Words, Kinds, and Causal Powers

Abstract

Abstract For some 25 years, the prevailing theories of categorization in philosophy have invoked the idea of “kinds” (Kripke, 1972; Putnam, 1975). When we look at how adults use words to refer to categories of things, we find that they only rarely categorize objects on the basis of their common properties. Instead, adults seem to categorize objects together when they believe that they belong to the same “kind,” that is, that they share some common, abstract “essence.” Psychological investigations of adults have largely confirmed these philosophical intuitions; adults do seem to group objects together based on “kinds” rather than properties (Murphy & Medin, 1985; Rips, 1989). Several investigators, particularly Gelman and her colleagues (Gelman & Coley, 1990; Gelman & Markman, 1986), have argued that children as young as 2 years old also categorize and name objects based on kinds (see also Mandler & McDonough, 1993; Mervis & Bertrand, 1994; Soja, Carey, & Spelke, 1991). Other investigators, in contrast, have suggested that young children categorize and name objects on the basis of perceptual properties such as shape (Imai, Gentner, & Uchida, 1994; Landau, Smith, & Jones, 1988). However, the question of whether children use names to refer to kinds has been bedeviled by the problem that the philosophical notion is not easily translatable into empirical predictions. In the philosophical literature, the concept of kinds refers to the idea that members of a category share an “essence,” a common, abstract, ontological property, and that names refer to this essence (Putnam, 1975). Obviously, it is difficult to ask 3-year-olds if they conceive of objects or use names in this way.