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A Counterexample to the Uniqueness Thesis

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In this essay, I present a straightforward counterexample to the Uniqueness Thesis, which holds, roughly speaking, that there is a unique rational response to any particular body of evidence.

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  1. 1.

    See Ballantyne and Coffman (2012), Feldman (2006), (2007), Kelly (2005), (2010), (2013), and White (2005), (2013).

  2. 2.

    For a recent sketch of various versions of Epistemic Instrumentalism, see Lockard (2013).

  3. 3.

    See Brueckner and Bundy (2012), Kelly (2013).

  4. 4.

    I believe it’s crucial to frame the thesis as holding that there is at most one rational attitude, as Feldman (2007) does, as opposed to holding that there is exactly one rational attitude, as White (2005), and those who follow his lead, have done. Here’s why. Take the following case, adapted from Kukla (1994). The Oracle decides to have a chat with the hare (from Aesop’s fable “The Tortoise and the Hare”), explaining to the hare the situation she is in. The Oracle convinces the hare of two conditionals: 1) If you believe that you will win the race, then you will not win the race, and 2) if you disbelieve that you will win the race, or suspend judgment on the matter, then you will win the race. Given that she has now been convinced of these two conditionals, the hare is in an awkward epistemic position. She knows ahead of time that if she believes that she will win, then this belief will be false, and thus such a belief is irrational to form. Similarly, if she believes she won’t win, or suspends judgment on the matter, then she knows that she will win, and so neither of these attitudes is rational to form. What must the hare do? It seems she must simply ignore the proposition ‘I will win the race’, since she is doomed if she forms any positive attitude about it. This example suggests that there are some cases where there is no rational attitude to take toward a proposition given a body of evidence, and therefore, the above formulation of Uniqueness is false. Of course, some might find this example controversial. But since the “at most one” version is logically weaker, it’s the preferable target. A counterexample to it brings down both versions.

  5. 5.

    It’s at least plausible that the coarse-grained version is logically weaker, and thus it’s the more fitting target. Of course, there is some controversy here as well. But regardless, the same general strategy used later in the counterexample could easily be revised to apply to the fine-grained version as well.

  6. 6.

    For example, if we were to plug these probabilities into Bayes’ Theorem, the credence the agent ought to have in the assessment of Trustworthy Weather is 0.5. See M. Titelbaum and M. Kopec, Plausible Permissivism, unpublished for the mathematical details.

  7. 7.

    I thank an anonymous referee for suggesting this case as a way to clarify exactly what the Trustworthy Principle entails.

  8. 8.

    Because of this, we can’t simply plug the values into Bayes’ Theorem to yield a credence of 0.5 like we could in the case of Trustworthy vs. Reliable Weather.

  9. 9.

    Thanks to Michael Goldsby for pressing this objection.

  10. 10.

    Here I’m thinking of Kukla (1994) and, more recently, Greaves (2013) who uses such examples to put pressure on various views in the budding field of epistemic decision theory. I thank an anonymous referee for pointing out the latter connection.


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  2. Brueckner, A., & Bundy, A. (2012). On ‘epistemic permissiveness.’. Synthese, 188, 165–177.

  3. Christensen, D. (2009). Disagreement as evidence: the epistemology of controversy. Philosophy Compass, 4, 756–767.

  4. Christensen, D. forthcoming. Conciliation, uniqueness and rational toxicity. Noûs

  5. Feldman, R. (2006). Epistemological puzzles about disagreement. In S. Hetherington (Ed.), Epistemology Futures (pp. 216–236). Oxford University Press.

  6. Feldman, R. (2007). Reasonable religious disagreements. In L. Antony (Ed.), Philosophers without Gods (pp. 194–214). Oxford University Press.

  7. Greaves, H. (2013). Epistemic decision theory. Mind, 122, 915–952.

  8. Kelly, T. (2005). The epistemic significance of disagreement. In J. Hawthorne & T. Gendler (Eds.), Oxford Studies in Epistemology (pp. 167–196). Oxford University Press.

  9. Kelly, T. (2010). Peer disagreement and higher order evidence. In R. Feldman & T. Warfield (Eds.), Disagreement (pp. 111–174). Oxford University Press.

  10. Kelly, T. (2013). Evidence can be permissive. In M. Steup, J. Turri, E. Sosa (Eds.), Contemporary Debates in Epistemology (pp. 298–312). Wiley.

  11. Kukla, A. (1994). Some limits to empirical inquiry. Analysis, 54, 153–159.

  12. Lockard, M. (2013). Epistemic instrumentalism. Synthese, 190, 1701–1718.

  13. White, R. (2005). Epistemic permissiveness. Philosophical Perspectives, 19, 445–459.

  14. White, R. (2013). Evidence Cannot Be Permissive. In M. Steup, J. Turri, E. Sosa (Eds.), Contemporary Debates in Epistemology (pp. 312–323). Wiley.

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I would like to thank John Basl, Michael Goldsby, and Michael Titelbaum for helpful discussion, as well as three anonymous referees for their suggestions and criticisms. This research was supported, in part, by the Andrew W. Mellon Foundation through their Sawyer Seminar entitled Theoretical Issues in Social Epistemology.

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Correspondence to Matthew Kopec.

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Kopec, M. A Counterexample to the Uniqueness Thesis. Philosophia 43, 403–409 (2015). https://doi.org/10.1007/s11406-014-9579-x

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  • Uniqueness
  • Epistemic permissiveness
  • Disagreement
  • Subjective bayesianism
  • Epistemic instrumentalism