Species

Species Realism 359

3. The species conception applied in each case depends on whether that spe-
   cies meets the conditions for that conception.


4. Each species is a phenomenon that calls for a conception and an explanation.

So, we do not need to have a monistic or singular definition of species, because

species are things to be explained, they are explicanda, not an a priori category or

rank into which every biological organism must be fitted.^70

Final Thoughts

We have rejected classical essentialism as an adequate account of species, and along
with it the idea they are classical (i.e., Millian) natural kinds. However, species taxa
remain kinds, and they remain natural (at least, prospectively, until further investi-
gated). So, we must finish with a discussion of the kind of kinds species taxa are.
There is a distinction made by Zachos between T-species (the species of tax-
onomic description) and E-species (the things that evolve), and another related
distinction between synchronic views of species at a moment in time (Mayr’s “non-
dimensional” conception) and diachronic views of species over time. The debate
about the species concept is over whether T-species are E-species, and under what
conditions. It is my argument that there is no necessary connection between the two
for all T-species, but they may be E-species in some individual cases. This lack of
identity, however, suggests that species is not a theoretical category at all, but instead
is an empirical classification that is a prelude to further investigation. As such, it is an
empirical category, partially constructed but from evidence rather than convention
alone. This is not to be a thoroughgoing empiricist, however, as theoretical and prior
knowledge constrains the ways in which species are identified and studied. Instead,
I presume that evidence matters to scientists even when theory and experience are
employed.
One point that is not often discussed in this context is whether biology overall
even has an ontology. If species are not “units” of evolution or life, what are they?
I  have argued they are phenomena in need of explanation in each particular case.
This implies that there is no rank of species. I believe few if any ontological catego-
ries touted as biological kinds are in fact real object kinds. Instead, they are mostly
either theoretical kinds of interest to those who use those kinds in their practices, as
in the ways models are used in science, or they are assay-relative kinds, as in the use
of genetic sequences as “barcodes.” These have their utility in science, of course, but
they stand as ways of organizing the data and applying them, not as ontic categories
per se. Some, indeed quite a few, may be real (types of molecules, for example), but
the more “biological” categories are, the less “real” they tend to be. We arrange the
data we acquire (through naïve or sophisticated techniques) in ways that make the
patterns in the data tractable and useful. Species are just such patterns. They are
patterns in observations that permit us to do further work. They may be objects

(^70) Ingo Brigandt first made the claim that species are phenomena, not theoretical objects [Brigandt
2003], to my knowledge.