Categorization is an essential and unavoidable instrumentality for conceptually navigating a world--indeed for being able to conceptualize a world to be navigated. Classification is a pivotal instrument for scientific systemization, featured as a basis for the philosophical understanding of reality since Aristotle, but classificatory concepts of sorts, types and natural kinds inevitably pervade our understanding of ourselves and our position in the social as well as the natural world at all levels. The authors argue that the character, purpose-, context-, and culture-relativity of categories and categorization have been widely misunderstood--that standard philosophical views are substantially correct in some respects but markedly mistaken in others. The book offers a comprehensive survey of basic principles of classification and categorization, a survey of relevant empirical work, and a multitude of illustrative examples accompanied by instructive analysis of ways and means. The work traces wide-ranging implications of the current approach for philosophical problematic and paradox in philosophy of mind, epistemology and metaphysics, philosophy of science, social philosophy and ethics.