ABSTRACT
This chapter provides what Marjorie Grene and David Depew did for the philosophy of biology in general, and use the historical context to arrange and discuss the philosophical ideas that are posed and debated by philosophers and biologists alike. Having covered as best we can the history of the notion of species, one may wonder what this has to do either with the philosophy or the science of species. The species problem is actually a number of problems that biologists have dealt with since the term was first applied to biological organisms by Aristotle. The chapter discusses the three main problems the grouping problem, the ranking problem, and the commensurability problem. Immediately the commensurability problem rears its head. Species among animals are not commensurate with species among many single-celled organisms or species among symbionts. One reason why philosophers find the monism-pluralism debate so interesting is its apparent connection to the dispute over realism and antirealism.
