A growing consensus in the philosophy and psychology of concepts is that while theories such as the prototype, exemplar, and theory theories successfully account for some instances of concept formation and application, none of them successfully accounts for all such instances. I argue against this 'new consensus' and show that the problem is, in fact, more severe: the explanatory force of each of these theories is limited even with respect to the phenomena often cited to support it, as each fails to satisfy an important explanatory desideratum with respect to these phenomena. I argue that these explanatory shortcomings arise from a shared assumption on the part of these theories, namely, they take similarity judgements and application of causal knowledge to be discrete elements in a theory of concepts. I further propose that the same assumption carries over into alternative theories offered by proponents of the new consensus: pluralism, eliminativism, and hybrid theories. I put forth a sketch of an integrated model of concept formation and application, which rejects this shared assumption and satisfies the explanatory desiderata I discuss. I suggest that this model undermines the motivation for hybrid, pluralist, and eliminativist accounts of concepts. • 1 Introduction • 2 The Similarity-Based Approach and the Importance of Theory o 2.1 The similarity-based approach

This review discusses recent work on foundational questions about concepts. The first of these questions is whether concepts are context-independent bodies of knowledge, or context-dependent constructs, created on the f ly. The second question is whether concepts are abstract, amodal representations, or whether they are embedded within the sensory-motor system. I discuss these two questions in light of empirical data from psychology and neuroscience, as well as theoretical considerations, and examine their implications for theories of concepts.

This paper examines the interplay between conceptual structure and the evolution of scientific concepts, arguing that concepts are fundamentally ‘forward-looking’ constructs. Drawing on empirical studies of similarity and categorization, I explicate the way in which the conceptual taxonomy highlights the ‘relevant respects’ for similarity judgments involved in categorization. I then propose that this taxonomy provides some of the cognitive underpinnings of the ongoing development of scientific concepts. I use the concept synapse to illustrate my proposal, showing how conceptual taxonomy both facilitates and constrains the accommodation of newly discovered phenomena. I end by briefly considering the implications of the proposed approach for a normative evaluation of scientific concepts.

Similarity‐based theories of concepts have a broad intuitive appeal and have been successful in accounting for various phenomena related to the formation and application of concepts. Their adequacy as theories of concepts has been questioned, however, as similarity is often taken as too flexible, too unconstrained, to be explanatory of categorization. In this article, I propose an account of similarity that takes the “foil” against which the target items are measured as integral to the process of comparison, making the similarity relation a fundamentally triadic one. I argue that this account delivers more internal constraints on the process of comparison than the traditional, dyadic account of similarity does. Finally, I propose that this account is advantageous for a similarity‐based theory of concepts, as it easily integrates with the notion of conceptual taxonomy and uses it to deliver additional constraints on categorization. On such a theory of concepts, the foil, whose variability is in large part responsible for the flexible nature of similarity judgements, is turned within the framework of conceptual taxonomy to the very element that constrains similarity judgements in categorization. Therefore, this notion of similarity mitigates the worry that similarity is too flexible to be explanatory of categorization.

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