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Dialetheism in Action: A New Strategy for Solving the Equal Validity Paradox?

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Dialetheism and its Applications

Part of the book series: Trends in Logic ((TREN,volume 52))

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Abstract

This paper starts from the Equal Validity Paradox, a paradoxical argument connected to the so-called phenomenon of faultless disagreement. It is argued that there are at least six strategies for solving the paradox. After presenting the first five strategies and their main problems, the paper focuses on the sixth strategy which rejects the assumption that every proposition cannot be both true and false. Dialetheism is the natural candidate for developing strategy six. After presenting strategy six in detail, we formulate a normative problem for the dialetheist and offer a tentative solution to it. We then elaborate further considerations connecting strategy six to pluralism about truth and logic. Even if strategy six is a hard path to take, its scrutiny highlights some important points on truth, logic and the norms for acceptance and rejection.

This paper has been developed along a considerable amount of time. The general strategy of considering the prospects of dialetheism for making sense of relativism was first sketched in [11]; Sects. 14.2 have been elaborated jointly, while part of Sects. 5 and 5.16 have been developed by Sebastiano Moruzzi.

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Notes

  1. 1.

    The expression “faultless disagreement” has been introduced in the literature by Kölbel [27]. See [18] for a useful normative analysis of the phenomenon.

  2. 2.

    We use italics for referring to propositions.

  3. 3.

    Grim [21] has in fact calculated that there at least 240 possible formulations of LNC!

  4. 4.

    See [10, pp. 166–69] for a discussion of the semantic formulation.

  5. 5.

    We use ‘<p>’ to name the proposition that p, and ‘circ(<s,c>)’ to name the circumstances of evaluation relative to the utterance of ‘s’ in context c.

  6. 6.

    We are appealing to contradiction because in the example in question are involved sentences of the from “p” and “not-p”. The more general relation should be the one of incompatibility which can involve also being contraries.

  7. 7.

    For a more detailed and slightly different reconstruction of the Equal Validity Paradox see [13].

  8. 8.

    See for example [24] for the thesis that there is no faultless disagreement.

  9. 9.

    Following [53], this solution is an “unhappy face” solution to the paradox.

  10. 10.

    See also [13].

  11. 11.

    For realism see [4, 52]; for assessment-sensitive relativism see [29, 30, 32], for non-indexical contextualism (aka truth relativism) see [28].

  12. 12.

    See [61].

  13. 13.

    The critical literature on MacFarlane’s relativism is huge. For some recent critical points see [19, 20, 34, 35, 49, 55, 58, 60].

  14. 14.

    The debate on the normativity of truth is wide and complex. We are here assuming a rather weak norm. See Ferrari 2016 and ms for an analysis on the different varieties of normativity that could exert on truth.

  15. 15.

    Ayer [2] is the first example of this strategy in relation to aesthetics and morality. For contemporary examples of this strategy see [22, 23, 50].

  16. 16.

    See [57].

  17. 17.

    See [17].

  18. 18.

    For the basic worry of the lost disagreement problem see [12]. For sophisticated forms of contextualism see [14, 56, 63].

  19. 19.

    Notice that in order to avoid violation of LNC, it should claimed that either (a) one proposition is true and the other is false; or (b) the propositions expressed are not contradictory; or (c) that <p> is untrue (but not false) and that <not-p> is false. As for option (a), it seems tantamount to realism, so option (a) collapses into strategy (ii). Analogously, option (b) seems just indexical contextualism, so we have a collapse into strategy (iv). Finally, option (c) requires to adopt some version of three-valued semantics with a value (call it “untruth only”) that is excluded by truth of a negation. This latter option seems the most promising option for avoiding the collapse into other strategies.

  20. 20.

    Assuming that propositions are objects of belief.

  21. 21.

    The idea of using dialetheism for accounting for the phenomenon of faultless disagreement is sketched in [7] where it is claimed that analetheism—which interprets gappy propositions as designated—is a better option. See [9] for a presentation of analetheism. Beall [7] prefers this strategy to dialetheism in relation to taste on the grounds that analetheism makes sense of the idea that there is no fact of the matter in matters of sense (taste propositions are neither true nor false). We agree with [1] in thinking that analetheism does not do justice to the truth-norm for the same problems we have raised before in relation to the indeterminist gappy theory (see supra Sect. 3.1). Insofar as truth is the norm for assertion, we do not think that this model of indeterminacy is sufficient for accounting for the rational sustainability of a dispute. We will thus focus on dialetheism.

  22. 22.

    Recall that we are using a semantic reading of LNC. In LP the formula \(\lnot (p \wedge \lnot p)\) is never false only since, when p is dialetheia, the formula itself is a dialetheia.

  23. 23.

    “I am frequently asked for a criterion as to when contradictions are acceptable and when they are not. It would be nice if there were a substantial answer to this question—or even if one could give a partial answer, in the form of some algorithm to demonstrate that an area of discourse is contradiction free. But I doubt that this is possible. Nor is this a matter for surprise. Few would now seriously suppose that one can give an algorithm—or any other informative criterion—to determine when it is rational to accept something. There is no reason why the fact that something has a certain syntactic form—be it \(p \wedge \lnot p\) or anything else—should change this. One can determine the acceptability of any given contradiction, as of anything else, only on its individual merits” [45, p. 423].

  24. 24.

    See [3, 11].

  25. 25.

    Aristotle (Metaphysics, \(\Gamma \) 4) famously held that LNC cannot admit exceptions. See [44] for a discussion of Aristotle on LNC.

  26. 26.

    This normative problem in relation to faultless disagreement is outlined in [11, pp. 151–152]. See also [59, p. 438].

  27. 27.

    The equivalence between acceptance of not-P and rejection (or denial) of P is known as “denial equivalence” in [51] and as “classical denial” in [36]. Also gappy theorists reject this equivalence—see [37].

  28. 28.

    We can interpret acceptance of p and rejection of p as “yes-or-no questions, respectively reading A? Yes! and A? No!” [36, \(\S 2\)].

  29. 29.

    See [10, 21]. Berto [10, pp. 174–178] states some worries regarding the idea that acceptance and rejection are primitively exclusive mental states. Berto argues that it is better to explain this incompatibility between attitudes through a notion of content exclusion. We agree with Berto’s point, however this issue will not be crucial for the following discussion.

  30. 30.

    In other words the exclusivity relation between acceptance and rejection involve that accepting p and rejecting p cannot be jointly correct attitudes. For the notion of joint correctness and its relation to disagreement see [32].

  31. 31.

    “If denial is to serve as a means to express disagreement, it must be rationally impermissible to both assert and deny A. Yet, in view of the Paradox of Deniability, no comprehensive set of norms for exclusive denial can be formulated in the glut-theorist’s language” [36]. See also [51] for similar worries.

  32. 32.

    This a modified version considered by Murzi and Carrara [36] under the label “Deny(U)*”.

  33. 33.

    It is also doubtful that in mathematics the evidence for an assertion must always be a proof.

  34. 34.

    The other option Carrara and Murzi consider is [6]’s proposal according to which we can add the so-called shriek-rules to express that a sentence is true-only. For each sentence A which is not glutty it is added a non-logical rule of the form: \(A, \lnot A \vdash \bot \), where ‘\(\bot \)’ is an operator that implies triviality. By means of the shriek-rules we can then express that a theory is consistent by stating shriek-rules for all the predicates—a shrieked theory. A shrieked-theory is thus either consistent or trivial. Notice, however, that this proposal will not work if the dialetheist position for the Equal Validity Paradox entails local triviality as argued below—see infra Sect. 6.

  35. 35.

    For issues related to domains of discourse see [62].

  36. 36.

    “LP has its so-called trivial model: if all atomic sentences of the relevant language are both true and false (or both true and false at the base world where truth is evaluated, if we have a worlds semantics for LP plus arrow), then all sentences are true and false.” [10, p. 170].

  37. 37.

    Together with all the other propositions targeted by the dialetheist such as the liar, Russell’s paradox, sentences expressing change etc.

  38. 38.

    For domain-based logical pluralism see [31, Chap. 5], [39, 40].

  39. 39.

    For alethic pluralism see [31] and the collection [41].

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Moruzzi, S., Coliva, A. (2019). Dialetheism in Action: A New Strategy for Solving the Equal Validity Paradox?. In: Rieger, A., Young, G. (eds) Dialetheism and its Applications. Trends in Logic, vol 52. Springer, Cham. https://doi.org/10.1007/978-3-030-30221-4_4

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