Introduction: Vagueness and Ontology


The article introduces a special issue of the journal Metaphysica on vagueness and ontology. The conventional view has it that all vagueness is semantic or representational. Russell, Dummett, Evans and Lewis, inter alia, have argued that the notion of “ontic” or “metaphysical” vagueness is not even intelligible. In recent years, a growing minority of philosophers have tried to make sense of the notion and have spelled it out in various ways. The article gives an overview and relates the idea of ontic vagueness to the unquestioned phenomenon of fuzzy spatiotemporal boundaries and to the associated “problem of the many”. It briefly discusses the question of whether ontic vagueness can be spelled out in terms of “vague identity”, emphasizes the often neglected role of the difference between sortal and non-sortal ontologies and suggests a deflationary answer to the ill-conceived question of whether the “ultimate source” of vagueness lies either in language or in the world.

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  1. 1.

    Almost all of these phrases can be found in the titles of the books and papers in the list of references. For an overview over the debate, see Sainsbury (1989), Zemach (1991), Tye (2000), Edgington (2000), Morreau (2002), Williamson (2003), Akiba (2004), Rosen and Smith (2004), Hyde (2008), and Barnes (2010).

  2. 2.

    In this introduction, I will use the expressions “metaphysical vagueness” and “ontic vagueness” interchangeably.

  3. 3.

    “We may express this metaphorically as follows: the concept must have a sharp boundary. If we represent concepts on extension by areas on a plane, this is admittedly a picture that may be used only with caution, but here it can do us good service. To a concept without sharp boundary there would correspond an area that had not a sharp boundary-line all around, but in places just vaguely faded away into the background. This would not really be an area at all; and likewise a concept that is not sharply defined is wrongly termed a concept.” (Frege 1903, p. 159 [§ 56]).

  4. 4.

    “We might try to define the category-inappropriateness of a predicate to an individual directly as follows: an individual i and a predicate P are category-mismatched if, and only if, P and the denial of P are alike a priori rejectable for every adequate identifying designation of i.” (Strawson 1970, p. 190)

  5. 5.

    See for example Garrett (1988), Garrett (1991), Parsons and Woodruff (1995), Parsons (2000).

  6. 6.

    See also Wittgenstein, Tractatus, 5.5303.

  7. 7.

    For a more substantial treatment of the topic of vague, indeterminate or indefinite identity, see the contributions of Cobreros et al. (2013), Noonan (2013) and Weber (2013). See also the papers in the fourth part of Akiba's (2013) collection.

  8. 8.

    “There can be no borderline cases of existence, because an object has to be there to be a borderline case of anything, and if it's there it exists” (van Inwagen 2009, p. 6). Van Inwagen himself rejects what he calls “the sensible theory of indeterminacy (which denies that there can be indeterminate cases of identity and existence)”, on the grounds that it “cannot accommodate a workable metaphysic of the material world” (ibid., 7). In particular, the sensible theory cannot adequately handle “the Special Composition Question: ‘When are things proper parts—when do things together compose some larger whole?’” (ibid.). For a discussion of van Inwagen's view, see Noonan's paper in this issue.

  9. 9.

    I cannot argue for these bold Fregean claims here. For a defence, see Cappelen and Hawthorne (2009) and Keil (2010). See also Noonan (2013, p. 240): “The apparatus of first-order logic with identity—the truth-functional connectives, the quantifiers and the identity predicate—is not vague, so predicates constructed from this apparatus are not vague. So ‘x = x’, ‘∃y(x = y)’ and ‘x = y’ are not vague, i.e., are not referentially indeterminate. The first two predicates denote the property of existence and the last the relation of identity. Since this is so, there are no borderline cases of existence or borderline cases of identity.”

  10. 10.

    Merricks himself does not advocate this view.

  11. 11.

    For a discussion, see Salmon (2010) and López de Sa (2013) in this issue.

  12. 12.

    For the topic of vagueness in geography, see for example Varzi (2001), Bittner and Stell (2002) and Galton (2003).

  13. 13.

    In this volume, mountains figure prominently in the contributions of Noonan, Sattig and Weber.

  14. 14.

    See for example Tye (1990, pp. 535–536): “I shall classify a concrete object o as vague […] if, and only if, (a) o has borderline spatio-temporal parts and (b) there is no determinate fact of the matter about whether there are objects that are neither parts, borderline parts, nor non-parts of o”.

  15. 15.

    “Thus take the general term ‘mountain’: it is vague on the score of how much terrain to reckon into each of the indisputable mountains, and it is vague on the score of what lesser eminences to count as mountains at all.” (Quine 1960, p. 126)

  16. 16.

    For a discussion of the problem of the many, see the contributions of Lowe (2013), Noonan (2013) and Sattig (2013). A radical reaction to the problem of the many is existence monism, which argues that since the ordinary objects that common sense commits us to are vague, and since the world cannot contain vague objects, the whole cosmos is but one large concrete object without proper parts. Lowe discusses and dismisses this view in his paper.

  17. 17.

    Aristotle, Categories, 3b32, transl. Ackrill.

  18. 18.

    Simons (2013, p. 275), this issue.

  19. 19.

    Sattig (2013, p. 217), this issue.

  20. 20.

    For an explication of combinatory vagueness, see also Hyde (2008, 16–19).

  21. 21.

    See Sainsbury's afterword to his paper in this issue for a brief discussion of this topic.

  22. 22.

    Sainsbury (2013, p. 235), this issue.

  23. 23.

    The latter view is rare. Merricks (2001, p. 151) comes close to it: “I think linguistic vagueness does justice to the intuitions that standardly motivate it only when understood as a species of metaphysical vagueness.”

  24. 24.

    See for example Lewis (1986, pp. 212–213): “The reason it's vague where the outback begins is not that there's this thing, the outback, with imprecise borders; rather, there are many things, with different borders, and nobody has been fool enough to try to enforce a choice of one of them as the official referent of the word ‘outback’. Vagueness is semantic indecision.”

  25. 25.

    Eklund (2013, p. 176), this issue.

  26. 26.

    For similar explications of “ontic vagueness”, see Hawley (2001, p. 104) and Barnes (2010, p. 604). For a brief discussion of these negative characterizations, see López de Sa (2013), this issue.

  27. 27.

    Noonan (2013, p. 243), this issue. He continues: “To successfully refer requires not only that we engage in reference-fixing activities but also that there be eligible referents. But, even once we have done everything that we can do, there may still be ties in eligibility, and so referential indeterminacy. And such referential indeterminacy will be properly classified as ontic rather than semantic, for it will be the world, and not us, that is not playing its part” (ibid.).

  28. 28.

    See for example Sattig (2010) and Sattig (2013), in this issue.

  29. 29.

    Charles S. Peirce, Collected Papers vol. 1, Cambridge: HUP 1931, vii.

  30. 30.

    “Let us understand a physical object […] simply as the aggregate material content of any portion of space-time, however ragged and discontinuous.” (Quine 1976, p. 497)

  31. 31.

    See Eklund's distinction between a “robust” and a “deflationist” conception of ontology: “The robust ontologist holds that there are real metaphysical joints in nature. The deflationary ontologist, by contrast, subscribes to the ‘picture of reality as an amorphous lump’ as Michael Dummett puts it” (Eklund 2008, p. 383).

  32. 32.

    A theory's ideology, “to give a good sense to a bad word”, rests in its predicates, which determine “what ideas can be expressed in it”, whereas the theory's ontology is simply “the range of the variables of quantification of the theory” (Quine 1953, p. 131). Given this distinction, it is obvious why a sortal ontology is no option for Quine. It makes no sense to ask whether values of variables are sortal in character or not. Sortality is an attribute of terms or concepts, not of entities.

  33. 33.

    Eklund (2013, p. 171), this issue. See also Sainsbury (1994, p. 79).

  34. 34.

    The Lego example is vulnerable, though, to the Platonic argument that no physical surface is perfectly flat, no brick ever cubic, no edge ever straight. Regarding sharp boundaries, a Lego world is still infinitely worse off than a Pythagorean world of numbers. Hence, some idealisation is necessary to make the example work.


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Correspondence to Geert Keil.

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Keil, G. Introduction: Vagueness and Ontology. Int Ontology Metaphysics 14, 149–164 (2013).

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  • Ontic vagueness
  • Vague identity
  • Problem of the many
  • Spatiotemporal boundaries
  • Sortal concepts