Individual Essentialism in Biology

Abstract A few philosophers of biology have recently explicitly rejected Essential Membership, the doctrine that if an individual organism belongs to a taxon, particularly a species, it does so essentially. But philosophers of biology have not addressed the broader issue, much discussed by metaphysicians on the basis of modal intuitions, of what is essential to the organism. In this chapter, I address that issue from a biological basis, arguing for the Kripkean view that an organism has a partly intrinsic, partly historical, essence. The arguments appeal to the demands of biological explanation and are analogous to arguments that I have given earlier that a taxon has a partly intrinsic, partly historical, essence. These conclusions about the essences of individuals and taxa yield an argument for Essential Membership. Finally, I reject four objections that LaPorte has made to Essential Membership.