Mereology, Set Theory, Biological Ontology

Abstract

Since 1974, date of publication of M. Ghiselin’s paper “A radical solution to the species problem”, a vigorous polemic has been raging among philosophers of biology on the question of whether biological taxa, and specially biospecies, are classes or individuals. Obviously they are neither, but the lack of adequate conceptual tools has tended to cloud the issue. D. Hull has convincingly shown that biospecies (entities which originate, evolve, and split or become extinct) are not classes, but has been less successful with his claim that species are individuals. Some philosophers, like A. Rosenberg and M. Williams, have accepted Hull’s position. Others, like P. Kitcher and A. Caplan, have remained unconvinced. Several biologists specially concerned with systematics have also accepted the claim that species are individuals, among them E. Mayr, N. Eldredge and R. Willmann. Many others are somehow bewildered by the use of the word individual (normally reserved for organisms) to refer to species.