Philosophy Uniqueness and Permissiveness in Epistemology
Luis Rosa
  • LAST REVIEWED: 25 October 2018
  • LAST MODIFIED: 25 October 2018
  • DOI: 10.1093/obo/9780195396577-0378


Permissivism is roughly the view that different doxastic attitudes toward a given proposition—e.g., the attitudes of believing and doubting a proposition, respectively—may be licensed by the same body of evidence. This view is in direct conflict with the Uniqueness Thesis, which says that for any body of evidence E and any proposition p there is at most one kind of doxastic attitude toward p that is licensed by E. The latter view is a rather strong one, and it seems to be at odds with the observation that rational subjects with access to the same evidence can sometimes disagree with each other. Epistemologists have motivated permissivist views in a number of different ways: not only by appealing to facts about disagreement such as the one just mentioned, but also by pointing out that the relation of evidential support is itself a permissive one—the same evidence can give support to a proposition or fail to give support to it, depending on some third relatum or subjective element (e.g., the subject’s prior degrees of belief or her evidential standards). They also have done so by arguing that the adoption of different doxastic attitudes might equally lead to the satisfaction of our epistemic goals. It is fair to say that Permissivism is nowadays a popular position among epistemologists. Despite its popularity and initial appeal, however, Permissivism has also been under attack. The objections have mostly to do with the fact that a permissive body of evidence would seem to make it arbitrary for one to adopt any of the permitted attitudes in the face of that evidence, and that a permissive body of evidence would fail to secure a safe connection with the truth. Another source of worry is with whether one could coherently acknowledge that one is in a permissive situation while maintaining one’s original opinion. These considerations in turn motivate the Uniqueness Thesis.

First Readings

There aren’t many overviews of the ever-growing literature on the Permissivism versus Uniqueness Thesis debate yet. Widespread attention to and controversy about Permissivism is a somewhat recent phenomenon in epistemology. Kopec and Titelbaum 2016 provides a useful survey of arguments in support of and against the Uniqueness Thesis. The authors also make a number of important distinctions, such as that between Permissivism and Uniqueness theses at the propositional and doxastic levels, intrapersonal versus interpersonal permissiveness, and acknowledged versus unacknowledged permissiveness. The introduction to chapter 12 of Steup, Turri and Sosa 2013 also sums up the positions of two influential contenders in this debate, i.e., the authors of Kelly 2013 and White 2013. Another introductory material can be found in chapter 5 of Bradley 2015, where the author discusses some of the problems with an influential permissivist theory of confirmation and rational credences: subjective Bayesianism. As Bradley emphasizes, however, the alternative view, according to which the relation of evidential support is an objective one, is also problematic.

  • Bradley, Darren. A Critical Introduction to Formal Epistemology. Bloomsbury Introductions to Contemporary Epistemology. London: Bloomsbury Academic, 2015.

    Chapter 5 discusses an influential permissivist theory—i.e., subjective Bayesianism—against the backdrop of objectivist views about evidential support.

  • Kelly, Thomas. “Evidence Can Be Permissive.” In Contemporary Debates in Epistemology. 2d ed. Edited by Matthias Steup, John Turri, and Ernest Sosa, 298–312. Malden, MA: Wiley-Blackwell, 2013.

    Discusses a “Jamesian” permissivist thesis, according to which the rationality of a doxastic attitude is also a function of how important different epistemic goals are to the subject. Kelly also makes the important point that permissivists may grant that no body of evidence admits of “intrapersonal slack,” even though sometimes the evidence admits of “interpersonal slack.”

  • Kopec, Matthew, and Michael G. Titelbaum. “The Uniqueness Thesis.” Philosophy Compass 11.4 (2016): 189–200.

    DOI: 10.1111/phc3.12318

    An overview of influential arguments in support of the Uniqueness Thesis and purported counterexamples to it.

  • Steup, Matthias, John Turri, and Ernest Sosa, eds. Contemporary Debates in Epistemology. 2d ed. Malden, MA: Wiley-Blackwell, 2013.

    This is a collection of essays on contentious issues in contemporary epistemology. Each chapter features a debate between philosophers with different takes on a given topic. Chapter 12 is concerned with the Uniqueness Thesis versus Permissivism debate.

  • White, Roger. “Evidence Cannot Be Permissive.” In Contemporary Debates in Epistemology. 2d ed. Edited by Matthias Steup, John Turri and Ernest Sosa, 312–323. Malden, MA: Wiley-Blackwell, 2013.

    White elaborates on his previous anti-permissivist moves. This includes White’s thought experiment of belief-inducing pills, which is designed to show (among other things) that following the evidence ceases to be a reliable belief-forming procedure when one is in a permissive case.

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