Session : New light on species essentialisms in biology (F.Merlin, A.Barberousse, E.Casetta, T.Reydon)

The syncretic essentialism of Devitt (2008) – the essence of biological species is made up of intrinsic properties possibly completed by historical and relational properties – can be seen as a tentative to accommodate the various explanatory expectations of different branches of biology as well as of everyday life. Without contesting the legitimacy of pluralistic essences, I first argue that it is doubtful that a unique sort of essence, be it pluralistic or not, may correspond to the notion of biological species. Then I explore the puzzling idea that a bundle of related essences might correspond to it. I show that the idea is not problematic from an ontological perspective if one intends by essence a real (possibly unknown) cause of unity. The difficulty lies in the semantics. As a matter of fact, a NK term, according to Putnam's and Kripke's semantic theory, is supposed to hook either one NK, i.e one essence, or nothing at all. Taking some inspiration from the analysis Bloom (2007) offers of the concept of “water”, I defend that there is a way out of this difficulty that does not challenge the core of Kripkean semantics of NK terms. Bloom (2007) claims that “water” is a “hybrid concept”(and not two homonymous concepts) referring both to a chemical NK and a related artefact kind. I argue that it is indeed possible to associate a less restrictive condition to NK terms than “one essence or nothing”.