Putting modal metaphysics first


I propose that we approach the epistemology of modality by putting modal metaphysics first and, specifically, by investigating the metaphysics of essence. Following a prominent Neo-Aristotelian view, I hold that metaphysical necessity depends on the nature of things, namely their essences. I further clarify that essences are core properties having distinctive superexplanatory powers. In the case of natural kinds, which is my focus in the paper, superexplanatoriness is due to the fact that the essence of a kind is what causes all the many properties and behaviors that are typically shared by all the instances of the kind. Accordingly, we know what is necessarily true of kinds by knowing what is essential to them in the sense of actually playing such causal-explanatory roles. Modal reasoning aimed at discovering metaphysical necessity thus proceeds via essentialist deduction: we move from essentialist truths to reach necessary truths.

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  1. 1.

    For a discussion of other typical cases of metaphysical necessities, see Godman, Mallozzi, and Papineau: “Essential Properties are Super-Explanatory. Taming Metaphysical Modality” (ms.).

  2. 2.

    An even more radical challenge comes from recent forms of modal anti-realism such as Thomasson’s Modal Normativism (2007) and Sidelle’s Conventionalism (1989). These theorists deny that our modal language describes real facts “out there” in the world and offer non-descriptivist accounts of the meaning and function of our modal expressions. For Sidelle, modal claims are fully grounded in our linguistic conventions. For Thomasson, they express constitutive semantic rules of our language. They both think that these sorts of solutions in turn simplify the modal epistemology. Here I am granting that our modal notions track genuine modal facts—specifically, facts about essence—which are independent of the way we shape the world linguistically or conceptually. My aim is to clarify what those essentialist facts are, which in turn I also believe simplifies the modal epistemology for a wide range of cases. This is a fundamental contrast between “conventionalism” versus “realism” about essence and modality worth exploring further (cf. Vaidya 2017). (Thanks to an anonymous referee for pushing me on this issue.)

  3. 3.

    For more on this contrast see my (2018).

  4. 4.

    More precisely, in the case of kind-membership, we can distinguish between “essential properties” and “essences”. ‘P is an essential property of being an F iff anything is an F partly in virtue of having P’. Whereas, essences qua the sum or collection of the essential properties of an instance of a kind fully determine kind-membership: ‘P is the essence of being an F iff anything is an F in virtue of having P’ (cf. Devitt 2008: p. 345).

  5. 5.

    Cf. Devitt “Defending Intrinsic Biological Essentialism” (ms.).

  6. 6.

    Incidentally, for cases of individual essentialism we have a corresponding basic principle


    If x is essentially F, then necessarily x is F

    At the sentential level, (E) and (E)i can be expressed in a straightforward way with the Finean notation:


    xP → ☐P

    which reads, “If a proposition P is true in virtue of the essence of x, P is metaphysically necessary”; where “x”, depending on the cases, stands for either an individual or a kind (I here leave out some complications discussed in Fine 1994b). See also Vaidya and Wallner (ms.), cit.

    It is important to stress that there is no direct entailment from (E) to the distinct thesis of Essential Membership: i.e., the doctrine that if an individual belongs to a kind it does so essentially (in Devitt’s terminology, “Individual Essentialism in Biology” ms.). According to Essential Membership, an individual I is essentially a member of kind K iff its having Ei (a certain individual essence) entails its having Ek (a certain kind-essence). So for example, a particular chunk of silver, call it Chunk, would essentially belong to the kind silver because having atomic number 47 is part of its individual essence. But that is not obvious. Granted that having atomic number 47 is essential to being an instance of silver, it is not clear that Chunk would stop existing altogether, i.e., it would go out of existence as an individual, were it somehow to lose or change its subatomic structure. A further nice example that I heard from David Papineau is a lead statue that turns into silver (imagine a conceptual artist making one). Arguably, the statue qua that very individual would still exist, though its kind-membership would have changed, from being a sample of lead to one of silver. Here I do not commit to non-conditional individual essences, but only to the relatively uncontroversial principle (E)i. The intended moral is that knowledge of individual essence still requires careful investigation (but see Godman, Mallozzi, and Papineau (ms.), cit. for further discussion. I thank an anonymous referee for suggesting the Chunk case and pushing me on this point).

  7. 7.

    I thus disagree with a certain reading of Kripke that wants him to hold a modalist conception of essence. His famous essentialist examples all appeal to properties that are distinctive of the individual or kind he considers (perhaps uniquely distinctive), in the sense that they appear to be constitutive of the very nature of the individual or kind—of its identity. Think of the “internal structure” of tigers; of the genetic material of the Queen, and her particular biological origin; think of the specific chunk of wood that this lectern is made of.

  8. 8.

    One issue that I do not address here is the ontology of kinds or what sorts of entities they are (if they are entities at all). Not only would answering this question require its own paper; but, strictly, my view does not commit me to the existence of kinds (or properties, for that matter), since I am not quantifying over them. Take principle (E): this is a schema into which one substitutes real predicates for “F” and “G”, which means it is committed to Fs but not to F-hood. The central thesis presented here is neutral with respect to this issue, and indeed compatible with a variety of answers (ranging from kinds being some sort of universals to being just sets).

  9. 9.

    Similarly, Devitt (2008), Millikan (1999, 2000), Papineau (1993, 2010).

  10. 10.

    The causal structure of a natural kind might not be as simple as I am picturing it here. For Khalidi (2018), natural kinds are defined by multiple networks of causal properties. Causal relationships might thus not be strictly “horizontal” and “one-to-many” as I sketched them. Instead, the properties of a kind would be organized hierarchically and in web-like causal structures. Khalidi thinks that such a “hierarchy or series of cascading layers of properties” characterizes especially chemical elements. Still, his picture is consistent with the thesis that there is a single essential core or mechanism, which grounds the whole causal network and to which the various multiple relationships could be ultimately traced back.

  11. 11.

    For a recent criticism of the idea that natural kinds depend on a core causal ground, see e.g. Slater (2015), who argues that natural kinds, although they may in fact be causally grounded, should be nonetheless defined in terms of the stability and cohesiveness of “cliquish” clusters of (superficial) properties. For a response to Slater, see Lemeire: “The Causal Structure of Natural Kinds” (ms.).

  12. 12.

    Strevens (2014) suggests that we think of kinds as “entangled” with such underlying core properties or causal mechanisms. Being an instance of silver, in Strevens’ picture, is thus more precisely a concomitant cause of all the properties and behaviors shared by all instances of silver. All Fs are Gs because Fs are entangled with an underlying core C, which in turn is causally responsible for all the occurrences of G in all the instances of F. Strevens’ analysis has the advantage of clarifying that being an instance of e.g. silver strictly doesn’t cause anything; and to allow for exceptions to the relevant causal generalizations.

  13. 13.

    Perhaps the story may be further complicated by adding that mass number (which equals the number of protons plus neutrons) also plays a role in the occurrence of the typical chemical properties and behaviors of elements. But note that the neutron number per se has only a slight influence on chemical behavior, which argues that the atomic number is after all the main feature responsible for the resulting properties.

  14. 14.

    Contra Elder (2004). According to Elder, essential properties rather come in clusters held together by virtue of the laws of nature. All that matters for the existence of a kind is that “in combination they ensure, by virtue of the laws of nature, a package found in no other natural kind” (27). There appears to be no real distinction between the essential or underlying properties of a kind, and the accidental, often superficial, properties of the kind. All the properties possessed by an instance of a kind seem indeed essential to being an instance of the kind. Couldn’t silver have had a different melting point, say, if certain laws of nature happened to be different? Elder’s answer is that this would not have been silver—even if it still had atomic number 47 (39–41).

  15. 15.

    See esp. Bird (2007) and Ellis (2001). See also Swoyer’s seminal paper (1982).

  16. 16.

    By contrast, for Millikan biological kinds are rather historical kinds, in that they are identified by their histories (1999). Similarly, Godman and Papineau (forthcoming), and the above-mentioned Godman, Mallozzi, and Papineau (ms.), where we hold that copying mechanisms from common ancestors play the relevant superexplanatory roles for biological species. Note that Devitt (2008), forthcoming, “Defending Intrinsic Biological Essentialism” (ms.) cit., and “Individual Essentialism in Biology” (ms.) cit., also defends a version of biological essentialism where essences have crucial causal-explanatory roles. In his view, essences are partly relational and historical, and partly intrinsic (largely genetic).

  17. 17.

    An analogous point could be made in response to certain criticisms of Putnam’s example that water is essentially H2O (Needham 2011; Tahko 2015). I take it to be a philosophically minor issue, and one that we can disregard, whether the molecular structure of water is exactly H2O, or rather something more complex. Whatever that structure or mechanism is exactly, we can identify it as what plays the relevant causal and explanatory roles for kind-membership. As Devitt puts it, the talk of certain specific essences, like H2O in the case of water, should be seen as “nothing more than a philosopher’s hand wave toward the scientific facts” (“Defending Intrinsic Biological Essentialism” ms. cit.: 12, fn. 21).

  18. 18.

    This is also Bennett’s stance. We can think of causal and non-causal determination as part of the same family, which she calls “building”. Importantly, as she remarks, “the class of building relations—causation together with vertical building—is unified not just on the cheap, but in explanatorily useful ways” (2017: p. 103. My emphasis).

  19. 19.

    Thanks to Jonathan Schaffer for raising a version of this objection. For a classic criticism of kind-essentialism centered on the idea that traditional categories like “essence” and “kind” have pragmatic, interest-dependent roles, especially in biology, see Dupré (1993).

  20. 20.

    Thanks to Michael Devitt for helpful discussion of this point. See also Devitt (1991), esp. ch. 13.

  21. 21.

    I assume that we can generally trust the scientific knowledge that is already available to us and that we can use it to make progress in modal epistemology. Fischer (2016) raises the question how we know the scientific theories themselves, and how we can trust that our philosophical interpretations of such theories are correct. One of his worries is that some modal knowledge might be needed to assess those theories in the first place. These are crucial questions for both the epistemology of science and of metaphysics, and like Fischer, I am not aiming to answer them. Note however a crucial difference between Fischer’s and my view. Fischer has a deflationary view of modal epistemology, which is based on knowledge of theories. If Fischer's view gives us modal knowledge on the cheap from non-modal theories, such as chemistry, then he needs to make sure that we never adopt a theory in virtue of modal knowledge, on pain of circularity. But no such a problem arises for my view.

  22. 22.

    What about all the other modal knowledge that needs explaining, especially the necessities of logics and mathematics, as well as conceptual necessities and normative necessities? The crucial problem is that in those areas empirical factors do not seem to contribute to knowledge of necessity. Specifically, we do not seem to have any causally-mediated connection to their relevant objects, e.g. numbers, or sets. One might perhaps develop an analogous story for such cases of purely a priori necessities—as I call them—trying to preserve the general thesis that essences have “superexplanatory” powers. One could, for example, appeal to conceptual entailments from real definitions as the analogues of causal connections from essential properties and mechanisms. Clearly, addressing those issues adequately requires its own paper, which is why I leave it to future work. (Thanks to Paul Boghossian for pressing me on this issue).

  23. 23.

    Compare Horvath’s criticism of Lowe’s account of modal knowledge (2014). Horvath crucially draws the general moral that essence-based accounts of modal knowledge need to integrate knowledge of the fundamental connection between essence and metaphysical necessity. Tahko (2016: pp. 34–35) disagrees. For him, reductionism just follows from a Finean constitutive conception of essence. While this may be true, nonetheless I do not think that it exonerates us, for epistemological purposes, from making knowledge of that underlying connection explicit. Similarly, Vaidya and Wallner (ms.) cit.

  24. 24.

    We can further specify two sub-principles of (E), depending on whether we are considering essential properties or essences:


    If E is an essential property of being an F, then necessarily anything that is an F has E


    If E is the essence of being an F, then necessarily anything that has E is an F

    If, as I hold, having a certain atomic number is the essence of being an instance of a certain element, then as per (E)e we should conclude that e.g. necessarily anything that has atomic number 47 is an instance of silver.

  25. 25.

    For an opposite view, see e.g. Strohminger (2015), who argues that we have perceptual knowledge of possibility. Indeed, a number of authors in the literature have recently advocated a sharply empirical turn in modal epistemology, often with the goal of eschewing traditional a priori means for knowledge of metaphysical modality (e.g. Bueno and Shalkowski 2015; Fischer and Leon 2017; Vetter 2016). But note also that there has already been an opposite push-back (see Mallozzi: forthcoming).

  26. 26.

    Cf. the classic Benacerraf (1973).

  27. 27.

    A further option could be that the principle is neither strictly a priori nor a posteriori. The friend of Williamson’s views would claim that its justification is perhaps “armchair”, as it seemingly straddles our ordinary epistemological categories (Williamson 2007, 2013).


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I am grateful to Paul Boghossian, Michael Devitt, Boris Kment, David Papineau, Andrea Raimondi, Jonathan Schaffer, Tuomas Tahko, Anand Vaidya, Michael Wallner, and two anonymous referees for useful comments on earlier drafts of this paper. Thanks also to audiences at the Saul Kripke Center in March 2017, at the Conceivability and Modality conference in Rome in June 2017, and at the Pacific Meeting of the APA in San Diego in March 2018.

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Correspondence to Antonella Mallozzi.

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Inspired by the title of Michael Devitt’s book Putting Metaphysics First, Oxford: OUP (2010).

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Mallozzi, A. Putting modal metaphysics first. Synthese 198, 1937–1956 (2021). https://doi.org/10.1007/s11229-018-1828-2

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  • Modal epistemology
  • Essentialism
  • Natural kinds
  • Kripke
  • A priori knowledge