Abstract

SPECIES INITIALLY APPEAR TO US AS OMNIPRESENT, familiar, even as rather simple objects of our experience. On closer inspection, however, the appearance of intelligibility is supplanted by mystery. Although scientists now possess a commanding grasp of the general structure and function of biological species, there is as yet no consensus on the philosophical question of exactly what kind of entity species are. Are they class entities, as a traditional view has it? Or are species actual, substantial beings? If they are among the latter, what, if anything, is the ontological difference between species and those paradigms of substantial being, organisms? Is it true, as many now suppose, that both organisms and species belong in the category of individuality? These questions and the more general problems they imply remain unresolved by scientists and philosophers alike. Perhaps the single matter on which all agree is that species have a long history of frustrating our attempts to account for them.