Philosophy of Biology

SPECIES, TAXONOMY, AND SYSTEMATICS

Marc Ereshefsky

1 INTRODUCTION

Conceptual issues in biological taxonomy often straddle the boundary between
biology and philosophy. Consider questions over the nature of species. Are species
natural kinds or individuals? Does ‘species’ refer to a category in nature or is it
merely a useful device for organizing our biological knowledge? These questions
involve elements of metaphysics, epistemology, and philosophy of science. These
questions also turn on empirical information and biological theory. When we ask
about the nature of species are we asking a philosophical or biological question?
The answer is ‘both.’
Three conceptual issues in biological taxonomy and systematics will be dis-
cussed in this chapter. One is the ontological status of species. Many if not most
philosophers believe that species are natural kinds –classes of organisms with the-
oretically significant similarities. Other philosophers, and many biologists, believe
that species are individuals akin to particular entities. The outcome of this debate
has implications beyond biological taxonomy, for example, it has implications for
our conception of human nature. IsHomo sapiensa kind defined by similarities
among its members, or isHomo sapiensan evolving lineage defined by genealogy?
If species are individuals, then no qualitative trait is necessary and sufficient for
being a human.
Another conceptual issue is taxonomic pluralism. A common scientific and
philosophical view is that, from a God’s eye perspective, there is a single correct
classification of the organic world. A number of authors respond that this view
is wrong. They argue that there is no single correct classification of the organic
world and that the organic world itself is pluralistic. This issue has implications
outside of taxonomy. In philosophy of science it raises the question of whether
philosophers should promote scientific unity as an aim of science. If taxonomic
pluralism occurs in biology then biology, and science as a whole, lacks unity.
A third conceptual issue concerns the Linnaean hierarchy: should biologists keep
using the Linnaean hierarchy or should they adopt a new system of classification?
The Linnaean hierarchy was developed prior to the Darwinian revolution. Many
biologists and some philosophers believe that the Linnaean hierarchy faces pressing
problems. Some even suggest junking the Linnaean hierarchy. Again, important
issues outside of classification hinge on this debate. Most biodiversity studies are
given in terms of Linnaean ranks, for example, the rank of family. If those ranks do

General editors: Dov M. Gabbay,
©c2007 Elsevier B.V. All rights reserved.

Handbook of the Philosophy of Science. Philosophy of Biology

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