Blackwell Reference Online

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M etaphysics, philosophy of science Things which are naturally distinguished, including the species of things such as whales and apples and elements or mass items such as water and gold. These things occur naturally, in contrast to things such as televisions and tables, which are invented by human beings. Traditionally, terms naming natural kinds, that is, natural kind terms, are taken to be general names that should be defined by giving a connotation or by specifying the necessary and sufficient conditions of their application. In the 1970s, Kripke and Putnam , arguing against the traditional theory, suggested that natural kind terms, like proper names , are not connotative. While proper names are rigid designators of an individual , natural kind terms are rigid designators of a kind. They have an essential property , namely, the underlying structure discovered through empirical investigation. Water is H 2 O in all possible worlds , so anything that is not H 2 O is not water, even if it satisfies some list of superficial features that we think characterize water. Accordingly, it is a necessary truth that water is H 2 O, although this truth is a posteriori , that is, empirically known. A natural kind term is ascribed historically, and the justification for its use is passed on through a causal chain. “What really distinguishes the classes we count as natural kinds ... log in or subscribe to read full text