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Understanding undermining defeat


Taking the inspiration from some points made by Scott Sturgeon and Albert Casullo, I articulate a view according to which an important difference between undermining and overriding defeaters is that the former require the subject to engage in some higher-order epistemic thinking, while the latter don’t. With the help of some examples, I argue that underminers push the cognizer to reflect on the way she formed a belief by challenging the epistemic worthiness of either the source of justification or the specific justificatory process. By contrast, overriders needn’t pose any such challenge. I also consider some problems for the proposed view, and I put forward some possible solutions. Finally, I provide some details on how undermining defeat works in different cases.

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  1. For two examples of how undermining defeat plays a role in those debates, see Christensen (2010) and Pryor (2013).

  2. As it will be evident by my constant reference in cases where the belief is based on some evidence, I’m working with a notion of doxastic justification.

  3. I will appeal to justificational triads e, p, d throughout and, for ease of exposition, I will take e, p and d to be propositions. However, I don’t wish to commit myself to the claim that all evidence is propositional, but only to the much weaker claim that for every piece of evidence available to a subject, there is a proposition that can be used to represent it.

  4. The parenthetic remark is meant to rule out cases of epistemic overdetermination, where the subject has access to other pieces of information for or against p, besides the mentioned e and p.

  5. Assuming that ‘see’ is factive.

  6. In general, underminers appear to be source-sensitive (they defeat only the justification provided by a specific source), while overriders appear to be source-neutral (they defeat regardless of the source of justification). This difference, noted by Casullo (2003, pp. 45–46), might very well be a symptom of the feature Sturgeon describes.

  7. This is the notion of source endorsed by Casullo himself (2003, pp. 35–38).

  8. Square brackets are meant to suggest that e and p are propositions, rather than the mere stand-in for propositions that are inside the brackets.

  9. The choice to focus on evidence-supported justified beliefs is not due to a disregard for other options, but only to a desire to keep the exposition as simple as possible.

  10. There might be another reply available here: in a nutshell, one could agree that both overriders and underminers suggest that something went wrong in the justificatory process, but still contend that while the consideration of that thought plays a role in the process of belief revision generated by an underminer, it needn’t play any role in the belief-revision process generated by an overrider.

  11. It’s worth saying something on the notion of disturbing event at this stage. By ‘disturbing event’ I mean something that interfered with the justificatory process and caused its failure. I take disturbing events to belong to two main categories: those for which the agent can be blamed (e.g. a mistake in a proof due to carelessness), and those for which the agent cannot be blamed (e.g. the acquisition of a false information from a reliable source).

  12. One could argue that faculties like memory and perception, if they are working at the best of their possibilities in optimal circumstances cannot deliver a false belief. On this view, the acknowledgment that memory and perception are not infallible is, at bottom, an acknowledgement that they hardly ever work at their best in optimal circumstances. If this view is correct, there is a sense in which overriders entail that something went wrong in the process in the sense I attach to underminers. However, the point stands that overriders do not suggest that things are so, and don’t need things to be so to defeat the subject’s original belief.

  13. The specification that e is evidence for p is meant to make it clear that the suggestion made by the underminer is a higher-order one.

  14. One might think that the suggestion here is that e is false, but that the suggestion isn’t strong enough to warrant belief in the falsity of e. I don’t disagree with this way of putting it; it’s just that I understand the suggestion made by the underminer to be the higher-order thought—about the basing of the first-order belief—that the thinker is warranted to believe. And what the thinker is warranted to believe in this case is that there is no justification to believe that e is true, not that that e—the evidence for p—is false.

  15. It might be a little tricky to specify the source here. One option might be: vision plus the required theoretical luggage needed to read timetables.

  16. This example pushes for a further refinement on (View #3): the suggestion made by underminers with respect to the source or the process can be either that they were defective, or that they might have been defective.

  17. Or, maybe more precisely, “vision plus the theoretical luggage needed to handle notions like orbit, astronomical theory, sun, earth”.

  18. Pryor (2013, §2), by using a framework different than mine, comes to the conclusion that there are cases of mixed overriding/undermining defeat.

  19. In other words, it is a consequence of the view presented that unreflective agents cannot suffer undermining defeat.


  • Casullo, A. (2003). A priori justification. Oxford: Oxford University Press.

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  • Christensen, D. (2010). Higher-order evidence. Philosophy and Phenomenological Research, 81(1), 185–215.

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  • Pollock, J. L. (1974). Knowledge and justification. Princeton: Princeton University Press.

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  • Pryor, J. (2013). Problems for credulism. In C. Tucker (Ed.), Seemings and justification: New essays on dogmatism and phenomenal conservatism (pp. 89–132). Oxford: Oxford University Press.

  • Sturgeon, S. (2012). Pollock on defeasible reasons. Philosophical Studies, published online: 17 April 2012.

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I wish to thank everyone at the Northern Institute of Philosophy for creating such a supportive environment, and especially Crispin Wright, Carrie Jenkins, and Federico Luzzi for discussions and feedback that have been crucial in shaping the ideas here presented. A predecessor of the present article was presented at the SIFA Graduate Conference, at the University of Cagliari in September 2013: I am grateful to the organizers and to the participants for constructive and helpful comments.

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Correspondence to Giacomo Melis.

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Melis, G. Understanding undermining defeat. Philos Stud 170, 433–442 (2014).

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  • Epistemology
  • Defeaters
  • Undermining
  • Overriding
  • Justificatory process
  • Higher-order