Abstract
Disagreement plays an important role in several philosophical debates, with intuitions about ordinary or exotic cases of agreement and disagreement being invoked to support or undermine competing semantic, epistemological and metaphysical views. In this paper we discuss cases of (alleged) interworld doxastic disagreement, that is to say, cases of doxastic disagreement supposedly obtaining between (the beliefs of) individuals inhabiting different possible worlds, in particular between an individual inhabiting the actual world and his/her counterpart in another possible world. We draw a distinction between propositional and attitudinal disagreement, bring it to bear on the issue of the conditions of this kind of disagreement, and raise some metaphysical and epistemological worries about the claim that an individual inhabiting the actual world can disagree with an attitude or a speech act of his/her own counterpart, or of another individual, in a different possible world.
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Notes
If they were, the argument would involve a fallacy of equivocation, for failing to disagree out of normative insulation is crucially different from failing to disagree on a shared normative background. We are grateful to Filippo Ferrari for drawing our attention to this point.
We owe this suggestion to Matteo Plebani.
Disagreement being a symmetric relation, any situation in which someone would have disagreed with the proposition that they, or someone else, actually asserted or believed will be a situation in which someone disagrees with the proposition that they, or someone else, would have asserted or believed. This, however, need not detain us here.
Cappelen and Hawthorne (2009, pp. 54–66) would likely resist describing their view of disagreement as the view that disagreeing is essentially disagreeing with a proposition: they say that disagreement is primarily a relation between persons. However, they expressly subscribe to the Simple View of disagreement, which is what really matters for our purposes.
MacFarlane initially defended his usage of possible worlds talk in the description of the case of Jane and June by arguing that, “[h]owever you think of modality, it makes sense to ask whether in saying what one would have said, in some counterfactual situation, one would have disagreed with what one actually did say” (MacFarlane 2007, p. 23), exposing his flank to Cappelen and Hawtorne’s criticism by suggesting that disagreement is a relation to a proposition. But he is now fully explicit that the logical form of states of (intraworld and interworld) disagreement should be articulated by schemas such as
x is in disagreement with ϕ-ing-in-context-c,
the underlying thought being that the accuracy of a belief or assertion depends not only on its content, but, crucially, also on its context, which includes the relevant agent (MacFarlane 2014, p. 120). For a defence of interworld disagreement along roughly the same lines, see Marques 2014, pp. 129–130. Incidentally, discussions of Conciliationism in the epistemology of disagreement have recently focused on cases of merely possible (as opposed to actual) disagreement (see, e.g., Kelly 2005; Carey 2011; Barnett and Li 2016); but the cases considered are typically construed as cases of either propositional or intraworld disagreement.
That propositions exist in all worlds or in none is a presupposition of everything that has been said so far concerning propositional disagreement: to challenge it would be to challenge the integrity of the very notion of propositional disagreement.
Note that we are not claiming, here, that the notion of attitudinal disagreement is in any sense explanatorily prior to the notion of propositional disagreement. The claim is just that whenever an attribution of disagreement is correct, it must be possible to offer an attitudinal reading of it.
It is interesting to note that MacFarlane’s discussion of the case of Jane and June in Assessment and Sensitivity no longer assumes that the latter is the former’s counterpart in another possible world: Jane and June are introduced as just two individuals inhabiting different worlds. MacFarlane does not mention the change, but cautiously concludes his discussion by saying that, since ‘it is difficult to have any stable intuitions about the case’, he does not want ‘to rest too much weight on this argument’ (MacFarlane 2014, p. 128).
We are grateful to an anonymous referee for Erkenntnis for pressing us on this point.
It is perhaps worth recalling here that MacFarlane has himself come very close to accepting this conclusion in the passage quoted in n. 8 above.
Here we are presupposing that attitudinal disagreement cannot be reduced to propositional disagreement: our argument would not go through if disagreeing with someone’s believing that p boiled down to having beliefs whose contents are jointly incompatible with the proposition that p (thanks to an anonymous referee for Erkenntnis for calling our attention to this point). However, we have already emphasised in Sect. 3 that there are strong reasons for resisting the proposed reduction.
To be clear: we are not claiming that counterfactuals violate modus ponens, but only that an instance of modus ponens featuring a true counterfactual conditional among its premises will necessarily have a false (minor) premise.
The same epistemological difficulty affects the counterfactual associated with propositional disagreement:
Basic PD. A accepts P, and if A were to accept not-P in circumstances sufficiently similar to the actual ones, A would disagree with P.
In this case, too, the conditional’s antecedent is not available for running a sound modus ponens. One might think that here the situation is different: the counterfactual conditional associated with propositional disagreement is a tautology, because in the case of disagreement with a proposition ‘accepting not-P’ is actually equivalent to ‘disagreeing with P’. But again, there is reason to think that there cannot be any interesting case of interworld propositional disagreement without a corresponding case of interworld attitudinal disagreement.
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Acknowledgements
An earlier version of this paper was presented at the Disagreement: Current Topics workshop held in Bologna in September 2017. Thanks to all present for discussion. We are especially grateful to Filippo Ferrari for reading and commenting a draft of the paper and to Matteo Plebani for some very helpful suggestions.
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Moruzzi, S., Volpe, G. Interworld Disagreement. Erkenn 86, 1585–1598 (2021). https://doi.org/10.1007/s10670-019-00171-w
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DOI: https://doi.org/10.1007/s10670-019-00171-w