Eric Funkhouser uncovers a logical structure that is common to many, if not all, classificatory systems or taxonomies. Every conceptual scheme--including the sciences, mathematics, and ethics--classifies things into kinds. Given their ubiquity across theoretical contexts, we would benefit from understanding the nature of such kinds. Significantly, most conceptual schemes posit kinds that vary in their degree of specificity. Species-genus taxonomies provide us with familiar examples, with the species classification being more specific than the genus classification. This book instead focuses on...