In science there are uses many classifications of entities - plants, animals, rocks, soils, stars, diseases, occupations, and so on. In these taxonomies a classification must display genetic relations - for example, an evolutionary family tree of animal species - but its prime purpose is to aid in the identification of entities... Classification enables us to select, from the whole universe of known entities, the one that best matches one newly encountered.

p. 3. - Classification and indexing in science (1958) - Chapter 1: The need for classification