Online research in philosophy

Joseph LaPorte in an article on `Kind and Rigidity'(Philosophical Studies, Volume 97) resurrects an oldsolution to the problem of how to understand the rigidityof kind terms and other general terms. Despite LaPorte'sarguments to the contrary, his solution trivializes thenotion of rigidity when applied to general terms. Hisarguments do lead to an important insight however. Thenotions of rigidity and non-rigidity do not usefullyapply at all to kind or other general terms. Extendingthe notion of rigidity from singular terms such as propernames to general terms such as natural kind terms is amistake.

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.

It has been suggested that the theory of reference advanced by Kripke and Putnam implies, or presupposes, an aristotelian vision of natural kinds and essences. I argue that what is in fact established is that there are degrees of naturalness among kinds. A parallel argument shows that there are degrees of naturalness among individuals. A subsidiary theme of the paper is that the definition of "natural kind term" as "rigid designator of a natural kind" is mistaken. Names and natural kind terms are defined by ostension to a spatiotemporal part of what they ostend. This helps us understand why 'Hesperus' and 'Phosphorus' are cognitively non-equivalent.

Kripke and Putnam have convinced most philosophers that we cannot do metaphysics of nature by analysing the senses of natural kind terms -- simply because natural kind terms do not have senses. Neo-descriptivists, especially Frank Jackson and David Chalmers, believe that this view is mistaken. Merging classical descriptivism with a Kaplan-inspired two-dimensional framework, neo-descriptivists devise a semantics for natural kind terms that assigns natural kind terms so-called 'primary intensions'. Since primary intensions are senses by other names, Jackson and Chalmers conclude that we can and should do metaphysics of nature by analysing the natural kind concepts competent speakers possess. I argue that neo-descriptivism does not provide a suitable basis for doing this kind of metaphysics. I first of all give a detailed account of the neo-descriptivist semantics and deflate the intuitive support neo-descriptivists try to draw from their case of the XYZ-world. I then present three arguments -- the Argument from Ignorance, the Argument from Conceptual Analysis, and the Argument from Laziness. Taken together, these arguments undermine the neo-descriptivist analysis of natural kind terms. I conclude that natural kind terms do not have senses, that we cannot do metaphysics of nature by analysing the senses of our kind terms, and that the Kripke-Putnam account still provides the best semantics for natural kind terms we have.

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.

Kripke claims that certainkind terms, particularly natural kind terms,are, like names, rigid designators. However,kind terms are more complicated than names aseach is connected both to a principle ofinclusion and an extension. So, there is aquestion regarding what it is that rigidlydesignating kind terms rigidly designate. Inthis paper, I assume that there are rigidlydesignating kind terms and attempt to answerthe question as to what it is that they rigidlydesignate. I then use this analysis of rigidlydesignating kind terms to show how Kripke''sreasoning regarding the necessity of `Hesperusis Phosphorus'' can be extended to statementsinvolving kind terms like `Water is H2O''and `Tigers are mammals''.

This paper discusses whether it can be known a priori that a particular term, such as water, is a natural kind term, and how this problem relates to Putnams claim that natural kind terms require an externalist semantics. Two conceptions of natural kind terms are contrasted: The first holds that whether water is a natural kind term depends on its a priori knowable semantic features. The second.

This paper considers the problem of assigning meanings to empty natural kind terms. It does so in the context of the Twin-Earth externalist-internalist debate about whether the meanings of natural kind terms are individuated by the external physical environment of the speakers using these terms. The paper clarifies and outlines the different ways in which meanings could be assigned to empty natural kind terms. And it argues that externalists do not have the semantic resources to assign them meanings. The paper ends on a sceptical note concerning the fruitfulness of using the Twin-Earth setting in debates about the semantics of empty natural kind terms.

A paradigmatic case of rigidity for singular terms is that of proper names. And it would seem that a paradigmatic case of rigidity for general terms is that of natural kind terms. However, many philosophers think that rigidity cannot be extended from singular terms to general terms. The reason for this is that rigidity appears to become trivial when such terms are considered: natural kind terms come out as rigid, but so do all other general terms, and in particular all descriptive general terms. This paper offers an account of rigidity for natural kind terms which does not trivialise in this way. On this account, natural kind terms are de jure obstinately rigid designators and other general terms, such as descriptive general terms, are not.

In lecture III of Naming and Necessity, Kripke extends his claim that names are non-descriptive to natural kind terms, and in so doing includes a brief supporting discussion of terms for natural phenomena, in particular the terms ‘light’ and ‘heat’. Whilst natural kind terms continue to feature centrally in the recent literature, natural phenomenon terms have barely figured. The purpose of the present paper is to show how the apparent similarities between natural kind terms and the natural phenomenon terms on which Kripke focuses are outweighed by more significant differences. Thus, rather than providing additional support for non-descriptivism, natural phenomenon terms turn out to challenge that thesis.