On Natural Kind Terms
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AbstractThis dissertation concerns natural kinds and natural kind terms. It presents Kuhn's, Putnam's, Kripke's theories of natural kind terms and my criticisms to these theories. I propose that knowledge about a kind, scientific or not, allow people to know its term and to use the term to refer to the kind. Possible candidates to account for why kind terms stand for their kinds are not just scientific stipulation or paradigms but also knowledge.Chapter one begins with a discussion on Putnam’s, Kripke’s, and Kuhn’s accounts of natural kinds. Putnam explains natural kinds in terms of indexical examples and sameness relations; Kripke asserts that a natural kind includes natural existents with the same essence; and Kuhn holds that scientific paradigms determine their kinds. I formulate two definitions that are relevant to these accounts, in particular, one related to Putnam’s and Kripke’s and the other to Kuhn’s. There are, however, some issues with Putnam’s and Kripke’s accounts. In their accounts, there are kinds without obvious representative indexicals and kinds can be assigned new essences with scientific progress. These issues call into question their assertion of the rigidity of natural kind terms. Although Kuhn offers a more comprehensive account for natural kinds, he does not explain how natural kind terms can be used in non-scientific discussions.I propose that a natural kind is a collection of natural existents that resemble one another in certain respect or respects, and these resemblances can generate knowledge about the existents as a kind. Based on this notion of natural kinds, I hope to provide an inclusive theory for natural kind terms, one which considers the fact that they are used in scientific and non-scientific discussions. I discuss three natural kind terms: ‘neutron,’ ‘whale,’ and ‘water.’ The case of ‘neutron’ illustrates Kripke’s and Putnam’s accounts of natural kinds and kind terms—they hold that a particular science determines the essence of a kind and referents for its term. The case of ‘whale’ illustrates Kuhn’s view, which maintains that different scientific accounts can provide different comprehensions of a kind and use the kind term to express different concepts. However, the case of ‘water’ reveals an aspect that none of the three philosophers notice—non-scientific knowledge can also help people know a kind and know referents of the kind term. The case of ‘water’ shows that natural kinds and kind terms can be understood in non-scientific contexts. In chapter two, I present Kuhn’s theory of natural kind terms—different paradigms can provide different concepts for a kind term because the paradigms may address the kind differently. Thus, a kind term needs to be understood with respect to a particular paradigm. However, Kuhn’s account doe not note that some kinds and their terms are precedent to scientific theories and paradigms. Languages used by isolated tribes where there are no scientific practices contain kind terms such as ‘water.’ A five-year-old without any scientific education acquires kind terms such as ‘dog’ and ‘banana.’ Natural kind terms are used in scientific and non-scientific discussions. In chapter three, I discuss Putnam’s Twin Earth argument and his account of reference. I agree with the idea defended by the Twin Earth argument that psychological states in the narrow sense do not determine the extension of a kind term, however, the argument itself is problematic. First of all, ‘determining the extension of a kind term’ is ambiguous. When it means ‘delineating the contour of a kind term,’ the defended claim is either not interesting (intension along does not delineate the contour of a kind term) or not true (intension does not play any role in delineating the contour of a kind term). When it means ‘referring an example of a kind,’ the argument is irrelevant. (The duplicates do refer to examples of water. It is irrelevant whether they refer to the examples of H2O or XYZ.) Second, the story of scientists’ arriving the Twin Earth indicates that the assertion of the rigidity of ‘water’ and the claim that intension does not determine its extension are not compatible. Third, by modus tollens, the situation that the extension of ‘water’ includes XZY—a negation of the situation that the extension of ‘water’ is H2O—results from the claim that the intension of ‘water’ does not determine its extension. That is, Putnam’s intended claim—intension of a kind term does not determine its extension—could be inferred by denying his own assertion from the Twin Earth scenario. Finally, there are no cases of two extensions of a kind term—there are only cases of multiple constituents in the extension. Chapter four begins with Kripke’s discussion of descriptivism. The descriptivist claims that names are abbreviated definite descriptions. Kripke suggests three arguments against descriptivism, and he suggests that names and kind terms are instead rigid designators. He argues that contingent properties have no influence on the identities of natural kinds. There are essential properties of natural kinds, and they make natural kind terms rigid. Things with the same essential properties belong to the same kinds in all possible worlds. The kind terms are thus rigid because they refer to whatever have the essential properties in all possible worlds.However, the claim that kind terms are rigid is based on an inappropriate assumption that science determines the ultimate essences of kinds. There have been many modifications throughout the history of science, and science has assigned different essences to the same kind in different historical periods. For example, in Greek times, ‘aether’ referred to the fifth element. In the 19th century, ‘aether’ referred to a mass-free medium that fills up the universe. Nowadays we don’t believe that aether exists. Moreover, Kripke’s argument for the rigidity of kind terms is circular. In particular, Kripke supposes that gold is something that has the atomic number 79; then, he claims that ‘gold’ refers to gold; finally, he claims that ‘gold’ refers to whatever has the atomic number 79. But, given his premise that gold has the essence of having 79 protons, ‘gold’ is constructed to refer to things with that essence rigidly. Finally, some kinds are themselves scientific models; it is not appropriate to claim essences of them. This dissertation proposes a new approach to the issue of natural kind terms. It offers a semantic externalist view without asserting the rigidity of kind terms. The reference of a kind term and the connection between a kind term and its kind can be based on knowledge about the kind. By understanding natural kind terms in terms of knowledge of their kinds, which can be generated by everyday life activities and be irrelevant to scientific accounts of the kinds, the fact that natural kind terms can be used and understood within and outside the context of science is explained. Knowledge of kinds offers a more inclusive context for kind terms.