Peer Disagreement and the Bridge Principle


One explanation of rational peer disagreement is that agents find themselves in an epistemically permissive situation. In fact, some authors have suggested that, while evidence could be impermissive at the intrapersonal level, it is permissive at the interpersonal level. In this paper, I challenge such a claim. I will argue that, at least in cases of rational disagreement under full disclosure (i.e., the cases in which epistemic peers are fully aware of each other’s evidence and arguments), there cannot be more interpersonal epistemically permissive situations than there are intrapersonal epistemically permissive situations. In other words, with respect to cases of disagreement under full disclosure, I will argue that there is a necessary connection (or a “bridge”) between interpersonal permissiveness and its intrapersonal counterpart. Specifically, I claim that a plausible principle of correct argumentation supports such a bridge.

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  1. 1.

    See Dogramaci and Horowitz (2016), Greco and Hedden (2016), Hedden (2015), Horowitz (2014) and Matheson (2011). White (2005, 2014) also argued for interpersonal uniqueness, but many authors suggested that his arguments support only intrapersonal uniqueness (see Kopec and Titelbaum (2016) on this specific issue).

  2. 2.

    See Drake (2016), Douven (2009), Titelbaum and Kopec (forthcoming, m.s.), Kopec (2015) and Raleigh (2015). Brueckner and Bundy (2012) reject White’s argument for uniqueness, but they do not endorse a specific view concerning permissiveness.A quick clarificatory remark: it is close to trivial that intrapersonal permissiveness implies its interpersonal counterpart. If, relative to a body of evidence, one agent is rationally permitted to believe P and rationally permitted to believe ~ P, then (at least in theory) we can imagine another epistemically rational agent who is also permitted to believe P and permitted to believe ~ P. This is why, in the remainder of this paper, I will address only the bridge between interpersonal permissiveness and its intrapersonal counterpart.

  3. 3.

    See Kelly (2014), Meacham (2014), Schoenfield (2014) and Sharadin (2015). While Titelbaum endorses both intrapersonal and interpersonal permissiveness (see the previous footnote), he endorses diachronic requirements of epistemic rationality typically leading to the compromise between intrapersonal uniqueness and interpersonal permissiveness (Titelbaum 2013, Chap. 7).

  4. 4.

    This is a fairly common account of peerage. Other accounts of peerage have been proposed. For instance, it could be suggested that being equally competent in evaluating the evidence is a necessary condition of peerage (see Warfield and Feldman 2010, p. 2).

  5. 5.

    See Christensen (2009) for an overview of this debate.

  6. 6.

    One might wonder, if agents share the same relevant evidence, aren’t they already aware of each other’s evidence and reasoning? Accordingly, aren’t the Bridge and the restricted bridge coextensive? This is an open question left to the reader. See Cohen (2013) and Titelbaum (2017) on why full disclosure can affect an agent’s rational response to the evidence.

  7. 7.

    Diachronic Prohibition is implicit in various arguments against the restricted bridge. The arguments from conditionalization (Meacham 2014), epistemic conservatism or self-perpetuation (Podgorski 2016a, b), “epistemic path dependence” [e.g., our past doxastic decisions affect the doxastic decisions it is epistemically optimal for us to make in the future—see Sharadin (2015, pp. 10–13) or Titelbaum (2015a)] or immodesty (Schoenfield 2014) entail Diachronic Prohibition. Apart from Diachronic Prohibition, there could be other explanations of why the restricted bridge is false. For instance, Simpson (2017) argues that, even if there are distinct incompatible but equally rational epistemic standards, we should maintain ours because they are more suitable to our cognitive capacities.

  8. 8.

    Christensen (1994, 2000) reaches similar conclusions.

  9. 9.

    See, for instance, Pettigrew (2016) on the relationship between risk-based decisions rules and prior functions.

  10. 10.

    By way of contrast, (i) an immodest agent estimates that his or her beliefs and epistemic standards are at least as accurate as others (relative to a body of evidence) and (ii) modest agents estimate that their beliefs and epistemic standards can be less accurate than others (relative to a body of evidence). See Elga (2010), Lewis (1971), Christensen (2013), and Mayo-Wilson and Wheeler (2016) on modesty, immodesty and strict immodesty.

  11. 11.

    Compare Titelbaum and Kopec (forthcoming) and Daoust (2018) on this possibility.

  12. 12.

    Under the assumption that epistemic rationality has to do with reliability, Strict Immodesty leads agents to form false beliefs concerning facts of rationality. That is, when agents falsely believe that their rational standards are more reliable than others, they are mistaken concerning a fact of rationality. This is incompatible with the Fixed Point Thesis (Titelbaum 2015b), which roughly states that mistakes concerning the facts of rationality are mistakes of rationality. I leave this problem aside here.

  13. 13.

    Schoenfield also seems to think that agents acquire epistemic standards over time. If irrelevant influences (such as growing up in one particular community rather than in another) lead agents to adopt distinct incompatible epistemic standards, this means that agents adopt some new epistemic standards over time. In other words, they do not start their epistemic lives with all the epistemic standards they can have.

  14. 14.

    Note that the scanners could reveal other relevant information to participants. For instance, some participants could falsely believe that they have failed to satisfy their own epistemic standards. The scanners could reveal to them that they have satisfied their own epistemic standards.

  15. 15.

    Schoenfield insists that we cannot provide independent evidence in favour of our own epistemic standards. I will come back to this point in Sect. 3.

  16. 16.

    See Walton (2009) for an overview of the literature. See Fogelin (1985) on argumentation and resolving deep disagreement. See Godden (2008) on the problem of acceptance of starting points.

  17. 17.

    See Dare and Kingsbury (2008), Gordon et al. (2007), Hahn and Oaksford (2007) and Walton (2014) on this issue.

  18. 18.

    See Aberdein (2016), Cohen (2005) and Godden (2016) on virtue-based argumentation theory. See Cohen and Miller (2016) on empathy, sympathy and cognitive compathy as features of correct argumentation. See Kidd (2016) on intellectual humility as an intellectual virtue. See Kwong (2016) on open-mindedness as an intellectual virtue. The relationship between good arguments and good argumentation is controversial: some authors think that the study of good arguments can be subsumed under the study of good argumentation, while others reject such an approach. See Godden (2016) for an overview of this debate.

  19. 19.

    See notably Goldman (1986) on reliabilism.

  20. 20.

    See notably van Eemeren and Houtlosser (2015, Sect. 21.3) on the burden of proof in argumentative contexts. See also footnote 17.

  21. 21.

    I am here glossing over some subtleties. Cohen (2005, pp. 62–63) argues that it is correct for an agent to challenge premises and assumptions, as long as he or she does not become an “un-assuring assurer” who questions everything (including the obvious). Such agents are vicious arguers, in the sense that their willingness to question the obvious is excessive (Aberdein 2016, p. 416). We could here assume that an arguer should provide support in favour of his or her assumptions if they are challenged by a virtuous arguer, which excludes un-assuring assurers.

  22. 22.

    As Dare and Kingsbury note, “findings of criminal guilt may have significant consequences, most obviously loss of default liberties and rights. Since we regard those liberties and rights as important, we place a weighty burden on those who seek to have them removed or limited” (Dare and Kingsbury 2008, p. 507).

  23. 23.

    See notably Dare and Kingsbury (2008) on this line of reasoning. According to them, we ought to make a distinction between non-truth-directed and truth-directed activities. In non-truth-directed activities, a claim might enjoy a preferential status, and, unless the burden of proof is met, this claim is accepted as correct. Special contexts such as legal disputes would not count as truth-directed activities.


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Thanks to Charles Côté-Bouchard, Samuel Dishaw, Ulf Hlobil, Daniel Laurier, Samuel Montplaisir, Andrew Reisner, Olle Risberg, Xander Selene, Folke Tersman and three anonymous referees for helpful comments on this project. I warmly thank David Godden and Patrick Bondy, the editors of this special issue, for their useful comments and suggestions. This research was financed by the Groupe de Recherche Interuniversitaire sur la Normativité (GRIN) and the Social Sciences and Humanities Research Council.


This study was funded by the Social Sciences and Humanities Research Council (Grant #767-2016-1771).

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Daoust, M. Peer Disagreement and the Bridge Principle. Topoi (2018).

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  • Epistemic rationality
  • Uniqueness
  • Argumentation
  • Epistemic peer
  • Evidence