This paper discusses how we understand and use a concept or the meaningof a general term to identify the objects falling under the term. There aretwo distinct approaches to research on the problems of concepts and meaningthe psychological approach and the formal (or logical) approach. My majorconcern is to consider the possibility of reconciling these two differentapproaches, and for this I propose to build a psychologically plausibleformal system of conceptualization. That is, I will develop a theory-basedaccount of concepts and propose (...) an explanation of how an agent activates aperspective (which consists of theories) in response to a situation in whichreasoning using a concept is called for. Theories are represented as sets offacts and rules, both strict and defeasible. Each theory is organized in acoherent perspective which stands for an agent's mental state or an agent'smodel of another agent's perspective. Perspectives are organized intohierarchies and the theory for a concept in one perspective may defeat thetheory for the same concept in another perspective. Which perspective issuperior is context-dependent. (shrink)

Theories concerning the structure, or format, of mental representation should (1) be formulated in mechanistic, rather than metaphorical terms; (2) do justice to several philosophical intuitions about mental representation; and (3) explain the human capacity to predict the consequences of worldly alterations (i.e., to think before we act). The hypothesis that thinking involves the application of syntax-sensitive inference rules to syntactically structured mental representations has been said to satisfy all three conditions. An alternative hypothesis is that thinking requires the construction (...) and manipulation of the cognitive equivalent of scale models. A reading of this hypothesis is provided that satisfies condition (1) and which, even though it may not fully satisfy condition (2), turns out (in light of the frame problem) to be the only known way to satisfy condition (3). (shrink)