Principios de Taxonomia

3.11 The Relational Properties of the Members of a Species are the Essence of the Speciesj65
The descent cohesion and gene flow relation between organisms makes an
organism a member of its species. Any particular organism belongs to a species
because its species affiliation depends ontologically on the existence of other species
members. Every organism that is excluded from the gene-flow community and is
therefore separated from the other organisms is not a member of this species. Vice
versa, every organism that is part of the gene-flow community and is thus connected
to the other organisms must belong to this species.
This realization compels one to accept that there is an essential species affiliation.
However, it is not an essence based on intrinsic traits, but an essence based on
relational connections. Why should the application of the philosophical concept of an
essence be restricted to intrinsic traits only? Nothing compels one to restrict applying
the concept of essence to traits only (Okasha, 2002). The integration into a gene-flow
community is a necessary and sufficient condition for an organism s species
affiliation.
Authors from Aristotle to Linnaeus to some more modern authors (Putnam, 1975
and Kripke, 1980) took the view that species essences had to be intrinsic traits of the
species members, with the consequence of the biological species being treated as
universal. Darwin s theory of evolution put an end to this view, after which species
essentialism was called untenable (Dupre, 1999). Okasha (2002), on the other hand,
has once more taken up species essentialism by breaking the connection between the
concepts essential and intrinsic trait. Instead, he presents the idea that species
essentialism could be based on relational connections.