaphysics ===
Quine has had numerous influences on contemporary [[metaphysics]]. He coined the term "[[Abstract and concrete|abstract object]]".<ref>{{cite book|last=Armstrong|first=D. M.|title=Sketch for a systematic metaphysics|year=2010|publisher=Oxford University Press|location=Oxford|isbn=9780199655915|page=2}}</ref>

In his famous essay "On What There Is", he connected each of the three main metaphysical ontological positions—[[Philosophical realism|realism]]/[[conceptualism]]/[[nominalism]]—with one of three dominant schools in the modern [[philosophy of mathematics]]: [[logicism]], [[intuitionism]], and [[Formalism (philosophy of mathematics)|formalism]] respectively. In the same work, he coined the term "[[Plato's beard]]" to refer to the problem of [[empty name]]s: 

<blockquote>
Suppose now that two philosophers, McX and I, differ over [[ontology]]. Suppose McX maintains there is something which I maintain there is not. McX can, quite consistently with his own point of view, describe our difference of opinion by saying that I refuse to recognize certain entities ... When ''I'' try to formulate our difference of opinion, on the other hand, I seem to be in a predicament. I cannot admit that there are some things which McX countenances and I do not, for in admitting that there are such things I should be contradicting my own rejection of them ... This is the old Platonic riddle of nonbeing. Nonbeing must in some sense be, otherwise what is it that there is not? This tangled doctrine might be nicknamed ''Plato's beard''; historically it has proved tough, frequently dulling the edge of Occam’s razor.<ref name=OWTI/><ref>{{cite book |last1=van Inwagen |first1=Peter |last2=Zimmerman |first2=Dean W. |title=Metaphysics: the big questions |date=2008 |publisher=Blackwell |location=Malden, Mass. |isbn=978-1-4051-2586-4 |page=28-29 |edition=2. rev. and expanded |url=https://www.wiley.com/en-gb/Metaphysics%3A+The+Big+Questions%2C+2nd+Edition-p-9781405125864 }}</ref>
</blockquote>

Quine was unsympathetic, however, to the claim that saying 'X does not exist' is a tacit acceptance of X's existence and, thus, a contradiction. Appealing to [[Bertrand Russell]] and his theory of "singular descriptions", Quine explains how Russell was able to make sense of "complex descriptive names" ('the present King of France', 'the author of ''Waverly''{{'}}, etc.) by thinking about them as merely "fragments of the whole sentences". For example, 'The author of ''Waverly'' was a poet' becomes 'some thing is such that it is the author of ''Waverly'' and was a poet, and nothing else is such that it is the author of ''Waverly'''.<ref>{{cite book |last1=van Inwagen |first1=Peter |last2=Zimmerman |first2=Dean W. |title=Metaphysics: the big questions |date=2008 |publisher=Blackwell |location=Malden, Mass. |isbn=978-1-4051-2586-4 |page=31 |edition=2. rev. and expanded |url=https://www.wiley.com/en-gb/Metaphysics%3A+The+Big+Questions%2C+2nd+Edition-p-9781405125864 }}</ref>

Using this sort of analysis with the word '[[Pegasus]]' (that which Quine is wanting to assert does not exist), he turns Pegasus into a description. Turning the word 'Pegasus' into a description is to turn 'Pegasus' into a predicate, to use a term of [[First-order logic]]: i.e. a property. As such, when we say 'Pegasus', we are really saying 'the thing that is Pegasus' or 'the thing that ''Pegasizes'''. This introduces, to use another term from logic, bound variables (ex: 'everything', 'something,' etc.) As Quine explains, bound variables, "far from purporting to be names specifically...do not purport to be names at all: they refer to entities generally, with a kind of studied ambiguity peculiar to themselves."<ref>{{cite book |last1=van Inwagen |first1=Peter |last2=Zimmerman |first2=Dean W. |title=Metaphysics: the big questions |date=2008 |publisher=Blackwell |location=Malden, Mass. |isbn=978-1-4051-2586-4 |page=31-32 |edition=2. rev. and expanded |url=https://www.wiley.com/en-gb/Metaphysics%3A+The+Big+Questions%2C+2nd+Edition-p-9781405125864 }}</ref>

Putting it another way, to say 'I hate everything' is a very different statement than saying 'I hate Bertrand Russell', because the words 'Bertrand Russell' are a [[proper name]] that refer to a very specific person. Whereas the word 'everything' is a placeholder. It does not refer to a specific entity or entities. Quine is able, therefore, to make a meaningful claim about Pegasus' nonexistence for the simple reason that the placeholder (a thing) happens to be empty. It just so happens that the world does not contain a thing that is such that it is winged and it is a horse. 

====Rejection of the analytic–synthetic distinction====
{{See also|Two Dogmas of Empiricism#Analyticity and circularity|l1=Two Dogmas of Empiricism}}
In the 1930s and 40s, discussions with [[Rudolf Carnap]], [[Nelson Goodman]] and [[Alfred Tarski]], among others, led Quine to doubt the tenability of the distinction between "analytic" statements<ref>{{Cite book|title=Carnap, Tarski, and Quine at Harvard: Conversations on Logic, Mathematics, and Science|last=Frost-Arnold|first=Greg|publisher=Open Court|year=2013|isbn=9780812698374|location=Chicago|page=89}}</ref>—those true simply by the meanings of their words, such as "No bachelor is married"— and "synthetic" statements, those true or false by virtue of facts about the world, such as "There is a cat on the mat."<ref name="Quine 1961 p. 22">{{cite book | last=Quine | first=W. V. | title=From a Logical Point of View: Nine Logico-Philosophical Essays, Second Revised Edition | publisher=Harvard University Press | series=Harper torchbooks | orig-year=1961 | year=1980 | isbn=978-0-674-32351-3 | url=https://books.google.com/books?id=OalXwuw3MvMC | pages=22}}</ref> This distinction was central to [[logical positivism]]. Although Quine is not normally associated with [[verificationism]], some philosophers believe the tenet is not incompatible with his general philosophy of language, citing his Harvard colleague [[B. F. Skinner]] and his analysis of language in ''[[Verbal Behavior (book)|Verbal Behavior]]''.<ref>{{Cite journal |last=Prawitz |first=Dag |date=1994|title=Quine and verificationism |url=http://www.tandfonline.com/doi/abs/10.1080/00201749408602369 |journal=Inquiry |language=en |volume=37 |issue=4 |pages=487–494 |doi=10.1080/00201749408602369 |issn=0020-174X}}</ref> But Quine believes, with all due respect to his "great friend"<ref name="Burrhus">{{Cite book |title=The American Philosopher: Conversations with Quine, Davidson, Putnam, Nozick, Danto, Rorty, Cavell, MacIntyre, Kuhn |last=Borradori |first=Giovanna |author-link=Giovanna Borradori |publisher=University of Chicago Press |date=1994 |page=35 |isbn=978-0-226-06647-9}}</ref> Skinner, that the ultimate reason is to be found in neurology and not in behavior. For him, behavioral criteria establish only the terms of the problem, the solution of which, however, lies in [[neurology]].<ref name="Burrhus" />

Like other analytic philosophers before him, Quine accepted the [[definition]] of "analytic" as "true in virtue of meaning alone." Unlike them, however, he concluded that ultimately the definition was [[circular definition|circular]]. In other words, Quine accepted that analytic statements are those that are true by definition, then argued that the notion of truth by definition was unsatisfactory.

Quine's chief objection to analyticity is with the notion of [[cognitive synonymy]] (sameness of meaning). He argues that analytical sentences are typically divided into two kinds; sentences that are clearly logically true (e.g. "no unmarried man is married") and the more dubious ones; sentences like "no bachelor is married." Previously it was thought that if you can prove that there is synonymity between "unmarried man" and "bachelor," you have proved that both sentences are logically true and therefore self evident. Quine however gives several arguments for why this is not possible, for instance that "bachelor" in some contexts means a [[Bachelor of Arts]], not an unmarried man.<ref name="Quine 1961 p. 22-23, 28">{{cite book | last=Quine | first=W. V. | title=From a Logical Point of View: Nine Logico-Philosophical Essays, Second Revised Edition | publisher=Harvard University Press | series=Harper torchbooks | orig-year=1961 | year=1980| isbn=978-0-674-32351-3 | url=https://books.google.com/books?id=OalXwuw3MvMC | pages=22–23, 28}}</ref>

====Confirmation holism and ontological relativity====
Colleague [[Hilary Putnam]] called Quine's [[indeterminacy of translation]] thesis "the most fascinating and the most discussed philosophical argument since [[Immanuel Kant|Kant]]'s ''[[Critique of Pure Reason|Transcendental Deduction of the Categories]]''".<ref>{{Cite journal |last=Putnam |first=Hilary |title=The refutation of conventionalism |journal=Noûs  |volume=8 |number=1 |date=March 1974 |pages= 25–40 |jstor=2214643 |doi=10.2307/2214643}}  Reprinted in {{cite book |last=Putnam |first=Hilary |date=1979 |isbn=0521295513 |title=Philosophical Papers; Volume 2: Mind, Language and Reality |publisher=Cambridge University Press |chapter=Chapter 9: The refutation of conventionalism |pages=153–191 |chapter-url=https://books.google.com/books?id=_0W5ByvEPEgC&pg=PA159}} Quote on p. 159.
</ref> The central theses underlying it are [[ontological relativity]] and the related [[doctrine]] of [[confirmation holism]]. The premise of confirmation [[holism]] is that all theories (and the propositions derived from them) are [[underdetermination|under-determined]] by empirical data (data, [[Sense data|sensory-data]], evidence); although some theories are not justifiable, failing to fit with the data or being unworkably complex, there are many equally justifiable alternatives. While the [[Ancient Greece|Greeks]]' assumption that (unobservable) [[Homer]]ic gods exist is false and our supposition of (unobservable) [[electromagnetic radiation|electromagnetic waves]] is true, both are to be justified solely by their ability to explain our observations.

The ''[[gavagai]]'' [[thought experiment]] tells about a linguist, who tries to find out, what the expression ''gavagai'' means, when uttered by a speaker of a yet unknown, native language upon seeing a rabbit. At first glance, it seems that ''gavagai'' simply translates with ''rabbit''. Now, Quine points out that the background language and its referring devices might fool the linguist here, because he is misled in a sense that he always makes direct comparisons between the foreign language and his own. However, when shouting ''gavagai'', and pointing at a rabbit, the natives could as well refer to something like ''undetached rabbit-parts'', or ''rabbit-[[Trope (philosophy)|tropes]]'' and it would not make any observable difference. The behavioural data the linguist could collect from the native speaker would be the same in every case, or to reword it, several translation hypotheses could be built on the same sensoric stimuli.

Quine concluded his "[[Two Dogmas of Empiricism]]" as follows:
<blockquote>
As an empiricist I continue to think of the conceptual scheme of science as a tool, ultimately, for predicting future experience in the light of past experience. Physical objects are conceptually imported into the situation as convenient intermediaries not by definition in terms of experience, but simply as irreducible posits comparable, epistemologically, to the gods of Homer …. For my part I do, ''qua'' lay physicist, believe in physical objects and not in Homer's gods; and I consider it a scientific error to believe otherwise. But in point of epistemological footing, the physical objects and the gods differ only in degree and not in kind. Both sorts of entities enter our conceptions only as cultural posits.
</blockquote>

Quine's ontological [[relativism]] (evident in the passage above) led him to agree with [[Pierre Duhem]] that for any collection of [[empirical evidence]], there would always be many theories able to account for it, known as the [[Duhem–Quine thesis]]. However, Duhem's [[holism]] is much more restricted and limited than Quine's. For Duhem, [[underdetermination]] applies only to [[physics]] or possibly to [[natural science]], while for Quine it applies to all of human knowledge. Thus, while it is possible to verify or [[falsifiability|falsify]] whole theories, it is not possible to verify or falsify individual statements. Almost any particular statement can be saved, given sufficiently radical modifications of the containing theory. For Quine, scientific thought forms a [[Coherentism|coherent]] web in which any part could be altered in the light of empirical evidence, and in which no empirical evidence could force the revision of a given part.

====Existence and its contrary====
The [[Empty name|problem of non-referring names]] is an old puzzle in philosophy, which Quine captured when he wrote,

<blockquote>A curious thing about the ontological problem is its simplicity. It can be put into three Anglo-Saxon monosyllables: 'What is there?' It can be answered, moreover, in a word—'Everything'—and everyone will accept this answer as true.<ref name=OWTI>W. V. O. Quine, "[[:s:On What There Is|On What There Is]]", ''The Review of Metaphysics'' '''2'''(5), 1948.</ref></blockquote>

More directly, the controversy goes:
<blockquote>
How can we talk about [[Pegasus]]? To what does the word 'Pegasus' refer? If our answer is, 'Something', then we seem to believe in mystical entities; if our answer is, 'nothing', then we seem to talk about nothing and what sense can be made of this? Certainly when we said that Pegasus was a mythological winged horse we make sense, and moreover we speak the truth! If we speak the truth, this must be truth ''about something''. So we cannot be speaking of nothing.
</blockquote>

Quine resists the temptation to say that non-referring terms are meaningless for reasons made clear above. Instead he tells us that we must first determine whether our terms refer or not before we know the proper way to understand them. However, [[Czesław Lejewski]] criticizes this belief for reducing the matter to empirical discovery when it seems we should have a formal distinction between referring and non-referring terms or elements of our domain. Lejewski writes further:
<blockquote>
This state of affairs does not seem to be very satisfactory. The idea that some of our rules of inference should depend on empirical information, which may not be forthcoming, is so foreign to the character of logical inquiry that a thorough re-examination of the two inferences [existential generalization and universal instantiation] may prove worth our while.
</blockquote>

Lejewski then goes on to offer a description of [[free logic]], which he claims accommodates an answer to the problem.

Lejewski also points out that free logic additionally can handle the problem of the empty set for statements like <math>\forall x\,Fx \rightarrow \exists x\,Fx</math>. Quine had considered the problem of the empty set unrealistic, which left Lejewski unsatisfied.<ref>Czeslaw Lejewski, "Logic and Existence". ''British Journal for the Philosophy of Science'', Vol. 5 (1954–1955), pp. 104–119.</ref>

==== Ontological commitment ====
The notion of [[ontological commitment]] plays a central role in Quine's contributions to ontology.<ref>{{cite book |last1=Craig |first1=Edward |title=Routledge Encyclopedia of Philosophy |date=1996 |publisher=Routledge |url=https://philpapers.org/rec/BEAREO |chapter=Ontological commitment}}</ref><ref>{{cite web |last1=Simons |first1=Peter M. |title=Ontology |url=https://www.britannica.com/topic/ontology-metaphysics |website=Encyclopedia Britannica |access-date=December 13, 2020 |language=en}}</ref> A theory is ontologically committed to an entity if that entity must exist in order for the theory to be true.<ref name="Bricker">{{cite web |last1=Bricker |first1=Phillip |title=Ontological Commitment |url=https://plato.stanford.edu/entries/ontological-commitment/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=December 13, 2020 |date=2016}}</ref> Quine proposed that the best way to determine this is by translating the theory in question into [[first-order predicate logic]]. Of special interest in this translation are the logical constants known as [[existential quantification|existential quantifiers]] ('{{math|∃}}'), whose meaning corresponds to expressions like "there exists..." or "for some...". They are used to [[First-order logic#Free and bound variables|bind the variables]] in the expression following the quantifier.<ref>{{cite book |last1=Magnus |first1=P. D. |last2=Ichikawa |first2=Jonathan Jenkins |title=Forall X |date=2020 |publisher=Creative Commons: Attribution-ShareAlike 3.0 |url=https://philpapers.org/rec/MAGFXU |chapter=V. First-order logic|edition=UBC }}</ref> The ontological commitments of the theory then correspond to the variables bound by existential quantifiers.<ref>{{cite book |last1=Schaffer |first1=Jonathan |title=Metametaphysics: New Essays on the Foundations of Ontology |publisher=Oxford University Press |pages=347–383 |url=https://philpapers.org/rec/SCHOWG |chapter=On What Grounds What|year=2009 }}</ref> For example, the sentence "There are electrons" could be translated as "{{math|∃''x'' ''Electron''(''x'')}}", in which the bound variable ''x'' ranges over electrons, resulting in an ontological commitment to electrons.<ref name="Bricker"/> This approach is summed up by Quine's famous dictum that "[t]o be is to be the value of a variable".<ref name="Quine">{{cite journal |last1=Quine |first1=Willard Van Orman |title=On What There Is |journal=Review of Metaphysics |date=1948 |volume=2 |issue=5 |pages=21–38 |url=https://philpapers.org/rec/QUIOWT-7}}</ref> Quine applied this method to various traditional disputes in ontology. For example, he reasoned from the sentence "There are prime numbers between 1000 and 1010" to an ontological commitment to the existence of numbers, i.e. [[Philosophy of mathematics#Mathematical realism|realism]] about numbers.<ref name="Quine"/> This method by itself is not sufficient for ontology since it depends on a theory in order to result in ontological commitments. Quine proposed that we should base our ontology on our best scientific theory.<ref name="Bricker"/> Various followers of Quine's method chose to apply it to different fields, for example to "everyday conceptions expressed in natural language".<ref>{{cite book |last1=Inwagen |first1=Peter van |title=Oxford Studies in Metaphysics, Volume 1 |date=2004 |publisher=Clarendon Press |pages=107–138 |url=https://philpapers.org/rec/VANATO-2 |chapter=A Theory of Properties}}</ref><ref>{{cite book |last1=Kapelner |first1=Zsolt-kristof |title=Reconciling Quinean and neo-Aristotelian Metaontology |date=2015 |url=http://www.etd.ceu.hu/2015/kapelner_zsolt-kristof.pdf |chapter=3. Quinean Metaontology}}</ref>

====Indispensability argument for mathematical realism====
In [[philosophy of mathematics]], he and his Harvard colleague [[Hilary Putnam]] developed the [[Quine–Putnam indispensability argument|Quine–Putnam indispensability thesis]], an argument for the [[Philosophy of mathematics#Empiricism|reality of mathematical entities]].<ref name="plato.stanford.edu" />

The form of the argument is as follows.
#One must have [[ontological]] commitments to ''all'' entities that are indispensable to the best scientific theories, and to those entities ''only'' (commonly referred to as "all and only").
#Mathematical entities are indispensable to the best scientific theories. Therefore,
#One must have ontological commitments to mathematical entities.<ref name="MMM">Putnam, H. ''Mathematics, Matter and Method. Philosophical Papers'', vol. 1. Cambridge: Cambridge University Press, 1975. 2nd. ed., 1985.</ref>

The justification for the first premise is the most controversial. Both Putnam and Quine invoke [[naturalism (philosophy)|naturalism]] to justify the exclusion of all non-scientific entities, and hence to defend the "only" part of "all and only". The assertion that "all" entities postulated in scientific theories, including numbers, should be accepted as real is justified by [[confirmation holism]]. Since theories are not confirmed in a piecemeal fashion, but as a whole, there is no justification for excluding any of the entities referred to in well-confirmed theories. This puts the [[nominalism|nominalist]] who wishes to exclude the existence of [[Set (mathematics)|sets]] and [[non-Euclidean geometry]], but to include the existence of [[quark]]s and other undetectable entities of physics, for example, in a difficult position.<ref name="MMM" />