Abstract
The paper explores the project of an ambitious modal epistemology that attempts to combine the a priori methods of Chalmers’ 2D semantics with Kripke’s modal metaphysics. I argue that such a project is not viable. The ambitious modal epistemology involves an inconsistent triad composed of (1) Modal Monism, (2) Two-Dimensionalism, and what I call (3) “Metaphysical Kripkeanism”. I present the three theses and show how only two of those can be true at a time. There is a fundamental incompatibility between Chalmers’ Modal Rationalism and Kripke’s modal metaphysics. Specifically, Chalmers’ conceivability entails possibilities that a Kripkean rejects as genuinely metaphysical. However, three positive stances in modal epistemology emerge from the combinations that the triad allows. One of those offers a promising way forward for 2D modal epistemologies. But it comes with a cost, as it requires abandoning modal monism and reshaping the scope of what a priori conceivability can give us access to.
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Notes
Some might reject desideratum (i): one might be skeptical that there is a distinctive kind of metaphysical possibility as opposed to other kinds of possibilities, and hold instead a monistic view with only one kind of modality. However, even modal monists usually acknowledge at least a minimal distinction between two notions of modality—indeed, the 2D framework rests on this distinction. I take it that the skeptical reader will grant (i) under such a minimal understanding. At any rate, she should grant it as a dialectical point: for this distinction is shared by both Chalmers and the Kripkeans.
Some might reject desideratum (ii): Kripke’s essentialist bridge-principles and examples are not uncontroversial. But note that complying with desideratum (ii) does not require further endorsing Kripke’s modal metaphysics (what I call here metaphysical Kripkeanism). In fact, Chalmers’ Modal Rationalism is a working example of how to fix the cases of the necessary a posteriori without endorsing the Kripkean modal metaphysics. Because of that, the skeptical reader should grant (ii) as a dialectical point.
Cf. Peacocke (1999: p. 41). See also Hale (forthcoming, 2013: ch. 11), and Lowe (2012). For recent discussion of the connection between apriority and modality, see Bueno and Shalkowski (2018); Casullo (2014); Vaidya (2017a, b). Some might reject desideratum (iii). I mentioned a recent empirical turn in modal epistemology: modal empiricists eschew a priori means and defend non-traditional epistemic sources and procedures for modal knowledge like perception, inductive and abductive reasoning, and (quasi-perceptual) imagination. They typically frame modal investigation as an extension of scientific investigation, and prefer naturalist and externalist stances in epistemology. Also, they tend to focus on knowledge of “nearby” possibilities as opposed to the remote “extravagant” ones (see e.g. the essays in Fischer and Leon 2017; Strohminger 2015; Williamson 2016a, b, 2007: ch. 5). Although I also see metaphysical modal knowledge as generally grounded in empirical knowledge (specifically, in essentialist knowledge: see my ‘Putting Modal Metaphysics First’, (ms.)), I also distance myself from the more radical aspects of modal empiricism. First, I am skeptical that a posteriori ways of knowing by themselves can lead us to knowledge of metaphysical modality. The non-actual is something that structurally or by its very nature escapes empirical observation and experience. Second, I question the scope of those theories. While they seem to safely range over physical-nomological possibility, it is less clear that they cast light beyond that into the metaphysical realm. Metaphysical possibility is covered to the extent that it coincides with physical-nomological possibility; thereby it remains largely unexplored. Third, it is not obvious that the methods modal empiricists appeal to are themselves purely empirical. The justification of induction, for example, is a longstanding problem: e.g. BonJour (1998) argues that it is a priori. Biggs and Wilson (2017) argue that abduction is a priori. In any case, the skeptical reader should still grant (iii) as a dialectical point, as a priori methods and justification play a central role for modal knowledge for both Chalmers and the Kripkeans.
Chalmers defends Modal Rationalism in his (2002a), but see also his (2004, 2010), (2011). As mentioned, most contemporary accounts fail to satisfy one or another of the desiderata above. A notable exception is Hale (2013: ch. 11), which in my view has the further merit of grounding knowledge of necessity in knowledge of essence.
More precisely, positive ideal primary conceivability. Whereas negative conceivability is the inability to exclude certain possibilities a priori, positive conceivability requires construing positive hypotheses and coherently filling in relevant details. This distinction is not relevant for what follows and I set it aside. Roca-Royes (2011) offers an excellent criticism of a variety of conceivability-based accounts of de re modal knowledge. However, I disagree with her that Chalmers’ primary aim is to elucidate de re and essentialist modal knowledge. That seems rather a nice potential advantage of his view (if it holds). Moreover, Chalmers’ basic link between (idealized) conceivability and (primary) possibility, which is one of Roca-Royes’ main targets, is not problematic from the point of view of metaphysical Kripkeanism, and thereby it would not be problematic for an ambitious modal epistemology.
Chalmers mentions highly difficult unsolved mathematical problems, e.g. Goldbach’s conjecture: both its truth and its falsity are prima facie conceivable, but only one is ideally conceivable (2004: p. 145). Many have objected to this notion of ideal conceivability, e.g. Priest: “the ideality involved is that of some infinite and infallible a priori reasoner—not a very useful notion for mere mortals” (2016: p. 2660, fn.37). See also Worley (2003). Priest further objects that any decent mathematician can conceive of the conjecture being true and also of the conjecture being false, and they would not magically lose this ability if a proof of one or the other were found: examples proliferates in history. We might further note that mathematicians seem to conceive of contradictory scenarios any time they engage in a proof by contradiction. But Chalmers reiterates (in conversation) that while we might negatively conceive these proofs (we might not exclude them a priori), we cannot positively conceive them (building the proof itself).
I am only sketching the basics of Chalmers’ 2D framework, assuming that the reader is already familiar with it and narrowing my focus to those aspects that are relevant for my discussion of Modal Rationalism. Another notable example of a 2D framework with a similar program as Chalmers’ is Frank Jackson’s (1998), though Jackson does not apply it to modal epistemology. For an extensive discussion of 2D semantics and a comparison between Chalmers’ and other 2D programs (including Jackson’s), see Chalmers (2004).
Chalmers works with a broad notion of a priori justification: “S is a priori when it expresses a thought that can be justified independently of experience” (2010: p. 548). Some (e.g. Devitt 2005) have objected to such negative formulations on the grounds that they do not say what the a priori is. The epistemology of the a priori is notoriously a thorny issue. Here I grant Chalmers’ broad formulation.
A distinction between trivial vs. non-trivial essentialist import of Kripke’s a posteriori necessities has become standard (probably after Salmon 1981: pp. 82–87). Cases involving identities between rigid designators may only commit one to the “trivially” essential property of self-identity (and, although more tentatively, so do the cases of theoretical identifications. See also fn.13 below). Whereas, cases of kind essentialism and origin essentialism rather involve a commitment to “substantive” or non-trivially essential properties. I will discuss examples of both types.
Not in all cases. The truths of logic and mathematics are presumably both necessary and purely a priori, for Kripke.
If Kripke is right, essences are not hidden substrata or mysterious entities, but rather an object of scientific investigation. Unfortunately, Kripke does not further explore the metaphysics and epistemology of essence. In my ‘Putting Modal Metaphysics First’, (ms.), I argue that we can effectively do so by pursuing the thesis that, at least in the case of natural kinds, the essence of the kind is what causes and explains all the many, many other properties and behaviors shared by all the instances of the kind.
This is one of Kripke’s paradigmatic theoretical identifications, typically having the form of identity sentences involving a rigid (general) term for natural kinds on the left-hand side and a rigid semantically complex expression on the right-hand side (1980: pp. 125–140). It is a matter of debate what exactly the semantic status of the right-hand side expressions is (for a survey, see Beebee and Sabbarton-Leary 2010), but this is an issue at the level of language and reference that we do not have to settle here.
Thanks to Jonathan Schaffer for suggesting this distinction.
What about a scenario where e.g. ‘Tully’ refers to the actual individual, while ‘Cicero’ to someone else? For the Monistic Kripkean this would still not be a possibility where Tully is not Cicero; but rather one where Tully is not alsocalled Cicero. For surely the metalinguistic statement “Cicero and Tully are names of the same Roman orator” might have been false (cf. 1971: p. 154).
Pace Chalmers (2010: pp. 188–189, fn.3).
See Yablo (2006) for an insightful discussion of such cases.
Kripke’s discussion suggests some form of nomological necessitarianism, for which the laws of nature are metaphysically necessary. Theoretical identifications and scientific statements more generally are “not contingent truths but necessary truths in the strictest possible sense” (1980: p. 125, my emphasis). And at least for a range of cases, “it might be that when something’s physically necessary, it always is necessary tout court” (99). Still, Kripke is also cautious: “physical necessity might turn out to be necessity in the highest degree. But that’s a question which I don’t wish to prejudge” (ivi). Overall, it seems safe to say that Kripke endorses a weak necessitarianism for which properties are individuated by their role in laws or their causal role. E.g.: “It’s not just that it’s a scientific law [that gold has atomic number 79], but of course we can imagine a world in which it would fail. Any world in which we imagine a substance which does not have these properties is a world in which we imagine a substance which is not gold, provided these properties form the basis of what the substance is” (125).
Kripkean Monism entails a sort of direct reference about meaning. This is the view, as Devitt puts it regarding names, that “the meaning of a name is simply its bearer” (2015: p. 128). Cf. Soames (2002, 2005), Salmon (1986). However, it is worth stressing that although Kripke rejected descriptivism, he never explicitly endorsed direct reference. Perhaps more in seminars than in print, Kripke has remarked that senses qua associated descriptions are fine so long as they are not treated as definitions of the corresponding expressions. They are not part of the content of an expression, and do not provide necessary and sufficient conditions to determine their extension. Does this leave any room for Chalmers’ intensions? Perhaps only for a sort of secondary ones: “in the formal semantics of modal logic, the ‘sense’ of a term t is usually taken to be the (possibly partial) function which assigns to each possible world H the referent of t at H. For a rigid designator, such a function is constant” (Kripke 1980: p. 56, fn. 22). ‘Cicero’ or ‘Hesperus’ cannot fail to pick out the very same individual at all possible worlds where that individual exists. Those names would not pick out someone else in the primary dimension, like Chalmers wants. But, again, this does not necessarily make of Kripke himself a Monistic Kripkean.
Thus, I disagree with Goff (in Goff and Papineau 2014) that radically opaque expressions provide examples of strong necessities, because those expressions lack the further dimension of meaning that is needed to build such cases. Chalmers characterizes a strong (a posteriori) necessity as what a counterexample to (CP) would look like, if there were such a thing (then of course everyone took up the challenge and tried to come up with a good case. For discussion: Chalmers 2010: pp. 170–180). A strong necessity must be: (i) metaphysically-secondarily necessary; (ii) epistemically-primarily necessary; (iii) conceivably false. In the case of radically opaque expressions, against Goff, I do not see how (ii) is satisfied, given that no extra descriptive content motivates such a further dimension. Instead, the Monistic Kripkean neutralizes Chalmers’ challenge by simply rejecting his 2D analysis of a posteriori necessities as weakly necessary because primarily contingent. It is rather the 2D Kripkean the one who has the theoretical resources to build cases of strong necessities (i.e., modal dualism). However, I recommend against engaging with such a quest after strong necessities. Given Chalmers’ setup, any such attempt is doomed to failure. Since he treats conceivability and epistemic-primary possibility as de facto coextensive, any conceivable falsity (iii) automatically denies epistemic-primary necessity (ii).
Strictly, with only some metaphysical import. For scenarios in some cases map metaphysical possibility. So, although we cannot generally infer metaphysical possibility from epistemic possibility, the relevant intensional contents might provide a connection that does allow for such inferences in certain cases (Thanks to an anonymous referee for drawing my attention to this point).
Arguably, epistemic necessities include, at a first approximation, mathematical, logical, and traditional analytic/conceptual truths. What distinguishes this class of truths is that they are necessarily truth-preserving patterns of inference (Cf. Hale 2013: pp. 60–62; see also his forthcoming).
Chalmers does not reject in principle modal dualism. He concedes that “a two-space model is coherent and useful for various purposes” (2011: p. 79, fn. 9). Moreover, he has devised a technical account of possibility in terms of purely epistemic scenarios—constituted by maximally consistent sentence-types of an ideal language. However, he admits that his metaphysical claims will not go through if one works with the pure epistemic construction (2010: pp. 552–553).
Similarly, Soames: “[Kripke] did not view language as the source of the necessary a posteriori status of his examples. Instead, he looked to metaphysics” (2005: p. 203).
Cf. Vaidya: “[Chalmers’ considerations] suggest that the conception of modality at play is one that eliminates the notion of metaphysical modality as originally conceived by Kripke” (2008: p. 196).
In a talk at Princeton in November 2012, Chalmers presented this idea by recalling David Armstrong’s point that “There is a picture in Leibniz, in Lewis, and in other metaphysicians that the actual swims in a wider sea, the sea of the possible. The actual is just one case of the possible” (Chalmers, ‘Two Concepts of Metaphysical Possibility’, quoting from Armstrong, A World of States of Affairs, Cambridge University Press 1997: pp. 173–174 my emphasis. Slides available at http://consc.net/slides/possibility.pdf).
The only cases where primary conceivability captures secondary possibility are those where the primary and secondary intensions of the relevant expressions coincide. For Chalmers, those include mathematical and analytic truths, and phenomenal truths (2010: ch.6). However, it might be objected that whereas mathematical and analytic truths seem to obviously verify the thesis, the class of phenomenal truths makes it on the other hand extremely controversial.
Thanks to Nate Bice, Paul Boghossian, David Chalmers, Michael Devitt, Mateo Duque, David Papineau, Jonathan Schaffer, Anand Vaidya, and two anonymous referees for useful comments on earlier drafts of this paper. Thanks also to the audiences at the GEM—Ground Essence and Modality conference in Helsinki in June 2016 and at the PLM Masterclass in Stockholm in June 2015.
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Mallozzi, A. Two notions of metaphysical modality. Synthese 198 (Suppl 6), 1387–1408 (2021). https://doi.org/10.1007/s11229-018-1702-2
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DOI: https://doi.org/10.1007/s11229-018-1702-2