Concepts stand at the centre of human cognition. We use concepts in categorizing objects and events in the world, in reasoning and action, and in social interaction. It is therefore not surprising that the study of concepts constitutes a central area of research in philosophy and psychology, yet only recently have the two disciplines developed greater interaction. Recent experiments in psychology that test the role of concepts in categorizing and reasoning have found a great deal of variation, across individuals and cultures, in categorization behaviour. Meanwhile, philosophers of language and mind have investigated the semantic properties of concepts, and how concepts are related to linguistic meaning and linguistic communication. A key motivation behind this was the idea that concepts must be shared across individuals and cultures. With the dawn of experimental philosophy, the proposal that the experimental data from psychology lacks relevance to semantics is increasingly difficult to defend. This volume brings together leading psychologists and philosophers to advance the interdisciplinary debate on the role of concepts in categorizing and reasoning, the relationship between concepts and linguistic meaning and communication, the challenges conceptual variation poses to communication, and the social and political effects of conceptual change.