1 Against Hybrid Theories of Concepts

Psychologists of concepts’ traditional assumption that there are many properties common to all concepts has been subject to devastating critiques in psychology and in the philosophy of psychology. However, it is currently unclear what approach to concepts is best suited to replace this traditional assumption. In this article, we compare two competing approaches, the Heterogeneity Hypothesis and the hybrid theories of concepts, and we present an empirical argument that tentatively supports the former over the latter. Psychologists working on human higher cognitive competences (e.g., categorization, induction, analogy-making, etc.) have traditionally assumed that there are numerous properties common to all concepts, and theories of concepts have attempted to characterize these common properties. There is however a growing consensus against this assumption in psychology (Medin, Lynch, & Solomon, 2000; Murphy, 2002) and in the philosophy of psychology (Machery, 2005, Machery, 2006, Machery, in press; Piccinini & Scott, 2006; Weiskopf, forthcoming). Psychologists and philosophers concur that in order to explain why there are different kinds of categorization judgments, of episodes of inductive reasoning, of analogies (etc.), it is necessary to postulate that the cognitive processes that underlie our higher cognitive competences rely on several distinct kinds of bodies of information that are very different from one another. However, psychologists and philosophers disagree about how to characterize these diverse kinds of bodies of information. In this article, we compare two competing approaches: the Heterogeneity Hypothesis and the hybrid theories of concepts. We present some new evidence that 1 We would like to thank Elisabetta Lalumera for editing the issue of Dialectica on concepts and for her insightful comments on a previous version of this article. 2 But see Danks, 2007.