Philosophy Modal Epistemology
Kelly Becker
  • LAST REVIEWED: 08 October 2015
  • LAST MODIFIED: 27 November 2013
  • DOI: 10.1093/obo/9780195396577-0139


Modal epistemologies aim to explicate the necessary link between belief and truth that constitutes knowledge. This strain of epistemological theorizing is typically externalist; hence, it does not require that the agent know or understand the nature of the knowledge-constituting link. A central concern of modal epistemology is to articulate conditions on knowing such that no merely lucky true belief—very roughly, a belief that might easily have been false—counts as knowledge. In the effort to eliminate luck, epistemic principles are often cast modally, requiring that an agent’s belief is true not only in the actual world but also in relevant possible worlds, indicating that the link between truth and belief is more than an actual world lucky coincidence. (Note, then, that this entry is not about the epistemology of modals—statements involving modal operators such as “necessarily,” “possibly,” and the like—but about the use of modal principles in characterizing the nature of knowledge in general.) Modal epistemologies typically have antiskeptical consequences, but the strength of the antiskeptical result varies significantly, especially between the two best-known modal principles, sensitivity and safety.

General Overviews

Because modal epistemologies are relative newcomers in the theory of knowledge, and because they occupy a niche in the epistemological landscape, there are few general overviews on the topic. Pritchard 2005 offers a general taxonomy of various strains of knowledge-precluding luck and defends a safety-based theory. Safety says that S knows that p only if, in nearby worlds where S believes that p, p is true. Becker 2007 investigates various modal theories—modalized process reliabilism, sensitivity, and safety—and argues for a combination of the first two. Modalized process reliabilism says that S knows that p only if S’s belief that p is formed from a general belief-forming process that produces mostly true beliefs in the actual world and, typically, in nearby worlds. Sensitivity: S knows that p only if, were p false, S would not believe that p. Pritchard 2008 provides a succinct appraisal and comparison of sensitivity and safety. As textbooks are typically geared to more general themes, there are none available that are concerned specifically with modal theories. However, most epistemology anthologies designed for upper-level undergraduate courses contain many of the seminal papers or book excerpts on modal epistemology, including, with few exceptions, selections from Nozick’s original presentation of sensitivity (Nozick 1981, cited under Sensitivity). One excellent such anthology is Sosa, et al. 2008. Finally, only one anthology focused on modalized epistemology, specifically Nozick’s sensitivity-based (“tracking”) theory, has been published to date. Luper-Foy 1987 begins with an extensive excerpt from Nozick 1981 and follows with twelve critical essays. This book has provided a point of departure for many future investigations of Nozick’s tracking epistemology.

  • Becker, Kelly. Epistemology Modalized. New York: Routledge, 2007.

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    Offers a critical analysis of modalized process reliabilism, sensitivity, and safety, and defends a theory that incorporates the first two. Sensitivity is defended on the grounds that knowledge requires the capacity to discriminate truth in the actual world from the closest worlds where the target proposition is false.

  • Luper-Foy, Steven, ed. The Possibility of Knowledge: Nozick and His Critics. Totowa, NJ: Rowman & Littlefield, 1987.

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    Presents a well-rounded critical investigation of Nozick’s epistemology in general, with a focus on sensitivity. Critical issues discussed are the extent of Nozick’s antiskepticism, Nozick’s commitment to violation of the principle that knowledge is closed under known entailment (see Closure), and the possible incompatibility of sensitivity with inductive knowledge (see Specific Criticism).

  • Pritchard, D. H. Epistemic Luck. Oxford: Oxford University Press, 2005.

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    This book presents a valuable taxonomy of luck, some types of which preclude knowledge, in response to which a modalized account of knowledge may be desirable. That taxonomy in hand, Pritchard then defends a neo-Moorean response to skepticism involving safety as a necessary antiluck condition for knowing.

  • Pritchard, D. H. “Sensitivity, Safety, and Anti-Luck Epistemology.” In Oxford Handbook of Skepticism. Edited by John Greco, 437–455. Oxford: Oxford University Press, 2008.

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    Presents an especially clear and concise discussion of the relative merits and disadvantages of sensitivity and safety. The general antiluck insight is that a knowledgeable belief is one that could not easily have been false. On the safety view, one can know that radical skeptical hypotheses are false because they are true only in far-off possible worlds, and so those beliefs could not easily be false.

  • Sosa, Ernest, Jaegwon Kim, Jeremy Fantl, and Matthew McGrath, eds. Epistemology: An Anthology. 2d ed. Oxford: Blackwell, 2008.

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    This is one of the more comprehensive anthologies in epistemology, with sixty selections. It includes work from both safety advocates (Pritchard, Sosa, and Williamson) and sensitivity theorists (Dretske and Nozick), and from Goldman, a seminal figure in reliabilism, in addition to coverage of all central topics in epistemology.

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