Ontological pluralism

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In philosophy the branch called ontological pluralism is the doctrine that there are different ways or modes of being.[1] "There are numbers, fictional characters, impossible things, and holes. But, we don’t think these things all exist in the same sense as cars and human beings."[2][3]

It is common to refer to a film, novel or otherwise fictitious or virtual narrative as not being 'real'. Thus, the characters in the film or novel are not real, where the 'real world' is the everyday world in which we live. However, as authors are wont to say, fiction informs our concept of reality, and so has some kind of reality.[4][5]

In the sciences, theories are developed to explain observations, giving rise to specialized vocabularies with specific meanings in the context of a given theory. Thus, 'electron's exist in different senses in different theoretical contexts. The meanings of 'electron' in chemistry, in the Standard Model of particle physics, in electromagnetism are connected, but from a practical standpoint vary with context. Perhaps an even more striking example is the concept of 'temperature' which has a different definition in thermodynamics than in statistical mechanics: the two definitions can be related, but the concept has two logically distinct existences, one entirely macroscopic, the other at an atomic level.

Technically, ontological pluralism claims that an accurate description of reality uses multiple quantifiers (see below for more on this term) that do not range over a single domain.[1] A very brief outline of some technical terms is proved next to make this second description clearer.


The word quantifier in the introduction refers to a variable used in a domain of discourse, a collection of objects under discussion. In daily life, the domain of discourse could be 'apples', or 'persons', or even everything.[6] In a more technical arena, the domain of discourse could be 'integers', say. The quantifier variable x, say, in the given domain of discourse can take on the 'value' or designate any object in the domain. The presence of a particular object, say a 'unicorn' is expressed in the manner of symbolic logic as:

x; x is a unicorn.

Here the 'turned E ' or ∃ is read as "there exists..." and is called the symbol for existential quantification. Relations between objects also can be expressed using quantifiers. For example, in the domain of integers (denoting the quantifier by n, a customary choice for an integer) we can indirectly identify '5' by its relation with the number '25':

n; n × n = 25.

If we want to point out specifically that the domain of integers is meant, we could write:

n ∈ ℤ; n × n = 25.

Here, ∈ = is a member of... and ∈ is called the symbol for set membership; and ℤ denotes the set of integers.


For more information, see: Ontology (philosophy).

The term 'ontology' refers to the assembly of objects in a domain of discourse, but more than that, to their properties, to the relations between them, and to the rules governing their use.[7] The subject of ontology also includes its metatheory, meta-ontology. According to Hofweber:

"The larger discipline of ontology can thus be seen as having four parts:
°1. the study of ontological commitment, i.e. what we or others are committed to,
°2. the study of what there is,
°3. the study of the most general features of what there is, and how the things there are relate to each other in the metaphysically most general ways,
°4. the study of meta-ontology, that is, saying what task it is that the discipline of ontology should aim to accomplish, if any, how the questions it aims to answer should be understood, and with what methodology they can be answered."[8]
—— Thomas Hofweber, Logic and Ontology in The Stanford Encyclopedia of Philosophy

Comparing ontologies

See also: Meta-ontology and Ontological commitment

The question of comparing ontologies arises. Such comparisons can be simple (like comparing the objects in two ontologies) or much more complicated (looking also at the relations between the objects). Such comparisons can be discussed on the basis of quantifier variance.[9]


In a number of papers, Rudolf Carnap proposed a difference between "internal" and "external" questions. The internal questions are answered within a framework, for example, a mathematical structure such as Maxwell's equations, while the external questions involve whether or not observation suggests it is practical to adopt a framework, for example, whether Faraday's laws are suitably described using Maxwell's equations. According to Eklund,[10] Carnap holds that argument over the existence of objects involved in the 'internal' framework is nonsense: the only sensible question is whether the terminology is useful. Eli Hirsch, says that “many familiar questions about the ontology of physical objects are merely verbal. Nothing is substantively at stake in these questions beyond the correct use of language [and the claim that] quantifier expressions can have different meaning in different languages”.[11]

The issue is raised, however, that some objects exist in multiple ontologies, and so perhaps they can lay claim to a more general existence than simply within one or another framework. In particular, Hirsch suggests existence within 'common sense' is a more general form of existence than existence inside any particular framework.[11]

Another issue is raised when comparing frameworks as to which is preferable. “Ontological anti-realism is often traced to Carnap (1950), who held that there are many different ontological frameworks, holding that different sorts of entities exist, and that while some frameworks may be more useful for some purposes, there is no fact of the matter as to which framework is correct”[12]


In a very influential series of papers and books, Willard v.O. Quine argued against the position of Carnap.[13][14][15] In his view, the distinction between internal and external questions and objects was not sharp. Although a particular object within a conceptual framework can have properties and connections with other objects in that framework that are fundamentally decided by the rules of the framework itself, there are interactions between the framework and the 'real' world that cannot be discounted.[16] On one hand, the objects of the framework can be suggested as abstractions from the 'real' world, which might be viewed as the 'muse' leading to the framework. (This view resembles somewhat that of Aristotle, that idealized concepts like 'circle' are abstractions from observations of real objects that approximate a circle.) A classic example is Euclidean geometry, initially thought to express the way the world worked, and later considered to be a 'model' suggested by 'reality', but that applied only approximately to reality under strict limitations.[17] On the other hand, and more significantly, the application of the framework to the real world is very strongly colored by the framework itself; the framework suggests the direction that observations should take, what connections should be looked for, what properties are to be expected.

"Rather than being divided between contingent synthetic claims and indubitable analytic propositions, our beliefs constitute a continuous range from a periphery of sense-reports to interior concepts that are comparatively theory-laden and general."[16]
—— Frank X. Ryan, discussing Quine's position in Analytic: Analytic/Synthetic; American Philosophy: An Encyclopedia

Of course, observations may prove surprising and suggest the application of the framework has discrepancies with reality. But the application of the framework to the real world is a continuing process, with our 'interpretation of what we see' and 'what we see' related as inseparable partners in a dance.

The key objection made by Quine was that no clear definition of a 'framework' can be found. In trying to establish the meaning of a term within a framework, its analytic or tautological meaning, one is caught up in a process that inevitably involves real objects, 'synthetic' objects.

It begins to appear, then, that Carnap’s dichotomy of questions of existence is a dichotomy between questions of the form “Are there so-and-sos?” where the so-and-sos purport to exhaust the range of a particular style of bound variables, and questions of the form “Are there so-and-sos?” where the so-and-sos do not purport to exhaust the range of a particular style of bound variables. Let me call the former questions category questions, and the latter ones subclass questions. I need this new terminology because Carnap’s terms ‘external’ and ‘internal’ draw a somewhat different distinction which is derivative from the distinction between category questions and subclass questions. The external questions are the category questions conceived as propounded before the adoption of a given language; and they are, Carnap holds, properly to be construed as questions of the desirability of a given language form. The internal questions comprise the subclass questions and, in addition, the category questions when these are construed as treated within an adopted language as questions having trivially analytic or contradictory answers.[14]
—— Willard v. O. Quine On Carnap’s Views on Ontology

Quine's chief objection to analyticity is with the notion of synonymy (sameness of meaning), a sentence being analytic, just in case it substitutes a synonym for one "black" in a proposition like "All black things are black" (or any other logical truth). The objection to synonymy hinges upon the problem of collateral information. We intuitively feel that there is a distinction between "All unmarried men are bachelors" and "There have been black dogs", but a competent English speaker will assent to both sentences under all conditions since such speakers also have access to collateral information bearing on the historical existence of black dogs. Quine maintains that there is no distinction between universally known collateral information and conceptual or analytic truths.

Another approach to Quine's objection to analyticity and synonymy emerges from the modal notion of logical possibility. A traditional Wittgensteinian view of meaning held that each meaningful sentence was associated with a region in the space of possible worlds. Quine finds the notion of such a space problematic, arguing that there is no distinction between those truths which are universally and confidently believed and those which are necessarily true.

From Carnap's point of view the analytic-synthetic distinction is an 'internal' question, about the relation between the logical portion of a framework and its observational portion. Quine basically pooh-poohed the 'external' questions of Carnap as simply a question of a more or a less inclusive vocabulary:

"Whether the statement that there are physical objects and the statement that there are black swans should be put on the same side of the dichotomy, or on opposite sides, comes to depend upon the rather trivial consideration of whether we use one style of variables or two for physical objects and classes."[14]
—— Willard Quine, On Carnap's views on ontolgy

Recent authors consider this elimination of the internal-external distinction as a mistake. The real issue is not one of language as such, but the difference between questions asked using a linguistic framework and those asked somehow before the adoption of a linguistic framework, the difference between questions about the construction and rules of a framework, and questions about the decision whether to use a framework.[18] This distinction is called by Thomasson and Price the difference between ‘’using’’ a term and ‘’mentioning’’ a term.[18][19] Thus, unlike Quine's view of a 'flat' ontology without distinctions, Carnap allows a multiplicity of frameworks, which may allow ontological pluralism.


Wittgenstein is credited as the originator of the internal/external contrast.[20] It is suggested that although Carnap acknowledged his indebtedness to Wittgenstein, in fact a closer understanding by Carnap would have provided a better foundation for Carnap's philosophy:

All that Carnap had to do was to take a good hard look at his state-descriptions and to ask: what are they supposed to be descriptions of in some realistic, down-to-earth sense? One natural answer is that they are descriptions of the different possible states of affairs or courses of events (in short 'possible worlds') in which the speaker of a language could possibly find himself and which he could in principle distinguish from each other. From this answer it is only a short step to the crucial idea that the rules for using the language will have to be shown - in principle - by the way a well-informed speaker would use it in these different circumstances according to the rules, i.e. by the extensions which the expressions of the language would have in those several 'possible worlds'. This is all we need to arrive at the basic ideas of possible worlds semantics.[21]
—— Jakko Hintikka as quoted by Bradley Carnap's Semantics in Retrospect, p. 375

Hawking and Mlodinow

Stephen Hawking and Leonard Mlodinow have proposed model-dependent realism, which is the notion that the existence of some background all-encompassing reality can never be known beyond a patchwork of different theories, and anything deeper is speculation. Every theory is associated with its own conceptions and observations that encompass only some small slice of reality.[22] This viewpoint is very similar to Carnap's multiple frameworks.

Whatever might be the ultimate goals of some scientists, science, as it is currently practiced, depends on multiple overlapping descriptions of the world, each of which has a domain of applicability. In some cases this domain is very large, but in others quite small.[23]
—— E.B. Davies Epistemological pluralism, p. 4


Assuming a multiplicity of ontologies, can we choose between them? One approach to selecting a framework is based upon an examination of the conceptual relations between entities in a framework, which entities are more 'fundamental'. One framework may then 'include' another because the entities in one framework apparently can be derived from or 'supervene' upon those in the more fundamental one.[24] While Carnap claims such decisions are pragmatic in nature, external questions with no philosophical importance, Schaffer suggests we avoid this formulation. Instead, we should go back to Aristotle and look upon nature as hierarchical, and pursue philosophical diagnostics: that is, examination of criteria for what is fundamental and what relations exist between all entities and these fundamental ones.[25] But "how can we discover what grounds what?...questions regarding not only what grounds what, but also what the grounding consists in, and how one may discover or discern grounding facts, seem to be part of an emerging set of relational research problems in metaphysics."[26]

A different approach that is more commonly seen among scientists is the use of rather subjective 'criteria': What criteria are satisfied by a 'good' theory?. The objective of such criteria is selecting between theories without introducing cognitive bias.[27] Several often proposed criteria were summarized by Colyvan.[28] A good theory:

  1. Is elegant (Formal elegance; no ad hoc modifications)
  2. Contains few arbitrary or adjustable elements (Simplicity/Parsimony)
  3. Agrees with and explains all existing observations (Unificatory/Explanatory power)
  4. Makes detailed predictions about future observations that can disprove or falsify the model if they are not borne out.
  5. Is fruitful: the emphasis by Colyvan is not only upon prediction and falsification, but also upon a theory's seminality in suggesting future work.

Stephen Hawking supports items 1-4, but does not mention fruitfulness.[22] On the other hand, Kuhn emphasizes the importance of seminality.[29]


  1. 1.0 1.1 Jason Turner (April 2012). "Logic and ontological pluralism". Journal of Philosophical Logic 41 (2): pp. 419-448. DOI:10.1007/s10992-010-9167-x. Research Blogging.
  2. Joshua Spencer (November 12, 2012). "Ways of being". Philosophy Compass 7 (12): 910–918. DOI:10.1111/j.1747-9991.2012.00527.x. Research Blogging.
  3. Martin Gardner makes the same point: Martin Gardner (December 2005). Science in the looking glass: What do scientists really know? (a book review). Notices of the American Mathematical Society pp. 1344 ff. “No modern realist believes for a moment that numbers and theorems “exist” in the same way that stones and stars exist. Of course mathematical concepts are mental constructs and products of human culture.”
  4. Deborah A Prentice, Richard J Gerrig (1999). “Chapter 26: Exploring the boundary between fiction and reality”, Shelly Chaiken, Yaacov Trope, eds: Dual-process theories in social psychology. Guilford Press, pp. 529-546. ISBN 1572304219. 
  5. Hector-Neri Castañeda (April 1979). "Fiction and reality: Their fundamental connections: An essay on the ontology of total experience". Poetics 8 (1-2): 31-62.
  6. Alan Hausman, Howard. Kahane, Paul. Tidman (2012). “Domain of discourse”, Logic and Philosophy: A Modern Introduction, 12th. Cengage Learning, p. 194. ISBN 113305000X. 
  7. Barry Smith, Bert Klagges (2008). “The historical background of applied ontology”, Katherine Munn, Barry Smith: Applied ontology: an introduction. Ontos Verlag, p. 22. ISBN 3938793988. 
  8. Hofweber, Thomas (Aug 30, 2011). Edward N. Zalta ed:Logic and Ontology. The Stanford Encyclopedia of Philosophy (Spring 2013 Edition).
  9. Eli Hirsch (2011). Quantifier Variance and Realism : Essays in Metaontology. Oxford University Press. ISBN 0199780714. 
  10. Matti Eklund (2009). “Chapter 4: Carnap and ontological pluralism”, David Chalmers, David Manley, Ryan Wasserman: Metametaphysics: New Essays on the Foundations of Ontology. Oxford University Press, pp. 130-156. ISBN 0199546045.  See also Carnap's Metaontology
  11. 11.0 11.1 Hirsch, E. (2005). "Physical-Object Ontology, Verbal Disputes, and Common Sense". Philosophy and Phenomenological Research, 70: pp. 67-97. See also Chapter 9 in Quantifier Variance and Realism : Essays in Metaontology.
  12. David J. Chalmers (2009). “Chapter 3: Ontological anti-realism”, Chalmers, D., Manley D., & Wasserman R., eds: Metametaphysics: New Essays on the Foundations of Ontology. Oxford University Press, pp. 77-129. ISBN 0199546045. 
  13. Quine, W. v.O. (1948). "On what there is". The Review of Metaphysics 2: pp. 21-38.
  14. 14.0 14.1 14.2 Quine, W. v.O. (1951). "On Carnap’s views on ontology". Philosophical Studies 2: pp. 65-72.
  15. Quine, W. v. O. (2013). Word and object. MIT Press. ISBN 0262518317.  In addition to Patricia Smith Churchland's foreword, this edition offers a new preface by Quine's student and colleague Dagfinn Føllesdal.
  16. 16.0 16.1 Frank X Ryan (2004). “Analytic: Analytic/Synthetic”, John Lachs, Robert B. Talisse, eds: American Philosophy: An Encyclopedia. Psychology Press, pp. 36-39. ISBN 020349279X. 
  17. Michael Friedman (2008). “Einstein, Kant and the A Priori”, Michela Massimi, ed: Kant and Philosophy of Science Today: Royal Institute of Philosophy Supplement: 63. Cambridge University Press, pp. 95-112. ISBN 0521748518. “Kant's original version of transcendental philosophy took both Euclidean geometry and the Newtonian laws of motion to be synthetic a priori constitutive principles - which, form Kant's point of view, function as necessary presuppositions for appyling our fundamental concepts of space, time, matter and motion to our sensible experience of the natural world...we now know...that they are not in fact a priori in the stronger sense of being fixed necessary conditions for all human experience in general, eternally valid once and for all.” 
  18. 18.0 18.1 Amie L Thomasson (to be published). “Carnap and the prospects for easy ontology”, Ontology after Carnap. Oxford University Press. 
  19. Huw Price (2009). “Chapter 11: Metaphysics After Carnap: the Ghost Who Walks?”, David Chalmers, Ryan Wasserman and David Manley, eds: Metametaphysics: New Essays on the Foundations of Ontology. Oxford University Press, pp. 320-346. ISBN 0199546045. 
  20. Raymond Bradley (1992). The Nature of All Being : A Study of Wittgenstein's Modal Atomism. Oxford University Press, p. 189. ISBN 0195361245. 
  21. Jaakko Hintikka (1973). "Carnap's semantics in retrospect". Synthese 25 (3): pp. 372-397.
  22. 22.0 22.1 Hawking, Stephen W., and Leonard Mlodinow (2010). “Chapter 3: What Is Reality?”, The Grand Design, 1rst. Bantam Books (a division of Random House, Inc.), 39-59. ISBN 9780553805376. . As e-book: isbn=9780553907070
  23. E Brian Davies (2006). Epistemological pluralism. PhilSci Archive.
  24. Some caution is warranted here. For example, Newton's laws of motion suffice for practical engineering work like building and bridge design, even though the more 'fundamental' theory of the Standard model of elementary particle physics is available. The more 'fundamental' model is, for such engineering, superfluous.
  25. Jonathan Schaffer (2009). “Chapter 12: On what grounds what”, David Chalmers, David Manley, Ryan Wasserman: Metametaphysics: New Essays on the Foundations of Ontology. Oxford University Press. ISBN 0199546045. 
  26. Amie Thomasson (2012). “Chapter 1: Research Problems and Methods in Metaphysics”, Robert Barnard & Neil Manson, eds: The Continuum companion to metaphysics. Continuum International Publishing Group, pp. 14-45. ISBN 978-1-4411-3022-8. 
  27. Thomas Kuhn formally stated this need for the "norms for rational theory choice". One of his discussions is reprinted in Thomas S Kuhn. “Chapter 9: Rationality and Theory Choice”, James Conant, John Haugeland, eds: The Road since Structure: Philosophical Essays, 1970-1993,, 2nd. University of Chicago Press, pp. 208 ff. ISBN 0226457990. 
  28. Mark Colyvan (2001). The Indispensability of Mathematics. Oxford University Press, 78–79. ISBN 0195166612. 
  29. Thomas S Kuhn (1966). The structure of scientific revolutions, 3rd. University of Chicago Press. ISBN 0226458083. “That decision must be based less on past achievement than on future promise.” 

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