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Moore’s proof, theory-ladenness of perception, and many proofs

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I argue that if we allow that Moore’s Method, which involves taking an ordinary knowledge claim to support a substantive metaphysical conclusion, can be used to support Moore’s proof an external world, then we should accept that Moore’s Method can be used to support a variety of incompatible metaphysical conclusions. I shall refer to this as “the problem of many proofs”. The problem of many proofs, I claim, stems from the theory-ladenness of perception. I shall argue further that this plethora of proofs for incompatible positions leads to a darker form of skepticism, one which maintains that each of the dogmatic views is probably false. We will conclude by considering various ways a Moorean might respond to these difficulties.

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  1. As Annalisa Coliva notes (2007). I have added ‘material’ to the canonical formulation here to clarify a contrast which will later become important. It is clear that Moore takes hands to be examples of “material” or “physical objects”. Indeed, Crispin Wright suggests that the proof depends on the “conceptual necessity that any hand is a material object existing in space.” (2007, p. 26) Moore, as I understand him, takes it that there can be external objects that are not physical or material. Moore appeals to shadows as an example of objects which are not material or physical, but can be met in space.

  2. Even those sympathetic to Moore’s Proof, e.g., James Pryor, believe that it is not successful against the determined skeptic. Pryor, however, says the fault lies with the skeptic, not with the proof (2004).

  3. This use of ‘dogmatist’ is substantially different from other uses of the term (Tucker 2013).

  4. I say “at least” since, as we shall see below, there is a “darker” form of skepticism that recommends a stronger reaction to the claims of dogmatists, namely: that dogmatists’ views are wrong, or probably wrong. See below.

  5. For more on underdetermination skepticism, see Pritchard (2015).

  6. Some commentators try to bolster Moore’s argument here by referring to other anti-skeptical work by Moore. In particular, Moore at various stages of his career asserted that the skeptic’s position depends on assumptions that are less certain than his appeal to everyday claims like “Here is a hand” (Weatherall 2017). I do not address this point directly in the paper, although the discussion in the final section may bear on this issue.

  7. Below, we will consider this passage further in terms of a potential ambiguity.

  8. Below, we will consider the point that it is not sufficient to be in a position to claim knowledge, one must actually know the premises.

  9. Before one gets too excited about the prospect of dismissing this as a mere thought experiment, recall that even the most cursory review of the history of human thought reveals that there is a plethora of views about the ultimate nature of reality. There is a long tradition of idealism in Hindu and Buddhist thinking (Raju 2013). Animism, the idea that reality is infused with spirits rather than dead matter, is also a common metaphysics ((Bird-David 1991). Some Australian Aboriginals believe that rocks listen (Povinelli 1995). My point here is simply that it is wrong to suppose that a material metaphysics is somehow the default metaphysical view of reality. I am not making the claim that each of these views is true, or epistemically on par with a material metaphysics.

  10. Sorry.

  11. Dickens appears to leave open the possibility that the ghosts are merely dreamt, which would satisfy the idea that they exist only so long as they are perceived.

  12. I take it that this is the sort of belief we might have about the epistemic possibility of a set of lottery tickets: each is probably not the winner even if we belief that the winner is amongst the set of lottery tickets.

  13. I discuss naturalized versions of this Kantian possibility in (Walker 2004).

  14. Note that this is weaker than the Laplacian assumption that all three are equiprobable. The principle here says simply that no one possibility is more likely than the combined probability of the other two possibilities. For more on this see (Walker 2016b).

  15. This point will be explored below.

  16. Sextus says, “The Skeptic Way is a disposition to oppose phenomena and noumena to one another in any way whatever, with the result that, owing to the equipollence among the things and statements thus opposed, we are brought first to epoché and then to ataraxia….By "equipollence" we mean equality as regards credibility and the lack of it, that is, that no one of the inconsistent statements takes precedence over any other as being more credible” (Mates 1996).

  17. Some writers insist that this is the only sort of skepticism that properly deserves the name, e.g., Coliva (2010).

  18. To translate this to belief talk, the idea would be to believe “there is an epistemic probability of 0.33 for each hypothesis”.

  19. Pryor writes, “We’ve focused on the skeptic who doubts whether our perceptual experiences give us any justification at all for our perceptual beliefs.” (2004, p. 369). Crispin Wright writes, “It is of paramount importance to us to find our way around the world, make use of its resources, avoid danger, and so on. If we are to do these things, we need to be able to form reliable beliefs about the locations and dispositions of material objects” (2004, p. 186).

  20. I’m assuming here that Berkeley has some sort of reply to Samuel Johnson’s (in)famous kicking of a stone as refutation of idealism, and Jonathan Swift’s refusal to open the door for his friend Berkeley on the grounds that Berkeley should be able to walk right through (Musgrave 1993). It is generally agreed that Berkeley attempted to provide an account of why walking into a mailbox would hurt. Whether he was successful, of course, is a distinct question.

  21. For more on the competency of perception once metaphysical skepticism is endorsed see my (Forthcoming).

  22. I won’t consider here the possibility of relativizing truth or proof to a “framework”, a “form of life”, etc. to relieve the paradox.

  23. For a defense of MC along these lines, see, for example, (Vogel 1990). I argue against this strategy in part by noting that simplicity will have to adjudicate between many metaphysical hypotheses (Walker 2016b).

  24. I have in mind here the strategy of invoking the Wittgensteinian idea of hinge propositions to defend MC. In (Walker, Forthcoming) I criticize Wright’s (2004) version of this strategy.

  25. Also relevant here are two other anti-skeptical strategies: externalism and epistemological disjunctivism. Connecting these strategies with the present argument would take us too far afield. I have argued that externalism faces similar skeptical considerations to those canvassed here (Walker 2016a). Pritchard, inspired by McDowell’s pioneering efforts, offers a powerful case for disjunctivism as an antidote against (underdetermination) skepticism (Pritchard 2015; Pritchard 2012). I hope in future work to examine whether disjunctivism is subject to a similar problem to that of too many proofs.

  26. This is a point familiar from contextualist responses to skepticism. It also seems relevant to Moore’s claim that skeptical arguments always depend on premises more implausible than the views that they seek to impugn.


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Thanks to Tim Cleveland, Peter Hutcheson, and Jean-Paul “Eudicus” Vessel for helpful discussion. Thanks also to an anonymous referee for this journal for some great suggestions and saving me from several embarrassing errors.

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Walker, M. Moore’s proof, theory-ladenness of perception, and many proofs. Philos Stud 177, 2163–2183 (2020).

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