Genealogical classification, also described in different contexts as “genetic”, “phylogenetic”, “historical” or “evolutionary”, is the classification of any set of entities according to their origin from pre-existing entities. Entities that share a common ancestry are thus grouped together. Scientific taxonomies of organisms are famously based on this principle, especially after Darwin’s introduction of historical methodology in biology. The competing biological schools of cladistic, evolutionary and phenetic taxonomy are good examples of general issues involved in taking genealogy as, respectfully, the only principle, or just one principle along with diversity, or a completely excluded principle. However, a variety of other special sciences have also considered genetic principles for classification, including astronomy, Earth sciences, linguistics, cultural anthropology and musicology; tentative applications of “phylomemetics” to LIS have also been proposed. Many library classifications, notably the Bliss Bibliographic Classification, have applied evolutionary principles to the general order of disciplines. Other authors have suggested that historical relationships among disciplines themselves, or among individual scholars and works, can be represented by an analogous genealogical approach.