The aim of this article is to illustrate how a belief in the existence of kinds may be justified for the particular case of natural kinds: particularly noteworthy in this respect is the weight borne by scientific natural kinds (e.g., physical, chemical, and biological kinds) in (i) inductive arguments; (ii) the laws of nature; and (iii) causal explanations. It is argued that biological taxa are properly viewed as kinds as well, despite the fact that they have been by some alleged (...) to be individuals. Since it turns out that the arguments associated with the standard Kripke/Putnam semantics for natural kind terms only establish the non-descriptiveness of natural kind terms and not their rigidity, the door is open to analyze these terms as denoting traditional predicate-extensions. Finally, special issues raised by physical and chemical kinds are considered briefly, in particular impurities, isotopes and the threat of incommensurability. (shrink)

What does it mean for a general term to be rigid? It is argued by some that if we take general terms to designate their extensions, then almost no empirical general term will turn out to be rigid; and if we take them to designate some abstract entity, such as a kind, then it turns out that almost all general terms will be rigid. Various authors who pursue this line of reasoning have attempted to capture Kripke’s intent by defining a (...) rigid general term as one that applies to the objects in its extension essentially. I argue that this account is significantly mistaken for various reasons: it conflates a metaphysical notion (essentialism) with a semantic one (rigidity); it fails to countenance the fact that any term can be introduced into a language by stipulating that it be a rigid designator; it limits the extension of rigid terms so much that terms such as ‘meter’, ‘rectangle’, ‘truth’, etc. do not turn out to be rigid, when they obviously are; and it wrongly concentrates on the predicative use of a general term in applying a certain test offered by Kripke to determine whether a term is rigid. (shrink)

Philosophical treatments of natural kinds are embedded in two distinct projects. I call these the philosophy of science approach and the philosophy of language approach. Each is characterized by its own set of philosophical questions, concerns, and assumptions. The kinds studied in the philosophy of science approach are projectible categories that can ground inductive inferences and scientific explanation. The kinds studied in the philosophy of language approach are the referential objects of a special linguistic category—natural kind terms—thought to refer directly. (...) Philosophers may hope for a unified account addresses both sets of concerns. This paper argues that this cannot be done successfully. No single account can satisfy both the semantic objectives of the philosophy of language approach and the explanatory projects of the philosophy of science approach. After analyzing where the tensions arise, I make recommendations about assumptions and projects that are best abandoned, those that should be retained, and those that should go their separate ways. I also recommend adopting the disambiguating terminology of “scientific kinds” and “natural kinds” for the different notions of kinds developed in these different approaches. (shrink)

The notion of rigidity looms large in philosophy of language, but is beset by difficulties. This paper proposes a simple theory of rigidity, according to which an expression has a world-relative semantic property rigidly when it has that property at, or with respect to, all worlds. Just as names, and certain descriptions like The square root of 4, rigidly designate their referents, so too are necessary truths rigidly true, and so too does cat rigidly have only animals in its extension. (...) After spelling out the theory, I argue that it enables us to avoid the headaches that attend the misbegotten desire to have a simple rigid/non-rigid distinction that applies to expressions, giving us a simple solution to the problem of generalizing the notion of rigidity beyond singular terms. (shrink)

The principal question addressed is whether there is a division among common nouns which is similar to a familiar division among noun phrases that designate particular-level individuals: the one which is captured in the relevant literature as the difference between de jure rigid and not de jure rigid singular terms. In relation with the previous philosophical literature relevant to noun rigidity it is argued that the extant positions on the matter are not defended on the basis of well-founded syntactic categories (...) and proper semantic arguments. Proper ways to argue for rigidity ascriptions to nouns are described. Then, such arguments are sought for the case of rigid/non-rigid division among count common nouns. It is shown that there are plausible, albeit inconclusive, reasons to hold that among common nouns (N-bar expressions) only simple common nouns are kind designators, and that if that is the case these simple common nouns will have to be reckoned as de jure rigid designators. (shrink)

examine Nathan Salmon’s solution to the problem of trivialization, as it arises for conceptions of general term rigidity that construe it as identity of designation across possible worlds. I argue that he does not succeed in showing that some alleged general terms, such as “the colour of the sky” are non-rigid, but also that a small class of different examples that he presents, which can be construed as second order descriptions, are indeed non-rigid general terms, although for reasons different from (...) those he thought. (shrink)

This article defends the thesis that Putnam's theory of the use of empirical concepts constitutes a continuous backbone of his philosophy early and late. Thus, Putnam's theory of empirical concepts should be at least compatible with the most distinctive features of both, his realism (viz., semantic externalism) and his pragmatism (viz., conceptual pluralism). The article suggests the even stronger thesis that Putnam's theory of concepts is essential for the explanatory purposes of both. In doing so, the article proposes reading Putnam's (...) theory as a theory displaying contextual features of language use rather than as one describing metaphysical, epistemic, or cognitional 'underpinnings'. The theory's continuity is thus taken to show that Putnam's realism and pragmatism are and always have been inseparable. (shrink)

In this paper I take issue with the doctrine that organisms belong of their very essence to the natural kinds (or biological taxa, if these are not kinds) to which they belong. This view holds that any human essentially belongs to the species Homo sapiens, any feline essentially belongs to the cat family, and so on. I survey the various competing views in biological systematics. These offer different explanations for what it is that makes a member of one species, family, (...) etc. a member of that taxon. Unfortunately, none of them offers an explanation that is compatible with the essentialism in question. (shrink)

Natural kind terms have exercised philosophical fancy ever since Kripke, in Naming and Necessity, claimed them to be rigid designators. He there drew attention to the peculiar, name-like behavior of a family of prima facie loosely related general terms of ordinary English: terms such as ‘water’, ‘tiger’, ‘heat’, and ‘red’. Just as for ordinary proper names, Kripke argued that such terms cannot be synonymous with any of the definite descriptions ordinary speakers associate with them. Rather, the name-like behavior of these (...) so-called natural kind terms is to be explained, just as in in the case of proper names, by the doctrine of rigid designation. And as a consequence of thus extending the notion of rigid designation to general terms, he famously endorsed the claim that so-called ‘theoretical identifications’, i.e. statements like (1) Water is H2O, are necessary, if true. (shrink)

It is generally assumed that rigidity plays a key role in explaining the necessary a posteriori status of identity statements, both between proper names and between natural kind terms. However, while the notion of rigid designation is well defined for singular terms, there is no generally accepted definition of what it is for a general term to be rigid. In this paper I argue that the most common view, according to which rigid general terms are the ones which designate the (...) same kind in all possible worlds, fails to deliver a posteriori necessities. I also present an alternative view, on which the work of explaining a posteriori necessities is not done by rigidity, but by a related metasemantic notion, which I call actuality - dependence. (shrink)

The phrase "natural kind term" has come into the linguistic and philosophical literature in connection with well-known work of Kripke (1972) and Putnam (1970, 1975a). I use that phrase here in the sense it has acquired from those and subseqnent works on related topics. This is not the transparent sense of the phrase. That is, if I am right in what follows there are words for kinds of things existing in nature which are not natural kind terms in the current (...) sense - e.g. planet, woman, and weed. I use the term "nondescriptional", following Salmon (1981), to mean "lacking a Fregean sense", where a Fregean sense is taken to be a property or group of properties semantically associated with an expression which determines its denotation. I hope that the term "nondescriptional" will be clarified in subsequent discussion, but perhaps a few words about it and its opposite, "descriptional", would be useful here. These terms (as Salmon notes (p.15, n. 11)) should be taken as technical terms. The idea is that descriptional words, of which bachelor is the overwhelmingly favorite example, express a semantic content, or sense, which is what mediates their denotation. Entities fall in their denotation in virtue of possessing the property or properties expressed as their sense. (It is not necessary, however, that this sense be as easily paraphrasable with descriptive synonyms as it is typically held to be in the case of bachelor, or even that it be paraphrasable at all.) In the case of nondescriptional words there is no Fregean sense to mediate the link between word and object. Hence such terms are described by what Salmon, following Kaplan, calls "the theory of direct reference". What it is that does associate such terms with their denotations is another question which will be touched on briefly at the end. I have several aims in this paper. The first is to defend a conservative position on nondescriptionality. I will argue that relatively few natural language words have this property. My other aims are primarily clarificatory. Among the issues I would like to clarify are those connected with the determination of this property and flae explanation of why it exists, its relationship with other properties such as rigid designation and essentiality, and its significance for lexical semantics. The organization of the paper is as follows. The first section identifies the position taken here on the question of which expressions are nondescriptional and provides a general defense of it. The second section is a critical examination of criteria associated with nondescriptionality. In the third section provide further defense for the conservative position, and in the fourth section we turn to related issues in lexical semantics. (shrink)

Theoria, Volume 88, Issue 2, Page 406-433, April 2022.

The article discusses an idea of how to extend the notion of rigidity to predicates, namely the idea that predicates stand in a certain systematic semantic relation to properties, such that this relation may hold rigidly or nonrigidly. The relation (which I call signification) can be characterised by recourse to canonical property designators which are derived from predicates (or general terms) by means of nominalization: a predicate signifies that property which the derived property designator designates. Whether signification divides into rigid (...) and non-rigid cases will then depend uponwhether canonical property designators divide into rigid and non-rigid ones. But, I shall argue, they do not, and so the only notion of rigidity gained this way is trivial. To show this, I first focus on the kind of canonical property designators which could be thought to be nonrigid, canonical designators such as having the colour of ripe tomatoes which themselves contain non-rigid property designators. An argument to the effect that such complex canonical designators are non-rigid is rebutted, five arguments to the effect that they are rigid are formulated, and finally an explanation of their rigidity based on the general nature of canonical property designators is presented. (shrink)

According to Michael Devitt, the primary work of a rigidity distinction for kind terms is to distinguish non-descriptional predicates from descriptional predicates. The standard conception of rigidity fails to do this work when it is extended to kind terms. Against the standard conception, Devitt defends rigid application: a predicate is a rigid applier iff, if it applies to an object in one world, it applies to that object in every world in which it exists. Devitt maintains that rigid application does (...) the job of identifying nondescriptional predicates perfectly. I argue that Devitt is wrong about this. When we examine more closely alternative theories about the identity and persistence conditions of those entities to which mass terms apply, we find no plausible theory that has the result that a term is rigid iff it is non-descriptional. (shrink)

Kripke defines a rigid designator as one that designates the same object in every possible world in which that object exists. He argues that proper names are rigid. So also, he claims, are various natural kind terms. But we wonder how they could be. These terms are general and it is not obvious that they designate at all. It has been proposed that these kind terms rigidly designate abstract objects. This proposal has been criticized because all terms then seem to (...) come out rigid, thus trivializing rigidity. The paper starts with further criticisms of this proposal aimed particularly at a recent version given by LaPorte. The paper goes on to develop and defend an alternative proposal presented briefly in Devitt and Sterelny (1999): instead of taking those natural kind terms to rigidly designate an object we take them to rigidly apply to the members of their extensions. Schwartz has rightly insisted that a notion of rigidity must do some theoretical work if it is to be interesting. The paper argues that rigid application for kind terms does the same primary work as rigid designation for singular terms, the work of refuting description theories of some terms; and it does the same secondary work, of explaining certain modal phenomena (with one exception). (shrink)