The study of concepts lies at the intersection of various disciplines, both analytic and empiric. The rising cognitive sciences, for instance, are interested in concepts insofar as they are used in an explanation of such diverse epistemic phenomena like categorization, inference, memory, learning, and decision-making. In philosophy, the challenge imposed by conceptualization consists, among other things, in accommodating reverse intuitions about concepts like shareability, mind-dependency, mediation between reference, knowledge and reality, etc. While researchers have collaborated more and more to contribute to a unified understanding of concepts and categorization, the joint venture unfortunately suffers (so far) from the fact that it is generally left unclear how exactly the different approaches undertaken in the participating sciences relate to each other. What do psychologists and philosophers mean by the notion of a concept? Is there a core-theory of concepts and categorization underlying analytical and empirical studies? The present collection of essays addresses these and related questions and tries to answer them from both a systematic and a historical perspective.