The reality of species

Abstract

This thesis examines the nature of biological species, and argues that species are real. The thesis starts with a descriptive account of species drawn from biology. This includes taxonomic views, theories of speciation and theories in ecology. In this chapter a particular definition of species, 'the biospecies 1, is reached. The thesis continues in Chapter Two with a philosophical account of species, which aims at reaching an understanding of the kind of entities species are. The chapter concludes that species are natural kinds, but not as traditionally construed. Chapter Three looks closely at the use biologists make of species terms, and argues that biological theories are committed to such terms. That species terms cannot be dispensed with in biological statements indicates that species are real. If species are real, they are entities for which questions of identity make sense. Chapter Four reviews different criteria for the individuation and identity of species. All the criteria are found to suffer from problems of vagueness. In view of the difficulty of providing criteria for species identity, the thesis turns in the fifth chapter to two biological views---numerical taxonomy and neo-Darwinism---which claim that biological theories can dispense with species terms. But a look at these reductive theories shows that one loses a certain measure of explanation if species are dispensed with. In the light of the failure of the reductive theories, a fresh attempt is made in Chapter Six at giving a criterion for species sameness. This last chapter also serves as a general conclusion to the thesis.