Nigel Leary

In this thesis I argue that we should break with the dominant Kripkean tradition concerning natural kind terms and theoretical identity. I claim that there is just no interesting connection between the metaphysics and semantics of natural kind terms, and demonstrate this by constructing a version of descriptivism that is combined with the same metaphysics – that is, a nontrivial version of essentialism – found in Kripke, but which effectively avoids all of the standard criticisms. With my version of descriptivism in place, I present what I take to be the most reasonable version of metaphysical essentialism, positing only what I call 'thin' essences. I claim that thin essences are perfectly adequate to underpin scientific realism, and moreover that they are sufficient to support the version of descriptivism developed here. In effect, what I offer here is an error theory of the Kripkean tradition: Kripke is right to think that there are interesting things to say about meaning and essence, but just wrong about what those things are. Thus whilst Kripke thinks that it is possible to make discoveries about the meanings of natural kind terms, I think, rather, that we make empirical discoveries that lead to revisions in meaning. Furthermore, whilst Kripke thinks there is a dichotomy between de re and de dicto necessity, and that theoretical identities are necessary de re, I think this distinction is both misleading and inaccurate, and that the necessity of theoretical identities is neither entirely de re nor entirely de dicto. By separating and insulating questions concerning meaning from questions concerning essence I show that whilst scientific discoveries are contingent and a posteriori, the definition of scientific terms are both necessary and a priori.

Essentialism--roughly, the view that natural kinds have discrete essences, generating truths that are necessary but knowable only _a posteriori_--is an increasingly popular view in the metaphysics of science. At the same time, philosophers of language have been subjecting Kripke’s views about the existence and scope of the necessary _a posteriori_ to rigorous analysis and criticism. Essentialists typically appeal to Kripkean semantics to motivate their radical extension of the realm of the necessary _a posteriori_; but they rarely attempt to provide any semantic arguments for this extension, or engage with the critical work being done by philosophers of language. This collection brings authors on both sides together in one volume, thus helping the reader to see the connections between views in philosophy of language on the one hand and the metaphysics of science on the other. The result is a book that will have a significant impact on the debate about essentialism, encouraging essentialists to engage with debates about the semantic presuppositions that underpin their position, and, encouraging philosophers of language to engage with the metaphysical presuppositions enshrined in Kripkean semantics.

The paper considers whether psychiatric kinds can be natural kinds and concludes that they can. This depends, however, on a particular conception of ‘natural kind’. We briefly describe and reject two standard accounts – what we call the ‘stipulative account’ (according to which apparently a priori criteria, such as the possession of intrinsic essences, are laid down for natural kindhood) and the ‘Kripkean account’ (according to which the natural kinds are just those kinds that obey Kripkean semantics). We then rehearse a more permissive account: Richard Boyd’s ‘homeostatic property cluster’ (HPC) account. We argue that psychiatric kinds can in principle count as natural kinds on the HPC account. Moreover, specific psychiatric kinds (Tourette’s, schizophrenia, etc.) can be natural kinds even if the category psychiatric disorder is not itself a natural kind.

Scott Soames (2002) has recently developed and defended strategies for (i) accounting for the meaning of Millian terms, and (ii) extending Kripke's insights from proper names to natural kind terms. In this paper I argue that if we accept these strategies, and their implausible assumptions and consequences, then we can present a novel defence of descriptivism for at least some natural kind terms – those for substances – on that basis. The conclusion, then, will be that there is just no motivation for being a Soamesian Kripkean for an important class of natural kind terms.

Talk of “essences” has, since Saul Kripke and Hilary Putnam, gained significant currency in contemporary philosophy. It is no longer unfashionable to talk about the essence of this or that (natural) kind, and as such we now find a variety of brands of essentialism on the market including B.D. Ellis’s scientific essentialism, David Oderberg’s real Essentialism, Alexander Bird’s dispositional essentialism, and the contemporary essentialism of Kripke and Putnam. Almost all these brands of essentialism share a particular gloss on Locke’s famous objection to Aristotle that natural kinds are demarcated by nominal essences not real essences. Thus Oderberg claims that ‘Empiricists take [real] essences to be paradigmatically unobservable’ and that this ‘objection goes back at least to John Locke’ (Oderberg 2007: 21). Bird, presenting his dispositional essentialism, defines a notion of “being” as ‘the reverse of Locke’s definition of essence’ which he takes to be ‘the being of any thing, whereby it is what it is’ (Bird 2007: 100). Joseph LaPorte, discussing nominal and real essences, claims that ‘Kripke and Putnam seem to affirm something more substantive: that biological kinds have “real essences” in Locke’s terminology’ (LaPorte 2004: 49). Even avowed anti-essentialists such as John Dupré sanction the standard criticism of Locke that his scepticism about the knowability of real essences was ‘premature’, and claim that ‘genuine natural kinds provide the extensions of many terms of natural language, where these natural kinds are determined by true Lockean real essences’ (Dupré 1993: 22). All of these essentialisms (even Dupré’s anti-essentialism) are wrong about Locke. Oderberg is wrong to claim that Locke thought that real essences were paradigmatically unobservable; Bird is wrong to think that Locke’s notion of essence is the being of anything whereby it is what it is; LaPorte is wrong to think that Kripke and Putnam are talking about Lockean real essences (although so are Kripke and Putnam); and Dupré is wrong to think that genuine natural kinds (if by genuine he means objective or mind-independent) are determined but true Lockean real essences . The mistake stems from a standard, but ultimately incorrect, interpretation of Locke’s discussion of essences in An Essay Concerning Human Understanding . This mistaken interpretation (Lowe 1995, 2006, Von Leyden 1973, Wiggins 1974) takes Locke to mean, by “real essence”, the Aristotelian notion i.e. ‘the very being of anything, whereby it is what it is’ (Essay III.iii.15), and interprets his objection as epistemological: we cannot come to know what real essences are, and therefore they cannot figure in our classifications of things into kinds. This paper will present and defend the following two claims: i) that Locke’s notion of “real essence” is not the Aristotelian notion, and ii) that Locke’s objection to the Aristotelian notion was not merely epistemological. The first claim can be defended by presenting and applying Vienne’s (1993) terminological revision. Vienne argues that Locke did not introduce a dichotomy between real and nominal essence, but a trichotomy between real essence, nominal essence and real constitution. This terminological revision will be employed to highlight where ambiguous uses of the phrase “real essence” have caused some serious misunderstandings of Locke’s philosophy. The second claim (steering Locke around what is the classic objection to his thesis) can be defended by presenting a novel way of splitting up Locke’s objections to the Aristotelian notion of essence. The analysis will show that Locke’s anti-essentialism is still in good shape, and of contemporary significance.

Theoretical identity statements of the form "water is H2O‟ are allegedly necessary truths knowable a posteriori, and assert that nothing could be water and not be H2O. The necessary a posteriori nature of these identity claims has been taken by Kripke, Putnam and Donnellan to justify a move from talk of reference (language) to talk of essence (metaphysics), and has motivated much of contemporary essentialism. In this paper I will contest this move from reference to essence, and argue that (i.) the only way to derive essentialism from semantics (specifically direct reference) is to assume it as a premise, (ii.) that contemporary essentialism is a metaphysical assumption not a thesis, and (iii.) – assuming the accuracy of the analogy between proper names and natural kind terms – present an alternative version of natural kinds classification that is interest-relative, dependent on practical application and reflects the contingent state of affairs which is our world.