Philosophy Vagueness
Carl Ehrett
  • LAST REVIEWED: 08 October 2015
  • LAST MODIFIED: 29 June 2011
  • DOI: 10.1093/obo/9780195396577-0122


Much, or perhaps all, of natural language is vague: the concepts expressed in natural language seem to have unclear boundaries. A central example is that of “heap”—as grains of sand are removed from a heap, at what point does it cease to be a heap? It seems that the removal of a single grain of sand can never, by itself, transform a heap into a non-heap; but applying that idea consistently would entail that a heap is still a heap when reduced to only a single grain, or zero grains. Such “sorites” paradoxes provoke troubling questions about the nature of vague languages. Some theorists (epistemicists) take vagueness to consist in speaker ignorance of certain semantic facts (such as the minimum number of grains in a heap); others take vagueness to consist in some form of semantic underdetermination (indeterminists), or in extremely subtle variations of context (contextualists). Other controversies include whether vagueness compels the adoption of a nonclassical logic, whether there is “ontic vagueness” (vagueness as a feature of the world itself rather than of representations), and whether ‘vagueness’ itself is vague.

General Overviews

Overviews of the literature on vagueness are available in varying levels of detail, and with varying focuses and aims. Sainsbury 2009 is intended as an introductory guide to various paradoxes; chapter three introduces the sorites paradox, describes the supervaluationist and degree-theoretic resolutions, and briefly discusses the notion of vague objects. Sorensen 2006 does likewise, but is a bit broader in scope, discussing contextualist responses; and it is freely available online. So too is Hyde 2005, which focuses on the sorites paradox itself (rather than vagueness generally), describing the many different versions of the paradox and its most common resolutions; Hyde also describes the ways the paradox interacts with core issues in the philosophy of language. A somewhat more detailed overview of the debate surrounding vagueness is the introduction of Keefe and Smith 1999. It includes more thorough discussion of the epistemicist solution to the sorites, and provides illuminating summaries of many of the most important writings on vagueness. Keefe 2000 includes a defense of supervaluationism and detailed descriptions and criticisms of the contemporary rivals of that view. Williamson 1994 is perhaps the most comprehensive single text on vagueness available; in addition to its defense of the epistemicist position and criticisms of rival theories, it includes three chapters on the history of vagueness and the sorites, both in ancient Greece and in analytic philosophy, as well as a chapter on ontic vagueness.

  • Hyde, D. “Sorites Paradox.” In The Stanford Encyclopedia of Philosophy. Edited by Edward N. Zalta. 2005.

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    A comprehensive introduction to the sorites paradox. Includes discussion of the history of the paradox, explanations of its various forms, introductions to all major contemporary solutions to it, and its connections to related problems in the philosophy of language.

  • Keefe, R. Theories of Vagueness. New York: Cambridge University Press, 2000.

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    Argues for a supervaluationist account of vagueness. Keefe includes detailed critiques of rival theories. Light on discussion of contextualism and ontic vagueness.

  • Keefe, R., and P. Smith. “Introduction: Theories of Vagueness.” In Vagueness: A Reader. Edited by Rosanna Keefe and Peter Smith, 1–57. Cambridge, MA: MIT Press, 1999.

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    A detailed overview of the contemporary debate concerning the nature of vagueness. Provides illuminating summaries of many of the most important works on vagueness. Includes discussion of ontic vagueness.

  • Sainsbury, R. M. “Vagueness: the Paradox of the Heap.” In Paradoxes. 3d ed. By R. M. Sainsbury, 40–68. New York: Cambridge University Press, 2009.

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    Useful for students who want a brief introduction to the sorites paradox and the problem of vagueness. Includes discussion of the most common sorts of resolutions of the problem, as well as the notion of vague objects.

  • Sorensen, R. “Vagueness.” In The Stanford Encyclopedia of Philosophy. Edited by Edward N. Zalta. 2006.

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    Good quick overview of the problem of vagueness, introducing all the major contemporary theories. A bit light on discussion of epistemicist accounts. This work is freely available online.

  • Williamson, T. Vagueness. New York: Routledge, 1994.

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    Remains the most comprehensive single text on vagueness available, tracing its history and exploring all major contemporary theories, though it is light on contextualism. There is a chapter on ontic vagueness.

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