The concepts to be considered in this chapter are those that occur in everyday common human thought and language – the “natural history” of concepts in use. While many may appear to be constituted by similarity relations, which make them suitable for modelling in conceptual spaces for example, other concepts in everyday use may be differently constituted. These concepts include abstract concepts, essentialist kinds, natural kinds, and logical or mathematical concepts. I discuss the different sources, uses and epistemological bases of (...) these different forms of concept, and propose a three-level hierarchy of concepts based on their sources of validation. (shrink)