Species are central to biology, but there is currently no agreement on what the adequate species concept should be, and many have adopted a pluralist stance: different species concepts will be required for different purposes. This thesis is a multidimensional analysis of species pluralism. First I explicate how pluralism differs monism and relativism. I then consider the history of species pluralism. I argue that we must re-frame the species problem, and that re-evaluating Aristotle's role in the histories of systematics can (...) shed light on pluralism. Next I consider different forms of pluralism: evolutionary and extra-evolutionary species pluralism, which differ in their stance on evolutionary theory. I show that pluralism is more than a debate about the species category, but a debate about which concepts are legitimate and a claim about how they interact with one another. Following that, I consider what sort of ontology is required for different forms of species pluralism. I argue that pluralists who deny the unity of biology will require a further plurality of frameworks, while those that ground their pluralism in evolution need only one framework. Finally, I consider what pluralism means for biological practice. I argue that species concepts are tools, and reflect on how pluralism can illuminate the way systematists approach the discovery of new species of yeast. Pluralism can make sense of the way species concepts are used, and can be developed to aid researchers in thinking about how to use the right tools for the right jobs. (shrink)

We argue that the mathematization of science should be understood as a normative activity of advocating for a particular methodology with its own criteria for evaluating good research. As a case study, we examine the mathematization of taxonomic classification in systematic biology. We show how mathematization is a normative activity by contrasting its distinctive features in numerical taxonomy in the 1960s with an earlier reform advocated by Ernst Mayr starting in the 1940s. Both Mayr and the numerical taxonomists sought to (...) formalize the work of classification, but Mayr introduced a qualitative formalism based on human judgment for determining the taxonomic rank of populations, while the numerical taxonomists introduced a quantitative formalism based on automated procedures for computing classifications. The key contrast between Mayr and the numerical taxonomists is how they conceptualized the temporal structure of the workflow of classification, specifically where they allowed meta-level discourse about difficulties in producing the classification. (shrink)

The essentialism story is a version of the history of biological classification that was fabricated between 1953 and 1968 by Ernst Mayr, who combined contributions from Arthur Cain and David Hull with his own grudge against Plato. It portrays pre-Darwinian taxonomists as caught in the grip of an ancient philosophy called essentialism, from which they were not released until Charles Darwin's 1859 Origin of Species. Mayr's motive was to promote the Modern Synthesis in opposition to the typology of idealist morphologists; (...) demonizing Plato served this end. Arthur Cain's picture of Linnaeus as a follower of 'Aristotelian' (scholastic) logic was woven into the story, along with David Hull's application of Karl Popper's term, 'essentialism', which Mayr accepted in 1968 as a synonym for what he had called 'typological thinking'. Although Mayr also pointed out the importance of empiricism in the history of taxonomy, the essentialism story still dominates the secondary literature. The history of the first telling of the essentialism story exposes its scant basis in fact. (shrink)

Zoologist A. J. Cain began historical research on Linnaeus in 1956 in connection with his dissatisfaction over the standard taxonomic hierarchy and the rules of binomial nomenclature. His famous 1958 paper ‘Logic and Memory in Linnaeus's System of Taxonomy’ argues that Linnaeus was following Aristotle's method of logical division without appreciating that it properly applies only to ‘analysed entities’ such as geometric figures whose essential nature is already fully known. The essence of living things being unanalysed, there is no basis (...) on which to choose the right characters to define a genus nor on which to differentiate species. Yet Cain's understanding of Aristotle, which depended on a 1916 text by H. W. B. Joseph, was fatally flawed. In the 1990s Cain devoted himself to further historical study and softened his verdict on Linnaeus, praising his empiricism. The idea that Linnaeus was applying an ancient and inappropriate method cries out for fresh study and revision. (shrink)

The word ``deme'' was coined by the botanists J.S.L. Gilmour and J.W.Gregor in 1939, following the pattern of J.S. Huxley's ``cline''. Its purposewas not only to rationalize the plethora of terms describing chromosomaland genetic variation, but also to reduce hostility between traditionaltaxonomists and researchers on evolution, who sometimes scorned eachother's understanding of species. A multi-layered system of compoundterms based on deme was published by Gilmour and J. Heslop-Harrison in1954 but not widely used. Deme was adopted with a modified meaning byzoologists (...) leading the evolutionary synthesis – Huxley, Simpson, Wright,and Mayr. Connections are shown between Gilmour's ideas around definingthe deme, his role in founding the Systematics Association, and his chapter``Taxonomy and Philosophy'' in the book The New Systematics. Thishistorical episode raises questions about the role of carefully-definedwords in scientific practice. (shrink)

Ernst Mayr''s scientific career continues strongly 70 years after he published his first scientific paper in 1923. He is primarily a naturalist and ornithologist which has influenced his basic approach in science and later in philosophy and history of science. Mayr studied at the Natural History Museum in Berlin with Professor E. Stresemann, a leader in the most progressive school of avian systematics of the time. The contracts gained through Stresemann were central to Mayr''s participation in a three year expedition (...) to New Guinea and The Solomons, and the offer of a position in the Department of Ornithology, American Museum of Natural History, beginning in 1931. At the AMNH, Mayr was able to blend the best of the academic traditions of Europe with those of North America in developing a unified research program in biodiversity embracing systematics, biogeography and nomenclature. His tasks at the AMNH were to curate and study the huge collections amassed by the Whitney South Sea Expedition plus the just purchased Rothschild collection of birds. These studies provided Mayr with the empirical foundation essential for his 1942Systematics and the Origin of Species and his subsequent theoretical work in evolutionary biology as well as all his later work in the philosophy and history of science. Without a detailed understanding of Mayr''s empirical systematic and biogeographic work, one cannot possibly comprehend fully his immense contributions to evolutionary biology and his later analyses in the philosophy and history of science. (shrink)

The twentieth century witnessed a dramatic increase in the use of statistics by biologists, including systematists. The modern synthesis and new systematics stimulated this development, particularly after World War II. The rise of "the statistical frame of mind " resulted in a rethinking of the relationship between biological and mathematical points of view, the roles of objectivity and subjectivity in systematic research, the implications of new computing technologies, and the place of systematics among the biological disciplines.

A study is made of the history of the type and related concepts, from Greek Antiquity up to the present. It is demonstrated that the type-concept of eighteenth century biology was based on Leibniz's concept of substantial form, and was not related to a Platonic Idea, whilst it is now generally understood in the sense of model or norm. In the present paper, a type-concept is developed which includes ontogenetic and phylogenetic time and various evolutionary mechanisms. This type can serve (...) as a model of the evolutionary potentialities of a taxon, and as a standard of higher classification. All classifications based on the same archetype, whether typological, numerical or phylogenetic, will be comparable, although not necessarily identical. (shrink)