In this master's thesis classification is put into the bigger context of other human capacities of knowledge and action such as perception, language and categorization. By studying and analyzing recent research on categorization in psychology, anthropology and cognitive science and interpreting it through the philosophy of Henri Bergson the thesis  demonstrates how knowledge and action are two sides of the same coin and how this insight is a must for a proper understanding of classification. The analysis focuses primarily on the family resemblance categorization theory of Eleanor Rosch, the ethnobiological universal classication theory of Brent Berlin and Scott Atran, the presentation of evolutionary cognitive science by Peter Gärdenfors and the philosophical discussion on classification by Rebecca Bryant. The thesis removes classification from its assumed Aristotelian origin and connects it with psychological categorization and by extension all human (and nonhuman) acts of differentiation. This is a two years master’s thesis in Archive, Library and Museum studies.