"Species" is not just a biological concept. It is also a general concept in knowledge organization (KO). WordNet 2.1 defines: "

In biology have scientists found and described approximately 1.75 million species on Earth. New species are being discovered every day. The field of biological taxonomy provides principles for the classification of those species. The most famous biology taxonomy is the Linnaean hierarchy. The definition of biological species provided by WordNet above (taxonomic group whose members can interbreed) is, by the way, one among more biological species definitions or species concepts.


The importance of the species concept for KO is connected to the famous Aristotelian "Definition by species and genus" (See Wikipedia, 2006a and definition in Epistemological lifeboat). In order to organize something you most know what makes up a specific kind of something and how this specific kind of something is related to other kinds. In other words, the most important first step it to define the species in question.


Normally we cannot see there are problems in defining species. We see a Swan and have no problems categorizing is as such. However, the species concept is not trivial. Some "zebras" are more related to horses than to other zebras, for example, why the zebra species is a controversial concept in biology.


This "direct realism" was the philosophy of Ockham:


“For one thing, as was seen in the previous section, the process of concept formation is completely natural. It is the same in every human being and leaves no room for idiosyncratic vagaries. Secondly - and most importantly - this naturally acquired stock of concepts does cut the world at its joints, according to Ockham. Species and genera, of course, are denied any outside reality as distinct beings, but Ockham readily grants that whether an individual thing is or is not of the same species or of the same genus as another is not for the human mind to decide. The conditions of being in the same genus or of the same species are not subjective or arbitrary. They are determined, on the contrary, by what the individual things are in themselves and how they in fact stand to each other. Whether something resembles Bucephalus enough to be naturally represented by the same general concepts does not, Ockham insists, depend upon the human mental apparatus at all. It simply is a rock-bottom fact of the universe. Concept formation, being a natural process, derivatively mirrors the natural distribution of causal powers among individual things, which powers depend in turn on real singular essences and qualities. In this lies the adequacy of abstractive cognition.” (Panaccio, 1998).


When we realize that likeliness it not just a neutral and objective concept, a major problem arises: What criteria should be used to define a given species (either in biology or in any other domain)? (The definition of biological species quoted above (from WordNet) is just one among more species-concepts in biology: There are different schools or "paradigms" associated with the species concept.



In August of 2006 the International Astronomical Union redefined the term "planet", and classified Pluto along with some asteroids as dwarf planet. In this case, the species concept "planet" was redefined, and consequently the classification system used to classify the heavenly bodies. (We may also say that the concept of "planet" was changed). Not everybody agreed in this change of a species concept, but the example illustrates how species concepts are constructed scientifically in order to serve our understanding of phenomena. A specific way of defining a concept or a species may be more or less well argued and accepted, but the definition cannot be regarded as anything but a part of the scientific construction of representations.


"According to the nominalist species concept, only individuals exist in nature, and species are a human artifact; that is, a person (not nature) makes species by grouping individuals under a name. But such arbitrariness is unsubstantiated by the situation encountered in any actual exploration of the natural world. . . . It requires a vast ignorance of both living organisms and human behavior to adopt the nominalist species concept" (Mayr, 1997, p. 312).

Cooper (p. 47) writes:

“In recent years traditional essentialist accounts of natural kinds have come in for fierce criticism. A major difficulty is that for biological species, which are traditionally considered amongst the best examples of natural kinds, no plausible candidates for the essences can be found. Several different criteria may be employed by biologists seeking to determine species: morphological futures, evolutionary lineages, the criteria of reproductive isolation, or genetic features. On examination none of these appears suitable candidates for being the essential properties of biological species”





Cooper, Rachel  (2005). Classifying Madness: A Philosophical Examination of the Diagnostic and Statistical Manual of Mental Disorders. Berlin: Springer.


Mayr, Ernst (1997). This is biology: The science of the living world. Cambridge, Massachusetts: The Belknap Press.


Mishler, B. D. (1999). Getting Rid of Species? IN: R. Wilson (ed.). Species: New Interdisciplinary Essays, pp. 307-315. Cambridge, MA: MIT Press. http://persoon.si.edu/sbsarchives/sbs2001/Mishler.pdf


Panaccio, C. (1998). William of Ockham (c.1287-1347). Routledge Encyclopedia of Philosophy, Version 1.0, London: Routledge.


Sterelny, K. (1998). Species. IN: Routledge Encyclopedia of Philosophy, Version 1.0, London: Routledge.


Wheeler, Q. & Meier, R. (Eds.). (2000). Species Concepts and Phylogenetic Theory. New York: Columbia University Press.


Winston, J. (1999). Describing species: Practical taxonomic procedure for biologists. New York: Columbia University Press.


Wikipedia. The free encyclopedia. (2006a). Genus-differentia definition. http://en.wikipedia.org/wiki/Definition_by_genus_and_difference


Wikipedia. The free encyclopedia. (2006b). Species. http://en.wikipedia.org/wiki/Species


Wilkins, J. S. (2003). How to be a chaste species pluralist-realist: the origins of species modes and the synapomorphic species concept. Biology & Philosophy, 18(5), 621-638. http://www.springerlink.com/content/n4t3w63844134120/fulltext.pdf



WordNet 2.1. Species. http://wordnet.princeton.edu/perl/webwn?s=species




See also: Natural kind; Typology


Birger Hjørland

Last edited: 03-03-2008